PRELIMINARY INVESTIGATION TO EFFICIENCY OF PUMPING SYSTEM IN WUMISHAN RESERVOIRS OF RENQIU OIL FIELD

Measurement to pumping system in Wumishan reservoirs of Reqiu oil field conducted by CNPC experts showed that the efficiency of this system reaches to 51%~68%,the resu1t was unexpected. This paper, by analyzing the main factors influencing the well pumping unit system, finds out the main reasons why the efficiency of the pumping system in Wumishan reservolrs of Renqiu oil field is high. This paper points out:Wumishan reservoirs in Renqiu oil fleld are fractured carbonate reservoirs(limestone reservoirs), in which, frac-ture developed, permeabil1ty is good, oil reservoir is thick, formation temperature is high,gas/oil ratio is low, saturation pressure is low and so on, all these cause the oil producing with well pumping unit possess the following characteristics:(1) produce oil with large pump size, long stroke, low pump speed and high pumping rate;(2) pump setting depth is rniddle to shallow. submergence is small:(3) swabbing fluids are single phase liquid, full degree of pump is high;(4) some wells are in the state of " pumping accompanied by flowing" forces exerted on the bottorn of pump piston are large(5) viscosity of fluids in well is iow. paraffin does not deposit in well, friction loss is small. All these characteristics and the rlet’ type energy savlng weli pumping units used in recent years make the efficiency of pumping systern in thls oll f1eld more hlgher than that in the other oil fields.