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

Abstract

Matrix acidizing in sandstone reservoirs require a series of chemicals to dissolve the plugging materials around the wellbore. The selection of suitable chemicals is important because it is one of the key factors to ensure success in acidizing due to the complex mineralogy of sandstone reservoirs. Furthermore, limited studies have been done to compare the chemical selections between industry guidelines and the success rate from historical field execution, worldwide. In view of the current low oil prices and increasing treatment costs, the selection of the chemicals is important to maximize oil gain. Hence, this project was embarked to develop a database of the historical acid matrix stimulation chemicals used in a Malaysian brown field. This paper also includes recommendations of the suitable acid chemicals for matrix stimulation for future applications. The selection of chemicals can be enhanced by using the combination of historical experience, recommendations from industry guidelines and simulation results to model the estimated potential economic oil gain of future matrix stimulation candidates. The comparison on skin reduction and oil gain between the three chemicals short-listed from historical analysis and industry guidelines has been conducted using nodal analysis and acid placement software namely; Prosper and Stimpro, which enabled the selection of the most suitable chemicals. Where the selection of chemicals (Main flush chemicals are; 10% HCl - 1.5% HF, 12% HCl - 2% HF and 12% HCl - 3% HF) can be enhanced by using the combination of historical experience, recommendations from industry guidelines and simulation results to provide potential estimation in achieving economic in achieving economic oil gain for future matrix stimulation candidates. From the project, a database has been established to review the chemicals that have been applied in the selected Malaysia brown field and 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 nodal analysis and acid placement software, which enabled the selection of the most suitable chemicals. The most suitable chemicals were selected based on the highest average oil gain.