ABSTRACT: Thermal Maturity of Hydrocarbon Source Rocks Within Southeastern Palo Duro Basin

Gregg A. Norman

The Palo Duro has been defined as a relatively shallow, late Paleozoic, intracratonic basin located in the southern portion of the Texas Panhandle. In recent years, numerous studies have addressed this area and have documented the existence of adequate source rocks, migration pathways, reservoir quality, and trapping mechanisms. Low-level thermal maturity is the primary factor limiting the petroleum potential within the majority of the basin. Previous work concerning the thermal maturity has been of a broad-based nature, using only one data point per county in most instances. Application of a model-based approach, coupled with conventional laboratory analytical techniques, indicates the level of maturity to be regionally variable.

The Pennsylvanian rocks of the basin have the greatest potential for economic hydrocarbon accumulations. The thermal maturity of the Pennsylvanian source rocks is dependant on burial temperature. Although the majority of the basin is relatively cool, the southeastern part contains large areas with elevated temperatures. Mapping of geothermal gradient trends has delineated these thermal anomalies. The variability of thermal maturity with respect to the gradient trends has been determined by application of the Lopatin time-temperature modeling technique. When calibrated with laboratory measured maturity levels on cores and cuttings from selected wells, this method is an accurate way to determine the hydrocarbon-generating potential for an area or source rock interval. This procedure has been used to obtain a detailed thermal maturity assessment of the southeastern portion of the basin.

The Lopatin time-temperature model, as modified by Waples, is a practical and easily applied tool that can be used to high-grade exploration plays and prospects. In areas like the Palo Duro basin, where marginal maturity is the norm, this type of study should be an integral part of the exploration program.

AAPG Search and Discovery Article #90096©1990 AAPG Southwest Section Meeting, Wichita Falls, Texas, March 11-13, 1990