Application of Geochemical, Engineering, and Geological Methods to Petroleum Exploration--Bell Creek Field, Powder River Basin, Montana: an Example: ABSTRACT

Abstract

Various geochemical, engineering, and geological methods can be applied in a progressive series of steps for the exploration of oil. These steps are source, generation, migration, and entrapment. Source rock data for oil generation are usually obtained from geochemical analyses of the total organic carbon (TOC) content. Generally, a measurement of 0.5% TOC or more is considered adequate for a source rock. Generation of petroleum from a source rock is primarily dependent on the paleotemperature history. The oil-generating temperature window is approximately 125/degrees/-300/degrees/F (52/degrees/-149/degrees/C). A temperature indicator that defines these limits is the T/sub max/ value from rock pyrolysis analyses. Migration of petroleum can be inferred from oil chromatography. This geochemical method can determine if molecular separation (a migration characteristic) of the oil has occurred. A rough estimate of migration distance can be made by the degree of molecular separation. Entrapment areas for petroleum can be interpreted from a geologic paleostructure map of the producing formation at the time of oil accumulation. Time of oil accumulation can be ascertained from oil-gas solution data in the area. Final pinpointing of a well location is sometimes possible by calculating oil column height from capillary pressure data. Bell Creek field is an example,more » after the fact, of how a combination of geochemical, engineering, and geological methods could have been used in its discovery.« less