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Rock Compressive Strength: A Correlation from Formation Evaluation Data for the Niger Delta

Abstract

The purpose of this paper is to study the strength of rocks by determining their Unconfined Compressive Strength (UCS), correlate the determined strength to physical properties of rocks that can be measured from formation evaluation data and derive an equation that can be used to derive rock strength from formation evaluation measurements. The scope of this work is limited to the Niger delta basin from which core samples were taken. The method used for this research was to collect data of existing core samples at different depths and in various fields in the Niger Delta, then determine the strength of each sample by unconfined compressive tests. The derived strength was then analyzed with corresponding formation evaluation data utilizing regression analysis. Then, comparisons were drawn between the correlations derived and other existing correlations in the industry to check whether any of the existing correlations fits the Niger Delta region. The result is a model that takes formation evaluation data (Slowness, Young's Modulus and Poisson's ratio) as input in order to provide rock compressive strength for the Niger-Delta region. It was also observed that correlations built for other regions of the world do not yield accurate results when used for the Niger Delta region due to factors such as formation characteristics type of regression method, various sample collection conditions and so on.