Usually, the field then is waterflooded water is injected into the reservoir interval to push more hydrocarbons toward a production wellbore. Waterfloods in this enhanced-recovery phase can extend the life of a field for many years. At some point, when the waterflood production declines significantly, a decision must be made either to apply a tertiary recovery process such as carbon dioxide injection, fire flood, etc. Abandonment does not necessarily mean closure of the field.
As might be expected, individuals and teams with different backgrounds are responsible for the different phases. Entrepreneurial geologists tend to be in charge of mapping through prospect generation and discovery. When hydrocar- bons are discovered, reservoir engineers play the major role in delineating the reservoir, but geologists and geophysicists still should have a major impact in these phases. Facilities engineers are responsible for building the facilities into which the hydrocarbons are collected and processed.
Production is managed by production engineers. Divestiture of a field is usually handled by the financial and legal branches of an organization. Large companies have specialists in each area. However, smaller companies, particularly independent operators, often re- quire their people to wear several hats and conduct several, if not all of the activities. Many professionals will answer this question by stating that characteriza- tion begins as soon as the discovery is made and the first data become available usually from seismic and the discovery well and perhaps from earlier dry holes in the area.
As more wells are drilled Fig. Therefore, reservoir characterization is an ongoing process, and the characterization is or should be updated as new data are acquired. It is impor- tant to reiterate that, even with a large number of wells drilled in the field, the majority of the field acreage is still undrilled, and there can be many surprises at the interwell scale.
The smaller the well spacing, the fewer the surprises but the greater the expense and the greater degree of reservoir connectivity Fig. The goal of many reservoir characterization studies is to provide a 2D or 3D geologic model to petroleum engineers for reservoir performance simula- tion and for well planning. Modified from Al-Quahtani and Ershaghi Reprinted with per- mission of AAPG, whose permission is required for further use. Curves depicting the percent of uncontacted reservoir volumes in various types of reservoirs. Those reservoir types thought to have the highest degree of heterogene- ity and compartmentalization exhibit the highest proportion of uncontacted reservoir volume.
These reservoir types will have poor reservoir sweep efficiency. Modified from Ambrose et al. Basic principles and applications of reservoir characterization 27 Fig. Three stages in development of a 3D stratigraphic model for reservoir perfor- mance simulation. Stage 1 is to define key stratigraphic surfaces to subdivide the model into layers. The second stage is to fill the space between the layers with facies or architectural elements. The third stage is to grid the model and fill the grid blocks with reservoir pa- rameters.
Input of structural properties to the model is not illustrated here, but is equally important to building a final geologic model. Source of figure is unknown. Not shown in the figure is the addition of structural attributes such as faults, fractures, and folds, which is essential to complete the geologic model. The chapters in this book are geared toward these three steps in model-building, although not in the or- der presented in Fig. Chapters 4 and 11 deal with the identification of boundaries sequence boundaries and maximum flooding surfaces that can de- fine stratigraphic layers for model-building.
Chapters 6—10 deal with the strata that are placed between the boundaries. Chapters 3 and 5 deal with reservoir petrophysical properties that are input into the grid blocks of a model. Multi- ple random or constrained iterations of input parameters are generated until a desirable output model is produced Fig. The resulting geologic model may take many forms depending upon the input information and the character- istics of the reservoir. Example of multiple iterations of input parameter to a 2D gridded model. Sand blocks are randomly input into grid blocks through multiple iterations. After 1, iterations, the actual output values matched the target values.
After Srivastava These examples are of facies distribution and permeability distribu- tion. Many other parameters may be substituted for these two parameters within a model. In addition, the shapes and orientations of sand bodies may be modeled for simulation and well planning purposes Fig. Basic principles and applications of reservoir characterization 29 Fig. Examples of 3D models. A and C are two iterations of a 3D facies model. B is a model showing the distribution of permeability. D shows plan views of the models shown in A and C.
After Chapin et al. After Larue and Friedmann This book is intended to provide an overview, or introduction, to the field of reservoir characterization. Although the theme is heavily geologic, other aspects and disciplines are discussed. The strategy of this book is to present var- ious reservoir characterization procedures, tools, and knowledge, in brief funda- mental segments, and to follow these segments with case histories that provide examples of the fundamentals.
In my personal experience, the best way to make a point and ensure that it is understood is to present a case study. It is a mistake to reject case studies because of their location either geographic or geologic , because the principles that apply in a case study from one area usually also apply more globally. Thus, I encourage the readers of this book to be open to more widespread applications of the individual case studies presented here. Figure 2. Inter- pretation techniques and concepts are listed by year beneath the black curve, and related new technologies are listed above the curve.
Other technologies that also have vastly improved our ability to extract hydrocarbons include advances in well logging techniques, improvements in our ability to drill in deep water beyond the continental shelf, and the advent of horizontal drilling, to name a few. This chapter provides an overview of the common techniques for character- izing oil and gas reservoirs.
The techniques can be subdivided into those that measure static reservoir properties and those that measure dynamic reservoir properties. They are the result of primary deposi- tional processes coupled with postdepositional burial, diagenesis, and tectonics Fig. Graph showing the US discovery and recovery efficiencies since Figure is mod- ified significantly from Fisher Reprinted with permission of The Leading Edge.
Dynamic properties are those that do change significantly during the life of a field. For example, fluid saturations, compositions, and contacts, as well as reservoir pressure, change as the field is produced. Porosity and permeability can change as the reservoir pressure changes over time or as injected fluids react with formation minerals either to precipitate new minerals that fill pore spaces or to dissolve minerals and thereby provide new pore spaces. Acoustic properties, which are measured and documented as seismic at- tributes, are dependent upon porosity, fluid type and content, and the nature of the reservoir rock.
Seismic attributes are dynamic, because fluid type and content change during oil and gas production. By comparing seismic attributes at different times in the life of a field, it is possible to indirectly measure fluid movement in the reservoir. In exploration, one starts with a conceptual geo- logic model Fig. Conventional 2D or 3D seismic-reflection analysis Fig. If the seismic data reveal potential drill sites, and a well is drilled, the well is logged with conventional logging tools Fig.
If potentially economic accumulations of hydrocarbons are found in the ex- ploratory well labeled 4 in Fig. If this delineation phase is favorable, more-detailed knowledge of the reser- voir is required. Outcrop analog studies Fig. Of course, to appropriately compare outcrop features with a reservoir, the outcrop must be of the same depositional system as is the reservoir. This will be discussed more fully in sub- sequent chapters.
Also at this time, well tests, such as initial potential flow rates and pressure tests, are acquired to aid in the characterization process labeled 7 in Fig. With addition of hard data from wells and outcrops, and perhaps with additional 3D seismic-reflection analysis, the model can be quantified and a scaled, graphi- cal, 3D reservoir geologic model Fig. Diagram showing some of the different data types used in the study of reservoirs. Clockwise from upper left are conventional well logs, a conceptual geologic model, 2D and 3D seismic reflection data shallow and deep , outcrops, cores and borehole image logs, and geologic reservoir models.
Not shown are geochemical and biostratigraphic data, which also are important in reservoir characterization. Exploration, discovery, development, and production stages in the evolution of a reservoir over time steps 1—9. Geophysics, geology, and petroleum engineering all play dominant roles at different times in the life of a field. Tools and techniques for characterizing oil and gas reservoirs 35 Fig. Scales of measurement for different investigative techniques.
The scales range from basin scale to pore scale. Different types of instruments are used to measure properties at these different scales. Diagram courtesy of D. This workflow, from exploration to reservoir characterization to geologic modeling and field development, progresses from examining features at a large scale to examining very small features, using a variety of tools Fig. Once production begins, production information and new well data should be updated continually to refine the reservoir characterization labeled 9 in Fig. Most organizations provide adequate computing environments for their staff, from secretaries to geoscientists and engineers.
However, some individuals and very small compa- nies still prefer to hang cross sections on walls with a piece of string as a datum, or to interpret paper copies of seismic lines and well logs. Progressively more geoscientists and engineers who are entering the petro- leum industry grew up in a world in which, as toddlers, they had an early expo- sure to toy computers that helped them learn to visualize images on a screen.
