In common practice, gravel pack completion is beneficial as sand control in a typical unconsolidated sandstone reservoir. However, with poorly sorted sand grains, fines migrate and deposit at the gravel-pack matrix, causing permeability reduction and hence, decreasing well productivity. Matrix stimulation has been proven to remove the fines blocking the pore throat. The desired solution has been carefully selected to have prolonged well production. Organic clay acid is chosen for to its ability to have deeper penetration and to create a thin coating on the pore surface to prevent fines migration. Laboratory testing and field application were performed in parallel. A core flood test with reservoir core samples showed a result of 111% regained permeability. Ten treatments were conducted and showed good results. The productivity index increases 10 times on average. From those experiences, a benchmark was identified, which factor determines the success of a treatment. This paper presents the project preparation and execution, key reasons to success, and the way forward.