A laboratory measurement technique for axial and radial resistivity at ambient or reservoir stress state conditions

A laboratory technique was developed for measuring directional resistivity of a right cylindrical sample at ambient or reservoir stress state conditions. A simulation study was conducted to determine the geometric factor required in converting sample radial resistance to resistivity and the method validated using finite-element numerical simulation. The technique was found useful in investigating resistivity anisotropy and the effect of different stress states on the directional resistivity of small scale cylindrical samples and applied to the measurement of axial and radial resistivities at elevated hydrostatic stress states and triaxial stress state to failure. The resistivity was found to increase with hydrostatic stress increase but then decrease when the axial stress exceeded the confining stress and sharply decrease at failure. Similarly, a decrease in porosity was observed with increasing hydrostatic stress then a sharp increase found at failure. ► A test was developed to determine directional resistivity at ambient or stress state conditions. ► The conversion of radial resistance to resistivity was verified using finite element simulation. ► Resistivity stress sensitivity is governed by the stress state of the sample.