Mudstone P-wave anisotropy measurements with non-contacting lasers under confining pressure

Abstract

The increased interest in mudstone rocks as oil and gas reservoirs requires new ways to quantify the physical properties of these rocks from indirect geophysical measurements. We present a new methodology to measure dense waveforms to estimate P-wave anisotropy with non-contacting lasers under confining pressures. Our goal is to correlate the elastic anisotropy to rock microstructure observations. We select samples with a range of organic material, with one sample being fractured. Although textural anisotropy is observed in most samples, this does not always result in an elastic wave anisotropy. However, if organic content is high, large velocity anisotropy is measured. As we increase pressure, mostly the slow P-wave velocity is affected as laminae and fractures close, resulting in a decrease in Thomsen parameter ε. The unique capacity of this system is outlined and correlations between textural observations and elastic parameters presented.