ABSTRACT: Mapping Source Rock Properties of the Bakken Shale in North Dakota Using Porosity and Resistivity Well Logs

WEBSTER, RICK, Exxon Production Research Co., Houston, TX

Total organic carbon content, remaining generative capacity, and thermal maturity of the black shales of the Bakken Formation were assessed by utilizing both vertical and areal distributions of these properties estimated from porosity and resistivity well logs (method of Passey et al., 1990). The results of this analysis are compared to the large database of laboratory measured geochemical properties available for the Bakken. Total organic carbon determined from this method agreed quite well with the measured geochemical data with the exception of a few wells where the shales are very immature and have very low resistivity. Calibration of this well log technique using measured TOC values was necessary before it could be consistently applied across the basin. Resistivity in these shale is related to thermal maturity, but it starts to increase before maturity (as measured by conventional pyrolysis techniques) is reached and may at first be influenced by a change in pore water distribution, organic matter diagenesis, or clay mineralogy.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)