Integrated Trap and Seal Evaluation of Complex Reservoir Systems

Francesco V. Corona¹, Steve Davis², Peter Vrolijk³, and Jianhua Feng^4
1ExxonMobil Development Company, Houston, TX
²ExxonMobil Exploration Company, Houston, TX
³ExxonMobil Upstream Research Company, Houston, TX
⁴Esso Exploration & Production Nigeria, Ltd, Lagos, Nigeria

Regardless of upstream business stage, complete understanding of fluid distributions and plumbing in complex hydrocarbon reservoirs requires integration of fluid properties, bed seal properties, fracture gradients, and structural and stratigraphic models. Successful integrated trap analysis requires simultaneous evaluation of the multiple elements that control contact distributions.
Reservoir Connectivity Analysis (RCA) is an integrative methodology for analyzing hydrocarbon distributions in complex reservoir systems. RCA relates known or predicted fluid contacts to fluid properties (e.g., geochemistry, pressure), bed seal properties (e.g., capillary, mechanical), and a reservoir container topology.

RCA has been successfully applied to a major deepwater field in Nigeria which comprises a complex channel system draped across an intensely faulted anticline. The trap has primarily a single gas-oil contact, but across the structure the oil-water contacts are offset by several hundred meters. RCA shows that the hydrocarbons are in pressure communication, but the aquifers are separated by the base seal. The oil-water contacts are controlled by the spill and base seal, and the gas-oil contact by capillary entry pressure of the top seal. In this scenario, faults do not constitute flow barriers (i.e., seals) over geologic time, a prediction validated by recent interference tests across the faults.

AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery