Case history of Cotton Valley sand log interpretation for a North Louisiana field

Conference · Sat Oct 01 04:00:00 EDT 1983 · Soc. Pet. Eng. AIME, Pap.; (United States)

OSTI ID:5357783

Ganer, B L

Accurate porosity and water saturation determination of Cotton Valley sandstone is difficult since porosities below 12 are typically encountered. In this low porosity range the errors introduced in the process of obtaining log derived porosity and water saturation values can cause significant misinterpretation of productive potential. Such errors can be due to the presence of secondary matrix mineralization, parameters selected to calculate porosity and water saturation, and calibration inaccuracies. In the case of Cotton Valley sandstone, which is predominantly a sand-shale sequence, the occurrence of secondary minerals can be significant. The Cotton Valley sands are a complex intermingling of various minerals including quartz, chert, pyrite, mica, illite, chlorite and an assortment of carbonates. Carbonates in insolated intervals can account for as much as 50 of the rock matrix. The heavy minerals, when not accounted for, can result in pessimistic log derived porosity and hence overlooked commercial potential. Additionally, calibration inaccuracies can result in either optimistic or pessimistic porosity analysis further confounding commercial evaluation. Variations in grain size coupled with the mineral composition complicate permeability determination. The variables mentioned above account for the difficulty in predicting reserves experienced in Cotton Valley sand exploration.

• Research Organization: Union Texas Petroleum Co.
• OSTI ID: 5357783
• Report Number(s): CONF-8310121-
• Conference Information: Journal Name: Soc. Pet. Eng. AIME, Pap.; (United States) Journal Volume: SPE12182
• Country of Publication: United States
• Language: English

Related Subjects

04 OIL SHALES AND TAR SANDS
040100 -- Oil Shales & Tar Sands-- Reserves & Exploration-- (-1989)
040200* -- Oil Shales & Tar Sands-- Reserves
Geology
& Exploration
CALCULATION METHODS
CARBONATE ROCKS
CHALCOGENIDES
CHERT
CHLORITE MINERALS
CLAYS
CRYSTAL STRUCTURE
DATA ANALYSIS
ECONOMICS
ERRORS
EXPLORATION
EXPLORATORY WELLS
FEDERAL REGION VI
FLUIDS
FORECASTING
GEOLOGIC DEPOSITS
GEOPHYSICAL SURVEYS
GRAIN SIZE
ILLITE
IRON COMPOUNDS
IRON SULFIDES
LOUISIANA
MICA
MICROSTRUCTURE
MINERALIZATION
MINERALS
NORTH AMERICA
OIL SAND DEPOSITS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PERMEABILITY
POROSITY
PYRITE
QUARTZ
RESERVES
RESERVOIR FLUIDS
RESERVOIR ROCK
RESOURCES
ROCKS
SANDSTONES
SATURATION
SEDIMENTARY ROCKS
SILICATE MINERALS
SILICON COMPOUNDS
SILICON OXIDES
SIZE
SULFIDE MINERALS
SULFIDES
SULFUR COMPOUNDS
SURVEYS
TRANSITION ELEMENT COMPOUNDS
USA
WATER SATURATION
WELL LOGGING
WELLS