Abstract: Petroleum Geochemistry Using Wireline Logs: A Presentation of Concepts and Applications

LANCASTER, JAMES R. and JAMES C. ENGSTROM

Petroleum geochemistry values are computed using traditional wireline logs. The utilized data base is caliper, gamma ray, neutron porosity, bulk density, sonic delta-T, and resistivity logs. Also utilized is thermal gradient, burial history (removed overburden), and estimates of formation pressure and specific gravity of the expelled hydrocarbon.

The computed petroleum geochemical values are total organic carbon (TOC Wt%), S1, S2, S3, oxygen and hydrogen indices (OI and HI), equivalents of atomic oxygen/carbon and hydrogen/carbon ratios, and the transformation ratio S1 / (S1+S2) (TR). TR is converted to level of organic metamorphism (LOM), thermal alteration index (TAI), Tmax (from S2 pyrogram), time-temperature index (TTI), and vitrinite reflectance (Ro%).

Crossplots of laboratory vs. computed TOCs are presented with analog plots of other geochemical properties from the laboratory and the computer. Select logs of computed petroleum geochemical values from world wide case history data of Tertiary through Precambrian source rocks are presented. Crossplots of TOC vs. S2 and the van Krevelen diagram are shown. The discussed source rock formations have paleodepths that range from 9000 to 21,000 feet, and have paleotemperatures that range from 100 to greater than 230 degrees C.

Map views of quantities, kerogen type, and maturation levels are compared to production history data over a field wide area.

AAPG Search and Discovery Article #90946©1997 AAPG Rocky Mountain Section Meeting, Denver, Colorado