Abstract
Twenty-nine core plug samples of a wide range of Uniaxtial Compressive Strength (UCS) values were investigated using a suite of techniques including visual inspection at meso-scale on hand specimens and thin sections, microscopic examination, Scanning Electron Microscopic (SEM) analysis, laser particle analysis and X-ray Diffraction analysis to characterize their compositions, texture and sedimentary properties. An intimate intrinsic link is noticed between sedimentary features observed at meso-scale and that at the micro-scale, both of which can be directly correlated to rock strength. It has been demonstrated that one can empirically predict the rock strength (UCS range) of rocks from an inspection of core plug samples. A Rock Property Index parameter which combines a number of sedimentary parameters is found to be useful in qualifying or ranking the rock strength (UCS) of the samples investigated. A set of criteria of sedimentary characterization is proposed for empirically estimating the rock strength of core samples including the lithological compositions, heterogeneities, cementation, quartz and clay contents, grain contact nature, grain size distribution and visual porosity. This method may be applied to describe cutting samples at rig-site to provide timely information of the strength of the formation rocks while drilling.