In grade school, they will have used computers in their classrooms and school li- braries, and many of their families will have home computers. By the time they reach college and the work world, they are computer-literate and very comfort- able in the computing environment. They are used to collect and manipulate seismic data for generating images, to generate well logs, to make maps, to evaluate numerical variables, to develop mathematical formulations, and to simulate fluid flow in a numerical reservoir model, to name a few applications.
Improving computing speed is a constant challenge for hardware developers, because geoscientists always want to see the results of their studies as soon as possible. Even more importantly, geoscientists want to be able to input ever- larger volumes of data in order to build more-sophisticated and detailed realis- tic reservoir models for fluid-flow simulation. A key asset of modern computing is its ability to provide visual 3D images of features and processes that used to be displayed either in 2D space, or verbally or numerically Slatt et al.
Advances in computer storage capacity and speed of data manipulation now allow rapid analysis of vast amounts of infor- mation for exploration and production however, there is still the need for more and faster data gathering and manipulation. Visualization is a form of communication that bridges the gap between verbal and technical languages Fig. This communication gap is one reason why Fig. Picture showing one of the principal values of computing in the petroleum indus- try: that of improving communication among disciplines. The picture illustrates a geolo- gist left examining a computer geologic model built from well control, and a geophysicist right examining a seismic section on the computer screen.
Both are attempting to develop a realistic geologic model of the petroleum reservoir, and they can be aided in this endeavor by iterating their visions of the reservoir on their computer screens. Diagram courtesy of P. Tools and techniques for characterizing oil and gas reservoirs 37 Fig. Visualization theater CAVE. Images, such as from a 3D seismic survey, are pro- jected onto three walls, the floor, and the ceiling of the theater so that individuals and teams can appear to stand inside the seismic volume.
The lower-right figure shows a person inside the theater evaluating potential drilling sites near-vertical lines through high-amplitude seismic intervals. Diagrams courtesy of G. In this way, a seismically- defined reservoir can be examined from the inside, and drilling scenarios can be simulated and calculated. However, their high cost can be offset by the improvement in integrating disciplines and in the speed of solving reser- voir problems Shiralkar et al.
The same is true in education. Online internet distance learning is now global and, in many cases, more convenient and less expensive than traditional university education Fig. Illustration pointing to the ease with which information can be transferred elec- tronically to different locations, sometimes in different parts of the world, through satellite systems.
By looking at the surface, there is no way that someone can truly know the geologic structure and stratigraphy that lie beneath it. The Grand Canyon Fig. Seismic-reflection analysis has become the dominant tool used in hydrocarbon exploration, and with some resolution limitations, it is becoming widely used for characterizing reservoirs.
The seismic-reflection method is based on the principle that an energy source, such as dynamite, generates sound waves that travel through the earth Fig. The receivers are wired to a computer, inside a vehicle, that collects the reflected wave energy Fig. The large amount of data that is collected during a seismic shoot can be processed either on site or at a facility that has more powerful computing capabilities.
A A typical ground surface, with no indication of the geology that lies beneath the surface. B The Grand Canyon, which shows the internal structure and stratigraphy that is present beneath the ground surface at this locale. The roles of the geologist and the geophysicist are to image and evaluate the subsurface geology when it is not readily observable. The vertical axis is recorded not in depth be- neath the ground surface, but rather, as two-way traveltime TWT. Seismic reflection analysis has become the dominant tool for characterizing reser- voirs as well as for exploring for subsurface hydrocarbon accumulations.
It is based upon the principle that A an energy source such as dynamite generates sound waves that travel through the earth. A Cartoon showing the travel path of seismic energy down to rock interfaces, then back to the ground surface. After Brown The seismic amplitudes are representations of energy reflected off stratal boundaries. Notice the high-amplitude dark reflections at about 1. About two-thirds the distance from the left edge of the seismic line on the horizontal axis which represents distance , these reflections are offset, indicating the presence of a thrust fault that cuts through the strata and dips toward the left.
Tools and techniques for characterizing oil and gas reservoirs 41 Fig. A Seismic energy can also be generated by hitting a metal plate with a sledge- hammer. Behind the person is a geophone attached to a cable. B The reflected energy captured by the geophone is recorded on a laptop computer. In Fig. If just the shallow subsurface is to be imaged, a sledgeham- mer can be used to hit a plate on the ground Fig.
Seismic reflection is also the primary tool used for characterizing the struc- ture and stratigraphy beneath the seafloor in the marine environment Fig. In places like the US Gulf of Mexico and offshore West Africa, seismic shooting has gone beyond the shelf edge as the search for oil and gas has extended into deeper waters. A boat tows the sound source via a cable attached to the stern, while another cable holds the hydrophones the marine equivalent of a geophone that receive the reflected waves. The advantage of a 3D survey is obvious — a three-dimensional image of the subsurface is much more useful for exploration and field development than is one or more 2D vertical images.
Three-dimensional seismic is designed to image a large area of the subsurface, including up to and beyond the size of a reservoir, both areally horizontally and stratigraphically vertically Fig. Shooting a 3D seismic survey on land or in the marine environment requires rigorous planning, particularly in positioning the source and receivers. For land surveys, a 3D grid of geophones is placed on the ground surface Fig.
Sound waves reflecting off of individual stratal boundaries will be picked up by this 3D array of geophones, and a 3D image of the subsurface will be generated as a series of seismic reflections. Color is now a common processing and display tool for enhancing the 3D seismic image Fig. Tools and techniques for characterizing oil and gas reservoirs 43 Fig. Graph showing the vertical resolution of a reservoir on the horizontal axis and the horizontal coverage of the reservoir on the vertical axis.
Cores can exhibit sedimentary features down to the scale of a millimeter or less, but the areal coverage is very small 15 cm, or 6 in, diameter. At the other extreme, 3D surface seismic covers a large area of a reservoir, but the features must be on the order of tens of meters to be fully resolved and imaged. Various other tools measure properties between these two end members. Diagram courtesy of B. Marion and Z-Seis Corporation. Diagram showing three of many possible 2D images that can be generated from a 3D seismic survey.
In addition to these orientations, 2D sections can be generated at any orientation within the 3D data grid diagonal, tilted, etc. Af- ter Brown A A single seismic profile from a 3D seismic survey. A fault trace is shown. B Crossing profiles from the survey with the fault plane highlighted.
Because of the large quantity of data collected during a 3D seismic survey, computers are essential for data display, as well as for acquisition and process- ing procedures. Many displays are possible, including 2D crossline and inline displays for imaging planar features in 3D space Fig. Figures 2. Thus, 4D seismic measures dynamic reser- voir properties. The concept was that the heated reservoir fluids would move outward in all directions from the well arrows in the preburn seismic horizon. The bar scale shows the relative scale of seismic amplitude.
At preburn conditions, there was little variation in seismic amplitude throughout the field. By midburn time, amplitude had changed signif- icantly near the western production well, indicating fluid movement in that di- rection arrow. A A 3D seiscrop or horizon slice showing a buried meandering river channel.
The quality of the seismic image is so good that it gives almost the same appearance of the subsurface feature as if one were looking out of an airplane window at a similar feature on the ground surface; B shows a gas-charged fluvial sandstone in its true structural posi- tion — structural dip is toward the lower left. A and B after Brown C Areal photograph of a meandering river, similar in shape to that imaged in A. The light colored areas on C are accumulations of sand.
By knowing where sand accumulates in modern meandering channels, one can predict the occurrence of sand- stone accumulations on the horizon slice of a similar subsurface feature A. Here, three companies had run independent 3D seismic surveys at different times, using reasonably similar acquisition parameters. Comparison of the 3D surveys, in the area where all three surveys overlapped, formed the basis for a 4D seismic survey.
Tools and techniques for characterizing oil and gas reservoirs 47 Fig. B Modern-day pinnacle reef for comparison. The relative measures of amplitude are shown on the bar scale. Variations in amplitude from pre- to post-burn time indicate migration of reservoir fluids as a result of the fireflood. After Greaves and Fulp The results of the analysis were quite dramatic. Different colors represent seismic- amplitude change and lack thereof among the three 3D surveys.
