There is abundant heavy oil resource in Bohai Oilfield and thermal recovery is an effective method to realizethe high-efficient development.Till now,several field pilots have been conducted.However,for the offshorethermal recovery well,the onshore common used rod pump artificial lift technology is not applicable.Theordinary electric submersible pump(ESP)system cannot be directly used either,because it cannot stand thehigh-temperature steam.Therefore,artificial lift technologies suitable for offshore thermal recovery wellis developed in recent years.For the ESP system,a high-temperature safety control system was developed,consisting of downholesafety valve,cable packer,and vent valve.The overall temperature and pressure resistance value couldreach as high as 350°C and 21MPa,respectively.And the high temperature electric submersible pump couldstand 250°C cyclic steam.This ESP system has been used in about 30 thermal recovery wells in BohaiOilfild,satisfying the artificial lift requirements for the moment.With this ESP system,the overall processof each huff-and-puff cycle includes:lowering steam injection tubing,steam injecting,soaking,replacingproduction tubing,producing.That means two workover operations for tubing changes are required in eachhuff-and-puff cycle,which adds more cost to the oil production and has bad effect on the thermal recovery.Considering the drawbacks of the current ESP system,a new concentric-tubing jet pump system suitablefor offshore oilfield with function of both steam injection and oil production is developed.Besides,thematched surface equipment,such as oil-water-sand separator and power fluid pump,are designed.Thetemperature resistance of the designed jet pump system reaches 400°C.With this system,no workover fortubing replacement is needed any more during one huff-and-puff cycle.Till now,this new jet pump systemhas been put into field pilot in one thermal recovery well.Both the steam injection and oil production processcompleted successfully,indicating its applicability for the offshore thermal recovery wells.In this paper,thetubing string structure details of the jet pump system and the specific field operation process is introduced.This new artificial lift technology will be gradually applied in other wells to improve the thermal recoveryeffect because of its advantages comparing with ESP system.Great progress and breakthrough of the artificial lift technologies suitable for offshore thermal recoveryhave been achieved in recent years in Bohai Oilfield,which will provide powerful technical support for thehigh efficiency development of the heavy oil resource in Bohai Bay.
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