Selection of suitable chemicals for acid matrix stimulation: a Malaysia brown field scenario

Abstract

Matrix acidizing in sandstone reservoirs requires a series of chemicals to dissolve the plugging materials around the near wellbore. The selection of suitable chemicals is important because it is one of the key factors to acidizing success due to the complex mineralogy of sandstone reservoirs and limited studies that have been done to compare between the chemicals selection from the industry guidelines with success rate from historical field execution especially in Malaysia oil fields. In view of the current low oil price and increasing treatment cost, the selection of the chemicals is important to maximize the oil gain. Hence, this project was embarked to develop a database of the historical acid matrix stimulation chemicals used in a Malaysia brown field and recommend the suitable acid matrix stimulation chemicals for future applications. The chemicals selection can be enhanced by using the combination of historical experience, recommendations from industry guidelines, and simulation results to provide assurance in achieving economic oil gain for future matrix stimulation candidates. There were five main steps to achieve the objectives, namely historical analysis of previous acid stimulation jobs, chemicals selection using industry guidelines, nodal analysis on current well performance using Prosper software, acid placement analysis using Stimpro software to quantify skin reduction for each case, and finally the gain quantification using Prosper software. From the project, database has been established to review the chemicals that have been applied in the selected Malaysia brown field. The oil gain formula has been identified as the success rate indicator. The comparison on skin reduction and oil gain between the three chemicals shortlisted from historical analysis and industry guidelines has been conducted using Prosper and Stimpro software which has enabled the selection of the most suitable chemicals. The most suitable chemicals were selected based on the highest average oil gain.