An experimental platform for triaxial high-pressure/high-temperature testing of rocks using computed tomography

Abstract

A conventional high-pressure/high-temperature experimental apparatus for combined geomechanical and flow-through testing of rocks is not X-ray compatible. Additionally, current X-ray transparent systems for computed tomography (CT) of cm-sized samples are limited to design temperatures below 180 °C. We describe a novel, high-temperature (>400 °C), high-pressure (>2000 psi/>13.8 MPa confining, >10 000 psi/>68.9 MPa vertical load) triaxial core holder suitable for X-ray CT scanning. The new triaxial system permits time-lapse imaging to capture the role of effective stress on fluid distribution and porous medium mechanics. System capabilities are demonstrated using ultimate compressive strength (UCS) tests of Castlegate sandstone. In this case, flooding the porous medium with a radio-opaque gas such as krypton before and after the UCS test improves the discrimination of rock features such as fractures. The results of high-temperature tests are also presented. A Uintah Basin sample of immature oil shale is heated from room temperature to 459 °C under uniaxial compression. The sample contains kerogen that pyrolyzes as temperature rises, releasing hydrocarbons. Imaging reveals the formation of stress bands as well as the evolution and connectivity of the fracture network within the sample as a function of time.

Application of Digital Volume Correlation to X-ray Computed Tomography Images of Shale

“…The apparatus permits high-pressure and high-temperature (HPHT) triaxial conditions within an X-ray CT scanner. The system is capable of temperatures greater than 400 °C, confining pressures in excess of 13.8 MPa, and an axial load of 68.9 MPa axial load . Detailed description of components is found in the study of Kim et al…”

Mjölnir: a miniature triaxial rock deformation apparatus for 4D synchrotron X-ray microtomography

“…Mjö lnir differs from previously published cell designs primarily through simplicity of design and construction. Although unable to approach the upper temperature limits of the cells presented in the work by Voltolini et al (2019) and Glatz et al (2018), Mjö lnir exceeds their capability in confining pressure and axial load. The HADES cell presented in the work by Renard et al (2016) can operate under higher P and T conditions than Mjö lnir in its present format, yet has the limitation that its use is currently tied to a single, high-energy synchrotron beamline.…”

“…Recently the opportunity to use X-ray microtomography to image deformation processes in situ has been facilitated by the development of miniaturized rock deformation cells that operate on laboratory micro-computed tomography (mCT) instruments or at synchrotron beamlines (e.g. Viggiani et al, 2004;Lenoir et al, 2007;Tisato et al, 2014;Renard et al, 2016;Glatz et al, 2018;Voltolini et al, 2019). In this contribution, we outline the design, construction and deployment of a miniature rock-deformation press suitable for synchrotron X-ray microtomography studies.…”

Mesoscale Modelling of Concretes Subjected to Triaxial Loadings: Mechanical Properties and Fracture Behaviour

“…Javanmardi [8] calculated the strength relationship between the lateral confining stress and uniaxial stress by summarising the experimental data of extensive and systematic multiaxial tests and compared these with the proposed relationships by other researchers [9][10][11][12][13][14][15][16]. Glatz et al developed a novel, high-temperature and high-pressure triaxial system that is suitable for X-ray computed tomography (CT) scanning to capture the role of effective stress on the fluid distribution of rocks under high triaxial pressures [17]. Watanabe et al designed a new true triaxial cell to study the initiation and propagation of microfractures in granite under confining pressures [18].…”