Exploration Paradigm Shift: The Dynamic Petroleum System Concept

Kenneth E. Peters
Schlumberger and Stanford University, California

The traditional approach to exploration and production is based on finding and exploiting subsurface traps for petroleum. This static view ignores the fact that petroleum systems consist of complex elements and dynamic processes that control whether present-day traps are barren or filled with oil and gas. This presentation describes recent advances in geochemistry and a paradigm shift from static to dynamic understanding of petroleum systems, which we call the “Dynamic Petroleum System Concept.”

Basin and petroleum system modeling (BPSM) recreates basin history, but the primary goal is to quantify petroleum systems, including the extent of petroleum generation, migration, and accumulation. BPSM began with geochemical research in the 1970s and 1980s, which showed that petroleum accumulations result from the dynamic interplay of multiple elements and processes, as defined by the petroleum system concept. One of the first breakthroughs in quantifying petroleum systems was the finding that petroleum-generating reactions in source rock are irreversible and obey rate laws that can be quantified for both laboratory experiments and natural burial maturation. Petroleum generation exhibits first-order rate constants described by the Arrhenius equation; k = A • exp (-Ea/RT), where the generation rate of petroleum, k, depends on a pre-exponential factor A (frequency factor) and the exponent of -Ea/RT. Ea is the activation energy of the reaction, R is the universal gas constant and T is the absolute temperature in Kelvin. Recognition of this fundamental relationship paved the way for the development of the thermal algorithms used in numerical BPSM models.

In order to use this fundamental finding as a predictive tool to quantify petroleum systems, subsurface temperatures had to be reconstructed through space and time. Many of the concepts and data necessary to achieve this objective were already available in the 1970s. For example, knowledge of basin evolution and tectonics, crustal heat flow, heat transfer and porosity/permeability properties of sedimentary rocks, and geochemical calibration tools (e.g., vitrinite reflectance and corrected bottomhole temperatures) can be used to verify postulated thermal effects and fluid flow through rocks. However, all of this information was widely disseminated throughout the geosciences and had not yet been linked or organized into a coherent exploration tool.

Since the late 1980s, steady progress was made toward development of quantitative BPSM software. Current BPSM software attempts to systematically account for all petroleum system elements and processes ranging from generation-migration from the source rock to accumulation-preservation in the trap. These software packages use stratigraphy, subsurface maps, and basic well log, lithologic, paleontologic, and geochemical data to construct 1D, 2D, and 3D (one-, two-, and three-dimensional) models of petroleum systems through time that predict the extent of source-rock thermal maturity, petroleum migration paths, and the volumes and compositions of accumulations. The models are dynamic rather than static and they account for changes in trap configuration, seal capacity, and other factors during the thermal evolution of the petroleum.

AAPG Search and Discovery Article #90101 © 2010 AAPG Foundation Distinguished Lecturer Series 2009-2010