Impacts of Stress, Natural and Induced Fractures on Mechanical Properties of Organic-Rich Shales

Abstract

Summary URTeC 1619158 Mechanical properties play a critical role for optimizing the production from organic-rich shale reservoirs since such reservoirs have extremely low permeability. In situ stress conditions, intrinsic anisotropy due to layering, anisotropy due to fractures, mineral composition, porosity and maturity are among the key parameters affecting the mechanical properties. In this paper, we present experimental results on how Young’s modulus, Poisson’s ratio, and compressional velocity change with overburden and horizontal stresses for core samples from the oil window of the Eagle Ford shale, Green River immature oil shale and outcrop Mancos shale. These shales have distinct features that are discussed in detail and the intrinsic anisotropy of the shales due to layering is presented. Moreover, challenges in obtaining preserved shale core samples representative of the intact shale formation for the laboratory measurements and associated uncertainties in the laboratory measurements including the effect of natural and coring induced fractures parallel to bedding along with the sample size on the mechanical properties will be discussed.