Yuqian Li¹, Joel S. Watkins¹, Carrie L. Decker¹
(1) Texas A&M University, College Station, TX

Abstract: Simulation of leaking compartments over production time scales

Hydrocarbon movement across leaky compartment boundaries is indicated by production data from Ship Shoal 274/293, Gulf of Mexico. Field data indicate that small-displacement faults that juxtapose sand on sand can act as barriers prior to production and as baffles over production time scales. Baffles in turn affect production rates and can lead to erroneous reserve estimates if not recognized. To understand this process, we modeled the effect of fault properties and well pressure on cross-fault compartment communication during production, using finite-difference computer simulation software.

Our models consider depletion-driven production of a compartment separated from an adjacent compartment or series of compartments by a narrow fault zone. In our models, cross-fault flow occurs when the pressure drop across the fault exceeds the capillary pressure difference between the fault and the reservoir. If the pressure drop at the well (equal to the well flow pressure - hydrostatic pressure) is less than the capillary pressure difference between fault and reservoir, no cross-fault communication occurs. Increasing the pressure difference at the well decreases the amount of time before cross-fault flow is initiated and increases the overall production from both compartments. Low permeability faults with high displacement pressures can leak if the pressure drop at the well is sufficiently high. Compartment size and shape affect total production, production rates, and time required to initiate production from adjacent compartments. Hydrocarbon flow across multiple faults in series can occur during production, but more faults result in diminished production from all compartments.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana