Production Rate Optimization of Downhole Water Sink Technology Using Differential Evolution Method

• Main Author: Prayoga, Budi
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/40084
• Institution: Institut Teknologi Bandung

Downhole Water Sink is a technology that had been used to prevent water coning in a strong water drive reservoir. This technology can also increase oil recovery by delaying water coning around the wellbore. Perforations have been made in oil- and water- zone. The objective of making perfortaion in the water zone is to provide downward balance force against the upward movement of water encroachment to the top perforation. The presence of water near the wellbore can reduce the relative permeability of oil, decreasing oil production rate. The value of oil recovery depend on the combination between top- and bottom- rate. There are some methods to analyze the optimum combination of both rate such as Inflow Performance Window which is proposed by Inikori et al. (2002) and DWS Guideline Plot (DGP) which is introduced by Marhaendrajana et al. (2006) later. However, those methods are not consider the change of mobility ratio yet. It is not enough to represent the actual condition over the well production time. In order to give complete optimization scope, the reservoir model in the near wellbore area is needed for the optimization process. Differential Evolution is one of the best method to solve this problem because it help to reduce time in the process of finding the optimum solution. It has unique algorithm which is more effective than other direct optimization method. Total cumulative oil production is chosen to be global objective function with well total water cut limit, ranging from 74% to 92%, is taken into account as constrain variable. The optimization results show the optimum top rate is ranging from 106 stb/d to 500 stb/d, while optimum bottom rate is ranging from 0 stb to 1107 stb/d. The optimum flow regime condition for contraint value which is ranging from 74% to 84% is water coning, making DWS isn’t suitable to be applied. Meanwhile, oil coning has been optimum condition for constraint value which is ranging from 86% to 90%, making DWS role would be significant. When the constraint value is 92%, the optimum condition will change to water coning again with lower value of top perforation water cut profile, compared to the results that have constraint value which is ranging from 74% to 84%. However for this constraint value, the optimization result shows high bottom rate value, so DWS still has crucial role to get the optimum condition. Moreover, the optimum rate is validated using unified Inflow Performance Window (IPW). Generally, the optimum rate is located in the precise area of flow regime, matching with optimum flow regime evaluation based on top perforation water cut profile. The novelty of this study proposed new approach in finding and evaluating the optimum combination of top- and-bottom rate using differential evolution method that would reduce the optimization time and give comprehensive optimization.