Application of Digital Core Analysis (DCA) and Pore Network Modeling (PNM) Based on 3D Micro-CT Images for an EOR Project in a Mature Oil Field in East Malaysia

Abstract

For the optimization of an EOR project in a major mature oil field in East Malaysia, an extensive Routine and Special Core Analysis(RCA/SCAL) program has been performed on unconsolidated clastic reservoir rocks from a recently cored development well. Due to limited availability of suitable size of homogeneous core plugs for "conventional " flooding and lab experiments, a complementary analysis of petrophysical and mineralogical properties was performed based on the acquisition of high resolution 3D Micro-CT(MCT) images, SEM-EDX and application of Pore Network Modeling(PNM) techniques. Imaging enables to identify subregions of plugs damaged during coring and retrieval that remain in a good condition; from these region reliable static reservoir parameters are derived. Generation of "static" parameters and a comparison with routine RCA/SCAL results, PNM simulations of primary drainage and imbibition, resulting pc, Kr curves and the residual oil saturations(ROS) were undertaken. Mapping of wettability highlights the impact of clay and its role in characterizing the multiphase flow properties. Investigations were performed to visualize effects of wettability changes due to cleaning, restoration and flushing of the cores by acquisition of MCTs at "native"and "restored" state conditions; variation of the ROS due to wettability changes were observed. The impact of wettability is directly quantified via PNM sensitivity studies. In view of the planned iWAG process to increase the recovery, water injectivity tests and formation damage studies in the lab were compared. Potential causes for formation damage were monitored and visualized by comparing registrations of 3D MCTs at different stages of the flooding and formation damage experiments. The application of 3D MCTs and PNM proved to be a unique new option to visualize and understand the sensitivities during the handling of cores and to quantify potential effects of the experimental procedures on the multiphase flow in conventional flooding experiments. Thus, the Digital Core Analysis and PNM technology is a complementary alternative for the optimized investigation of EOR, especially in cases where the application of conventional laboratory investigations are limited due to the status of the core material and resulting potential experimental artefacts.