Design and Optimization of Autonomous Inflow Control Device in Water-Bearing Sour Gas Reservoirs

Abstract

Autonomous inflow control device (AICD) completion has been applied in many conventional oil and gas reservoirs and has effectively controlled the water invasion. However, the method for designing and optimizing of AICD in sour gas reservoirs is still lacking. The objective of the proposed paper is to establish a numerical simulation and optimization method to evaluate and optimize the performance of AICD completion in water-bearing sour gas reservoirs. Firstly, a sulfur deposition saturation model is established considering non-darcy flow and stress sensitivity in sour gas reservoirs, meanwhile, time-varying skin factor is introduced to represent the influence of sulfur deposition on permeability. Secondly, a new type of AICD is designed, which has large flow channels and vortex chamber to satisfy the need of restraining water invasion and sulfur plugging in sour gas reservoirs. Finally, a reservoir-wellbore simulation method is established, which considers the sulfur deposition in the reservoir and the new AICDs in the wellbore, then the key parameters of AICD is optimized by orthogonal test and range analysis. The results of the numerical simulation show that the simulation and optimization method can effectively optimized the key parameters of AICD and the optimized AICD completion has good water invasion restriction capacity in water-bearing sour gas reservoirs. The optimized AICD completion causes little additional pressure drop compared to perforation completion in sour gas reservoirs, and the maximum additional pressure drop is less than 0.67 MPa, which means the optimized AICD completion is able to control water invasion as well as maintain normal gas production of sour gas wells. Besides, the optimized AICD completion decreases both the daily water production and the cumulative water production compared to perforation completion in sour gas reservoirs. In the last stage of the tenth year prediction period, the cumulative water production with AICD completion decreases by about 22.7% compared to that with perforation completion. In conclusion, the simulation and optimization method can be used for guiding the rational application of AICD completion in water-bearing sour gas reservoirs.