SCAL for a Giant Carbonate Reservoir: A Critical Step Towards Identifying EOR Targets

Abstract

Abstract Relative permeability, residual oil saturation and capillary pressure curves are key inputs to understand and predict reservoir behavior in all phases of development and define the target for enhanced oil recovery (EOR). Experimental techniques to measure residual oil saturation (Sor), relative permeability (Kr) and capillary pressure (Pc) curves are well established. However, we frequently encounter quality compromised data due to challenges in experimental procedures, insufficient understanding of experimental techniques, and poor quality of raw data. As a result, this could lead to compromised development plan and poorly defined target for EOR. The objective of this paper is to present a comprehensive laboratory assessment using different experimental techniques, quality assessment/control (QA/QC) of raw experimental data and numerical interpretation of qualified laboratory tests to evaluate and obtain representative residual oil saturation and relative permeability curves for a Giant carbonate reservoir. The work also compares data obtained using composite and single core samples and highlights the challenges to obtain quality SCAL data using composite core steady state experiments. Conventional and special core analysis program is conducted using different rock types with variable petrophysical properties. The SCAL program includes steady state coreflood with X-Ray monitoring, porous plate experiments (PCRI) and ultra-fast centrifuge both single and multi-speed to measure residual oil saturation, relative permeability (Kr) and capillary pressure (Pc) curves. Steady-State coreflooding and PCRI experiments are performed at reservoir conditions, while centrifuge runs are done at 80°C. The Steady state experiments are executed on both single plug and composite core samples. Numerical simulation is used to reconcile the various SCAL datasets and derive a consistent set of saturation functions. The main conclusions of the study are: 1) Qualified advanced core analysis experiments have successfully revealed comparable Sor and Kr curves from the different techniques, 2) Initial water saturation is independent of core permeability and found less than 15%, 3) Residual oil saturation is found independent of the sample’s permeability and consistently less than or equal to 15%, 4) Most of composite coreflood tests are disqualified as the data is strongly dominated by capillary end-effect and core heterogeneity, while single plug floods have better quantification of Sor and Kr curves