Research On Stroke Lengthening And Power Saving Modification Of Oil Field Conventional Beam-Pumping Units In Service

This thesis makes a systematic and thorough research and study on the stroke lengthening and power saving modification of oil field conventional beam-pumping units in service ( four-bar linkage ).First, the condition of pumping unit application, the development situation of pumping units at home and abroad, the main problems existing in oil field pumping units in service, and some ways for pumping unit power saving are briefly stated and described, by which the author put forward the theme of this thesis, that is, by means of the structure model of power saving type pumping units to realize the stroke lengthening and power saving modification of oil field conventional beam-pumping units in service.Second, on the basis of available technical documents, the analysis and comparison of structure, kinematic performance and power saving effects of power saving type beam-pumping units developed and widely used at home has been made. As a result, a structure model of a new high efficiency power saving pumping unit with rear eccentric wheels ( six-bar linkage ) are proposed to be used to modify the type of conventional beam-pumping units ( four-bar linkage ) so as to realize the object of conventional pumping unit stroke lengthening and power saving.Third, the basic theories of beam-pumping units are introduced in detail. The kinematic performance, dynamic performance, polished-rod load and gearbox torque of the two types of pumping units, conventional beam-pumping units and high efficiency power saving pumping units with rear eccentric wheels, was illustrated in order to provide necessary theories for kinematic analysis and performance study and to form a foundation for subsequent specific modification work.Fourthly, a set of software system for performance analysis and comparison of the aforesaid two types of pumping units was developed, by which one can do the work of kinematic analysis and dynamic analysis for the units fast and accurately and determine some critical dimensions for the modified unit through numerical simulation and optimization methods, so as to supply a strong technical support for succeeding modification work.Fifthly, considering the reality of water has been pumping into formation in old fields to maintain stable oil production so that many reservoirs have progressively stepped into high water content period, the author has put forward a general plan for type modification of beam-pumping units in service and specific modification plan for local structure under typical working conditions. And, the performance analysis and comparison was made by using the aforesaid developed software system, thus the final plan of modification was determined. According to the plan, in-factory test for type modification was carried out. Then, the modified unit was made a field application test. After that, the effects of modification were evaluated.Finally, one conclusion has been drawn from the two tests that the plan of strokelengthening and power saving is feasible. Without replacing the original crank with new crank having offset angle, good effect of power saving can be gained, and not only can oil production be raised but also the matched motor power rate can be reduced by adopting the selected structure model to modify conventional beam-pumping units in service. Also, the innovative modification of existing manufacturer's product, high efficiency power saving pumping unit with rear eccentric wheels, has been realized. If permitting of wider application of the technique, better economic and social benefits would be gained.