Multiscale Digital Rock Imaging and Modeling for Measuring the Heterogeneous Carbonate and Conglomerate Permeability at the Laboratory Plug Scale

Abstract

Rock permeability is an essential petrophysical property for evaluating the hydrocarbon exploitation and CO2 geological sequestration. The large-scale rock heterogeneity by single-scale digital rock analysis (DRA) poses a challenge in predicting the permeability of the centimeter-scale core plug for fractured carbonates, vuggy carbonates, and conglomerates. The present study developed two multiscale workflows to upscale the permeability from the millimeter scale to the near centimeter scale. The basic two-step workflow consists of multiscale imaging and multiscale modeling to integrate the Darcy flow in the microporous matrix representative element volume and the Stokes flow in larger-sized pores/vugs/fractures. The basic two-step workflow was then extended to the four-step workflow to speed up the computation and reduce the computer memory. With experimental permeability as the benchmark, this study compared single-scale simulation methods and multiscale workflows to quantify the best permeability analysis method for the three rock types. The basic two-step workflow with binary segmentation is accurate for the fractured carbonate due to fully modeling the preferential flow and the fluid exchange between the fracture and matrix. The extended four-step workflow with ternary segmentation is optimal for the conglomerate to simulate fluid resistances of the gravel and matrix with satisfied computational efficiency. The permeability of some vuggy carbonates can be well evaluated by the single-scale simulation of the matrix flow where the vugs are isolated and cannot facilitate fluid communication. The acceptable agreement between the experimental and simulated permeabilities for 18 core plugs improves the confidence in using the developed DRA to predict the permeability for complex rocks.

Micro‐Continuum Modeling: An Hybrid‐Scale Approach for Solving Coupled Processes in Porous Media

“…They are mature enough to be included in DRP commercial packages such as GeoDict. They can account for the impact of SRP on the estimation of the rock sample absolute permeability (Apourvari & Arns, 2014; Kang et al., 2019; Knackstedt et al., 2006; Singh, 2019; Soulaine et al., 2016; Xu, Guan, et al., 2022). The assessment of the sub‐grid permeability, k , that quantifies the flow resistance of the microstructure that is not visible in the image is key.…”

Experimental Investigation of Injection and Production Cycles for Limestone Reservoirs via Micro-CT: Implications for Underground Gas Storage

“…This meticulous approach allowed for a detailed examination and analysis of the microscopic features and characteristics of the selected samples. In this study, the petrophysical evaluation incorporated the upscaled porosity method [26] and the upscaled permeability method [27]. These methods offer a more comprehensive understanding of the porosity and permeability characteristics of the porous media under investigation.…”

Practical Semianalytical Models for Pressure-Transient Analysis of Carbonate Reservoirs with Complex Fracture and Cave Distributions

“…Fracture-caved reservoirs have great development potential in carbonate reservoirs and are gradually becoming the focus of carbonate reservoir development. − As the demands for crude oil increase, the development of fracture-caved reservoirs is becoming an increasingly important field in energy production. − Fracture-caved reservoirs exhibit high heterogeneity due to the fractures and meter-scale caves located in the different distributions. − The large-scale caves offer ample storage space while fracture zones with higher conductivity enhance the fluid flow efficiency. − The flow behavior will be affected by the location of wells and the distribution of caves in the formation. − The complex wellbore–fracture–cave distributions and flow mechanism characterization are not clear in previous studies. Therefore, there is an urgent need to develop transient models suitable for various fracture-caved distributions.…”