Assessment of fracture-induced anisotropy in the Austin Chalk Formation (Upper Cretaceous), central Texas

Conference · Tue May 01 00:00:00 EDT 1990 · AAPG Bulletin (American Association of Petroleum Geologists); (USA)

OSTI ID:6729559

Edwards, D A ^[1]

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1. Baylor Univ., Waco, TX (USA)

This study relates geophysical and geological data to the detection of fractures and their influence on the movement of fluid in the Atco Member of the Austin Chalk in central Texas. In areas of production, the Austin Chalk has very low matrix permeabilities, with hydrocarbons confined to zones of near-vertical, stress-aligned fractures. Horizontal drilling has been estimated to increase per well reserves in the Austin Chalk from 75,000 bbl and 82 mmcf to 500,000 bbl and 500 mmcf. The objective of deviated wells in the Austin Chalk is to intersect at right angles as many of the hydrocarbon-prone fracture zones as possible. Therefore, the detection and description of these fracture zones prior to drilling is critical. Fractures have been proven to influence the velocities of shear waves. To assess shear wave velocities in different directions, several shear wave refraction and three-component vertical seismic profiles have been acquired. These data provided a measure of the fracture-induced shear wave anisotropy and an indication of the dominant fracture trend. Other data, including azimuthal resistivity surveys, cores, and aerial photographs, provided additional control for evaluating the fractures. The final phase of the study compares the geophysical and geological interpretations to the result of shallow groundwater pumping tests. The pumping tests have been conducted in vertical boreholes and were designed to evaluate the influence of the fracturing on fluid movement.

• OSTI ID: 6729559
• Report Number(s): CONF-900605-; CODEN: AABUD
• Journal Information: AAPG Bulletin (American Association of Petroleum Geologists); (USA), Vol. 74:5; Conference: Annual convention and exposition of the American Association of Petroleum Geologists, San Francisco, CA (USA), 3-6 Jun 1990; ISSN 0149-1423
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
58 GEOSCIENCES
PETROLEUM DEPOSITS
RESERVOIR ROCK
TEXAS
DIRECTIONAL DRILLING
GEOLOGIC FRACTURES
GROUND WATER
PERMEABILITY
POROSITY
SEISMIC SURVEYS
DRILLING
FEDERAL REGION VI
GEOLOGIC DEPOSITS
GEOLOGIC STRUCTURES
GEOPHYSICAL SURVEYS
HYDROGEN COMPOUNDS
MINERAL RESOURCES
NORTH AMERICA
OXYGEN COMPOUNDS
RESOURCES
SURVEYS
USA
WATER
020200* - Petroleum- Reserves
Geology
& Exploration
580000 - Geosciences