skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Control of reservoir porosity and permeability by original depositional fabric

Abstract

The Emma San Andres field exhibits many of the classic signs of a depleted reservoir including declining annual production rates and high water cuts. By the end of 1986, oil production from the Emma reservoir, more than 19 million bbl, totaled nearly 100% of the estimated ultimate recovery. Recent studies, however, indicate that as much as 25 million bbl of recoverable mobile oil still remain in the reservoir. These studies also indicate that the observed poor recovery efficiency (32%, typical for San Andres/Grayburg reservoirs) is due to reservoir heterogeneity caused primarily by variations in original depositional fabric. Two distinct porosity intervals are recognized in the Emma reservoir. The lower interval is composed of fusulinid packstone/wackestone that contains moldic and intercrystalline porosity and low (average 2 md) permeabilities. These deposits are continuous and relatively uniform throughout the area; net pay in this zone is controlled primarily by the field structure, a low-relief northwest-trending anticline. Comparison of production data with faces mapping suggests that most oil production has been controlled by the distribution of skeletal grainstone and not by structure. Effective exploitation of this remaining mobile oil must include selective completion and injection programs based on variations in the distribution of skeletalmore » grainstone. The absence of significant production from local grainstone thicks, for example, points to inefficient drainage in several parts of the field.« less

Authors:
Publication Date:
OSTI Identifier:
6776087
Alternate Identifier(s):
OSTI ID: 6776087
Report Number(s):
CONF-880301-
Resource Type:
Conference
Resource Relation:
Conference: Annual meeting of the American Association of Petroleum Geologists, Houston, TX, USA, 20 Mar 1988
Country of Publication:
United States
Language:
English
Subject:
02 PETROLEUM; OIL WELLS; PRODUCTION; PETROLEUM DEPOSITS; GEOPHYSICS; RESERVOIR ROCK; SEDIMENTATION; TEXAS; EXPLORATION; PERMEABILITY; PETROGENESIS; PETROLEUM GEOLOGY; POROSITY; RESERVOIR ENGINEERING; SANDSTONES; ENGINEERING; FEDERAL REGION VI; GEOLOGIC DEPOSITS; GEOLOGY; MINERAL RESOURCES; NORTH AMERICA; RESOURCES; ROCKS; SEDIMENTARY ROCKS; USA; WELLS 020200* -- Petroleum-- Reserves, Geology, & Exploration; 020300 -- Petroleum-- Drilling & Production

Citation Formats

Ruppel, S.C. Control of reservoir porosity and permeability by original depositional fabric. United States: N. p., 1988. Web.
Ruppel, S.C. Control of reservoir porosity and permeability by original depositional fabric. United States.
Ruppel, S.C. Fri . "Control of reservoir porosity and permeability by original depositional fabric". United States. doi:.
@article{osti_6776087,
title = {Control of reservoir porosity and permeability by original depositional fabric},
author = {Ruppel, S.C.},
abstractNote = {The Emma San Andres field exhibits many of the classic signs of a depleted reservoir including declining annual production rates and high water cuts. By the end of 1986, oil production from the Emma reservoir, more than 19 million bbl, totaled nearly 100% of the estimated ultimate recovery. Recent studies, however, indicate that as much as 25 million bbl of recoverable mobile oil still remain in the reservoir. These studies also indicate that the observed poor recovery efficiency (32%, typical for San Andres/Grayburg reservoirs) is due to reservoir heterogeneity caused primarily by variations in original depositional fabric. Two distinct porosity intervals are recognized in the Emma reservoir. The lower interval is composed of fusulinid packstone/wackestone that contains moldic and intercrystalline porosity and low (average 2 md) permeabilities. These deposits are continuous and relatively uniform throughout the area; net pay in this zone is controlled primarily by the field structure, a low-relief northwest-trending anticline. Comparison of production data with faces mapping suggests that most oil production has been controlled by the distribution of skeletal grainstone and not by structure. Effective exploitation of this remaining mobile oil must include selective completion and injection programs based on variations in the distribution of skeletal grainstone. The absence of significant production from local grainstone thicks, for example, points to inefficient drainage in several parts of the field.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Fri Jan 01 00:00:00 EST 1988},
month = {Fri Jan 01 00:00:00 EST 1988}
}

Conference:
Other availability
Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that hold this conference proceeding.

