Date of Graduation
Statler College of Engineering and Mineral Resources
Petroleum and Natural Gas Engineering
Permeability is one of the most time-consuming rock petro-physical properties to measure, especially in the case of shales and tight rocks with Micro-Darcy ranges. Several unsteady state methods like GRI, Pressure Pulse Decay (PPD) have been applied to measure permeability but unfortunately results are not accurate due to the limitations to in situ stress conditions, repeatability and reproducibility issues. To overcome this limitations a system under steady state condition and with equal confining and axial pressure has been developed, obtaining remarkable permeability measurements. This system was designed and assembled by Zamirian et al 2015 referred to as Precision Petrophysical Analysis Laboratory (PPAL). Shale reservoirs are heterogeneous, anisotropic and are subject to in-situ stress state. In-situ stresses are divided into overburden pressures (Î´_v), maximum (Î´_H) and minimum horizontal stresses (Î´_h) which are usually different in magnitude. Stress dependent permeability plays an important role since it contributes to the gas transport throughout the matrix, natural fractures and hydraulic fractures. A test has been done using the PPAL system, but still has stress limitations since the axial and confining stress applied to the core sample are equal, unlike the in situ stress conditions. Because of that, this research introduces the methodology of using a Tri-axial core holder in the PPAL system (T-PPAL) in order to understand how stress anisotropy affects permeability. Two cases will be studied, using T-PPAL, the first case is to measure vertical permeability (K_v), (when the core plug is vertically drilled) under in situ-stress state, where axial stress (Î´_v) is larger than confining stress (Î´_h). The second case is to measure horizontal permeability (K_h), (when the core plug is horizontally drilled) at different horizontal stress anisotropies defined as the ratio of maximum over minimum horizontal stress (Î´_H/Î´_h). The tri-axial test designed for PPAL will provide a better understanding of how stress anisotropy affects shale rock permeability.
Nasr, Charbel, "Study of stress anisotropy on shale rock permeability" (2017). Graduate Theses, Dissertations, and Problem Reports. 4011.