DOWNHOLE SEPARATION TECHNOLOGY—PAST, PRESENT AND FUTURE

In the 1990s, a new water management tool, downhole separation technology, was developed. It separates oil and gas from produced water inside the wellbore and injects the produced water into the disposal zone. Based on the different fluid the separators handle, they are categorised as downhole oil-water separators (DOWS) and downhole gas-water separators (DGWS). Two types of separators have been used: hydrocyclone and gravity separators. The authors reviewed the previous 59 DOWS installations and 62 DGWS installations worldwide, and discovered that only about 60% achieved success. Some major issues-including high costs, low reliability and low longevity-have slowed down its industrial adoption. Based on the field experiences, a good candidate well must have a high-quality disposal zone with sustainable permeability. To improve the performance of downhole separation tools, it is crucial to better understand the behaviour of the separator under downhole conditions and the behaviour of the injection zone under the invasion of various impurities in the produced water.