A Method for Reservoir Property Clustering and Analysis of Elastic Modulus and Strength Parameters Calculated Using Lithology Column and Porosity from Logs and Core Data
Subject Areas : زمین شناسی نفت
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Keywords: Reservoir Grouping, Multi-Resolution Graph-Based Clustering, Elasticity and Strength Parameters,
Abstract :
Determining rock types and calculating the elastic and strength parameters of formations are among the most fundamental and complex petrophysical–geomechanical parameters in hydrocarbon reservoirs. Their accurate calculation forms the basis for many petroleum engineering and reservoir geomechanics studies. To this end, in the first stage of the present research, the optimal number of electrofacies was obtained for the studied well using a multi-partition clustering method based on the MRGC[1] graph, derived from a combination of geological data and both conventional and synthetic logs, including VDL[2] and NDS[3]. The proposed algorithm incorporates lithology effects and porosity types into calculations for accurate reservoir grouping. At this stage, five optimal electrofacies classes and groups were identified for the studied well using the MRGC-based clustering method. In the second stage, considering that calculating and estimating elastic and rock strength coefficients is essential in geomechanical studies – and since core data is not available throughout the entire well – calculations were made for Young’s modulus, Poisson’s ratio, bulk modulus, shear modulus, and uniaxial compressive strength using dipole sonic imaging (DSI) logs. The comparison of calculated elastic moduli and strength parameters with variations in the lithology column and porosity from petrophysical evaluation and core data confirms that as core and log porosity increase, the values of elastic moduli and strength parameters decrease. Hence, porosity has an inverse relationship with elastic moduli and strength parameters. In the present study, the correlation coefficient between the calculated bulk modulus and porosity was found to be (R2 = 0.82), shear modulus (R2 = 0.73), Young’s modulus (R2 = 0.77), Poisson’s ratio (R2 = 0.049), uniaxial compressive strength (R2 = 0.84), and uniaxial tensile strength (R2 = 0.65).
[1] Multi-resolution graph-based clustering
[2] Velocity Deviation Log
[3] Neutron- Density Separation