Design Optimization of Multilateral Wells in Heterogeneous Reservoirs

Abstract

Abstract Maximizing profit with minimal costs is a top priority in the oil and gas industry. With the dynamics of today's oil market, finding economically feasible tools to maximizing the production is vital. Multilateral wells possess the potential of achieving such a goal. To date, different theoretical designs of multilateral wells are proposed in literature. One of the most common designs studied is the fishbone configuration. This configuration maximizes the reservoir contact and thus the productivity of the well. While the merits of the application of multilateral wells are well documented, an understanding of the best operating conditions for the use of multilateral wells is rare thus we answer cogent questions related to the optimization of multilateral wells under different reservoir conditions and well design parameters. To answer such questions, Design of Experiment (DOE) and Response Surface Methodology (RSM) was utilized. Selected factors to be optimized are the number of laterals, length of horizontal sections of laterals, correlation lengths for heterogeneity indication, reservoir thickness, and permeability anisotropy. These factors were chosen based on literature search, perceptions and deliberations while the objective function is the cumulative oil production. Several experiments were conducted using extensive three dimensional fine scale numerical simulations and the Box Behnken response surface methodology was used to derive the response surfaces. Single effects and interaction plots are made to show the interactions between parameters and the effect of these parameters and interactions on the objective function. Results show a high dependence of productivity on the horizontal section length and reservoir thickness. This implies that candidate reservoirs for the application of fishbone multilateral wells should possess larger thickness. However, where the reservoir is thin production can be improved using longer horizontal sections. The outcome of this study indicates the importance of the horizontal section and lateral lengths on a fishbone multilateral well productivity from the same reservoir. This study provides a template for decision making in field development operations thereby reducing uncertainties and maximizing gains.