One of the most popularized 4D seismic surveys was done in the Eugene Island area of offshore Gulf of Mexico. After He et al. An early 3D seismic survey was shot in , followed by another survey nearby in , then a third survey in Modified from He et al. Reprinted with permission of Oil and Gas Journal. A horizontal well was drilled into the bypassed area. During the period — prior to the seismic sur- vey , 1. The combination of 4D seis- mic and horizontal drilling paid off in handsome dividends to the operators and demonstrated a new technique that is becoming more widely used.
The results of the 4D Eugene Island seismic survey. The 3D block shows the reser- voir area, and the different colors represent areas in which seismic amplitudes changed or remained the same among the three 3D surveys.
A fairway is highlighted in which there was no change in amplitude, which suggests the presence of bypassed or untapped oil. Blue denotes areas in which impedances increased over time. In this case, a hor- izontal well was drilled into the zone that appeared to contain bypassed oil and, as is shown on the lower left graph, production improved dramatically. During the period — prior to the seismic survey , 1. This technology essentially reduces seismic noise, thus enhancing seismic signals from real geologic features.
The sharper image of faults on the right-hand diagram is obvious. Illustration from the cover of the October issue of The Leading Edge techni- cal journal Bahorich and Farmer, A 3D horizon slice without left coherence-cube image processing is compared with a slice with right coherence-cube image processing.
The clear outlines of faults on the right-hand diagram are much more difficult to interpret on the standard 3D seismic horizon slice on the left. Spectral decomposition is another technique that is proving to be quite valu- able in improving the clarity and resolution of seismic images of reservoirs. A seismic waveform is composed of a series of sinusoidal components that have variable frequencies and amplitudes Fig.
The spectral decomposi- tion process separates the seismic signal very precisely into individual frequen- cies, so that the associated amplitudes can be observed one at a time. Acoustic properties of rock and the fluids contained in that rock also vary with frequency. Tools and techniques for characterizing oil and gas reservoirs 51 Fig. Graph that shows the frequency dependence of seismic amplitude.
The three seis- mic profiles on the right show amplitudes at , , and Hz frequencies. Different fea- tures are highlighted at each frequency. After Sanchez Thus, by decomposing the seismic signal into individual spectral components, associated amplitudes can be observed that vary with frequency as a function of the reservoir-rock and reservoir-fluid properties. Also shown are three seismic profiles of differing frequency. The amplitude variations with frequency represent the response of specific rock and fluid properties to the seismic signal.
An offshoot of the spectral decomposition technique is multi-attribute in- version, a technique that provides excellent lithology resolution when it is compared with extracted seismic amplitudes. Evolving technologies like these will continue to improve our ability to image and understand subsurface reservoirs. The same seismic horizon slice, displayed at , , and Hz frequencies. Dif- ferent features are highlighted at each of the three frequencies.
Example showing that properly combined multiple attributes provide superior lithology resolution, compared with that from extracted seismic amplitude. The seismic amplitude exhibits poor correlation with the presence of sand in an area, whereas the multi-attribute inversion provides details of sand deposition within a meandering channel. Figures courtesy of Fusion Petroleum Technologies, Inc. Because the source and receivers are beneath the surficial weather- ing zone and are closely spaced, the resolution is an order of magnitude higher than that from surface seismic in the vertical dimension, though the aerial cov- erage is less Figs.
Cross-well seismic provides an energy source that generates sound waves within a borehole. Receivers arranged in a series are placed down another well to detect the sound waves. Behavior of the waves from source to receiver can be related back to rock and fluid properties, such as lateral and vertical variations in porosity, at much higher resolutions than can be acquired from conventional surface seismic reflection.
A comparison of the resolution of cross-well seismic to that of surface seismic. The cross-well seismic provides much better resolution of features that can be related back to properties of the reservoir. Drawbacks to the method include its expense and the small areal extent of its coverage. Reservoir heterogeneities imaged from carbonate structures. The vertical and lateral extent of individual buildups requires cross-well seismic resolution to detect the buildups and to help target horizontal wells.
Cross-well seismic showing small offset faults between wells and amplitude dis- continuities representing stratigraphic discontinuities. These features are all beneath the resolution of conventional seismic data. Marion and Z-Seis Corpo- ration. Tools and techniques for characterizing oil and gas reservoirs 55 2. These two very different types of waveforms travel at different velocities through media, so that Vp P-wave velocity and Vs S-wave veloc- ity can be measured and compared. Dipping surfaces, such as faults and fold limbs, disperse seismic energy such that considerable post- acquisition processing of data is required, and even then, an uncertain image emerges.
Because the seismic energy is in the form of wavefronts, the velocity of the waves and the medium through which they travel in a surveyed area must Fig. A A sandstone-thickness isopach map based on well control after Mark, After Blott et al. Seismic resolution and detection are determined as a function of the wavelength of the seismic waveform. Many features that control, or at least affect, fluid flow in a reservoir are smaller than the seismic-reflection resolution and detection limits, and thus, are subseismic in scale. No single definition of the term subseismic exists, because resolution varies with wavelength and frequency of the waveform, subsurface depth of the reflecting surface, and other factors.
But, if the wavelength is much longer than the thickness of the interval of interest, that interval will not be imaged Fig. Tools and techniques for characterizing oil and gas reservoirs 57 Fig. A Conventional well log and a section of core. The response of the log can be cal- ibrated to the different rock types comprising the core, so that the remainder of the well can be interpreted in terms of rock type.
From these data, the geolo- gist works to predict the rock types and their geometry away from the wellbore, where there are no real data. This is difficult and often is not assisted by seismic data if the rock strat- ification is beneath the resolution of the seismic wavelet, as is the case on the left. B This common situation is analogous to a seismic wavelet being superimposed upon the building. Internally the building consists of a series of rooms separated by floors, ceilings, and walls, but none of these compartments can be imaged because they are beneath the resolution and detection of the seismic wavelet.
Source of picture A is unknown. Picture B provided by D. Wells can be drilled on land with a land rig, or at sea from a floating platform or drillship Fig. The basic parts of a drill rig are shown in Fig. The drill bit is attached to a drill string of pipe that rotates through a turntable on the rig floor. At the end of the drill string is a drill bit that cuts through the rock. The only real way to determine the types of rocks in the subsurface is to drill a well. Except in very structurally complex areas, seismic reflection data normally are ac- quired before an expensive well is drilled.
Wells are drilled both on land and in the ocean, as is shown in these pictures. Normally, a mud logger examines the cuttings on the drill floor, records the lithology, and measures the contained reservoir fluids, then bags the cuttings for future, more-detailed examination. To facilitate a thorough examination of cuttings samples for their lithology, composition, and for the presence of microflora and microfauna, the drilling mud must be washed from the cuttings to provide a clean sample Fig.
Cuttings analysis may include relative proportions of rock types, biostratigraphy, and mineralogy Fig. Tools and techniques for characterizing oil and gas reservoirs 59 Fig. A Basic parts of a drilling rig, including the derrick, the turntable that turns the drill string, and the bit that rotates and cuts through the rock. B Whole core that is boxed and ready to be shipped to a core analysis facility after being washed. C Slabbed core that has been cut lengthwise in two, with the side shown having been polished.
D Close-up of a core piece from which a core plug has been obtained for porosity and permeability measurement. These plugs are obtained while the core is still whole B. This figure shows five trays of cuttings from a well. The cuttings have been thoroughly washed and cleaned and are ready for examination by a geologist, who will determine the proportions of different rock types comprising the cuttings. In this case, the cuttings represent a composite of rocks over 3 m 10 ft intervals. After Garich The cuttings log shows the proportions of each rock type throughout the entire ft interval in this well.
Various well logs are shown to the right. After Romero If one wishes to obtain a core from a subsurface formation, a different as- sembly is attached to the drill string and a whole core of the subsurface rock formations is cut through a predetermined depth interval. When a core is ob- tained, it too is described at the wellsite. After the core is described at the wellsite, normally it is stored for later shipping to a laboratory for further treatment and examina- tion.
