Pulley-free directly-connected hydraulic pumping unit lift technology, developed based on the characteristics of Jilin Oilfield, can be applied to produce cost-effectively the difficult-to-produce reserves, and to improve the low fluid production and reduce the high energy consumption of developed oilfields.

Featuring low cost, low energy consumption and high efficiency with one unit serving several wells, this technology can meet the lift demand of different flow rate at different well depth. The hydraulic pumping system consists of three discrete units, namely main frame, hydraulic station and electric cabinet. The piston and sucker rod of the main frame are connected directly. When the system works, the pump of the hydraulic station provides power for the hydraulic cylinder of the main frame, which drives directly the reciprocating movements of the sucker rod to lift fluid via the reciprocating movements of the piston. The centerline of the main frame coincides with that of the casing, and so there is no unbalance loading. Substituting for the polish rod, the piston rod of the pumping unit connects directly with the sucker rod. The elimination of pulley, wire rope, rope hanger and packing box minimizes the wear parts of the system. Besides, when the system is in service, the main frame can be disassembled like tubing, having no impact on workover. The electric cabinet acquires signals via the displacement sensor and pressure sensor on the main frame and processes them, with such information as indicator diagram, stroke and stroke times displayed on the touch screen.

The ground equipment in this technology has light weight, which is about 15% of a beam pumping unit of the same model. With this technology, long stroke, low stroke times, big pump size lift, reduced rod-casing wear, prolonged maintenance free period and improved operation efficiency can be realized. Compared with existing pumping units, its investment in equipment is less. The cost of a twin well system can be reduced by more than 30%, and the energy conservation at the same fluid production rate is above 25%.

By December 2016, 24 wells of different depth in Jilin Oilfield had been subjected to pilot test successively. The "one driving one" hydraulic pumping units applied to two wells had operated stably for more than 700 days free of trouble, and the pumping efficiency had been improved by 35% compared with other types. The successful application of this system has verified its overall stability and its adaptability to the extremely cold environment in the northeast China. The "one driving two" hydraulic pumping units had been applied to 22 wells, and the test results show that both the process flow and the system are stable.

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