New well pattern optimization methodology in mature low-permeability anisotropic reservoirs

Abstract

In China, lots of well patterns were designed before people know the principal permeability direction in low-permeability anisotropic reservoirs. After several years' production, it turns out that well line direction is unparallel with principal permeability direction. However, traditional well location optimization methods (in terms of the objective function such as NPV and/or ultimate recovery) are inapplicable since wells are not free to move around in mature oilfield. Thus, well pattern optimization (WPO) of mature low-permeability anisotropic reservoir is a significant but challenging task since original well pattern (WP) will be distorted and reconstructed due to permeability anisotropy. In this paper, we investigate the destruction and reconstruction of WP when principal permeability direction and well line direction are unparallel. A new methodology was developed to quantitatively optimize well locations of mature large-scale WP through WPO algorithm on the basis of coordinate transformation (i.e. rotating and stretching). For mature oilfield, large-scale WP has been settled, so it is not economically viable to carry out further infill drilling. This paper circumvents the difficulty by combining WPO algorithm with well status (open or shut-in) and schedule adjustment. Finally, this methodology is applied to an example. Cumulative oil production rates of the optimized WP are higher, and water-cut is lower, which highlights the potential of the WPO methodology application in mature large-scale field development projects.