Relationships between cement, rock fabric, porosity and permeability, Lower Vicksburg Formation, McAllen Ranch field, south Texas

Conference · Fri Mar 01 00:00:00 EST 1991 · AAPG Bulletin (American Association of Petroleum Geologists); (United States)

OSTI ID:5684268

Grigsby, J D; Langford, R P ^[1]

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1. Univ. of Texas, Austin (United States)

Detailed petrographic mapping of cement distribution, combined with sedimentologic description and petrophysical data, is a powerful technique for describing distribution of reservoir properties. Two cores from the lower Vicksburg Formation, McAllen Ranch field, south Texas, indicate that porosity and permeability, which vary over several orders of magnitude, are related to a complex interplay between centimeter-scale cement variations, grain size, sedimentary structures, and the development of secondary porosity. Porosity and permeability plugs in combination with thin section analysis, taken every 5 cm through several representative intervals, reveal the complex controls on reservoir properties. For example, within an upward-coarsening interval a strong relationship exists between grain size, the development of secondary porosity, and permeability. The coarsest sands of the interval are cemented by quartz overgrowths and variable amounts of calcite. The preferential development of secondary porosity in this 'band' results in an average permeability of 0.169 md. In contrast, as grain size decreases, calcite cementation increases, resulting in a decrease in the development of secondary porosity and an average permeability of 0.008 md. When chlorite is the predominant cement, permeability is dependent on the development of secondary porosity and is independent of grain size. Within a chlorite-cemented interval, with a relatively constant measured porosity of 16.6 ({plus minus}1)%, permeability ranged from 0.026 md to 0.372 md. Secondary porosity ranged from 1.5% to 5.5% over this same interval. These variations, which occur in distinct bands in core, result in a complex but predictable distribution in porosity and permeability.

• OSTI ID: 5684268
• Report Number(s): CONF-910403-; CODEN: AABUD
• Journal Information: AAPG Bulletin (American Association of Petroleum Geologists); (United States), Vol. 75:3; Conference: Annual meeting of the American Association of Petroleum Geologists (AAPG), Dallas, TX (United States), 7-10 Apr 1991; ISSN 0149-1423
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
03 NATURAL GAS
RESERVOIR ROCK
PERMEABILITY
PETROGRAPHY
POROSITY
TEXAS
NATURAL GAS DEPOSITS
PETROLEUM DEPOSITS
CEMENTS
COMPARATIVE EVALUATIONS
GEOLOGIC FORMATIONS
GRAIN SIZE
BUILDING MATERIALS
CRYSTAL STRUCTURE
DEVELOPED COUNTRIES
EVALUATION
FEDERAL REGION VI
GEOLOGIC DEPOSITS
MATERIALS
MICROSTRUCTURE
MINERAL RESOURCES
NORTH AMERICA
RESOURCES
SIZE
USA
020200* - Petroleum- Reserves
Geology
& Exploration
030200 - Natural Gas- Reserves
Geology
& Exploration