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Title: Seismic estimation of porosity in the Permian San Andres carbonate reservoir, Welch Field, Dawson, County, Texas

Abstract

OXY and the DOE Are partners in a advanced technology demonstration project at OXY`s West Welch Unit. Production is from a low permeability San Andres reservoir of Permian age similar to many shallow shelf carbonate reservoirs in the Permian Basin. The project involves the construction of a detailed geological model for numerical simulation to design and then conduct a CO{sub 2} flood of the reservoir. Depositional textures of the reservoir rock are highly variable from diagenesis, mostly anhydritic cementing, creating a highly complex pore system. Identification of the interwell reservoir continuity and flow units present the greatest challenge to the reservoir description. A 1993 vintage 3-D seismic survey with a bin spacing of 110{prime} by 165{prime} has been used to assist with the interwell reservoir description. The structure definition at the top and base of the reservoir have been accurately mapped with respect to the well data. Core and well log measurements of porosity, permeability and water saturation were computed and summed across the seismic reservoir interval. Measurements of amplitude, frequency and phase within the 3-D volume were summed across the reservoir interval. All seismic attributes were sampled to the wells and compared through scatterplots to the well log andmore » core measurements. Excellent correlation between three seismic attributes and porosity has been documented. A deterministic method has been used to estimate porosity values at each seismic bin location. The method uses the seismic measurements to shape the geology between the wells while maintaining agreement with the well data at the well locations.« less

Authors:
;  [1]
  1. OXY USA Inc., Midland, TX (United States)
Publication Date:
OSTI Identifier:
425937
Report Number(s):
CONF-960527-
TRN: 96:004994-0578
Resource Type:
Conference
Resource Relation:
Conference: Annual convention of the American Association of Petroleum Geologists, Inc. and the Society for Sedimentary Geology: global exploration and geotechnology, San Diego, CA (United States), 19-22 May 1996; Other Information: PBD: 1996; Related Information: Is Part Of 1996 AAPG annual convention. Volume 5; PB: 231 p.
Country of Publication:
United States
Language:
English
Subject:
02 PETROLEUM; TEXAS; OIL FIELDS; SEISMIC SURVEYS; RESERVOIR ENGINEERING; RESERVOIR ROCK; GEOLOGIC MODELS; PETROLEUM; PRODUCTION; ENHANCED RECOVERY; PERMIAN PERIOD

Citation Formats

Watts, G.P., and Hinterlong, G.D. Seismic estimation of porosity in the Permian San Andres carbonate reservoir, Welch Field, Dawson, County, Texas. United States: N. p., 1996. Web.
Watts, G.P., & Hinterlong, G.D. Seismic estimation of porosity in the Permian San Andres carbonate reservoir, Welch Field, Dawson, County, Texas. United States.
Watts, G.P., and Hinterlong, G.D. Tue . "Seismic estimation of porosity in the Permian San Andres carbonate reservoir, Welch Field, Dawson, County, Texas". United States. doi:.
@article{osti_425937,
title = {Seismic estimation of porosity in the Permian San Andres carbonate reservoir, Welch Field, Dawson, County, Texas},
author = {Watts, G.P. and Hinterlong, G.D.},
abstractNote = {OXY and the DOE Are partners in a advanced technology demonstration project at OXY`s West Welch Unit. Production is from a low permeability San Andres reservoir of Permian age similar to many shallow shelf carbonate reservoirs in the Permian Basin. The project involves the construction of a detailed geological model for numerical simulation to design and then conduct a CO{sub 2} flood of the reservoir. Depositional textures of the reservoir rock are highly variable from diagenesis, mostly anhydritic cementing, creating a highly complex pore system. Identification of the interwell reservoir continuity and flow units present the greatest challenge to the reservoir description. A 1993 vintage 3-D seismic survey with a bin spacing of 110{prime} by 165{prime} has been used to assist with the interwell reservoir description. The structure definition at the top and base of the reservoir have been accurately mapped with respect to the well data. Core and well log measurements of porosity, permeability and water saturation were computed and summed across the seismic reservoir interval. Measurements of amplitude, frequency and phase within the 3-D volume were summed across the reservoir interval. All seismic attributes were sampled to the wells and compared through scatterplots to the well log and core measurements. Excellent correlation between three seismic attributes and porosity has been documented. A deterministic method has been used to estimate porosity values at each seismic bin location. The method uses the seismic measurements to shape the geology between the wells while maintaining agreement with the well data at the well locations.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Dec 31 00:00:00 EST 1996},
month = {Tue Dec 31 00:00:00 EST 1996}
}

