| Tahe Oilfield is a large marine carbonatite oil field in China. Cumulative proved reserves of oil and gas reaches 780 million tons, which accounts for about 48.75 percent of total heavy oil reserves resource of Chinese. With deep burial depth of reservoir, high density and high viscosity, Tahe oilfield has become a typical representative of super heavy and deep oil reservoir and one of the most difficult exploitation heavy oil blocks in China.After years of test, validation and selection, electric submersible pump lifting has developed as the major method of lifting process of heavy oil. But there are still some problems, such as abundant consumption of thin oil in mixing, low pump efficiency, poor mixing of thin oil and heavy oil. So it is crucial to improve submersible pump lifting process and technology, which is beneficial to improve exploitation efficiency and lower cost.To solve the above problems, this Paper uses simulation technology as the main research methods and field test, and carries out key technology of electric submersible pump lifting process in block twelve of Tahe oilfield. Specific contents and results are as follows:(1) According to failure analysis of submersible pump lifting process in block twelve of Tahe oilfield, we think uneven mixture is the main reason of pump failure, thus improving mixture of thin and heavy oil through optimizing mixing conditions and equipment is the key to reduce the failure.(2) Based on the actual working conditions of electric pump wells, viscosity-temperature field and pressure field of wellbore are carried out. Simulation calculation results show that deeper mixing point, higher temperature, smaller viscosity of crude oil, and bigger than 0.65 blending ratio are beneficial to lower the loss of crude oil flow pressure and more conducive to the flow out of oil. And on this basis, we put forward an improved lifting process of moving down mixing point and moving up pump hanging position.(3) Simulation model of tail pipe mixing process is established based on computational fluid dynamics theory. The results show that thin oil phase volume fraction is about 35% in the central Part of the tail tube, and it is about 65% close to the shell of the pipe. Oil phase distribution is not uniform that thin oil doesn't spread to the central region to the tail pipe.(4) Mixing process of mixing tool combing with tail pipe is simulated based on six degrees of freedom CFD technology is conducted. The results show that:thin oil phase volume fraction reached 50% in the central region of tail pipe, while close to the pipe shell thin oil phase volume fraction is about 34.9%. Vortex generates and improves the mixing effect. In addition, the mixer impeller blade number and blade angle are selected, that leaf number is 4, and the inclination is 45 degrees when diluting the best mixing effect.(5) Achievement of this research have been successfully applied to the Tahe oilfield, it is helpful to lift super heavy oil could be lifted, improve the pump operating condition, reduce the amount of oil diluting, prolong the service life of the pump for 105 days, save the production cost of 31 million 720 thousand yuan, which has great significance to ensure stable oil production. |
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