156 research outputs found
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Geoscience/Engineering Characterization of the Interwell Environment in Carbonate Reservoirs Based on Outcrop Analogs, Permian Basin, West Texas and New Mexico.
The objective of this project is to investigate styles of reservoir heterogeneity found in low permeability pelleted wackestone/packstone facies and mixed carbonate/clastic facies found in Permian Basin reservoirs by studying similar facies exposed in the Guadalupe Mountains. Specific objectives for the outcrop study include construction of a stratigraphic framework, petrophysical quantification of the framework, and testing the outcrop reservoir model for effects of reservoir heterogeneity on production performance. Specific objectives for the subsurface study parallel objectives for the outcrop study
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San Andres/Grayburg Reservoir Characterization Research Laboratory
The Bureau of Economic Geology's Reservoir Characterization Research Laboratory project, "Characterization of San Andres and Grayburg Reservoirs," was initiated in September 1988 and has completed the first year of a proposed 2-year program. Substantial progress has been made toward the goals of this program, which are focused on development of advanced approaches to reservoir characterization for improving recovery efficiency of substantial remaining mobile oil resources in these prolific reservoirs. Key research results are in the areas of (1) quantitative description and geostatistical modeling of interwell and reservoir-scale heterogeneity from San Andres outcrops, and (2) preliminary studies on integration of the quantitative outcrop models with a geologic/engineering characterization of the Seminole San Andres Unit.
Outcrop geologic studies were carried out at play, reservoir, and interwell scales along the Algerita Escarpment, Guadalupe Mountains, New Mexico. This 17-mile play-scale study area provides a dip-section framework for detailed investigations and serves as an analogous reservoir framework for comparison with producing San Andres fields. Reservoir-scale mapping of a 4-mile dip section of the upper San Andres with measured sections spaced 1,000 to 2,000 ft apart demonstrates the compartmentalization of individual grainstone shoal complexes on the scale of several thousand feet laterally and 50 to 100 ft vertically.Bureau of Economic Geolog
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Reservoir Characterization Research LaboratoryCarbonate Reservoirs
Characterization of a carbonate reservoir for fluid flow simulation is a highly complicated task. What is clear is that the end product must be a three-dimensional numerical image of petrophysical properties: porosity, fluid saturation, permeability, and relative permeability. The principal problems are (1) determining petrophysical values to be imaged and (2) distributing petrophysical values in space. Petrophysical properties are determined by measurements on core and outcrop material, by calculations using wireline log data, and by well tests and tracers. Methods of distributing the petrophysical values usually involve a combination of geologic and statistical modeling.
This report emphasizes wireline log calculations and geologic modeling using a rock-fabric approach developed in outcrop studies (Lucia and others, 1992; Senger and others, 1993; Kerans and others, 1994). The approach is to construct a detailed chronostratigraphic framework using sequences of geologic features that are related to water depth and to fill the framework with petrophysical attributes using relationships between rock-fabric and petrophysical properties. Geologic and petrophysical studies of the San Andres Formation in Lawyer Canyon, Algerita Escarpment, Guadalupe Mountains of New Mexico, suggest that (1) petrophysical properties are near-randomly distributed within rock-fabric facies; (2) rock-fabric facies are systematically stacked within high-frequency cycles (HFC's); (3) rock-fabric facies can have significantly different petrophysical properties; (4) vertical changes in properties can be abrupt, whereas lateral changes are gradual; and (5) thin, discontinuous, tight mudstone beds are effective vertical barriers to fluid flow. These findings have been applied to a detailed reservoir characterization study of two sections of the Seminole San Andres Unit operated by Amerada Hess Corporation.Bureau of Economic Geolog
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University Lands Advanced Recovery Initative
Hydrocarbon production from West Texas lands held by The University of Texas System has been in decline since the 1960s (fig. 1). Nonetheless, analysis of resources on University lands indicates that of the 7,252 million stock tank barrels (MMSTB) of original oil in place, only 1,679 MMSTB has been recovered since production was established early in this century, and only 150 MMSTB of reserves exist. Unless advanced development practices are applied to University lands fields, some 5,423 MMSTB will therefore remain unrecovered in existing fields. Importantly, 2,140 MMSTB of this resource, nearly one-third of the original oil in place, is mobile oil that can be recovered using standard drilling and completion practices, provided that wellbores and completion intervals are geologically targeted to access this unrecovered resource (fig. 2).
