Maximization of the Productivity Index Through Geometrical Optimization of Multi-Lateral Wells in Heterogeneous Reservoir System

Abstract

In the recent decades, it is becoming the new norm to drill multi-laterals wells for better reservoir coverage, improved productivity index, and superior financial return on investment. Optimum design and placement of this type of wells can be studied through rigorous modeling. This study presents a multi-parametric optimization approach that optimizes the design of multi-lateral wells and maximizes the contact with highly productive hydrocarbon zones in the reservoir. Advanced transient numerical models built in 3D by incorporating the dynamic data into the geological model to mimic the transient-pressure behaviors of multi-lateral wells for a given set of geometrical parameters. Such compliant models with dynamic data indeed capture the reservoir description and dynamics. The optimization process is subject to a number of input variables, such as maximum number of laterals, minimum spacing between wells, and maximum lateral length based on the reservoir characteristics. The multi-parametric optimization generates multiple realizations with different patterns. The productivity index of each pattern is calculated to look for the best multi-lateral well to be drilled. This study presents a numerical methodology of geometrically optimizing multi-lateral wells. Several local optimizations are performed around each main wellbore to place the lateral sections, and to determine the number of lateral sections. Main objectives of all these realizations are to minimize the competition among the lateral sections, and maximize the drainage area, which do subsequently affect the well productivity index. In permeable reservoirs, interference or competition among the lateral sections comes very quickly, and however, in tight reservoirs, such an occurrence is delayed. After running each realization, well productivity index is calculated, and the productivity index graph is generated against each constraint based on the advanced transient numerical model. Graphical presentation of the productivity index helps decide on the best optimum multi-lateral design. Additional sensitivity analysis is presented to show the impact of reservoir heterogeneity, lateral-section lengths, lateral spacing, number of lateral sections, and the impact of offset producers or injectors. This workflow will help design the most optimum multi-lateral well with a maximum productivity index under different reservoir conditions in an actual dynamic environment. The proposed workflow has been tested successfully.