Determination of the poroelasticity of shale
- PDF / 1,272,941 Bytes
- 14 Pages / 595.276 x 790.866 pts Page_size
- 14 Downloads / 171 Views
(0123456789().,-volV)(0123456789().,-volV)
RESEARCH PAPER
Determination of the poroelasticity of shale Shuqi Ma1,2 • Marte Gutierrez2 Received: 3 April 2019 / Accepted: 18 August 2020 Ó Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Shales play important roles in various civil, energy and environmental engineering applications. Shales are categorized as poroelastic materials due to their tight and very stiff structure, and reliable poroelastic properties are required when dealing with shales. This paper presents simple procedures to determine the poroelastic properties of rocks using oedometer and triaxial consolidation tests. The procedures, which avoid the difficulty to perform determination of the unjacketed bulk modulus of the rock minerals, are demonstrated on a North Sea shale. The experimentally obtained Biot coefficient a and the drained bulk modulus K of the shale range from 0.95 to 0.99, and from 0.17 to 2.00 GPa, respectively. The Biot coefficient a and the drained bulk modulus K values determined from the oedometer and triaxial tests are compared and show good agreement and consistency between the two test procedures. The Skempton’s coefficient B-value of the triaxial samples was also experimentally measured prior to the triaxial consolidation tests. The theoretically predicted B-value varies from 0.81 to 0.96 which is, on the average, only about 10% higher than the experimentally obtained B-value which range from 0.80 to 0.85. Keywords Biot coefficient Biot’s theory Bulk modulus Oedometer test Poroelasticity Shale Skempton’s B coefficient Triaxial consolidation test
1 Introduction Shales are important rock materials which have been encountered in various civil, energy and environmental engineering applications. They constitute the most common cap rock for hydrocarbon reservoirs and potential CO2 geological storage reservoirs [14, 22]. They are used as geological barriers for the storage of nuclear waste because of their low hydraulic permeability [28, 54]. Shale gas and oil are also typical low-permeability unconventional energy resources [25, 59]. Despite very low permeability, shales in situ often contain high fluid content and can be fully saturated. The presence of fluid in the pores of shales affect their elastic properties. Due to their tight structure
& Shuqi Ma [email protected] 1
Key Laboratory of Transportation Tunnel Engineering, Ministry of Education, Southwest Jiaotong University, Chengdu 610031, China
2
Civil and Environmental Engineering, Colorado School of Mines, Golden, CO, USA
and often very low porosity, the stiffness of a shale matrix can become comparable to the stiffness of its constituent solid mineral grains [7, 28]. Thus, the deformation of fluid saturated shales must also account for deformability of the solid grains due to pore pressure changes [7, 28]. The earliest theory to approach the influence of pore fluid on the deformation of geomaterials was originally developed by Terzaghi [52, 53] for the one-dimensional consolidation
Data Loading...
