Abstract

Water injection is an effective way for maintenance of reservoir pressure, realization of high and stable oil production and improvement of oilfield development efficiency. Actually, it is a major way for oilfield development in China. Artificial island oilfields are often developed through highly-deviated wells. Existing water injection technologies feature a low pulling and running success ratio of downhole nozzles and pose difficulties in flowrate testing and adjustment, which can hardly meet the needs of zonal testing and adjustment of highly-deviated wells in offshore and artificial island oilfields. This paper proposes a concentric zonal water injection technology for highly-deviated wells. The technology adopts a concentric testing and adjustment scheme, wherein testing instruments and downhole regulators adopt concentric connection with a high connection success ratio for highly-deviated wells. Downhole regulator adopt a bridge channel design that can effectively eliminate the influence of interlayer interference and enhance the efficiency of testing and adjustment. Zonal flowrate is adjusted by adopting an eccentric valve design featuring small loss under fully closing state, small adjustment torque and more easy to adjust. Collected testing and non-collected testing are compatible to meet the requirements of low flowrate. Online packer seal test by cable is realized, ball sealing can be monitored, and all seal checking operations can be completed at one time. In order to achieve long-term continuous monitoring for zonal after-nozzle pressure, an equipped zonal pressure monitor is developed for acquiring long-term continuous data during water injection used for reservoir analysis. During testing and adjustment, online direct reading of multiple parameters (such as zonal flow, pressure and temperature) of any layer can be achieved together with the automatic testing and adjustment without pulling and running operation, which dramatically improves the efficiency of testing and flowrate adjustment. So far, field tests have been made for 14 wells with a maximum hole deviation angle of 59.4°. The flow testing error is less than 5%, and the time for packer seal checking, zonal testing and flowrate adjustment is less than 1 day. Comparing with existing technologies, this technology is of the characteristics of high efficiency of testing and adjustment, high accuracy, low cost, etc.

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