Core plugs, which generally are 2. If one desires, the core can then be cut into two vertical slabs. Horizontal drilling of wells, such as is illustrated in these figures, is ideally suited for the type of situation shown here. A Cartoon of horizontal well drilling. B Reservoir in the Gulf of Mexico, with three vertical wells that penetrated some of the different lenticular sandstones and a horizontal well that also penetrated multiple channel sandstones.
After Craig et al. Horizontal-well drilling has expanded considerably in recent years because of improved technology and reduced costs Fig. Although it is more expensive to drill a horizontal well than a vertical well, horizontal wells are particularly efficient for reaching compartmentalized reservoirs, such as sand- stone lenses that are separated by impermeable shales Fig.
Horizontal wells can also be used for cross-well monitoring of enhanced-recovery projects Fig. A Schematic cross-section, showing the horizontal well course of well UP through the thin D1 sand, and across two faults, Long Beach Unit, Wilmington field, Cal- ifornia. After Clarke and Phillips The most com- mon method of determining subsurface rock and fluid properties is from con- ventional wireline logs. A carbonate reservoir example that is the first stage, or baseline, of a CO2 in- jection monitoring project using horizontal wells.
Crosswell seismic attributes are shown in A and a crosswell porosity map superimposed on a regional porosity map is shown in B. Table 2. These tools measure static or dynamic reservoir properties at an instant in time. On a well log Fig. The log shown in Fig. Gamma-ray and SP logs provide indicators of lithology Fig. On a typical gamma-ray log, the logging tool measures natural gamma radiation of the rock formation. Higher gamma-ray counts indicate the presence of shale, because shale constituents, including clay minerals, K-spar, and organic mate- rial, emit natural gamma radiation.
With the exception of arkoses K-feldspar rich , sandstones contain fewer, if any, of these components and therefore emit less radiation and have a lower gamma-ray count. Similar trends hold for SP logs Fig. Density logs measure the density of the formation, which is generally in the range of 2. A Electrical recording tools are sent down the wellbore to the bottom and then returned up the hole at a slow, constant rate on a wireline—winch assembly. The effects of lithology are seen on the two logs in the picture. Gamma-ray counts in API units of measure are high for shales and low for sandstones and dolomite.
In most parasequences, there is no preservation of the proximal wave-dominated facies tracts foreshore, upper-shoreface , resulting in thin 4—7 m top-truncated packages. Each tongue records an episode of complex shoreline migration history multiple regressive—transgressive phases in an overall net-transgressive system. The ravinement surfaces provide a stratigraphic framework in which to understand partitioning of tide- and wave-dominated deposits in a net-transgressive system, and a model is presented to account for the sediment distribution and stratigraphic architecture observed in each parasequence.
Despite a complex internal architecture, parasequences exhibit a predictable pattern which can be related to the regressive and transgressive phases of deposition. Preservation of wave-dominated facies tracts is associated with shoreline regression, while tide-dominated facies tracts are interpreted to. Nearly all successions of the near-shore strata exhibit cyclical movements of the shoreline, which have commonly been attributed to cyclical oscillations in relative sea level combining eustasy and subsidence or, more rarely, to cyclical variations in sediment supply.
It has become accepted that cyclical change in sediment delivery from source catchments may lead to cyclical movement of boundaries such as the gravel front, particularly in the proximal segments of sediment-routing systems. In order to quantitatively assess how variations in sediment transport as a consequence of change in relative sea-level and surface run-off control stratigraphic architecture, we develop a simple numerical model of sediment transport and explore the sensitivity of moving boundaries within the sediment-routing system to change in upstream sediment flux, precipitation rate and downstream sea level controls.
We find that downstream controls impact the shoreline and sand front, while the upstream controls can impact the whole system depending on the amplitude of change in sediment flux and precipitation rate. The model implies that under certain conditions, the relative movement of the gravel front and shoreline is a diagnostic marker of whether the sediment-routing system experienced oscillations in sea level or climatic conditions.
The model is then used to assess the controls on stratigraphic architecture in a well-documented palaeo-sediment-routing system in the Late Cretaceous Western Interior Seaway of North America. The absence of such movement in gravel front position in the studied strata implies that time-equivalent movement of the shoreline was driven by relative sea-level change. We suggest that tracking the relative trajectories of internal boundaries such as the gravel front and shoreline is a powerful tool in constraining the.
Tidal heterolithic sandstones are commonly characterized by millimeter- to centimeter-scale intercalations of mudstone and sandstone. Consequently, their effective flow properties are poorly predicted by 1 data that do not sample a representative volume or 2 models that fail to capture the complex three-dimensional architecture of sandstone and mudstone layers. We present a modeling approach in which surfaces are used to represent all geologic heterogeneities that control the spatial distribution of reservoir rock properties surface-based modeling.
The workflow uses template surfaces to represent heterogeneities classified by geometry instead of length scale. The topology of the template surfaces is described mathematically by a small number of geometric input parameters, and models are constructed stochastically. The methodology has been applied to generate generic, three-dimensional minimodels 9 m3 volume of cross-bedded heterolithic sandstones representing trough and tabular cross-bedding with differing proportions of sandstone and mudstone, using conditioning data from two outcrop analogs from a tide-dominated deltaic deposit.
The minimodels capture the cross-stratified architectures observed in outcrop and are suitable for flow simulation, allowing computation of effective permeability values for use in larger-scale models. We show that mudstone drapes in cross-bedded heterolithic sandstones significantly reduce effective permeability and also impart permeability anisotropy in the horizontal as well as vertical flow directions. The workflow can be used with subsurface data, supplemented by outcrop analog observations, to generate effective permeability values to be derived for use in larger-scale reservoir models.
The methodology could be applied to the characterization and modeling of heterogeneities in other types of sandstone reservoirs. Facies models for regressive, tide-influenced deltaic systems are under-represented in the literature compared with their fluvial-dominated and wave-dominated counterparts. Here, a facies model is presented of the mixed, tide-influenced and wave-influenced deltaic strata of the Sego Sandstone, which was deposited in the Western Interior Seaway of North America during the Late Cretaceous. Previous work on the Sego Sandstone has focused on the medial to distal parts of the outcrop belt where tides and waves interact.
This study focuses on the proximal outcrop belt, in which fluvial and tidal processes interact. Five facies associations are recognized. Bioturbated mudstones Facies Association 1 were deposited in an offshore environment and are gradationally overlain by hummocky cross-stratified sandstones Facies Association 2 deposited in a wave-dominated lower shoreface environment. These facies associations are erosionally overlain by tide-dominated cross-bedded sandstones Facies Association 4 interbedded with ripple cross-laminated heterolithic sandstones Facies Association 3 and channelized mudstones Facies Association 5.
When distributary channels are abandoned they effectively become estuaries with landward sediment transport and fining trends. These estuaries have sandstones of Facies Association 4 at their mouth and fine landward through heterolithic sandstones of Facies Association 3 to channelized mudstones of Facies Association 5. Therefore, the complex distribution of relatively mud-rich and sand-rich deposits in the tide-dominated part of the lower Sego Sandstone is attributed to t. Syn-depositional deformation in salt-influenced rift basins is complex, being driven by a combination of normal faulting and the growth of salt structures such as diapirs.
Due to a lack of data with which to simultaneously constrain basin structure and syn-rift stratigraphic architecture, we have a poor understanding of how these processes control shallow marine deposition in such settings. To improve our understanding we here use seismic reflection and borehole data from the Norwegian Central North Sea to investigate the role that syn-depositional fault growth and salt movement played in controlling the sub-regional stratigraphic architecture of a net-transgressive shallow-marine syn-rift succession Middle-to-Late Jurassic.
The rift-related structural framework, which is usually dominated by normal fault-bound horst and graben, is strongly modified where an Upper Permian salt layer Zechstein Supergroup is sufficiently thick and mobile to act as an intra-stratal detachment, giving rise to decoupled rift-related basement and cover structural styles. Furthermore, cover extension allows the salt to rise diapirically, resulting in the formation of large salt diapirs and supra-salt normal faults formed due to late-stage salt withdrawal and diapir collapse.
