Abstract
As the deep reservoir development in Tarim oilfield, deep wells and ultra-deep wells increase day by day. Meanwhile, in order to stabilize and increase production, pump depth increases continuously because energy and dynamic liquid level of developed reservoirs decline. As the main lifting way, sucker rod pump wells accounts for 65% of the total number of wells in Tarim oilfield. Pump depth of the deepest rod pumped well reaches 5200 meters in Tarim. During lifting process of deep wells, many problems will appear, such as large load and low pump efficiency, and rod lock similar to gas lock may be aroused in extreme cases deep rod pumped wells can appear even, so a series of lifting equipment and parameters optimization measures are essential to realize efficient lifting of deep wells.
Aiming at the existing problems of deep well lifting, oil field adopts a variety of solutions. 1) Because of low density and high strength of carbon fiber rod, it can lower polished rod load and improve safe coefficient. Oilfield has conducted test and application of carbon fiber rod to validate the adaptability of carbon fiber rod in deep wells, and evaluate load shedding and energy saving effect; 2) A new type of no-beam long stroke pumping unit is chosen to replace large beam pumping unit, and the long stroke pumping unit can effectively improve pump efficiency; 3) In deep wells, conventional single lifting technology faces worse working conditions and more faults, while combined relay lifting method integrates the characteristics of two lifting processes to show the advantages of both, which can solve the problems that single lifting technology can't solve.
The results of field test and application are as follows: 1) Carbon fiber rod has obvious load shedding ability and the mixing rod (40% of carbon fiber rod ratio) can reduce load by nearly one third compared with steel rod. It also has higher stress intensity. The influence factors of stroke loss are complicated, and the adaptability of carbon fiber rod can be improved by rational optimization of rod string assemblage and production parameters. 2) No-beam long stroke pumping unit has a strong adaptability in deep wells of Tarim oilfield and has completely replaced the conventional beam pumping unit. 3) According to reservoir characteristics, well structure and fluid characteristics, the adaptive analysis of various combination lifting systems is carried out to select the combined lifting method suitable for Tarim oilfield. The design of combined relay lifting method is more complicated than that of conventional single pump system, which includes the design of pump depth interval, relevance and continuity of double pump drainage, and sensitivity analysis and comprehensive adjustment of production parameters of double pump.
Tarim oilfield has many deep and ultra-deep wells. Now, a wide variety of new technologies have been successful tested and applied, such as new no-beam pumping unit, HL level high strength sucker rod, carbon fiber sucker rod, lifting way of sucker-rod pump combined with jet pump, and lifting way of sucker-rod pump combined with gas lift.