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  • OXY and the DOE Are partners in a advanced technology demonstration project at OXY's West Welch Unit. Production is from a low permeability San Andres reservoir of Permian age similar to many shallow shelf carbonate reservoirs in the Permian Basin. The project involves the construction of a detailed geological model for numerical simulation to design and then conduct a CO[sub 2] flood of the reservoir. Depositional textures of the reservoir rock are highly variable from diagenesis, mostly anhydritic cementing, creating a highly complex pore system. Identification of the interwell reservoir continuity and flow units present the greatest challenge to themore » reservoir description. A 1993 vintage 3-D seismic survey with a bin spacing of 110[prime] by 165[prime] has been used to assist with the interwell reservoir description. The structure definition at the top and base of the reservoir have been accurately mapped with respect to the well data. Core and well log measurements of porosity, permeability and water saturation were computed and summed across the seismic reservoir interval. Measurements of amplitude, frequency and phase within the 3-D volume were summed across the reservoir interval. All seismic attributes were sampled to the wells and compared through scatterplots to the well log and core measurements. Excellent correlation between three seismic attributes and porosity has been documented. A deterministic method has been used to estimate porosity values at each seismic bin location. The method uses the seismic measurements to shape the geology between the wells while maintaining agreement with the well data at the well locations.« less
  • The ODC field, operated by American Petrofina Company of Texas, is located in Gaines County, Texas, on the northwestern shelf of the Midland basin (Central Basin platform). Consisting of 53 wells, the ODC field produces from 80,000 net ac involved in a waterflood injection program that was initiated in 1969. The primary reservoirs are dolomitic carbonates in the Permian San Andres Formation. Since flooding was initiated, 836,043 bbl of crude oil has been produced from an average reservoir depth of 5500 ft subsea. To maximize production using a proposed carbon dioxide injection program, porosity and permeability trends were analyzed, detailingmore » lateral and vertical continuity, and the depositional and diagenetic processes controlling porosity and permeability were investigated, using data from five well cores and corresponding laboratory reports.« less
  • Suniland field is located in the west Texas Permian basin. Production is primarily from peritidal shelf dolomites of the Permian (Guadalupian) San Andres Formation. San Andres deposition was highly cyclical, with at least two upward-shoaling megacycles comprising the lower 600 ft (183 m) of the formation; many smaller cycles occur within the megacycles. The field consists of an elongate, low-relief, east-west-trending anticline formed from draping over a pre-San Andres structural high. Hydrocarbon trapping is controlled primarily by structural closure and discontinuity of San Andres reservoir facies. Anhydrite cement precipitation also may cause an updip (northerly) permeability loss. Reservoirs occur inmore » thin, permeable oolitic grainstone intervals possessing primary intergranular porosity in combination with vugular and moldic pore systems. These grainstones interfinger with porous but generally impermeable oolitic packstones. Adjacent wackestones and mudstones are generally nonporous and impermeable. Porosity occlusion is primarily from precipitation of late dolomite cements. Anhydrite cements do not occlude porosity to a high degree. Oil production from the San Andres Formation at Suniland field is from nine separate reservoirs comprising two major pay categories, designated Sand Andres and lower San Andres. Pay depths range from 3,755 to 4,211 ft (1,144 to 1,283 m). Cumulative oil production to January 1986 is 7.35 million bbl from 69 wells. Permian (Leonardian) Glorieta production accounts for about 16% of total production. Reservoirs produce from solution gas expansion at low gas-to-oil ratios and high water cuts. Effective porosity in pay zones averages 14%; permeability averages 17 md.« less
  • An integrated reservoir characterization of Seminole San Andres Unit was conducted using outcrop and subsurface data. The high frequency cycles and rock-fabric facies identified on outcrop and cores were used to correlate wireline logs. Reservoir and simulation models of the outcrop and a two-section area of the Seminole San Andres field were constructed using rock-fabric units within high-frequency cycles (HFC`s) as a geologic framework. Simulations were performed using these models to investigate critical factors affecting recovery. High-frequency cycles and rock-fabric units are the two critical scales for modeling shallow-water carbonate ramp reservoirs. Descriptions of rock-fabric facies stacked within high-frequency cyclesmore » provide the most accurate framework for constructing geologic and reservoir models because discrete petrophysical functions can be fit to rock fabrics and fluid flow can be approximated by the k{sub vh} ratios among rock-fabric flow units. Permeability is calculated using rock-fabric-specific transforms between interparticle porosity and permeability. Core analysis data showed that separate-vug porosity has a very strong effect on relative permeability and capillary pressure measurements. The stratigraphic features of carbonates can be observed in stochastic realizations only when they are constrained by rock-fabric flow units. Simulation results from these realizations are similar in recovery but different in production and injection rates. Scale-up of permeability in the vertical direction was investigated in terms of the ratio of vertical permeability to horizontal permeability (k{sub vh}). This ratio decreases exponentially with the vertical grid-block size up to the average cycle size of 20 ft (6.1 m) and remains at a value of 0.06 for a grid-block size of more than 20 ft (>6.1 m), which is the average thickness of high-frequency cycles.« less
  • An older algal-bryozoan bioherm has contributed to the deposition of high-porosity reservoir rock and the creation of a hydrocarbon trap in the San Andres formation at Hanford field, Gaines County, Texas. The bioherm (mound) is nonporous, unproductive, and lies almost 1,000 ft (300 m) below the producing zone. Starting with almost 300 ft (90 m) of relief, this mound was first ''drowned'' during a transgression and was later gradually buried by prograding, cyclic, subtidal to supratidal carbonates and anhydrites. Approximately 80 ft (25m) of relief presently exists on the base of the producing interval. Relief on the top of themore » producing interval is approximately 140 ft (43 m). Lithology and porosity distribution within the producing interval suggest that compaction drape accounts for only part of this relief.The reservoir is thickest and most porous over the crest of the mound. Gainstones and packstones are more common within the reservoir over the crest of the mound than away from it. These observations indicate that the mound was reflected as a shoal in the subtidal zone during the deposition of the producing interval. Relief in this shoal was maintained by higher depositional rates and by the deposition of relatively uncompactible, mud-free sediments in the crestal portion of the mound. Sediments deposited within the subtidal zone, but away from the crest, were deposited at lower rates and contained more mud. Although this model is different from models for almost all other San Andres fields, we are confident that other fields of this type will be discovered in the Permian basin.« less