Design Of Vacuum Insulation Drill Pipe And Study Of Insulation Characteristics

With the development of the world,many industries still have great demand for petroleum resources,and the difficulty of underground petroleum development has gradually increased,and the proportion of exploration and development of deep wells and ultra-deep wells has started to increase massively.During drilling work,the high temperature of the formation can change the nature of drilling fluid,affect the performance of downhole drilling tools and followon instruments,reduce the service life of tools and increase the cost of drilling work,making some drilling projects difficult.In order to improve the downhole high temperature environment,this paper gives the structure of vacuum isolated drill pipe according to the heat transfer principle,establishes the heat transfer model of each layer unit structure of vacuum isolated drill pipe,and studies the heat transfer process and isolation characteristics of vacuum drill pipe.Firstly,the structure of the vacuum insulated drill pipe was proposed and the force analysis of the drill pipe was carried out.The drill pipe is designed as a double-layer structure,and the drill pipe is divided into the outer pipe,vacuum layer and inner pipe.The design of the drill pipe with the combination of vacuum layer and insulation material utilizes the principle of vacuum insulation in order to reduce the transfer of heat from the downhole formation to the drilling fluid heat,which alleviates the problem of high temperature environment faced by downhole tools and drilling fluid.Next,the basic way of downhole heat transfer and the thermal insulation mechanism of vacuum insulated drill pipe were analyzed,the differential equations of downhole heat conduction were derived,the downhole heat transfer model of vacuum insulated drill pipe was established,and the heat transfer conditions of drill pipe interior,drill pipe inner tube,vacuum layer,drill pipe outer tube and annulus were analyzed along the radial direction of the well,and the heat transfer equations of each structural unit were derived.Finally,a downhole heat transfer model was established and software was written to simulate the downhole temperature field of the vacuum insulated drill pipe to derive the temperature distribution in the well,the inner pipe of the drill pipe,the outer pipe and the annulus.And the heat insulation effect of the vacuum insulated drill pipe was analyzed and compared with that of the drill pipe filled with heat insulation material only,and the study showed that the cooling effect of the vacuum insulated drill pipe was better than that of the drill pipe filled with heat insulation material.The effects of drilling fluid density,displacement,surface heat transfer coefficient,drill pipe thermal conductivity,thermal conductivity and emissivity of insulation materials on downhole temperature were analyzed.The simulated temperature calculation results show that the vacuum insulated drill pipe can better isolate the heat transfer inside and outside the drill pipe,reduce the temperature of drilling fluid reaching the bottom of the well,and improve its cooling effect on drilling tools and downhole instruments,which provides theoretical support for future on-site deep well drilling.