ADAPTING BASIN AND PETROLEUM SYSTEM ANALYSIS FOR SOURCE ROCK PLAYS

Basin and petroleum system analysis reduces pre-drill uncertainty by modeling the petroleum system in a way that that is geodynamically viable and consistent with the structural, stratigraphic, and geochemical framework of the basin. This multi-disciplinary approach aids in the prediction of hydrocarbon occurrence, quality, and quantity in all types of basins regardless of age, size, or hydrocarbon potential. Various modeling techniques were developed for a broad range of structural and stratigraphically complex conventional petroleum systems. This paper discusses how the same tools are adapted to aid in the prediction of sweet spots within an in-source resource play.

A petroleum system is described by its elements (source rock, reservoir, seal, and overburden) and processes (trap formation and hydrocarbon generation, migration, accumulation, and preservation). In the deep water Gulf of Mexico, interbedded organic-rich source rock deposits followed the deposition of a thick layer of middle Jurassic salt. Sediment loading in the Tertiary resulted in allochthonous salt diapirs and nappes, which influenced sand deposition and initiated structural and stratigraphic trap formation. As the source rock matured, hydrocarbons migrated up faults, along carrier beds, and into traps where accumulations depend on the volume of charge and sealing capacity. This dynamic and highly variable system requires reasonable estimates of the pressure, temperature, and charge histories to ascertain the petroleum system’s pre-drill risk and uncertainty.

Although models of an in-source unconventional system focuses on the source rock (e.g., Barnett, Marcellus, Wolfcamp, etc.), the primary goal of basin and petroleum systems analysis is unchanged. Temperature and pressure histories, matrix porosity, and the formation of natural fractures within the source rocks are a function of the basin’s heat flow, burial, and uplift histories. Wettability directly influences the mobility of both water and hydrocarbons in organic-rich rocks, which may lead to capillary seals in interbedded horizons that retain fluids resulting in higher pore pressures and production volumes. Several challenges remain in analyzing both conventional and unconventional systems, but continued advances in technology will lead to improved outcomes.