Automatic determination of lithology from well logs

Conference · Sat Sep 01 04:00:00 EDT 1984 · Soc. Pet. Eng. AIME, Pap.; (United States)

OSTI ID:6326778

Delfiner, P C; Peyret, O; Serra, O

A procedure combining modern wireline measurements with a lithofacies database has been developed to produce an automatic lithological description of the formations crossed by a well. The database lithofacies are defined from petrographic knowledge and translated in terms of log responses. The assignment of depth levels to a lithofacies is done by reference to the database and a discriminant function (Bayesian decision rule). External knowledge can be taken into account using Artificial Intelligence methods. A confidence factor is produced for each result. Logs currently in the database are the density, neutron, sonic transit time, gamma ray, photoelectric cross-section, and thorium, potassium and uranium concentrations. Major lithofacies groups are represented in the database: sandstones, limestones, dolomites, shales, coal, evaporites, and miscellanea. They are subdivided by introducing cement and special minerals, and considering several porosity ranges. The construction of the database is a critical step. It is largely empirical and requires careful calibration against intervals whose lithology is well known (e.g. from cores). The database can be tuned to local conditions. The procedure has been tested in several environments and compared with cores and mudlogs descriptions. A detailed lithologic column can be produced at the wellsite and used as an aid to decision making. The results can also serve as input for further geological studies of facies and sequences or for quantitative evaluation of formations.

• Research Organization: Etudes et Productions Schlumberger
• OSTI ID: 6326778
• Report Number(s): CONF-8409104-
• Conference Information: Journal Name: Soc. Pet. Eng. AIME, Pap.; (United States) Journal Volume: SPE13290
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
020200* -- Petroleum-- Reserves
Geology
& Exploration
03 NATURAL GAS
030200 -- Natural Gas-- Reserves
Geology
& Exploration
DATA PROCESSING
DECISION MAKING
FUNCTIONS
LITHOLOGY
NATURAL GAS WELLS
OIL WELLS
PETROGRAPHY
PROCESSING
RESERVOIR ROCK
RESPONSE FUNCTIONS
WELL LOGGING
WELLS