Integrating Structural Reconstruction in Petroleum System Models Workflow, Value & Examples

Abstract

Petroleum system modeling is today recognized as a critical step in exploration workflows to assess the hydrocarbon charge risk through the evaluation of source rocks maturity, hydrocarbon generation, expulsion and migration processes. However, the structurally complex regions that underwent strong extensive or compressive tectonic regimes involving intense folding, thrusting and normal/inverse faulting remain particularly challenging. Thrusting often results in extremely rapid lateral displacements and burial variations which may have a critical impact on source rock maturity and hydrocarbon expulsion. More generally, active faults play a major role in fluids migration pathways by connecting or disconnecting reservoirs and compartments. Fault activity can often explain hydrocarbon charge issues in rugged areas where classic analyses of present-day geometries, related drainage areas and petroleum system elements appear inadequate or insufficient. This type of context requires a proper structural restoration and basin models capable of accounting for it. Doing so is however, when possible, very complex and time consuming as most of basin modeling tools do not accurately manage the combination of vertical and lateral tectonic displacements associated to folding and faulting. This communication introduces a specific 2D workflow linking structural reconstruction with petroleum system modeling in a timely manner. Two key technologies are part of it. The first one is a new kinematic restoration tool which outputs a single unstructured grid, faulted and continuously deformed through time honoring the basin tectonic evolution. The second is a dedicated simulator able to account for unstructured meshes with a specific fault model. Faults are represented as juxtaposition interfaces with an implicit volume for modeling fluids flow along and across fault planes (water and hydrocarbon). The workflow thus allows representing accurately the structural evolution of the basin through time while simulating the impact of faults on compaction, heat transfer and hydrocarbon generation and migration. Several examples from different regions across the globe are used to illustrate the methodology and its added value for petroleum exploration. Supported by calibration data, these cases indicate that hydrocarbon charge timing, drainage area extension through time and fault behavior have a major impact on the accumulations and that complex petroleum system modeling is needed to accurately evaluate the charge risk.

AAPG Datapages/Search and Discovery Article #90337 ©2019 AAPG Middle East Region GTW, Regional Variations in Charge Systems and the Impact on Hydrocarbon Fluid Properties in Exploration, Dubai, UAE, February 11-13, 2019