Hydrocarbon production increases effective vertical stress in a poroelastic media, while injections reverse the depletion processes, resulting in decreasing vertical effective stress; this procedure is proper before the rock reaches its elastic limits. This study aims to characterize the Permeability and porosity of sandstone samples subjected to a series of loading and unloading.
Porosity and Permeability have been initially mapped for a specific area in the number of core samples through three-dimensional (3D) X-ray computed tomography (CT) imaging acquired at multiple scales for digital rock characterization. Permeability and porosity for the same areas have been mapped using high-resolution micro-CT tomograms.
Digital rock modeling confirms porosity and permeability attenuation due to enhancement of the rock compaction and damage of the original rock structure. The cyclical experiments destroyed the pore network of the studied sandstones, thinning and closing the pore throats as illustrated by the high-resolution tomograms that led to permeability reduction. The results showed permeability variations depends on the initial Permeability, facies type, pore structure and geometry, cementation, and mechanical rock properties. Generally, porosity and Permeability showed slight changes in Permeability, while the model with large pore structures and poor cementation showed a high reduction in effective porosity and Permeability.
This innovative method played an essential role in planning production and injection strategies, leading to safe, effective, and economical operational scenarios.
Characterizing the petrophysical properties of the reservoir formation using multiple cycles of loading and unloading is essential for understanding the elastic and plastic rock behavior to predict reservoir quality during injection and production operations and provide a set of guidelines for safe operations.