Permeability model of fractured rock with consideration of elastic‐plastic deformation

Abstract

The evolution of rock permeability has been studied exhaustively, and a broad array of permeability models has been proposed. These models are normally derived under the assumption of elastic deformation when subjected to external stress. Under this assumption, these models define fracture permeability as a function of either gas pressure or effective stress. However, experimental observations indicate that rock fracture may experience unrecoverable deformation during the loading process. The goal of this study is to resolve this contradiction. In this study, derivation of fracture permeability correlation for elastoplastic contact of rough surfaces is presented. The proposed method for describing permeability evolution not only considers the topography of fracture surfaces but also and, more importantly, integrates the plastic deformation of rock fracture. Subsequently, the deformation and permeability change of shale sample containing a single rough‐walled fracture is experimentally investigated. The results show that the permeabilities obtained during the loading process are larger than the permeabilities obtained during the unloading process under the same stress conditions and that the fracture deformation cannot be fully recovered during the unloading process. At last, the proposed permeability model is applied to the experimental results and it is shown that the proposed model can predict the laboratory permeability data.

A method for simultaneously determining axial permeability and transverse permeability of tight reservoir cores by canister degassing test

“…Figure 7 shows the schematic sketch of the PPD technique. [28][29][30][31] The sample is first in equilibrium and then opens the valve between the upstream chamber and the sample as well as the valve between the sample and the downstream chamber to let fluid flowing from the upstream chamber to the downstream chamber through the sample driven by the pressure difference. The axial permeability can then be estimated from the pressure pulse decay curve (the upstreamdownstream pressure difference with time) using mathematical solutions of the related flow problem.…”

“…To compare with CDT results, we performed three groups using the PPD method with the core samples. Figure shows the schematic sketch of the PPD technique . The sample is first in equilibrium and then opens the valve between the upstream chamber and the sample as well as the valve between the sample and the downstream chamber to let fluid flowing from the upstream chamber to the downstream chamber through the sample driven by the pressure difference.…”

“…The schematic sketch of the pressure pulse decay technique . The sample is first in equilibrium and then opens the valve between the upstream chamber and the sample to let fluid flowing from the upstream chamber to the downstream chamber through the sample driven by the pressure difference…”

“…Experimental permeabilities obtained from CDT tests (A) for the vertical sample. Experimental permeabilities obtained from CDT tests (B) for the horizontal sampleF I G U R E 7The schematic sketch of the pressure pulse decay technique [28][29][30][31]. The sample is first in equilibrium and then opens the valve between the upstream chamber and the sample to let fluid flowing from the upstream chamber to the downstream chamber through the sample driven by the pressure difference…”

Effect of thermal cycling and hydro‐thermal cycling on physical and mechanical properties of sandstone

“…In order to improve the heat production, reservoir stimulation must be used to create a large number of interconnected fractures because of its ultralow permeability (0.001-0.1 md). 1,2 To stimulate the reservoir, researchers have proposed several methods, including traditional rock fracturing, [3][4][5][6][7][8][9][10][11][12][13] hydraulic fracturing, 14,15 thermal fracturing, 16,17 shear stimulation, 11 and multilateral wells. 1 And then, the mechanical characteristics of HDR under thermo-hydro-mechanical (THM) effect were also researched.…”