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Title: Depositional environments, diagenetic history, and porosity development, vacuum San Andres Field, Lea County, New Mexico

Abstract

The Permian San Andres Formation was deposited in environments ranging from supratidal to subtidal, protected shallow marine to open shallow marine. Pelletoid-skeletal packstone/wackestone and pelletoid-oolite-skeletal packstone/grainstone facies of the composite subtidal, marine environments were concentrated in the southern half of the field where grainstone deposition was linked to a paleotopographic high. Deposition in the northern half of the field was dominated by the pelletoid wackestone/mudstone facies of the supratidal, restricted shallow-marine environment. Porosity is mainly diagenetic in origin. San Andres rocks passed through the marine phreatic, the mixed phreatic, the meteoric phreatic, and the deeper subsurface diagenetic environments. Matrix dolomitization in the marine and mixed-phreatic environment produced intercrystalline porosity in all the facies. Leaching of nondolomitized grains in the mixed phreatic and meteoric-phreatic environments created large moldic pores. Diagenetic patterns follow structural and depositional trends so that suites of characteristic pore types exist for each facies. Individual pore types consist of moldic, intergranular, intragranular, vuggy, and intercrystalline categories. Intercrystalline pores are present nearly everywhere, and predicting the abundance of moldic pores is the largest variable in predicting porosity values for a given stratigraphic interval. Highest porosity exists in the southern half of the study area where grainier facies were depositedmore » on a paleotopographic high, and grains were partly dolomitized and subsequently were removed by leaching, leaving behind a composite intercrystalline-moldic pore network. Total porosity values do not correspond with facies boundaries, so porosity mapping was accomplished by dividing the San Andres into 20-ft-thick slices and computer contouring total porosity greater than 6% in each slice.« less

Authors:
 [1]
  1. (Texas A and M Univ., Dallas, TX (USA))
Publication Date:
OSTI Identifier:
6891172
Alternate Identifier(s):
OSTI ID: 6891172
Report Number(s):
CONF-9003145--
Journal ID: ISSN 0149-1423; CODEN: AABUD
Resource Type:
Conference
Resource Relation:
Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (USA); Journal Volume: 74:2; Conference: American Association of Petroleum Geologists (AAPG) southwest section meeting, Wichita Falls, TX (USA), 11-13 Mar 1990
Country of Publication:
United States
Language:
English
Subject:
02 PETROLEUM; 03 NATURAL GAS; NEW MEXICO; OIL FIELDS; RESERVOIR ROCK; DEPOSITION; DIAGENESIS; POROSITY; COMPUTER-AIDED DESIGN; GEOLOGIC FORMATIONS; MAPPING; SANDSTONES; SILTSTONES; FEDERAL REGION VI; GEOLOGIC DEPOSITS; MINERAL RESOURCES; NORTH AMERICA; PETROLEUM DEPOSITS; RESOURCES; ROCKS; SEDIMENTARY ROCKS; USA 020200* -- Petroleum-- Reserves, Geology, & Exploration; 030200 -- Natural Gas-- Reserves, Geology, & Exploration

Citation Formats

Robertson, J.W.. Depositional environments, diagenetic history, and porosity development, vacuum San Andres Field, Lea County, New Mexico. United States: N. p., 1990. Web.
Robertson, J.W.. Depositional environments, diagenetic history, and porosity development, vacuum San Andres Field, Lea County, New Mexico. United States.
Robertson, J.W.. Thu . "Depositional environments, diagenetic history, and porosity development, vacuum San Andres Field, Lea County, New Mexico". United States. doi:.
@article{osti_6891172,
title = {Depositional environments, diagenetic history, and porosity development, vacuum San Andres Field, Lea County, New Mexico},
author = {Robertson, J.W.},
abstractNote = {The Permian San Andres Formation was deposited in environments ranging from supratidal to subtidal, protected shallow marine to open shallow marine. Pelletoid-skeletal packstone/wackestone and pelletoid-oolite-skeletal packstone/grainstone facies of the composite subtidal, marine environments were concentrated in the southern half of the field where grainstone deposition was linked to a paleotopographic high. Deposition in the northern half of the field was dominated by the pelletoid wackestone/mudstone facies of the supratidal, restricted shallow-marine environment. Porosity is mainly diagenetic in origin. San Andres rocks passed through the marine phreatic, the mixed phreatic, the meteoric phreatic, and the deeper subsurface diagenetic environments. Matrix dolomitization in the marine and mixed-phreatic environment produced intercrystalline porosity in all the facies. Leaching of nondolomitized grains in the mixed phreatic and meteoric-phreatic environments created large moldic pores. Diagenetic patterns follow structural and depositional trends so that suites of characteristic pore types exist for each facies. Individual pore types consist of moldic, intergranular, intragranular, vuggy, and intercrystalline categories. Intercrystalline pores are present nearly everywhere, and predicting the abundance of moldic pores is the largest variable in predicting porosity values for a given stratigraphic interval. Highest porosity exists in the southern half of the study area where grainier facies were deposited on a paleotopographic high, and grains were partly dolomitized and subsequently were removed by leaching, leaving behind a composite intercrystalline-moldic pore network. Total porosity values do not correspond with facies boundaries, so porosity mapping was accomplished by dividing the San Andres into 20-ft-thick slices and computer contouring total porosity greater than 6% in each slice.},
doi = {},
journal = {AAPG Bulletin (American Association of Petroleum Geologists); (USA)},
number = ,
volume = 74:2,
place = {United States},
year = {Thu Feb 01 00:00:00 EST 1990},
month = {Thu Feb 01 00:00:00 EST 1990}
}

