Journal issues: 2/2008
INVESTIGATION OF WETTABILITY EFFECTS ON CAPILLARY PRESSURE, AND IRREDUCIBLE SATURATION FOR SAUDI CRUDE OILS, USING ROCK CENTRIFUGE
The main task of a petroleum reservoir engineer is to produce oil and gas reservoirs with maximum economic rate and reaching the ultimate recovery. Reservoir evaluation processes need a reservoir description as completely and accurately as possible using a variety of methods from seismic and well testing to logging, cuttings analysis and coring. These methods present the engineer with a valuable and wide range of scales of information to well evaluate the reservoir and control its performance and improve oil recovery. The main goal of core analysis is to reduce uncertainty in reservoir evaluation processes created by the uncertainty degree in the input parameters at the different levels from reserve estimate level to the enhancement of reservoir performance level. In order to reach these targets, the exact determination of certain petrophysical properties are necessary such as rock porosity, relative permeability, water saturation, and capillary pressure at all stages of reservoir life and rock wettability. Predicting reservoir wettability and its effect on fluid distribution and hydrocarbon recovery remains one of the major challenges in reservoir evaluation and engineering. Current laboratory based techniques require the use of rock-fluid systems that are representative of in situ reservoir wettability. Several parameters like relative permeability’s, residual saturations, and capillary depressurization curves change with the wettability state of the reservoir. In addition all these parameters, can greatly impact oil recovery. Thus, there is a need to relate all these parameter to wettability state of the reservoir.
In this study, irreducible oil saturation and capillary pressures using rock centrifuge measurements for Berea Sandstone rock samples and Saudi oils will be tested during drainage and imbibitions cycles by varying each time the wettability of the tested samples by using different Saudi oils (Heavy, Medium, and Light). The capillary pressure for the aged samples will be measured again by the rock centrifuge. Hence, the changes in capillary pressure curve before and after wettability alteration will be obtained. Hence, wettability, capillary pressure, initial fluids saturation, will be correlated for Saudi reservoirs.
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