The Lifting Design For Mixing Thermal Fluid Closed-Cycle Within The Inner Pipe And Hollow Rod In Heavy Oil Wells

Since the 1980s, China has started the industrial exploitations respectively in Liaohe, Shengli, Tahe and Henan heavy oil reservoirs. And they have achieved remarkably economic and social benefits. But there are still problems in the theoretical research and field applications, such as the bad fluid-flowing condition and lifting effect in the well bore filling with heavy oil. Also, the rod string stands huge friction forces while moving in tubing fluids especially in the down stroke process due to heavy oils'high viscosity. This may cause the difficulty of rod string's downward moving or produce shock load because of rod string's hysteresis to suspension center's motion which will affect oil wells'production. To solve these problems, closed type circulatory lifting process about tube-mixed heat flow in hollow stem of pumped well is studied. Using heat conduction theory, wellbore fluid temperature calculation model of tube-mixed heat flow which involves forward circulation and reverse circulation in hollow stem of pumped well is established. The influence of different mixing parameters on the temperature of wellbore fluid is also analysed. Based on four different types of pumped well's polished rod's movement characteristics and force analysis of sucker rod column, calculation model about movement rules for both polished rod and sucker rod column is also established. Besides, coordination between polished rod movement and sucker rod downward movement is analysed. Using node system analysis method, theory system about lifting process design which concerns closed circulation of tube-mixed heat fluid in heavy oil well stem is created. The results show that: In the process of doping hot liquid into the tube in rod, along with the increase in temperature and mass flow rate of the doped fluid, the temperature of wellbore liquid from the formation increases, and the temperature of liquid at the wellhead is higher in reverse circulation mode, which is conducive to surface gathering; in the process of doping hot liquid into the tube in rod,the temperature of wellbore liquid from the formation increases with increases in temperature and the dryness of the steam mixed and the mass flow rate, and there is an optimal mixing temperature of steam. The motion sucker rod column in borehole fluid is accelerates at first and finally achieved uniform motion, and the time of achieving uniform motion has an inverse relationship with the equivalent viscosity of formation fluid in the wellbore.There is a critical pumping speed when it comes to suspension's movement and sucker rod's downward movement of a beam pumping unit, and the coordination between suspension's movement and sucker rod's downward movement could be achieved only if the pumping speed is less than the critical pumping speed.The polished rod load has a strong sensitivity with the parameters of the thermal fluid flow. With the improvement of these parameters, the maximum polished rod load of the pumping unit would reduce and the minimum polished rod load would increase with a smaller load difference and better lifting effect, and positive cycle way lifting effect is better than that of reverse circulation mode. The application of comliled oil wells of "thermal fluid flow in mixed stem tube closed cycle lifting process design software" in shengli oilfield and application of tahe oilfield is good, and it's a reference for the production of other similar oilfields.