Practical Methods Employed in Determining Permeability Anisotropy for Optimization of a Planned Waterflood of the Elfisk Field

Abstract

Abstract This paper presents the various techniques and measurements undertaken to determine both the magnitude and direction of horizontal stress anisotropy present in the Eldfisk Field in preparation for a planned waterflood. Results from field measurements of in situ stress obtained from a vertical pilot hole designed specifically for gathering stress data reveal a highly an isotropic state of stress, with a maximum horizontal in situ stress oriented approximately 47 from grid North. These measurements include stress orientations measured from an elastic strain recovery (ASR) tests on core, oriented acoustic log data and 2 micro-frac tests with pre- and post fracture imaging log runs. Micro-fracture tests yield values of 5218 psi to 5326 psi for the minimum horizontal stress and 6904 psi to 7154 psi for the maximum horizontal stress. This represents a relatively large stress anisotropy which, in turn, could result in a sizeable permeability anisotropy. A numerical simulation study was conducted to investigate the impact of horizontal permeability an isotropy and completion strategy on hydrocarbon recovery. The results of this sensitivity study show that the optimum completion strategy consists of suitably staggered perforation schemes in the injection and producing wells. P. 49