Rock Physics Templates from Deviated Wells using Anisotropy Parameters

Abstract

Rock physics templates (RPTs) are locally constrained charts that provide information regarding lithology and fluid saturation encountered at an area of interest. Normally anisotropy is neglected and isotropy is prevalent when obtaining RPTs. In this study, the role of anisotropy is considered. In addition, the effect of well deviation and its effect on rock physics templates have been treated.

The main aim of this study is to improve the understanding and the information gained from rock physics templates of heterogeneous reservoir where a deviated well is encountered. The role of anisotropy is treated by considering the stiffness tensor for a VTI-media, where Thomsen parameters ε, δ & γ accounts for the anisotropic effect on the velocity. The role of the deviated well is treated by considering the wave propagation in group angle and velocity domain. The method has further been tested for model parameters of a real-case interbedded sand-shale layered VTI media. The result ofthis testing has been represented as rock physics derived RPTs.

Further, AVA-analysis has been carried out on interbedded sand and shale layered reservoir in the North Sea, from which the model parameter for the rock physics technique has been acquired. Rockphysics templates based on well logs has also been obtained, and these RPTs has been combined with the rock physics derived RPTs. The result of combining these RPTs has concluded in improvingthe understanding of anisotropy effected RPTs.