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  • A study of the Vacuum San Andres field reveals that porosity and permeability in this anhydritic dolomite reservoir are not limited by facies boundaries. Processes of early dolomitization followed by leaching created a mainly diagenetic pore system with five fundamental pore types: (1) intercrystalline; (2) intergranular; (3) intragranular; (4) moldic; and (5) vuggy. Percent porosity, from core analyses and derived from borehole logs, was mapped by dividing the San Andres Formation within the field into 20 slices of 20 feet each. Average porosity for each slice was contoured by computer and spot-checked by hand contouring. Sectors with porosity less thanmore » 6%, 6-12%, 12-18%, and greater than 18% were hand-colored to form a 4-dimensional map of percent porosity in space. The maps for each slice were stacked to create a physical model of field-wide porosity distribution. Measurements of pore dimensions in each pore category in each thin section were made to determine the distribution of mean pore size by type in each percent-porosity sector. mean pore size was plotted against permeability to test for correspondence. The distribution of pore types and sizes within each percent-porosity sector was compared with core lith logs and with values from borehole logs to identify co-variant pore, rock, and borehole log properties with which to construct a flow-unit map. The flow units are thereby defined by using the correspondence between rock type and pore properties to extend mapping capabilities beyond cored wells as an aid in reservoir characterization for enhanced oil recovery.« less
  • This paper presents a case history of the design, implementation, and results of a tertiary polymer EOR injection project conducted by Phillips Petroleum Co. in their Hale and Mable leases located in the Vacuum (Grayburg-San Andres) field, Lea County, NM. Polymer is being injected at a relatively low concentration, and the paper concludes that, given the reservoir rock and fluid properties prevalent in the Hale and Mable leases, a low-concentration polymer flood is just as effective as a higher-concentration flood as long as the total pounds of polymer injected is the same.
  • Paleoenvironmental reconstruction analysis characterize the Atoka sands of the North Vacuum field, Lea County, New Mexico, as being deposited in a braided fluvial system. The channels trend from northwest to southeast. In the past the only sure way of identifying the depositional environment of a sand was by cutting a whole core. With the addition of the Formation MicroScanner (FMS) images, now one can interpret the depositional environment with greater confidence and without the cost of a shale core. The depositional environment was determined for Atokan sands by using the FMS in two wells. The results were verified by wholemore » core and FMS in one well. The FMS data interpreted on Schlumberger's Sun workstation indicated that the sand was deposited in a braided channel system. The following sequence was observed: (1) erosion of the underlying shale, (2) then coarse-grained sands were deposited in a downflow direction until the eroded channel was filled, (3) then the sands were laterally accreted perpendicular to flow direction producing the thickest sand bodies, and (4) the final stage occurred during sea level transgression when fine-grained sand and shale lenses capped the massive sands with depositional current bedding in a landward direction indicating fluvial-marine influences. The conclusions based on the FMS images were supported by a whole core interpretation of a complete sandstone sequence in one well. Several additional locations have been chosen in the channel trend based on this model.« 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
  • The Bone Spring formation of the northern Delaware basin in southeastern New Mexico produces oil in Lea County from foreshelf detrital carbonate facies, such as in Scharb field. Production there comes from several intervals. Stratigraphic correlations between the various Bone Springs units and equivalent Leonardian facies of the Northwest shelf in Lea County suggest that the Bone Spring is correlative to the Yeso Formation of the Northwest shelf. The shelf facies there are divided into lower, middle, and upper Yeso. The upper part of what has generally been considered to be Wolfcamp in some areas, beneath the lowermost Bone Springmore » sandstone, is inferred to be lower Leonardian (lower Yeso) throughout the area studied. A model is proposed for the sedimentologic and reservoir evolution of the Bone Spring Formation in Lea County. Permian-Pennsylvanian tectonic activity provided the initial substrate for the development of a high-energy shelf edge in early Yeso time. In early middle Yeso time, the basin filled with sediments of the 3rd and 2nd Bone Spring units, and the shelf to basin transition was more subtle. As the basin subsided with infilling, a high-energy shelf edge again developed in late middle Yeso time. With continued basin infilling by 1st Bone Springs facies, the shelf to basin transition again evolved into a more subtle feature. Continued basin subsidence caused infilling by a thick sequence of upper Yeso carbonate, which was capped by progradational shelf carbonates of the upper Yeso.« less