Abstract

Formation plugging has occurred during water flooding process on B platform of Bohai oilfield, leading to an increase of injection pressures as well as the injected water volume due to the reduction in water layer adsorption within the formation. To overcome these issues, the present work intend to investigate the causes of such plugging, analyze the plugging sample, develop a new removal formula composed of surfactants and weak acids with ability of dissolving the plug, then characterize the solution and test its performances. SEM and XRD analysis were used to characterize structure and composition in elements of the plugging scale; the new developed removal solution did not contain strong acids, as they have been proved hazardous during the unplugging process for injection system. The new solution was found to dissolve up to 72% of the plug, with 2.12% corrosion rate. The solution was compatible with formation and injected waters, decreased the injection pressure system by 0.426MPa within 3PV of injection volume in a sand pack flooding experiment and has an acceptable pH of 5.8. A suitable removal solution for the plugging problems that the oilfield is facing.