Technology for water separation and re-injection at well pads in Tatneft PJSC

UDK: 622.276.438

DOI: 10.24887/0028-2448-2018-7-35-38

Key words: highly watered wellstream, well separation at well pad, technology modification

Authors: N.G. Ibragimov (Tatneft PJSC, RF, Almetyevsk), R.Z. Sakhabutdinov (TatNIPIneft, RF, Bugulma), F.R. Gubaidulin (TatNIPIneft, RF, Bugulma), A.N. Sudykin (TatNIPIneft, RF, Bugulma), O.Yu. Antonov (TatNIPIneft, RF, Bugulma)

An effective way to decrease operating costs associated with production of highly watered oil in mature fields is to separate the produced water at the well pad and to re-inject the separated water into injection wells at the same well pad. In this case, the operator saves energy needed to pump-over the fluid into oil gathering lines and inject treated water into formation pressure maintenance system, decreases consumption of fresh and formation water injected to support reservoir energy, unloads production and transportation facilities, and minimizes operational and environmental hazards resulting fr om commingled production. Tatneft PJSC successfully applies the technology of water separation and treatment in three modifications. The choice is dictated by the amount of the produced water, water quality requirements, and availability of infrastructure.

One of the technology modifications provides for separation of produced water in inclined tubular
gravity phase separators. The apparatus is a pipe of a certain ID and length fixed at an angle, wh ere phase separation of the wellstream takes place. Water separation and treatment is based on the principle of autofloatation. The separated oil and gas go to the oil gathering system, while the treated water is pumped into the formation pressure maintenance system. By now, 20 tubular
gravity phase separators have been installed at the Company’s fields. Another technology modification provides for separation of produced water in tanks. The assembly includes a surge vessel for initial separation of the associated
petroleum gas, a two-sectional settler for separation and settling of water, and a coalescing filter to improve water treatment to meet the requirements. By now, one system has been put into operation. One more technology modification provides for separation and treatment of produced water in a rathole. The assembly comprises a casing pipe with a blind bottom end installed in a
rathole, wellhead equipment at the top end that fixes a pipe branch needed to maintain the oil level in the casing-pipe branch annulus, and a tubing to take the treated water to the formation pressure maintenance system. By now, 5 systems have been installed at the Company’s fields.

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