| In the middle and late period,exploitation of oil and gas fields partly have features of low liquid production and high gas-liquid ratio.While using the pump way to extract oil,we always face a problem that gas-liquid phase simultaneously enter into the pump.This matter necessarily reduces the amount of liquid in the pump and full coefficient of pump,then lead to low pump efficiency,air even lock phenomenon when seriously,which have a greater influence on the economy of the oil field development investments.To reduce gas influence on pump efficiency,gas anchor or anti-gas pump or combination of the both is widely used by oil and gas fields both domestically and abroad.Additionally,many scholars also adopt CFD simulation technology to optimize the design of gas anchor or conventional oil pump.However,due to the complexity of the gas-liquid two-phase flow inside hole tool,nowadays gas anchor design or anti-gas pump optimization design still have some problems as follows:?CFD simulation technology does not consider oil pump,for whole working environment of gas anchor,adopt inlet conditions of given flow velocity and outlet conditions of given pressure,which cannot meet the real environment.?When research of conventional pump by CFD simulation technology,assumptions usually are that the pump is oil-free air,but for the anti-gas pump gas content as one of the most important parameters to be considered;?Using conventional methods,to study normal pump,assumptions usually are that two phase gas-liquid is evenly distributed.We count full efficiency of pump based on the assumptions above.However,anti-gas pump just take advantage of the difference of density to gas replacement between cylinder and exhaust couplings,to open fixed valve and traveling valve on time.To solve the above problems,this paper this paper takes advantage of the relevant technical information research for the use of gas anchor,anti gas pump to solve mining problems with high gas-liquid ratio wells both domestically and abroad,based on fluid mechanics,heat and mass transfer theory,using the theory and method of experiment combined with numerical simulation,to improve gas anchor-pump outlet boundary conditions combined CFD simulation and on the combined gas anchor and anti gas pump to simulate gas-liquid two-phase flow field,simulation and structure optimization.The establishment of the anti-gas anchor model and valve motion law of gas-liquid distribution pump system,and preparation of gas anchor-pump combined system transient simulation program is recommended for on-site implementation of the rod pumping gas prevention scheme,providing theoretical and technical support.Specific research contents and achieved results are as follows:(1)According to the ground dynamometer,movement of plunger pump was deduced.First,boundary conditions of gas anchor and anti-gas pump combination by CFD simulation were improved.Second,it has developed UDF files linked with pressure data whose system is gas anchor&anti-gas pump combination,so it can realize control of the fixed valve and the traveling valve,those function including open,close or move.Third,program adopt a joint language including Visual Basic language,C language and Scheme scripting language,when CFD simulation of gas anchor&anti-gas pump combination,coupled with Euler model and BP model,combined dynamic grid with static state grid,computing data can be real-time interacted and transferred.(2)Aiming at wells characteristics of low liquid production and high gas-liquid ratio,combined with the advantages of multi-cup-type air anchors and spiral gas anchor,concept that a new combined gas anchor with multi-cup&spiral gas anchor will be put forward.Multi-cup gas anchor carry out a transient simulation by the FLUENT,optimized inlet structure,gravity section of the suction pipe length,separation cup type and number of separate cup.On the premise of parameter program,spiral section and pitch were optimized.Based on optimization results,we develop a new gas anchor prototype.Through new combined gas anchor experiment,by establishing a special experimental facility,we can determine gas-efficiency and range condition of the combined gas anchor under different gas-liquid ratio.(3)By analyzing the mechanism of the anti-gas pump how to prevent air lock and to raise pump efficiency,making transient simulation of anti-gas pump by FLUENT,the exhaust coupling axial position,diameter and length can be optimized and developed anti-gas pump test specimen.(4)An experiment apparatus with a height of 18m,which can simulate the full scale of gas anchor-anti-gas pump system,was built.Developed a micro-line pumping unit,which in cooperation with the control cabinet and the switch provide the required pump reciprocating to pumping liquid.On the basis of the gas anchor-anti-gas pump system,the gas efficiency and pump efficiency was tested.The test result shows that the gas anchor-pump system in high gas-liquid ratio case is still tenacious work.Although the gas which enters the pump can not be discharged to the casing to improve pump efficiency,but can compulsory transfer the gas to the upper pump tubing.So that the pump can work under the condition of the lower pump efficiency,effectively avoiding the air lock.(5)Considering the bubble formed and moved,to calculate separation efficiency of gas anchor,to build two-dimensional matrix structure on anti-gas pump,to establish transient simulation model applied to anti-gas pump,to make program for gas anchor and anti-gas pump combination system transient simulation,to predict the pump cylinder gas-liquid distribution and pressure distribution and the pump cylinder diagram.(6)We made a test for the design of pumping and gas prevention on X4 well in X test district,forecast the pump dynamograph of the two schemes for the combined gas anchor-conventional pump and combined gas anchor-pump,compared the pump efficiency before and after the implementation of the scheme on wells X4,X7 and X10.We found that the combined gas anchor-anti gas pump scheme had no obvious advantage for wells lack of fluid in the bottom,but when the key factor affecting the pump efficiency is gas effect,pump efficiency of the combined gas anchor-anti gas pump scheme is obviously improved,compared with the conventional gas anchor-conventional pump scheme. |
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