The goal of the University Lands Advanced Recovery Initiative is to characterize selected University Lands reservoirs to aid operators in geologically targeting the remaining hydrocarbon resource to stem the decline in University Lands production. This project is funded by The University of Texas (U.T.) System and by matching funds from operators of University Lands fields chosen for site-specific studies. The agreement between the Bureau of Economic Geology and the U.T. System was finalized on July 29, 1996. Three individual site-specific projects have been initiated in the first year of the project: (1) Fuhrman-Mascho Block 10 Unit, a San Andres-Grayburg carbonate and sandstone reservoir in Andrews County operated by Arrow Operating Company, (2) University Waddell Devonian field, a Devonian chert reservoir in Crane County operated by Pennzoil, and (3) North McElroy Grayburg field, a Grayburg carbonate reservoir in Crane and Upton Counties newly acquired by Apache Corporation (fig. 3). Fuhrman-Mascho and University Waddell fields have recovery efficiencies significantly below that of comparable fields within the same geologically based play. McElroy field, although producing at an efficiency above play average, contains an enormous 832 million barrels of unrecovered mobile oil (table 1).Bureau of Economic Geolog
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Characterization of Facies and Permeability Patterns in Carbonate Reservoirs Based on Outcrop Analogs
More than 13 billion barrels (Bbbl) of mobile oil and 17 Bbbl of residual oil will remain in the San Andres and Grayburg reservoir at abandonment under current development practices. Through the development and application of new recovery technology, a large part of this resource can be recovered. This report focuses on research for the development and testing of new techniques for improving recovery of this resource. Outcrop and subsurface geologic and engineering data are utilized to develop new methodologies through the integration of geologic observations and engineering data for improving numerical models that predict reservoir performance more accurately.
Extensive regional mapping of the 14-mile by 1,200-foot San Andres outcrop, located on the Algerita Escarpment, Guadalupe Mountains, New Mexico, demonstrates that the San Andres carbonate-ramp complex is composed of multiple depositional sequences that have significant basinward shifts in reservoir-quality facies tracts occurring across sequence boundaries. Detailed geologic and petrophysical mapping of three reservoir-quality facies tracts demonstrates that the fundamental scale of geologic description for reservoir characterization is the parasequence and its component rock-fabric-based facies. Descriptions of cores from the Seminole San Andres Unit illustrate that the parasequence is also the fundamental geologic scale for reservoir mapping in the subsurface.Bureau of Economic Geolog
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Dominant Control of Reservoir-Flow Behavior in Carbonate Reservoirs as Determined from Outcrop Studies
The investigation of carbonate-ramp deposits of the upper San Andres Formation that crop out along the Algerita Escarpment, New Mexico, is a research element of ongoing geologic and petrophysical studies conducted at the Bureau of Economic Geology's Reservoir Characterization Research Laboratory (RCRL). The primary goal of the investigation is to develop an integrated strategy involving geological, petrophysical, geostatistical, and reservoir-simulation studies that can be used to better predict flow characteristics in analogous subsurface reservoirs. Geologic investigations and detailed measurements of petrophysical parameters on continuous outcrop were used to determine not only the vertical distribution of the data but also their lateral distribution, which is typically lacking in subsurface studies.
To characterize the complex heterogeneity associated with depositional and diagenetic processes at the interwell scale, detailed permeability data were collected within the overall geologic framework from the outcrop at Lawyer Canyon, Algerita Escarpment, New Mexico (fig. 1). Geologic mapping showed a series of upward-shallowing parasequences (10 to 40 ft thick and several thousand feet long). Parasequence boundaries are typically marked by tight mudstone/wackestone beds that display variable degrees of lateral continuity ranging from several hundred feet to more than 2,500 ft and are potentially important as flow barriers (fig. 2). Within these parasequences, distinct variability of facies and petrophysical characteristics is present at scales well below those of interwell spacing typical for their subsurface counterparts (660 to 1,330 ft). Pore types and permeability-porosity relationships can also be specific to individual parasequences.Bureau of Economic Geolog
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Opportunities for Additional Recovery in University Lands Reservoirs -- Characterization of University Lands Reservoirs, Final Report
In 1984, The University of Texas System funded a Bureau of Economic Geology project, "Characterization of University Lands Reservoirs," to assess in detail the potential for incremental recovery of oil from University Lands reservoirs by extended conventional methods. The objectives of the 5-year project were to quantify the volumes of unrecovered mobile oil remaining in reservoirs on University Lands, to determine whether the specific location of the unrecovered mobile oil could be delineated through integrated geoscience characterization of individual reservoirs, and to develop strategies to optimize recovery of this resource. Unrecovered mobile oil is mobile at reservoir conditions but is prevented from migrating to the wellbore by geologic complexities or heterogeneities. This final report describes results of the 5 years of research conducted on University Lands reservoirs.
