Abstract

80% reservoirs were developed by waterflooding in China. The average layer number lies between three and four. As old oilfields reached high water-cut period, the reservoir needs further subdivision, usually more than seven layers. Conventional zonal water injection technique cannot meet the need of more than seven-layer subdivision because of small distance between regulators, thin interlayer, big releasing force of tubing and low efficiency in zonal flowrate adjustment. To solve this problem, we developed a step-by-step type packer which was released by lifting. The release force has nothing to do with layer number. All the packers were designed to release one by one. The maximum force was 30t. For small distance of regulators, we used two types of eccentric bridges together called positive oriented type and negative oriented type. By this way, the smallest distance was less than 0.7m. Double tubing packer was applied to realize effective seal for thin interlayer and it could overcome tubing creep which made it successful seal within 0.5m. This technique has applied more than 1147 wells in Daqing. The minimum distance between regulators is 0.7m. The minimum interlayer is 0.5m and the maximum layer number was 10. The technique process is normal during whole operation including packer set, open every choke completely, packer seal status on-line test and on-line flowrate adjustment. Through zonal water injection for those more than 7 layers, we conclude that the ratio of water absorption has increased by 8.1%. And the corresponding production thickness increased by 7.5%. The production of surrounding well increased 0.43t and the water cut decreased by 0.56%. The average zonal test and flowrate adjustment time is within 3.98d. All in all, it is an effective way for further waterflooding oilfield. Conventional zonal water injection technique cannot meet the need of more than seven-layer subdivision because of small distance between regulators, thin interlayer, big releasing force of tubing and low efficiency in zonal flowrate adjustment. The technique this paper introduced can solve this problem and it is widely used in Daqing. The results showed its adaptability.

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