A laboratory fracture shear cell used for simulation of fracture reactivation
Mohammad Sadegh Asadi A and Vamegh Rasouli ACurtin University of Technology
The APPEA Journal 51(1) 487-498 https://doi.org/10.1071/AJ10032
Published: 2011
Abstract
Fault reactivation is an unfavourable incident during drilling and production that may occur due to changes in situ stresses and reservoir pressure. Only a few studies, in their analyses, have included the effects of fault geometrical properties—these are important parameters controlling fault slippage and damage around it.
In this paper, the significant influence of fracture morphology on the mechanical behaviour of rock fractures was investigated through experimental studies of shearing rock fractures in the lab. The experiments carried out using a fracture shear cell (FSC): the cell that was modified by adding a number of components to an existing true triaxial stress cell (TTSC) and designing a duplex high pressure cylinder that is capable of applying large normal stresses to the sample at a constant rate. A number of artificial blocks made of mortar material were subjected to shear tests using FSC under a wide range of normal stresses and at different shearing directions. The outputs of uniaxial compressive strength and fracture shear tests in the lab were used to plot the failure envelope of the fractured rock mass and discuss the failure mechanism through shearing. Accordingly, a calibrated, numerical discrete element method (DEM) was used to simulate the shear behaviour of fractures previously tested in the lab.
The results of lab tests and DEM simulations will be presented and different failure mechanisms that are expected during shearing will be explained. The results show the significant influence of surface roughness on shear strength and extent of damage zone along the fracture. It was found that the shearing response of fractures depends on the magnitude of normal stress, which indicates the importance of having a good knowledge of in-situ stresses when modelling fault reactivation and damage near the fault zones. The results of lab experiments and numerical simulations were compared and good agreements were observed.
Mohammad Sadegh Asadi is a PhD student of petroleum engineering at Curtin University of Technology. After completing his master of science in mining, rock mechanics engineering in 2006 from the science and research branch of Azad University, Tehran, Sadegh started his carrier as a geomechanics engineer at Bistun Rock Mechanics Service Co. (BRMS). He was involved with a number of consulting projects such as numerical modelling and stability analysis in Iran till 2007. Sadegh started his PhD in 2008 focusing on mechanical behaviour of rock fractures based on DEM numerical simulations and laboratorial experiments. He won the SPE second prize in postgraduate student contest held in conjunction with the Asia Pacific Oil and Gas Conference and Exhibition (2009) in Jakarta. He is also involved in teaching and tutoring in the department of petroleum engineering at Curtin University since 2008. Member: Curtin Petroleum Geomechanics Group (CPGG). M.asadi@postgrad.curtin.edu.au |
Vamegh Rasouli is an associate professor at the department of petroleum engineering. He is a Chartered Professional Engineer (CPEng) and is a registered engineer with the National Professional Engineers Register (NPER) of Australia. After completing his PhD in 2002 from Imperial College, London, Vamegh took up the position of assistant professor in the department of petroleum engineering at Amirkabir University of Technology (Iran). In 2006 Vamegh joined the department of petroleum engineering at Curtin University to support the delivery of the department’s master of petroleum well engineering—and to carry out research in his specialist area of wellbore stability, sanding, hydraulic fracturing, etctera. He established the Curtin Petroleum Geomechanics Group (CPGG); it has completed number of successful research and consulting projects. He now supervises six PhD students and numerous master students. Vamegh has also been a consulting engineer on various geomechanics-related projects with Schlumberger’s Data and Consulting Services (DCS) in Perth. v.rasouli@curtin.edu.au |
