Quantitative Evaluation of Microporosity in Arab D Carbonates of Saudi Arabia: Impact on Reservoir Quality

Abstract

Microporosity is pervasive in carbonate reservoirs throughout the Middle East and Saudi Arabia. Key decisions such as reservoir completion schemes, reservoir management strategies and enhanced oil recovery tactics require a rigorous understanding of the contribution of micropores to overall reservoir quality. Here, we investigate the quantitative relationships between porosity-permeability and connectivity in the microporosity of Arab D carbonates. Digital analysis of micropore geometry can be achieved by reconstructing the 3D pore architecture from 2D thin section images. In this study, a series of pore architecture models (PAMs) (Wu et al., 2006) was generated using high resolution (0.08 microns/pixel) thin section imagery acquired using confocal laser scanning fluorescence microscopy (CLSFM) to highlight the micropores. Once the micropore architecture models were reconstructed, the topological pore networks were extracted (Jiang et al., 2007; Jiang et al., 2012). The extracted networks consist of nodes (pore bodies) and bonds (pore throats) which are then used to calculate network statistics such as porosity, permeability, pore size distributions, and connectivity. Preliminary results support a distinct porosity/permeability relationship for the Arab D micropores that is consistent with the Kozeny-Carman Model. Specific Euler numbers (representing topological connectivity) indicate that micropores are connected and there may be storage capacity. Furthermore, there appears to be a global hydraulic element (GHE) class for microporosity in the Arab D, although initial results suggest that the contribution to reservoir flow is limited (with permeability below 2 mD). These results may have significant implications for reservoir quality, resource assessment and field development optimization. Based upon computed pore size distributions and published information on fluid properties a hypothetical oil column of 250 meter would be sufficient to overcome capillary entry pressures in micropores.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016