Application of a Multiphase Flow Simulator for Production Optimization of Tiebacks Using Subsea Multiphase Pumping

Abstract The objective of this paper is to optimize oil production of deepwater tiebacks using subsea processing such as multiphase pumping to improve recovery and accelerate production. The Helico-Axial multiphase pumps have been used to evaluate the added production of oil beyond natural production after the early life of the two selected long and short distance tiebacks typical to the deepwater environment using a multiphase flow simulator. A multiphase flow simulator such as OLGA has been used to develop a dynamic model for the assumed hydrocarbon composition, with low API gravity for the cases of two tiebacks: short-distance tiebacks (~1 mile) and long-distance tiebacks (~22 miles) typical to the Gulf-of-Mexico using their respective subsea architectures. The fluid properties used in the model were determined using a PVT simulator. The OLGA model is applied to perform the subsea production analysis to determine the increment in the production capacity of oil with and without the use of a Helico-Axial pump with varying differential pressures and capacities. In this study, the model results are presented for the increments of oil flow rate for the various differential pressures of Helico-Axial multiphase pumps over the life of the selected fields for the two base tieback cases. For both the short-distance and the long-distance tiebacks our results show a significant increase in the oil production rate using subsea pumping, over natural production. We also performed the analysis of Gas Volume Fraction (GVF) of the produced oil to investigate its impact on the performance of the Helico- Axial multiphase pump. Our analysis shows that multiphase pumping can be economical and can mitigate many flow assurance issues to reduce the cost and manage the risks during operations. It may also help reduce the greenhouse gas emissions at the production facility. In conclusion, subsea multiphase pumping appears to be a promising approach to develop the extended tiebacks in the deepwater environment. This paper presents an innovative modeling method to enhance recovery of oil production using one of the subsea processing tools such as multiphase pumping for the realistic cases of subsea tiebacks typical to the Gulf of Mexico. This research demonstrates the knowledge and skill required for subsea multiphase processing and multiphase modeling of critical tieback systems and cost-effective oil production to benefit the practicing engineers.