Coupled stratigraphic and petroleum system modeling: Examples from the Ordos Basin, China

Abstract

With the emergence of the “continuous petroleum accumulations” concept and unconventional petroleum exploration, the traditional source-to-trap petroleum system model becomes vague spatially because the source, reservoir, and seal may intermingle within the same stratigraphic unit. In such a system, the spatial distribution of key petroleum system elements therefore depends on sedimentary facies heterogeneities. Available basin modeling programs lack built-in sedimentary infill modeling capabilities to populate heterogeneities within the traditional “layer-cake” modeling framework where source, reservoir, and seal units are commonly represented as discrete and homogeneous layers. To address such a challenge, and to model both conventional and unconventional petroleum systems holistically in a single simulation, we coupled stratigraphic forward modeling with basin modeling, where the former provides a detailed three-dimensional sedimentary facies volume with finer-scale heterogeneities effectively captured as input for the latter. The forward stratigraphic model we used in our study is a hydrodynamics-based program, which is able to model clastic, carbonate, and organic deposition with spatial resolutions from centimeters to meters vertically and hundreds of meters to tens of kilometers horizontally. The Triassic tight (sandstone) oil plays and the upper Paleozoic tight (sandstone) gas plays from the Ordos Basin, central China, were modeled using the integrated approach. Compared to the conventional layer-cake models, the coupled stratigraphic forward modeling and basin modeling produced much more realistic results in terms of the quantity of petroleum accumulation and their spatial distributions.