Title: Laboratory scale characterisation of brittleness and permeability enhancement due to rock failure

Authors: Jihoon Wang; Peter P. Valkó; Ahmad Ghassemi

Addresses: Department of Petroleum and Natural Gas Engineering, New Mexico Tech University, 801 Leroy Place, Socorro, NM 87801, USA ' Department of Petroleum Engineering, Texas A&M University, 3116 TAMU, College Station, TX 77843-3116, USA ' Mewbourne School of Petroleum and Geological Engineering, Norman, OK 73019-1003, USA

Abstract: In this study, the multi-stage triaxial compression testing method is adopted to obtain geomechanical parameters without heterogeneity effect. Using the geomechanical characterisation we calculate various brittleness indices previously suggested in the literature. Before the triaxial test and after the ultimate rock failure, we also measure the permeability enhancement ratio caused by rock failure with characteristic time obtained from pulse decay permeameter. Analysing the relationship between the various brittleness indices and the permeability enhancement, we assess the ability of the former to predict the latter. The results show that no unique brittleness index can completely explain the permeability enhancement, but those indices perform better which contain information on post-peak behaviour in direct or indirect manner. We conclude that at least three aspects of the failure behaviour are important and hence at least two indices are required to characterise the potential of permeability enhancement. [Received: July 1, 2017; Accepted: August 17, 2017]

Keywords: brittleness index; permeability enhancement; pulse decay permeameter; characteristic time; multistage triaxial test.

DOI: 10.1504/IJOGCT.2019.102278

International Journal of Oil, Gas and Coal Technology, 2019 Vol.22 No.1, pp.64 - 91

Received: 01 Jul 2017
Accepted: 17 Aug 2017
Published online: 16 Sep 2019 *

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