Save / Share:
  • Burial diagenesis and reservoir quality modification in North Sea Jurassic reservoirs are shown to be largely controlled by the pre-burial composition of the sandstones. Mechanical compaction at shallow burial, chemical compaction and quartz cementation at deep burial, and clay mineral authigenesis are the three most important reservoir quality modifying diagenetic processes, and all these can largely be considered as being isochemical or partially isochemical. It follows that reservoir quality prediction will be successful if the initial mineralogy and texture of the reservoir rocks, the quantitative effects of changing rock composition, and the burial history are known. Although a highly accuratemore » prediction of initial sandstone composition is rarely achievable, an understanding of the effect of varying mineralogy on the most important reservoir quality modifying processes will in most cases provide the necessary basis for adequate reservoir quality prediction. The initial composition of the sandstones is controlled by the sedinmentological environment, depositional processes, climate and the type of material transported into the sedimentary basin. Hence, integrated sedimentological and petrological studies, addressing the links between three-dimensional distributions of depositional facies, initial sandstone composition and reservoir quality models are the key to successful reservoir quality prediction prior to drilling in frontier areas as well as detailed reservoir characterization during field development.« less
  • Burial diagenesis and reservoir quality modification in North Sea Jurassic reservoirs are shown to be largely controlled by the pre-burial composition of the sandstones. Mechanical compaction at shallow burial, chemical compaction and quartz cementation at deep burial, and clay mineral authigenesis are the three most important reservoir quality modifying diagenetic processes, and all these can largely be considered as being isochemical or partially isochemical. It follows that reservoir quality prediction will be successful if the initial mineralogy and texture of the reservoir rocks, the quantitative effects of changing rock composition, and the burial history are known. Although a highly accuratemore » prediction of initial sandstone composition is rarely achievable, an understanding of the effect of varying mineralogy on the most important reservoir quality modifying processes will in most cases provide the necessary basis for adequate reservoir quality prediction. The initial composition of the sandstones is controlled by the sedinmentological environment, depositional processes, climate and the type of material transported into the sedimentary basin. Hence, integrated sedimentological and petrological studies, addressing the links between three-dimensional distributions of depositional facies, initial sandstone composition and reservoir quality models are the key to successful reservoir quality prediction prior to drilling in frontier areas as well as detailed reservoir characterization during field development.« less
  • Permian shallow-water carbonate reservoirs are highly heterogeneous because of complex variations in depositional facies produced by high-frequency sea level rise and fall. Accordingly, establishment of a cycle stratigraphic framework is fundamental to defining reservoir heterogeneity. Because nearly all of these reservoirs have experienced multiple episodes of dolomitization and sulfate emplacement, however, permeability is a n of diagenetic overprint. The extent to which diagenesis can affect permeability development is dramatically displayed in the Grayburg Formation (middle Permian) at South Cowden field, Weit Texas. Three scales of cyclicity contribute to original depositional facies heterogeneity in the Grayburg; high-frequency cycles, averaging 3 metersmore » in thickness, constitute the fundamental architectural element in the main reservoir interval. Despite original depositional heterogeneity due to this cyclicity, however, permeability development is substantially the result of two diagenetic events: (1) dolomite diagenesis in vertically burrowed wackestones and packstones and (2) late alteration and removal of anhydrite. Dolomite diagenesis in vertically burrowed wackestones and packstones has produced irregular vertical zones of higher permeability in mud-dominated bases of high-frequency cycles in leeward ramp-crest highstand successions. Because dolomite diagenesis is concentrated in burrowed highstand successions, the distribution of resultant permeability trends is partly constrained by patterns of longterm accommodation and high frequency cyclicity. Anhydrite diagenesis, which is characterized by conversion to gypsum or by complete removal of sulfate, is developed along basinward margins of the field and cross cuts original depositional framework.« less
  • Permian shallow-water carbonate reservoirs are highly heterogeneous because of complex variations in depositional facies produced by high-frequency sea level rise and fall. Accordingly, establishment of a cycle stratigraphic framework is fundamental to defining reservoir heterogeneity. Because nearly all of these reservoirs have experienced multiple episodes of dolomitization and sulfate emplacement, however, permeability is a n of diagenetic overprint. The extent to which diagenesis can affect permeability development is dramatically displayed in the Grayburg Formation (middle Permian) at South Cowden field, Weit Texas. Three scales of cyclicity contribute to original depositional facies heterogeneity in the Grayburg; high-frequency cycles, averaging 3 metersmore » in thickness, constitute the fundamental architectural element in the main reservoir interval. Despite original depositional heterogeneity due to this cyclicity, however, permeability development is substantially the result of two diagenetic events: (1) dolomite diagenesis in vertically burrowed wackestones and packstones and (2) late alteration and removal of anhydrite. Dolomite diagenesis in vertically burrowed wackestones and packstones has produced irregular vertical zones of higher permeability in mud-dominated bases of high-frequency cycles in leeward ramp-crest highstand successions. Because dolomite diagenesis is concentrated in burrowed highstand successions, the distribution of resultant permeability trends is partly constrained by patterns of longterm accommodation and high frequency cyclicity. Anhydrite diagenesis, which is characterized by conversion to gypsum or by complete removal of sulfate, is developed along basinward margins of the field and cross cuts original depositional framework.« less
  • Superb exposures of variably cyclic, fusulinid-rich, outer ramp facies of the middle San Andres Formation in the Guadeloupe Mountains, NM provide a unique opportunity to evaluate spatial variability of permeability and its relationship to depositional and diagenetic fabric. Detailed geologic description and extensive permeability measurements have been utilized to decipher reservoir-analog flow units and the spatial variability of observed permeability patterns. Thin bedded, poorly developed cycles consisting of alternating fusulinid-peloid dolopackstones and dolowackestones occur within the middle portion of the middle San Andres. Four well developed cycles or parasequences containing dolomudstone bases and fusulinoid-peloid dolopackstone tops comprise the upper portionmore » of the middle San Andres. Upward increasing trends in permeability are evident within each of the well developed cycles whereas a distinct 30 foot thick zone of highly variable but higher mean permeability occurs within the poorly developed thin bedded cycles. Textural characteristics were compared with conventional air permeabilities. Statistically different mean permeabilities are related to variation of grain, matrix, fusulinid mold, and vug content. Permeability is also related to the abundance of white sucrosic dolomite, which appears to have inhibited the development of fusulinid moldic porosity. Based on these relationships, more accurate permeability transforms may be developed and used to map permeability distribution in similar facies within reservoirs. Geostatistical analysis of the permeability populations and within-cycle permeability trends indicate an association to facies and diagenetic-zone dimensions both vertically and laterally. Ranges of correlation support a nearly uncorrelated and highly-variable permeability model within fusulinid-rich cycles of a ramp-carbonate setting.« less