| At present,the sand mixing device for fracturing widely used in oil and gas fields has problems such as the inability to control the concentration of downhole sand,the inaccurate injection sand ratio,and the complicated operation of ground equipment.For this reason,a parallel tubular downhole supercritical carbon dioxide jet mixing device has been developed,thereby the ground sand mixing device is replaced by a downhole jet sand mixing device,which has the characteristics of real-time control of the downhole sand concentration and adjustment of the formation sand ratio.The main research contents of this paper are as follows:(1)By consulting the Chinese and foreign reference,realized that the development status of the sand mixing device for fracturing in recent years and the basic properties of supercritical carbon dioxide.Summarized the technical characteristics and field application of carbon dioxide dry fracturing.(2)According to the basic properties of carbon dioxide,studied the influence of temperature and pressure on its density,viscosity and diffusion coefficient.A wellbore temperature model and a pressure model was established to analyze the distribution of carbon dioxide characteristics in the wellbore.The type and performance of the proppant was summarized to determine the settlement law of the proppant in the wellbore.(3)Designed the structure of the parallel tubular downhole supercritical carbon dioxide jet mixing device,and used the finite element method to carry out static analysis of key components.(4)The model of sand mixing device was established by GAMBIT.The volume distribution of sand under different influencing factors was simulated by FLUENT software,and the optimal sand mixing effect was compared.Based on this,the sand carrying capacity of supercritical carbon dioxide fluid was studied,the research showed that the supercritical carbon dioxide has superior sand carrying capacity than liquid carbon dioxide in the device. |
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