Digital Core Analysis and Pore-Network Modeling in a Mature-Field Project

Abstract

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 24772, ’Application of Digital Core Analysis and Pore-Network Modeling on the Basis of 3D Micro-CT Images for an Enhanced-Oil-Recovery Project in a Mature Oil Field in East Malaysia,’ by W. Nur Safawati, Bt. W.M. Zainudin, Zahidah M. Zain, and Lutz Riepe, Petronas, prepared for the 2014 Offshore Technology Conference Asia, Kuala Lumpur, 25-28 March. The paper has not been peer reviewed. Reproduced by permission. For the planning of an enhanced-oil- recovery (EOR) project in a major mature oil field in east Malaysia, an extensive routine-core-analysis (RCA) and special-core-analysis (SCAL) program has been performed on unconsolidated clastic reservoir rocks. In view of the limited availability of homogeneous core plugs of suitable size for coreflooding experiments and for “conventional” SCAL laboratory investigations, a complementary analysis of petrophysical properties was performed on the basis of the acquisition of high-resolution 3D microcomputed-tomography (MCT) images. Introduction As part of an extensive core study for this field, the “conventional” core-analysis program was complemented by acquiring 3D images and applying digital-core-analysis (DCA) and pore-network- modeling (PNM) methods at different scales with the following main objectives: Visualize the status and monitor potential changes of pore morphology, fluid distributions, and wettability during the handling and execution of laboratory experiments on unconsolidated-friable-rock samples. Evaluate and model the impact of sample heterogeneity and wettability changes on petrophysical properties. Provide petrophysical properties for individual distinct rock types at pore scale for heterogeneous or irregularly shaped samples that are not suitable or available for RCA/SCAL and flooding experiments. Scale up drainage and imbibition predictions of subplugs from heterolithic/laminated plugs to full-plug scale and, potentially, further to reservoir scale. However, because of the lack of preserved core material from earlier wells, and the relatively poor recovery of new conventional cores from recent infill wells in this field, alternative data-acquisition options were investigated in this pilot test on the basis of the significant improvements in, and encouraging results from, DCA and PNM technologies in recent years. Procedures Sample Selection. Approximately 22 m of core was recovered from the shallower reservoir sections of two wells (three cores from Well A from a depth interval between 700 and 800 m and three cores from Well B from a depth interval between 1100 and 1300 m), but only 8 m was suitable for plugging. The low-resolution medical computed-tomography images from the whole core indicated a high extent of rubble and broken and highly fractured unconsolidated sections.