Optimal design of oilfield surface pipeline networks for the cyclic water injection development method

Abstract

Pipeline networks in oil fields, including gathering pipeline networks (GPNs) and water injection pipeline networks (WIPNs), are characterized by varied and complex structures and large investments. Optimizing the design of these networks is the key to reducing the development costs of oilfields. In the development method of cyclic water injection, some pipelines can be used for both production gathering and water injection; thus, GPN and WIPN can be designed simultaneously. Currently, separate designs do not form a unified scheme, and the cost is high. In view of these shortages, the integrated network should be considered. Based on mass and energy balance equations for networks, this paper proposes a mixed integer linear programming (MILP) model that takes the minimum construction investment as the objective function. The piecewise method is used to deal with the nonlinear terms in this model. Two common connection structures of pipeline networks, stellated pipeline networks (SPNs) and cascade dendritic pipeline networks (CDPNs) can be calculated by adjusting several constraints. Decision variables for the optimal locations of the central processing facility (CPF) and manifolds, detailed topological structure, diameter and route of each pipeline, pipeline flow and node pressure are obtained integrally by solving this model with the Gurobi solver. Two cases are studied to verify the effectiveness of the model. The results illustrate that the model can satisfy the needs of the designers in the actual design process, avoiding a qualitative or univariate decision in the comparison of different schemes. Comparing the results with those of the separated design scheme, the proposed model is proved to achieve lower investment costs. Therefore, the proposed model is feasible and practical.