Integrated Trap
and Seal Evaluation of Complex Reservoir Systems
Davis, J. Steven1, Francesco
V. Corona2, Peter J. Vrolijk3, Bill R. James4
(1) ExxonMobil Exploration Co, Houston, TX (2) ExxonMobil Development Co,
Houston, TX (3) ExxonMobil Upstream Research Co, Houston, TX (4) ExxonMobil
Upstream Research Co, Austin, TX
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. Traditional one element analyses
(e.g., fault seal analysis) run the risk of forcing improbable solutions.
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. The reservoir
container topology comprises the shapes of the reservoir volumes and their
structural and stratigraphic connections. Barriers to communication within a
reservoir system include internal seals, base seal draped across a structure in
a given reservoir, and faults.
RCA has been successfully applied to
hydrocarbon traps worldwide. An example demonstrates application of RCA to a complex
channel system draped across an intensely faulted anticline. The trap has 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. Thus, the faults do not
constitute flow barriers (i.e., seals) over geologic time, a prediction
validated by recent interference tests across the faults.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California