Rift-related normal faulting and the growth of salt structures had a dual control on the depositional thickness and facies distribution within the net-transgressive, predominantly shallow-marine, Middle-to-Upper Jurassic syn-rift succession. The resulting facies architecture reflects a delicate balance between fault- and salt flow-driven accommodation creation and intra- and extra-basinal sediment supply.
Where sediment supply and accumulation rate exceeded accommodation, little or no change in facies is observed across syn-depositional structures. In contrast, where accommodation outpaced sediment supply and accumulation rate, footwall-attached shorelines locally developed adjacent to large, thick-skinned normal f. Upper Cretaceous strata exposed in the Book Cliffs of east—central Utah are widely used as an archetype for the sequence stratigraphy of marginal-marine and shallow-marine deposits.
Their stratal architectures are classically interpreted in terms of accommodation controls that were external to the sediment routing system allogenic , and that forced the formation of flooding surfaces, sequence boundaries, and parasequence and parasequence-set stacking patterns. The various potential allogenic controls and autogenic processes are combined to form a sequence stratigraphic solution set.
This approach avoids anchoring of sequence stratigraphic interpretations on a specific control and acknowledges the non-unique origin of stratal architectures. Tidal heterolithic sandstone reservoirs are heterogeneous at the sub-meter scale, due to the ubiquitous presence of intercalated sandstone and mudstone laminae. Core-plug permeability measurements fail to sample a representative volume of this heterogeneity.
The impact of seven geometric parameters has been determined: 1 mudstone fraction, 2 sandstone laminae thickness, 3 mudstone drape continuity, 4 toeset dip, 5 climb angle of foreset-toeset surfaces, 6 proportion of foresets to toesets, and 7 trough or tabular geometry of the cross-beds. We begin by identifying a representative elementary volume REV of 1 m3, confirming that the model volume of 9 m3 yields representative permeability values.
Effective permeability decreases as the mudstone fraction increases, and is highly anisotropic: vertical permeability falls to c. There is considerable spread around these values, because each parameter investigated can significantly impact effective permeability, with the impact depending upon the flow direction and mudstone fraction. The results yield improved estimates of effective permeability in heterolithic, cross-bedded sandstones, which can be used to populate reservoir-scale model grid blocks using estimates of mudstone fraction and geometrical parameters obtained from core and outcrop-analog data.
Using photomosaics and measured sections, this outcrop study characterizes facies-to sandbody-scale heterogeneity in the fluvial and coastal-plain deposits of the Blackhawk Formation of the Wasatch Plateau, Utah, USA, as an outcrop analog for the fluvial tight-gas reservoirs of the adjacent greater western Rocky Mountain basins as well as for conventional fluvial reservoirs elsewhere. Distinct vertical or lateral compartmentalization, contrasting net-to-gross pattern, width-constraint by either large- or intermediate-scale heterogeneity, disparity in communication between principal reservoir compartments by intermediate-scale heterogeneity, and reservoir-quality segregation to barrier styles rendered by small-scale heterogeneity are documented in an array of trends.
These intriguing trends are challenging to correlate across the reservoir-scale dataset, contributing to multiple, analogous exploration and production uncertainties. For improved tigh. Numerical models and recent outcrop case studies of alluvial-to-coastal-plain stratasuggest that autogenic avulsion can control the stacking density and architecture of channelizedfluvial sandbodies. The application of these models to subsurface well data was tested by the analysisof upper coastal plain deposits of the late Bajocian Ness Formation in the Brent Field reservoir,UK North Sea.
Sedimentological facies analysis and palaeosolcharacterization in cores were used to interpret the styles of palaeochannel avulsion. The results indicate that the distributionsof channelized sandbodies may plausibly have been generated by avulsions and that they influencesandbody connectivity and pressure depletion patterns. Intervals of upper coastal plain strata withrelatively wide sandbodies that display some clustering in their stratigraphic architecture are associatedwith a high proportion of avulsions by incision and annexation in core samples.
Such intervalsdisplay relatively good vertical pressure communication and relatively slow, uniform pressuredepletion. The mode of emplacement of Neogene flood basalts in eastern Iceland: Facies architecture and structure of simple aphyric basalt groups. Simple flows tabular in the Neogene flood basalt sections of Iceland are described and their mode of emplacement assessed.
The groups have flow fields that display mixed volcanic facies architecture and can be classified after dominating type morphology. Simple flows are most common in the distal and medial areas from the vents, while more lobate flows in proximal areas.
(PDF) Stratigraphic Reservoir Characterization | AKM Eahsanul Haque - ynykyvykeb.tk
The main facies recognized were: i coarse-grained conglomeratic sandstones, locally pebbly conglomerates, with abundant silicified fossil trunks and several large-to-medium trough cross-stratifications and predominantly lenticular geometry; ii lenticular coarse-to-medium sandstones with some granules, abundant silicified fossil wood, and large-to-medium trough cross-stratifications, cut-and fill features and mud drapes on the foresets of cross-strata, iii poorly sorted medium-grained sandstones with sparse pebbles and with horizontal stratification, iv fine to very fine silty sandstones, laminated, interlayered with v decimetric muddy layers with horizontal lamination and climbing-ripple cross-lamination.
The lithofacies types and facies associations were interpreted as having been generated by alluvial systems characterized by i high energy perennial braided river systems and ii ephemeral river systems. Aeolian sand dunes and sand sheets generated by the reworking of braided alluvial deposits can also occur. The group J stratigraphic interval is lower Miocene Reduction in depositional relief and first evidence of widespread marine influence characterize the transition into this interval.
Twelve group J sequences have been identified. Reservoirs consist of progradational to aggradational tidally-dominated paralic to shallow marine sands deposited in the lowstand systems tract. Transgressive and highstand deposits are dominantly offshore shales. The reservoirs in these intervals are contained within the lowstand systems tracts of fourth-order sequences.
These fourth-order sequences stack to form sequence sets in response to a third-order change in relative sea level. Reservoir quality and continuity in group J reservoirs are dependent on depositional facies. An understanding of the controls on the distribution of facies types is crucial to the success of the current phase of field development and exploration programs in PM The architecture of dynamic reservoir in the echo state network. Echo state network ESN has recently attracted increasing interests because of its superior capability in modeling nonlinear dynamic systems.
In the conventional echo state network model, its dynamic reservoir DR has a random and sparse topology, which is far from the real biological neural networks from both structural and functional perspectives. We hereby propose three novel types of echo state networks with new dynamic reservoir topologies based on complex network theory, i. We then analyze the relationship between the dynamic reservoir structure and its prediction capability. We utilize two commonly used time series to evaluate the prediction performance of the three proposed echo state networks and compare them to the conventional model.
We also use independent and identically distributed time series to analyze the short-term memory and prediction precision of these echo state networks. Furthermore, we study the ratio of scale-free topology and the small-world topology in the mixed-topology network, and examine its influence on the performance of the echo state networks.
Our simulation results show that the proposed echo state network models have better prediction capabilities, a wider spectral radius, but retain almost the same short-term memory capacity as compared to the conventional echo state network model. We also find that the smaller the ratio of the scale-free topology over the small-world topology, the better the memory capacities.
The Miocene Sivas Basin is located within a collision zone, forming one of the largest basins in Central Turkey that developed unconformably on a foundered Paleozoic-Mesozoic basement and Eocene-Oligocene deposits. The time and space relationships of sedimentary environments and depositional evolution of Lower to Middle Miocene rocks exposed between Zara and Hafik towns is studied.
A 4 km thick continuous section is subdivided into the Agilkaya and Egribucak Formations. Each formation shows an overall fining upward trend and contains three members. Although a complete section is present at the western part near Hafik of the basin, to the east the uppermost two members near Zara are absent.
The lower members of both formations are composed of fluvial sheet-sandstone and red mudstone that migrate laterally on a flood basin within a semi-arid fan system. In the Agilkaya Formation that crops out near Zara, alluvial fans composed of red-pink volcanic pebbles are also present. In Hafik, bedded gypsums are intercalated with lagoonal dolomitic limestone and bituminous shale in the Agilkaya Formation and with fluvial red-pink sandstone-red mudstone in the Egribucak Formation.
The upper members are made up of fossiliferous mudstone and discontinuous sandy limestone beds with gutter casts, HCS, and 3-D ripples. They indicate storm-induced sedimentation in a shallow marine setting. The disorganized accumulations of ostreid and cerithiid shells, interpreted as coquina bars, are the products of storm generated reworking processes in brackish environments.
Rapid vertical and horizontal facies changes and the facies associations in both formations reflect the locally subsiding nature of this molassic. Volcanic facies architecture of an intra-arc strike-slip basin, Santa Rita Mountains, Southern Arizona. The three-dimensional arrangement of volcanic deposits in strike-slip basins is not only the product of volcanic processes, but also of tectonic processes. We use a strike-slip basin within the Jurassic arc of southern Arizona Santa Rita Glance Conglomerate to construct a facies model for a strike-slip basin dominated by volcanism.
This model is applicable to releasing-bend strike-slip basins, bounded on one side by a curved and dipping strike-slip fault, and on the other by curved normal faults. Numerous, very deep unconformities are formed during localized uplift in the basin as it passes through smaller restraining bends along the strike-slip fault. Talus cone-alluvial fan deposits are largely restricted to the master fault-proximal deep end of the basin. Volcanic centers are sited along the master fault and along splays of it within the master fault-proximal deep end of the basin.
To a lesser degree, volcanic centers also form along the curved faults that form structural highs between sub-basins and those that bound the distal ends of the basin. Abundant volcanism along the master fault and its splays kept the deep master fault-proximal end of the basin overfilled, so that it could not provide accommodation for reworked tuffs and extrabasinally-sourced ignimbrites that dominate the shallow underfilled end of the basin.
This pattern of basin fill contrasts markedly with that of nonvolcanic strike-slip basins on transform margins, where clastic sedimentation commonly cannot keep pace with subsidence in the master fault-proximal end. Volcanic and subvolcanic rocks in the strike-slip basin largely record polygenetic explosive and effusive small-volume eruptions from many vents in the complexly faulted basin, referred to here as multi. Stratigraphy, facies architecture , and palaeoenvironment of Neoproterozoic volcanics and volcaniclastic deposits in Fatira area, Central Eastern Desert, Egypt.
Fatira area in the Central Eastern Desert, Egypt, is a composite terrane consisting of Neoproterozoic volcanics and sediments laid down in submarine to subaerial environment, intruded by voluminous old to young granitic rocks. The various lithofacies of the study area can be grouped in three distinct lithostratigraphic sequences, which are described here in stratigraphic order, from base to top as the Fatira El Beida, Fatira El Zarqa and Gabal Fatira sequences.
Each depositional sequence, is intimately related to volcanic activity separated by time intervals of volcanic inactivity, such as marked hiatuses, reworked volcaniclasts, and or turbidite sedimentation. Four submarine facies groups have been recognized within the oldest, folded eruption sequence of Fatira El Beida. The coeval tholeiitic mafic and felsic volcaniclastic rocks of this sequence indicate an extensional back-arc tectonic setting. The El Beida depositional sequence appears to fit a submarine-fan and slope-apron environment in an intra-arc site.
The Fatira El Zarqa sequence involves a large volume of subaerial calc-alkaline intermediate to felsic volcanics and an unconformably overlying siliciclastic succession comprising clast-supported conglomerates Gm , massive sandstone sheet floods Sm and mudstones FI , together with a lateritic argillite paleosol P top formed in an alluvial-fan system. The youngest rock of Gabal Fatira sequence comprises anorogenic trachydacites and rhyolites with locally emergent domes associated with autobrecciation and sill-dyke rock swarms that could be interpreted as feeders and subvolcanic intrusions.
Unconformity and lithofacies assemblages. Surface and subsurface facies architecture of a small hydroexplosive, rhyolitic centre in the Mesoproterozoic Gawler Range Volcanics, South Australia. At Menninnie Dam, South Australia, a drilling program has revealed a complete section through the subsurface feeder system and erupted products of a small, hydroexplosive, rhyolitic centre within the Mesoproterozoic Gawler Range Volcanics.
Porphyritic rhyolite intruded near-vertical faults in the Palaeoproterozoic basement and at less than a few hundred metres depth, interacted with fault-hosted hot? Hydrofracturing of the wall rock occurred in advance of and at the margins of the rhyolitic intrusions. The rhyolitic intrusions have peperitic margins and grade into discordant lithic-rich PB facies. The advancing fragmentation front intersected the palaeosurface, triggering phreatic eruptions that deposited a poorly sorted, lithic-rich explosion breccia.
Rhyolite then rose to the surface through the intrusive breccias and shallow-seated magma-water interaction occurred in the conduit within m from the inferred source , the products include muddy sandstone and pumice breccia. At the end of the eruption, rhyolitic lava was extruded in the form of a small dome. The presence of contemporaneous Pb-Zn-Ag mineralisation in the wall rocks suggests that an active hydrothermal system may have been involved in the formation of the Menninnie Dam hydroexplosive volcanic centre. Within turbidite systems, fine-grained sediments are still the poor relation and sport several contrasting facies models linked to process of deposition.
These are volumetrically the dominant facies in deepwater and, from a resource perspective, they form important marginal and tight reservoirs , and have great potential for unconventional shale gas, source rocks and seals. They are also significant hosts of metals and rare earth elements. Based on a large number of studies of modern, ancient and subsurface systems, including s of metres of section logging, we define the principal genetic elements of fine-grained deepwater facies , present a new synthesis of facies models and their sedimentary attributes.
The principal architectural elements include: non-channelised slope-aprons, channel-fill, channel levee and overbank, turbidite lobes, mass-transport deposits, contourite drifts, basin sheets and drapes. These comprise a variable intercalation of fine-grained facies - thin-bedded and very thin-bedded turbidites, contourites, hemipelagites and pelagites - and associated coarse-grained facies.
Characteristic attributes used to discriminate between these different elements are: facies and facies associations; sand-shale ratio, sand and shale geometry and dimensions, sand connectivity; sediment texture and small-scale sedimentary structures; sediment fabric and microfabric; and small-scale vertical sequences of bed thickness. To some extent, we can relate facies and attribute characteristics to different depositional environments.
We identify four distinct facies models: a silt-laminated mud turbidites, b siliciclastic mud turbidites, c carbonate mud turbidites, d disorganized silty-mud turbidites, and e hemiturbidites. Within the grainsize-velocity matrix turbidite plot, these all fall within the region of mean size Design and Analysis of a Neuromemristive Reservoir Computing Architecture for Biosignal Processing.
Reservoir computing RC is gaining traction in several signal processing domains, owing to its non-linear stateful computation, spatiotemporal encoding, and reduced training complexity over recurrent neural networks RNNs. Previous studies have shown the effectiveness of software-based RCs for a wide spectrum of applications.
A parallel body of work indicates that realizing RNN architectures using custom integrated circuits and reconfigurable hardware platforms yields significant improvements in power and latency. In this research, we propose a neuromemristive RC architecture , with doubly twisted toroidal structure, that is validated for biosignal processing applications.
We exploit the device mismatch to implement the random weight distributions within the reservoir and propose mixed-signal subthreshold circuits for energy efficiency. A comprehensive analysis is performed to compare the efficiency of the neuromemristive RC architecture in both digital reconfigurable and subthreshold mixed-signal realizations. Anatomy of major coal successions: Facies analysis and sequence architecture of a brown coal-bearing valley fill to lacustrine tract Upper Valdarno Basin, Northern Apennines, Italy. A late Pliocene incised valley fill to lacustrine succession, which contains an interbedded brown coal seam facies analysis, physical stratigraphy and sequence architecture.
- The Power of Negotiation?
- Examples and Analogues?
- Cuenta regresiva (Spanish Edition);
- LIFE AND TIMES OF NATHAN BANGS.
