Effect of Steam Parameters and Injection Schedule on Cap-rock Integrity during CSS -Case Study, FNE, Sudan

Abstract

Production of hydrocarbons from geological reservoirs, and injection of fluids into geological strata are accompanied with stress changes in the reservoir and in the cap rock. If the stress changes are large enough, they may reactivate faults or pre-existing natural fractures, or induce new fractures in the reservoir and/or the cap rock. Fractures in the cap rock may threaten the cap rock integrity, while fractures within the reservoir may increase its injectivity. This work is studied the cap rock integrity and effect of the different CSS injection parameters on cap rock failure through FNE field in which steam flooding and CSS are used as a major EOR method in the field. Using (CMG) Computer Modeling Group and geo-mechanical concepts with iterative two-direction coupling for reservoir rock and fluids properties, many scenarios were conducted to study the effect of steam injection schedule in the rock deformation and cap rock interiority. Anderson's method were used to estimate the mechanical properties. Injection rate of 500, 750 and, 1000 m3/day were studied under constant steam volume of 144 m3, and steam temperature of 255oC with steam quality of 0.8 and 0.85. Elasto plastic Mohr–Coulomb was selected as the rock type model and the deformation observed from the normal effective stress which decreases with the of injection rate. The yield state was used as an indicator for fracture initiation as used in CMG. An injection rate of 750 m3/day can insure cap rock integrity while 1000 and 1500 m3/day will perform fracture in the caprock at different operations days; also, the time that the fracture can be initiated in early when compared to that of 1000 m3/day. water production increases with the injection rate as the aquifer will fractured at early time when the he injection rate is high.