A fully integrated reservoir/pipeline network model and its application on the evaluation of subsea water separation performance

Subsea water separation (SSWS) is a promising cutting-edge technology in handling specific problems related to offshore development, but the close evaluation of SSWS performance is quite lacking. This work develops an integrated production modeling (IPM) approach to comprehensively quantify the effect of SSWS both from technological and economical perspectives. A fully-implicit integrated production model is proposed, which assembles 3D reservoir equations and pipeline network equations together and seeks for simultaneous solutions. The feature of simultaneous hydro-thermal solution provides a remarkable value in the analysis of flow assurance issues related to wax deposition in the subsea flowlines. The indexing and mapping frameworks make the model prone to configuring different scenarios, both in temporal and spatial dimensions. A case study is presented to analyze the performance of SSWS under four subsea configurations in a pre-salt deepwater condition by three quantitative indicators: NPV, oil recovery, and wax-free index. Results show that subsea water separation has the potential to increase final oil recovery and project NPV for a clustered well system, while limited benefits shall be expected in a satellite well configuration. Also, higher risk of wax deposition is observed in a satellite well configuration compared to a clustered well system. The IPM approach, together with an economic model, provide decision makers with a way to estimate the break-even price on the investment of a subsea water separation station. The methodology proposed in this work also provides a guide in future assessment of other potential subsea technologies.