Plug removal and injection stimulation system with conjugate acid in ASP injection wells

Due to the presence of polymers and alkalis in ASP flooding, it is easy to form a micelle-like mixture, which will block the injection well. The conventional chemical plug removal technology has a small effective radius and a short period of validity, it is easy to generate secondary precipitation, and the residual acid need to flow back, which greatly increases the cost of stimulations and the hidden dangers to environment. In order to solve the problems of short validity period of stimulations and the dangers of residual acid to environment when flows back, the plug removal and injection stimulation system with conjugate acid in ASP injection wells was studied. The microscopic morphology and structural characteristics of the plugs were clarified by scanning electron microscopy and CT 3D reconstruction. Through the evaluation experiments on inorganic scale dissolution and ion complexation, a plug removal and injection stimulation system with conjugated acid was developed. The experiment results show that the plugs in the ASP injection wells are multi-component clump-like aggregates formed by polymers, scales, and wax colloids. The plug removal and injection stimulation system with conjugated acid can realize deep plug removal without secondary precipitation. Compared with conventional plug removal agent, the recovery rate of core permeability after using this system was increased by 29.2%, with an average validity period of 193 days. After stimulation, there is no need for residual acid to flow back, which realizes the high efficiency and environment protection during plug removal process in ASP injection wells.