| At present,as many oil fields have been in the high water content period,long-term water-flooding development made the formation cementation worse.At the same time,with the rapid development of oil drilling and production technologies,new drilling and production technologies such as sand filling fracturing have been widely used,which also aggravated sand falling.Sand falling has a severe impact on oil extraction,and it has always been one of the problems that the industry needs to solve urgently.Traditional field positive circulation or reverse circulation sand flushing technology is very costly in deep wells,especially for many open-hole completion oil wells.Due to the low formation pressure,the bottom hole loss is large and even the flushing fluid is returned.Unable to form an overall cycle,it is difficult to achieve the purpose of sand cleaning.In order to solve the problem of the difficulty of sand cleaning with traditional sand cleaning methods for lost wells and deep wells,a method of sand cleaning technology that uses jet pumps to form a partial reverse circulation in the lower half of the oil well is proposed.And the process flow is optimized,multi-stage sand settling improves the efficiency of sand removal.Overall and component structural design and optimization are carried out,as well as partial circulation flow field simulation analysis.The specific research content is as follows:(1)Based on the analysis and comparison of sand cleaning methods commonly used in oil wells at home and abroad,a downhole partial reverse circulation and multi-stage sand cleaning process and system with jet pump as the core are designed,and the sand carrying mechanism of the flushing fluid is analysed.For sand with an average particle size of 1.0mm and a density of 2632kg/m3,the lowest sand carrying speed when water is used as the flushing fluid is calculated to be u1=0.7m/s.(2)Research and application of jet pump design theory,combined with the design basis of jet pump for downhole oil extraction,with the requirements of sand cleaning technology,taking oil wells in a certain oil field block as the research object,according to the parameters such as flow and pressure provided by the field operation,the structure design and size calculation of the jet pump for sand cleaning were carried out.The fixed and positive circulation is selected as form of jet pump.The nozzle outlet diameter is calculated to be d1=4.4mm,and the throat diameter is d2=7.7mm.(3)Based on the design theory of jet pump,the design and selection software of jet pump for downhole sand cleaning was compiled,which could solve the problem of inconvenient selection of nozzle and throat size on oil field site,and avoid repeated calculation in the face of different working conditions.(4)Using CFD numerical simulation method to simulate and optimize the other structural dimensions of the jet pump for sand cleaning.The distance between the nozzle and throat is Lc=1.0d2=7.7mm,and the throat length is L2=6.2d2=48mm,and the total length of the segmented diffuser tube is L3=1 74mm.(5)The structure design and calculation of other main supporting sand cleaning tools are carried out,including sand collector and sander.And the dimensions were optimized using the CFD simulation analysis method.The ratio of the flow area inside and outside the sand collector should be above 0.2.The size of the sand outflow hole is 35×22mm,and the hole of the sander is 3×?36mm.(6)According to the design and simulation optimization,the jet pump for sand cleaning and sand collector are processed.High pressure and low pressure sealing tests are carried out on the jet pump for sand cleaning,and its strength and sealing performance are verified.The sand cleaning tools are used to carry out a downhole cleaning test in an oilfield block.Based on the analysis of the test results,the process optimization measures for the next sand cleaning are proposed. |
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