Research and Application of Efficient Blocking Removal Technology for Sewage Reinjection Wells in Offshore Oilfields

Aiming at the problem that the acidification effect of sewage reinjection wells was not ideal, the core flow experiment, suspended matter content and particle size test, and X-ray diffraction were used to analyze the blockage. On this basis, an acid system with both dirty oil cleaning and high dissolution rate was developed by using sand-filled pipe flow and core dissolution experiments. In addition, the acid placement process was optimized in combination with reservoir characteristics. The results show that the main reason for reservoir plugging is the composite plugging formed by waste oil and solid suspended matter in the near-wellbore area. The oil removal rate of 1% water-based cleaning agent reached 86.44%, and the dissolution rate of high dissolution acid to suspended solids reached 89.77%. The two compound systems can quickly disintegrate oil sludge pellets. Chemical micro-particle diverting agent can form an effective temporary plugging diversion for the reservoir, and automatically dissolve after acidification. The technology has been applied in 8 wells, and the average apparent water absorption index is increased by 1.74 times. This technology is suitable for plugging removal of sewage reinjection wells and provides theoretical and practical basis for improving the acidification effect of offshore sewage reinjection wells in offshore oil fields.