A digital rock physics approach to effective and total porosity for complex carbonates: pore-typing and applications to electrical conductivity

• Published in: E3S Web of Conferences Vol. 89; p. 5002
• Main Authors: Arns, Christoph H., Jiang, Han, Dai, Hongyi, Shikhov, Igor, Sayedakram, Nawaf, Arns, Ji-Youn
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Les Ulis EDP Sciences 01.01.2019
• Subjects: Carbonate rocks; Carbonates; Cementation; Computed tomography; Computer simulation; Core analysis; Electrical conductivity; Electrical properties; Electrical resistivity; Heterogeneity; Limestone; Porosity; Saturation
• DOI: 10.1051/e3sconf/20198905002
• ISSN: 2267-1242; 2555-0403

Recent advances in micro-CT techniques allow imaging heterogeneous carbonates at multiple scales and including voxel-wise registration of images at different resolution or in different saturation states. This enables characterising such carbonates at the pore-scale targeting the optimizing of hydrocarbon recovery in the face of structural heterogeneity, resulting in complex spatial fluid distributions. Here we determine effective and total porosity for different pore-types in a complex carbonate and apply this knowledge to improve our understanding of electrical properties by integrating experiment and simulation in a consistent manner via integrated core analysis. We consider Indiana Limestone as a surrogate for complex carbonate rock and type porosity in terms of macro- and micro-porosity using micro-CT images recorded at different resolution. Effective and total porosity fields are derived and partitioned into regions of macro-porosity, micro-porosity belonging to oolithes, and micro-porosity excluding oolithes’ rims. In a second step we use the partitioning of the micro-porosity to model the electrical conductivity of the limestone, matching experimental measurements by finding appropriate cementation exponents for the two different micro-porosity regions. We compare these calculations with calculations using a single cementation exponent for the full micro-porosity range. The comparison is extended to resistivity index at partial saturation, further testing the assignment of Archie parameters, providing insights into the regional connectivity of the different pore types.