Diagenesis of a tight gas formation: Jurassic Cotton Valley Sandstone, East Texas basin

Conference · Sat Sep 01 04:00:00 EDT 1984 · Am. Assoc. Pet. Geol., Bull.; (United States)

OSTI ID:6291049

Wescott, W A

The Upper Jurassic Cotton Valley Sandstone is a thick siliciclastic unit in the East Texas basin. Along the eastern flank of the basin, natural gas is produced from Cotton Valley reservoirs characterized by low porosity and permeability, which have been stimulated by massive hydraulic fracturing. Cotton Valley sandstones are generally very fine-grained, well-sorted quartz arenites and subarkoses. Principal framework constituents are monocrystalline quartz and feldspars. The sandstones have had a complex diagenetic history and are cemented by authigenic quartz, calcite, phyllosilicates, and iron oxides. The most common paragenetic sequence of pore-fill minerals was (1) development of clay coats on grains, (2) formation of syntaxial overgrowths, (3) dissolution of unstable grains followed by precipitation of phyllosilicates, (4) precipitation of calcite in relict primary and secondary pores, and (5) replacement of framework grains by calcite resulting in a poikilotopic texture. Cotton Valley sandstones are classified by R-mode factor analysis into three groups that can be related to porosity characteristics. Therefore, the groups can be used to predict potential reservoir rock. Type I rocks are tightly cemented by quartz and calcite and make poor reservoirs. Type II rocks have a high phyllosilicate content and abundant microporosity, and may produce gas. Type III rocks have a high content of unstable grains and have well-developed secondary porosity, which can be of reservoir quality. Depositional facies controlled the diagenesis of the Cotton Valley Sandstone.

• Research Organization: Amoco Production Co., Houston, TX
• OSTI ID: 6291049
• Report Number(s): CONF-8410143-
• Conference Information: Journal Name: Am. Assoc. Pet. Geol., Bull.; (United States) Journal Volume: 68:9
• Country of Publication: United States
• Language: English

Related Subjects

03 NATURAL GAS
030200* -- Natural Gas-- Reserves
Geology
& Exploration
CLASSIFICATION
DIAGENESIS
FEDERAL REGION VI
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC FORMATIONS
GEOLOGIC STRUCTURES
JURASSIC PERIOD
MESOZOIC ERA
MINERAL RESOURCES
NATURAL GAS DEPOSITS
NORTH AMERICA
POROSITY
RESERVOIR ROCK
RESOURCES
SEDIMENTARY BASINS
SEDIMENTATION
TEXAS
USA