One hundred and one reservoirs, each of which has produced more than 1 million stock tank barrels (MMSTB) of oil, were included in a resource assessment and play analysis undertaken (1) to determine the volumes and distribution of all components of the University Lands resource base and (2) to select reservoirs for detailed analysis. These reservoirs collectively contained 7.25 billion barrels (BSTB) of oil at discovery, have produced 1.5 BSTB, and contain 200 MMSTB of reserves. Ultimate recovery at implemented technology is projected to be 24 percent of the original oil in place; thus, 5.5 BSTB of oil will remain after recovery of existing reserves. Unrecovered mobile oil (exclusive of reserves) amounts to 2.2 BSTB, and immobile, or residual, oil totals 3.3 BSTB.Bureau of Economic Geolog
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Characterization of Facies and Permeability Patterns in Carbonate Reservoirs Based in Outcrop Analogs
More than 13 billion barrels (Bbbl) of mobile oil and 17 Bbbl of residual oil will remain in San Andres and Grayburg reservoirs at abandonment under current development practices. Through the development and application of new recovery technology, a large part of this resource can be recovered. This report focuses on research for the development and testing of new techniques for improving the recovery of this resource. Outcrop and subsurface geologic and engineering data are utilized to develop new methodologies through the integration of geologic observations and engineering data for improving numerical models that predict reservoir performance more accurately.
Extensive regional mapping of the 14-mile by 1,200-foot San Andres outcrop, located on the Algerita Escarpment, Guadalupe Mountains, New Mexico, demonstrates that the San Andres carbonate-ramp complex is composed of multiple depositional sequences that have significant basinward shifts in reservoir-quality facies tracts occurring across sequence boundaries. Detailed geologic and petrophysical mapping of three reservoir-quality facies tracts demonstrates that the fundamental scale of geologic description for reservoir characterization is the parasequence and its component rock-fabric-based facies. Descriptions of cores from the Seminole San Andres Unit illustrate that the parasequence is also the fundamental geologic scale for reservoir mapping in the subsurface.Bureau of Economic Geolog
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Characterization of Reservoir Heterogenity in Carbonate-Ramp Systems, San Andres/Grayburg Permian Basin
This report summarizes research carried out by the Bureau of Economic Geology's San Andres/Grayburg Reservoir Characterization Research Laboratory (RCRL) from September 1988 through September 1990. The goal of the RCRL program was to develop advanced approaches to reservoir characterization for improved recovery of the substantial remaining mobile oil in San Andres and Grayburg reservoirs. Emphasis was placed on developing an outcrop analog for San Andres strata that could be used as (1) a guide to interpreting the regional and local geologic framework of the subsurface reservoirs and (2) a data source illustrating the scales and patterns of variability of rock-fabric facies and petrophysical properties, particularly in lateral dimensions, and on scales that cannot be studied during subsurface reservoir characterization.
Areas selected for study were the San Andres exposures of the Algerita Escarpment in the northern Guadalupe Mountains and the Seminole San Andres Unit on the northern margin of the Central Basin Platform. The outcrop-analog research was emphasized because it had received little attention before this study by either industry or academe.
Reports in this summary involve (1) outcrop and subsurface geological characterization of the Algerita Escarpment San Andres and the Seminole San Andres Unit (Kerans), (2) correlation of detailed outcrop mapping in order to research cored wells at Lawyer Canyon, Algerita Escarpment (Nance), (3) diagenetic/petrographic analysis of selected upper San Andres facies focusing on the origin of moldic porosity (Hovorka), (4) geologic engineering description of the upper San Andres carbonates at Lawyer Canyon and the upper producing interval at Seminole (Lucia), (5) geostatistical analysis of permeability patterns and stochastic-based finite-difference modeling of the upper San Andres parasequence window (Senger and Fogg), and (6) deterministic finite element modeling of the upper San Andres parasequence window (Kasap).
Availability of basic data for these studies is summarized in the appendix.Bureau of Economic Geolog
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