Log-Based Rock Property Evaluation – A New Capability in A Specialized Log Data Management Platform

Abstract

Oil and gas companies are increasingly seeking production from more challenging reservoirs associated with costly geomechanical problems. Knowledge of in-situ rock strength is a fundamental element of geomechanical analysis for the oil and gas industry in estimating such elements as wellbore stability, solids production, hydraulic fracturing, bit selection, cap rock integrity, compaction, and subsidence studies. Specifically, this information is critical for successful drilling of directional, highly deviated, and horizontal wells. In production phase, this provides information to maximize the efficiency of wellbore perforations and hydraulic fracturing, and also assess the requirement for sand control equipment. Log-based rock strength modeling is a technique which enables estimation of in-situ mechanical rock properties from some petrophysical logs. This technique is currently the most popular approach in order to evaluate mechanical rock properties, as laboratory tests are costly and time consuming. The important rock properties which are desired to be determined include; Uniaxial Compressive Strength (UCS), friction angle and cohesion in addition to rock elastic constants (Young's modulus, Poisson's ratio, bulk modulus and shear modulus). This technique has a number of advantages over laboratory measurements of geomechanical properties including (but not limited to): availability of log data, providing continuous property profiles, possibility of modeling weak intervals, low cost, and time effectiveness. In this study, a comprehensive review of currently available empirical equations developed by different authors is provided. In addition, algorithms for all the equations are developed and subsequently coded into a specialized log data management platform designed for petrophysical and Image log Analysis, thus converting it into a powerful tool for rock property estimation for a variety of rock types and specifications.