The succession architecture reveals how a mixed palustrine-siliciclastic system differs substantially from a purely siliciclastic one. In the transgressive phases, terrigenous starvation induces prevailing peat accumulation, generating abnormally thick transgressive system tracts that eventually come to occupy much of the same transgression-generated accommodation space. In the highstand phases, the development of thick highstand system tracts is then prevented by sediment upstream. On learning navigation behaviors for small mobile robots with reservoir computing architectures.
This paper proposes a general reservoir computing RC learning framework that can be used to learn navigation behaviors for mobile robots in simple and complex unknown partially observable environments. RC provides an efficient way to train recurrent neural networks by letting the recurrent part of the network called reservoir be fixed while only a linear readout output layer is trained. The proposed RC framework builds upon the notion of navigation attractor or behavior that can be embedded in the high-dimensional space of the reservoir after learning. The learning of multiple behaviors is possible because the dynamic robot behavior, consisting of a sensory-motor sequence, can be linearly discriminated in the high-dimensional nonlinear space of the dynamic reservoir.
Three learning approaches for navigation behaviors are shown in this paper. The first approach learns multiple behaviors based on the examples of navigation behaviors generated by a supervisor, while the second approach learns goal-directed navigation behaviors based only on rewards. The third approach learns complex goal-directed behaviors, in a supervised way, using a hierarchical architecture whose internal predictions of contextual switches guide the sequence of basic navigation behaviors toward the goal. Trace fossils, sedimentary facies and parasequence architecture from the Lower Cretaceous Mulichinco Formation of Argentina: The role of fair-weather waves in shoreface deposits.
Wesolowski, Lindsey J. Shorefaces can display strong facies variability and integration of sedimentology and ichnology provides a high-resolution model to identify variations among strongly storm-dominated high energy , moderately storm-affected intermediate energy , and weakly storm-affected low energy shoreface deposits. In addition, ichnology has proved to be of help to delineate parasequences as trace-fossil associations are excellent indicators of environmental conditions which typically change along the depositional profile.
During storm-dominated conditions, the Skolithos Ichnofacies prevails within the offshore transition and lower shoreface represented by assemblages dominated by Thalassinoides isp. Under weakly storm-affected conditions, the Cruziana Ichnofacies is recognized, characterized by assemblages dominated by Thalassinoides isp. Storm-influenced conditions yield wider ichnologic variability, showing elements of both ichnofacies. Storm influence on sedimentation is affected by both allogenic e.
Four distinct types of parasequences were recognized, strongly storm-dominated, moderately storm-affected, moderately storm-affected - strongly fair-weather reworked, and weakly storm-affected, categorized based on parasequence architectural variability derived from varying degrees of storm and fair-weather wave influence. The new type of shoreface described here, the moderately storm-affected - strongly fair-weather reworked shoreface.
The purpose of phase 1 and phase 2 of the Department of Energy funded project Analysis of oil- bearing Cretaceous Sandstone Hydrocarbon Reservoirs , exclusive of the Dakota Sandstone, on the Jicarilla Apache Indian Reservation, New Mexico was to define the facies of the oil producing units within the Mancos Shale and interpret the depositional environments of these facies within a sequence stratigraphic context.
The recognition of these sand bodies is based on mappable geometries determined from wireline log correlations, log character, core facies , reservoir characteristics, and comparison to nearby age-equivalent outcrops. These turbidite sands are composed of unconsolidated arkosic late Miocene sandstones Stevens equivalent, Monterey Formation. They were deposited normal to paleoslope and trend southwest-northeast in an intraslope basin.
Areal distribution of sedimentary facies determined from seismic facies analysis and models of modern depositional systems. Seismic facies analysis was applied to 3. Nine sedimentary facies have been interpreted from seven seismic facies identified on the profiles. The interpretations are based on reflection characteristics and structural features of the seismic facies.
The following reflection characteristics and structural features are used: reflector spacing, amplitude and continuity of reflections, internal reflection configurations, attitude of reflection terminations at a facies boundary, body geometry of a facies , and the architectural associations of seismic facies within each basin.
Muir Inlet is a recently deglaciated fjord for which successive glacier terminus positions and consequent rates of glacial retreat are known. In this environment the depositional processes and sediment characteristics vary with distance from a glacier terminus, such that during a retreat a record of these variations is preserved in the aggrading sediment fill. Sedimentary facies within the basins of lower Muir Inlet are correlated with observed depositional processes near the present glacier terminus in the upper inlet.
The areal distribution of sedimentary facies within the basins is interpreted using the seismic facies architecture and inferences from known sediment characteristics proximal to present glacier termini. The Permian to Triassic Khuff carbonate reservoirs and equivalents in the Middle East are estimated to contain about Excellent exposed outcrops in central Saudi Arabia provide good outcrop equivalents to subsurface Khuff reservoirs. This study conduct high resolution outcrop scale investigations on an analog reservoir for upper Khartam of Khuff Formation.
The main objective is to reconstruct litho- and chemo- stratigraphic outcrop analog model that may serve to characterize reservoir high resolution interwell heterogeneity, continuity and architecture. Given the fact of the limitation of subsurface data and toolsin capturing interwell reservoir heterogeneity, which in turn increases the value of this study. The methods applied integrate sedimentological, stratigraphic petrographic, petrophysical data and chemical analyses for major, trace and rare earth elements.
The results of the stratigraphic investigations revealed that the lithofacies range from mudstone, wackestone, packestone and grainstone. These lithofacies represent environments ranging from supratidal, intertidal, subtidal and shoal complex. Several meter-scale and less high resolution sequences and composite sequences within 4th and 5th order cycles were also recognized in the outcrop analog. The lithofacies and architectural analysis revealed several vertically and laterally stacked sequences at the outcrop as revealed from the stratigraphic sections and the lidar scan.
Chemostratigraphy is effective in identifying lithofacies and sequences within the outcrop analog. Moreover, different chemical signatures were also recognized and allowed establishing and correlating high resolution lithofacies, reservoir zones, layers and surfaces bounding reservoirs and non- reservoir zones at scale of meters or less. The results of this high resolution outcrop analog study might help to understand. Architecture and reservoir quality of low-permeable Eocene lacustrine turbidite sandstone from the Dongying Depression, East China.
The architecture and quality of lacustrine turbidites that act as petroleum reservoirs are less well documented. Reservoir architecture and multiscale heterogeneity in turbidites represent serious challenges to production performance. Additionally, establishing a hierarchy profile to delineate heterogeneity is a challenging task in lacustrine turbidite deposits.
Here, we report on the turbidites in the middle third member of the Eocene Shahejie Formation Es3 , which was deposited during extensive Middle to Late Eocene rifting in the Dongying Depression. Seismic records, wireline log responses, and core observations were integrated to describe the reservoir heterogeneity by delineating the architectural elements, sequence stratigraphic framework and lithofacies assemblage. A petrographic approach was adopted to constrain microscopic heterogeneity using an optical microscope, routine core analyses and X-ray diffraction XRD analyses.
A total of forty-five sequences were identified within these four composite sequences. Sand bodies were mainly deposited as channels, levees, overbank splays, lobes and lobe fringes. The combination of fining-upward and coarsening-upward lithofacies patterns in the architectural elements produces highly complex composite flow units.
Microscopic heterogeneity is produced by diagenetic alteration processes i. The widespread kaolinization of feldspar and mobilization of materials enhanced the quality of the reservoir by producing secondary enlarged pores. Recovery rates are higher in the axial areas and smaller in the marginal areas of architectural elements. This study represents a significant insight into the reservoir architecture and. In the central and southern part of the Reservation, large areas, currently not productive or not tested, have the potential to contain oil in the El Vado simply based on the trend of the facies and structure.
There has been little oil or gas production from the overlying regressive-transgressive wedge of rock and much of this interval is untested. Thus, large areas of the Reservation could contain hydrocarbon resources in these strata. Most of the Reservation lies within the oil generation window based on new Rock-Eval data from the Mancos Shale just south of the southern part of the Reservation. If these observations are valid then oil could have been generated locally and would only have needed to migrate short distances in to sandy reservoirs and fractures.
