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Fines migration is the common formation damage mechanism in the sandstone reservoir of field B which has less established information on mineralogy distribution. There were many attempts to remediate the formation damage using conventional mud acid fluid system but resulted in mixed success rates. This situation warrant for the need for a modified acid recipe to avoid aggravation of fines migration problems in this field post acid treatment. This paper presents the pilot application of a modified HF acid recipe incorporating chelate. The paper also depict the evaluation process that includes candidate selection, laboratory workflow and results, treatment design, execution strategy and the post job analysis on well B-1S. In order to increase the acid stimulation success rate, the team analyzed numerous post job reports of the nearby wells that were previously treated with conventional mud acid system. The root causes of the previous job failures were identified, such as prolonged soaking of acid in the formation due to unplanned platform shutdown and limited platform deck space. Taking these factors into account, the modified HF acid system (with 1.0% HF) was selected for execution in B Field. The pilot execution resulted in double the production compared to the pre-treatment rate. The modified HF acid system has also improved the economics of the project due to its lower cost since it is a one-step system and has lower additives requirement.

Matrix acidizing is an attractive treatment choice in clastic reservoirs to remove near-wellbore damage due to its relatively low cost. It has been executed countless times in brownfields East Malaysia with a moderate to high success rate to arrest production decline due to fines migration and scale deposition. Nonetheless, there is a critical need to look back on the choice of treatment chemicals and treatment approach in order to ensure optimum chemical volume, attractive production gain and higher success rate, especially in the current low oil price era. This paper will focus on the planning and successful execution of single-stage acid (SSA) combined with wax solvent stimulation treatments resulting in fourfold increase in net oil production post treatment in two wells in Field X offshore East Malaysia. Well A18 and C33 experienced production impairment due to formation damage fines and organic scale. Combination of both wax solvent and SSA in the same treatment was used to remove the damage. Application of SSA eliminates the need for hydrochloric acid (HCl) pre and post flush thus reduces treatment volume, simplifies treatment execution and consequently reduces overall treatment time. Additionally, the usage of retarders eliminates fast reaction of hydrofluoric acid (HF) thereby allowing for deeper HF penetration. This paper also discusses the rapid decline observed post treatment for Well A18 is mainly contributed by re-mobilization of fines due to higher flow rates and re-buildup of wax within tubing and near wellbore. Proactive measures such as pressure drawdown management are suggested to prevent reoccurrence in future stimulation treatments. In conclusion, this paper finds that the combination of wax solvent and SSA was successful in both removing the damage and optimizing treatment schedule. Correct identification of damage source coupled with good treatment design was able to quadruple production from well A18 and C33 in Field X. This paper presents an innovative approach and cost effective solution in successfully mitigating formation damage caused by a combination of fines migration and organic scale. This single-stage stimulation treatment saves time, treatment volume and reduces job complexity.

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