Sensitivity Analysis of Choke Size Selections on Reservoir Pressure Drawdown Using Prosper Modelling for Reservoir Management

Abstract

It is important to know that analysis and selection of choke sizes for oil wells is imperative for production optimizations in reservoir management. Chokes are necessary in every wellhead completion for regulating flow from the reservoir. Random selection of choke sizes has been a bad practice. For the case study of this work, productions from 3 gas condensate wells have declined with pressure over three years. The initial reservoir pressures of 5870 psi, 4373 psi and 2248 psi, initial production rates ranging from 82.3 BOPD to 242.57 BOPD and 3.018 MMSCFD to 5.001 MMSCFD respectively, with choke sizes ranging from 22/64" to 24/64". However, these reservoir pressures have depleted over 3 years by about 100 psi to 3800 psi for each well with early water breakthrough ranging from 10% to 25% basic sediment and water (BS&W). No analysis of choke sizes selection to flow the wells at the initial stage. This research work has been carried out on pressure depletion control corresponding with its drawdown. This was achieved by modelling and simulating PVT data, completion data, IPR and VLP data and well-test data as well as sensitivity analysis with the aid of PROSPER. Results obtained indicated the need to reduce choke sizes, thereby reducing the drawdown. The reduction of choke size gave a decrease in production volume ranging from 15 to 59% for both oil and gas. However, the reduction in choke sizes also gave decrease in water production of about 92%, 100% and 22% for the respective wells. The choke size sensitivity analysis showed that continuation of the initial choke sizes on 24/64" gave a higher drawdown value above 100 psi, which increased the pull of water conning. Recommendation of the new choke sizes within 18/64" to 20/64" showed the drawdown of 79 psi, 71.5 psi and 80.5 psi. New choke size selection was recommended for the reservoir management of each well.