This does not rule out long distance migration of oil from the deeper, more thermally mature part of the basin to the north. However, low porosity and permeability characterize sandier rocks in the Mancos, with the exception of Tocito-like sandstones. These factors could retard long distance oil migration through the sediment package, except through fracture or fault conduits. Thus, it is suggested that future oil and gas explorations in the Mancos treat the accumulations and reservoirs as unconventional and consider whether the source and reservoir are in closer proximity than has previously been assumed.
Economics of most deep-water development projects require large reservoir volumes to be drained with relatively few wells. The presence of reservoir compartments must therefore be detected and planned for in a pre-development stage. Reservoir compartmentalization is influenced by stratigraphic shingling, which in turn is caused by low accommodation space predentin the upper portion of a ponded seismic sequence within a salt withdrawal mini-basin.
A geological interpretation derived from high-resolution 3-D seismic and three wells was linked to 3-D architecture models through seismic inversion, resulting in a reservoir all available data. Distinguishing subtle stratigraphical shingles from faults was accomplished by detailed, loop-level mapping, and was important to characterize the different types of reservoir compartments.
Seismic inversion was used to detune the seismic amplitude, adjust sandbody thickness, and update the rock properties. Recent development wells confirm the architectural style identified. This modeling project illustrates how high-quality seismic data and architecture models can be combined in a pre-development phase of a prospect, in order to optimize well placement. We have used 3-D seismic data to constrain large-scale, deterministic reservoir bodies in a 3-D architecture model of Pliocene-turbidite sands of the [open quotes]E[close quotes] or [open quotes]Pink[close quotes] reservoir , Prospect Mars, Mississippi Canyon Areas and , Gulf of Mexico.
The accumulation is limited by updip onlap onto a condensed section marl, and by lateral truncation by a large scale submarine erosion surface. Characterization of the facies associations and sequence stratigraphic framework was done by detailed description and logging of outcrops. Six facies associations were recognized: aeolian dunes and interdunes, aeolian sandsheets, fluvial channels, tidally-influenced fluvial channels, shoreface and shoreface-shelf transition.
Through correlation of stratigraphic surfaces, the facies associations were organized in system tracts, which formed eight high frequency depositional sequences, bounded by subaerial unconformities. Two low frequency cycles were determined by observing the stacking of the high frequency cycles. The Lower Sequence is characterized by aeolian deposits of the LST and an aggradational base followed by a progressive transgression, defining a general TST. The Upper Sequence is characterized by fluvial deposits and interfluve pedogenesis concurring with the aeolian deposits of the LST and records a subtle regression followed by transgression.
Even though, climate changes were associated with glacioeustatic phases and influenced the aeolian and fluvial deposition. The interplay of fractures and sedimentary architecture : Natural gas from reservoirs in the Molina sandstones, Piceance Basin, Colorado. The Molina Member is a distinctive sandstone that was deposited in a unique fluvial environment of shallow-water floods. This is recorded by the dominance of plane-parallel bedding in many of the sandstones. The Molina sandstones crop out on the western edge of the basin, and have been projected into the subsurface and across the basin to correlate with thinner sandy units of the Wasatch Formation at the eastern side of the basin.
Rather, the eastern sandstones represent separate and unrelated sedimentary systems that prograded into the basin from nearby source-area highlands. Reservoirs in the Grand Valley and Rulison gas fields were deposited in separate fluvial systems. These sandstones contain more typical fluvial sedimentary structures such as crossbeds and lateral accretion surfaces.
Natural fractures play an important role in enhancing the conductivity and permeability of the Molina and related sandstones of the Wasatch Formation. The shallow burial of these formations and limited post depositional changes allowed significant preservation of porosity at outcrop scale. The mixed carbonate-siliciclastic succession represents important reservoirs in the Mesozoic and Tertiary stratigraphic succession in the Arabian Plate. This study integrates field work sedimentological and stratigraphical and lithofacies data to model the spatial distribution of facies of this shallow marine and fluvial depositional setting.
The Dam Formation is characterized by very high percentage of grain- dominated textures representing high to low energy intertidal deposits a mixed of carbonate and siliciclastic succession. The middle Miocene Dam section is dominated by intra-clasts, ooids and peloids grainstones. The Hofuf Formation represents fluvial channel and overank facies which is characterized by mudclast abd gravel-rich erosive bases overlain by pebbly conglomerates which passes upward into medium to very coarse grained massive, horizontally stratified and trough cross-stratifed sandstone facies.
Lithological stratigraphic sections data distributed over the Al-lidam escarpment were correlated on the basis of facies types and sequences. This allow mapping and building a framework for modeling the spatial distribution of the carbonate and siliciclastic facies in the area. The geological model shows variations in the facies distribution patterns which mainly reflect both dynamic and static depositional controls on facies types distribution. The geological model may act as a guide for facies types distribution, and provide better understanding and prediction of reservoir quality and architecture of stratigraphically equivalent carbonate-siliciclastic successions in the subsurface.
Cultural Resources Survey, Harry S. Truman Dam and Reservoir Project, Missouri. Volume 3. Architectural Survey. West Central Missouri, by R. Ward and T. Thompson, pp. Truman Reservoir Attribute classification for generating GPR facies models. Ground-penetrating radar GPR is an established geophysical tool to explore near-surface sedimentary environments. It has been successfully used, for example, to reconstruct past depositional environments, to investigate sedimentary processes, to aid hydrogeological investigations, and to assist in hydrocarbon reservoir analog studies.
The resulting facies models are then interpreted in terms of depositional processes, sedimentary environments, litho-, and hydrofacies. Typically, such GPR facies analyses are implemented in a manual workflow being laborious and rather inefficient especially for 3D data sets. In addition, such a subjective strategy bears the potential of inconsistency because the outcome depends on the expertise and experience of the interpreter. In this presentation, we investigate the feasibility of delineating GPR facies in an objective and largely automated manner.
Our proposed workflow relies on a three-step procedure. First, we calculate a variety of geometrical and physical attributes from processed 2D and 3D GPR data sets. Then, we analyze and evaluate this attribute data base e. Finally, we integrate the reduced data base using tools such as composite imaging, cluster analysis, and neural networks. We conclude that our interpretation strategy allows to generate GPR facies models in a consistent and largely automated manner and might be helpful in.
The submarine lava balloon eruption at the Serreta ridge Azores archipelago : Constraints from volcanic facies architecture , isotope geochemistry and magnetic data. The most recent submarine eruption observed offshore the Azores archipelago occurred between and along the submarine Serreta ridge SSR , nautical miles WNW of Terceira Island. This submarine eruption delivered abundant basaltic lava balloons floating at the sea surface and significantly changed the bathymetry around the eruption area.
Our work combines bathymetry, volcanic facies cartography, petrography, rock magnetism and geochemistry in order to 1 track the possible vent source at seabed, 2 better constrain the Azores magma source s sampled through the Serreta submarine volcanic event, and 3 interpret the data within the small-scale mantle source heterogeneity framework that has been demonstrated for the Azores archipelago. SSR lavas are primitive, but incompatible trace-enriched. The collected data suggest that the freshest samples collected in the SSR may correspond to volcanic products of an unnoticed and more recent eruption than the episode.
Grainflow and translatent wind-ripple strata, and frequent presence of reactivation surface, compose the cross-bedding of crescent aeolian dune deposits. The aeolian cross-strata show a mean dip toward the ENE. The presence of NNW current ripple cross-lamination in wet interdune areas indicates streamflows confined to interdune corridors and oriented perpendicular to aeolian transport direction.
Lenses of damp and wet interdune strata exhibit mainly interdigitated and transitional relationships with the toe-sets of overlying aeolian dune units in sections parallel to aeolian transport, indicating that dune migration was contemporaneous with accumulation in adjacent interdunes. Lateral variations in the preserved thickness of the interdune units and the associated rare occurrence of abrupt and erosive contacts between interdune and overlying dune sets, suggest temporal variations in the angle of dune and interdune climb that may be related to high-frequency changes in water table position.