Research and Application of Micro-fracture Plugging Removal Technology for Water Injection Wells in Bohai Oilfield
Due to the difficulty of water treatment in Bohai Oilfield,although many measures have been taken to improve water quality,there are still compatibility issues between injected water and reservoir,resulting in reservoir damage near the wellbore of the injection well and a continuous decline in the water absorption capacity of the injection well.Acidification is the most commonly used measure for increasing injection in Bohai Oilfield.However,after multiple rounds of acidification,the effect of increasing injection becomes worse,and the effective period of increasing injection becomes shorter.Improving the water absorption capacity of injection wells,meeting the requirements of injection allocation,and reducing the cost of plugging removal are urgent technical problems that need to be addressed in Bohai Oilfield.Based on the existing conditions of offshore platforms and high-pressure and high displacement water injection,micro-fracturing is carried out in the contaminated zone near the wellbore of the injection well in order to improve the water absorption capacity of the injection well.Core experiments and theoretical studies show that micro-fracturing in unconsolidated sandstone water injection wells mainly forms micro-cracks near the wellbore of the injection well,and the crack extension distance is limited in unconsolidated sandstone reservoirs far away from the pollution zone.This is a technical means to restore the water absorption capacity of the injection well by relieving the damage caused by the pollution zone.Based on the above research conclusions,a micro-fracturing pilot test was conducted on Well F8,and the apparent water absorption index increased from 10 m3/(d·MPa)before micro-fracturing to 16.5 m3/(d·MPa),indicating a significant increase in injection efficiency.This technology has been promoted and applied 161 times in Bohai Oilfield,achieving the goal of improving the water absorption capacity of injection wells,meeting the requirements of injection allocation,and reducing the cost of plugging removal.
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