An effective acid combination for improved acidizing treatment of sandstone formation: A case study in Bach Ho field, Vietnam

The acidizing treatment of near-wellbore regions in oil and gas reservoirs is a critical technique for enhancing permeability and boosting hydrocarbon recovery. However, the conventional hydrochloric acid (HCl)-based solutions often face challenges such as the formation of stable emulsions, secondary precipitation, and incompatibility with reservoir fluids. This study focuses on evaluating the performance of modified acid systems (CKP+ and GKP+) for acidizing sandstone formations in the Bach Ho field. The experiments aimed at assessing the efficiency of these acid systems in enhancing permeability, mitigating clay swelling, and preventing the formation of secondary precipitates. Experimental results, including shale stability tests, dissolution experiments on formation rock, and permeability recovery evaluations, indicated that the proposed chemical systems effectively reduced the skin factor, enhancing oil permeability and sustaining recovery rates. The addition of anti-emulsifying agents and clay stabilizers improved the acid systems' compatibility with crude oil, reducing emulsion formation. Furthermore, the modified acid systems showed promising results in preventing iron-related precipitation, a common issue with conventional acid systems. Simulations conducted using Schlumberger's Kinetix Matrix software demonstrated that the proposed acid treatments could efficiently remove formation damage, especially in Miocene and Oligocene reservoirs, where traditional treatments had limitations. Overall, the study suggests that the CKP+ and GKP+ systems provide a cost-effective solution for improving well productivity and sustaining long-term hydrocarbon recovery.