Research On Drilling Theory And Method Based On Dual-circulation System To Reduce Pressure Lost And Improve Efficiency

With the continuous development of oil and gas exploration and development,the number of wells with complex structure wells such as ultra-deep wells and extended reach wells is increasing.Under certain conditions of surface pumps,it is necessary to optimize and control the cyclic pressure loss during operation,especially in large-displacement drilling,the hydraulic extension limit determines the extension length of the trajectory.During the drilling process,due to the difference in wellbore structure,the annulus size of each well section is different,the upper section annulus size is large,the return velocity is low,the lower section annulus size is small,the return velocity is high,and when designing the displacement,In order to meet the requirement of carrying rock,the displacement needs to be designed according to the critical return velocity of the upper large annulus,which makes the lower annulus size smaller well section annulus return velocity much higher than the critical return velocity,increasing the annulus pressure consumption.How to find a way to reduce cyclic pressure loss while keeping the existing drilling conditions unchanged and meeting the drilling needs will be a new topic.In response to this problem,this paper proposes a dual-circulation system based on the changes in the size of the wellbore annulus structure to carry out an exploratory study of the dual-circulation system for reducing consumption and improving efficiency.The dual-circulation system is to consider opening a bypass hole on the drill string facing the junction of the large and small annulus,so that part of the flow in the pipe will be diverted into the annulus,so that the flow of circulating down into the small annulus will be reduced.So as to achieve the purpose of reducing consumption.However,during the drilling process,the entire drill string is continuously descending,and the position of the bypass hole is constantly changing.For this reason,it is further considered to design a bypass valve that can be flexibly controlled on and off using Radio Frequency Identification(RFID).The bypass valve combination is used to achieve the goal of not only satisfying the annulus carrying rock in each well section,but also reducing the small-size annulus displacement and pressure consumption.Firstly,the design ideas and working principles of the dual-circulation system are introduced.On the basis of this analysis,th e work flow and structure of the dual-circulation system are analyzed,and a method to realize the diversion of the dual-circulation system is proposed by means of the bypass valveSecondly,the bypass valve used in the dual-circulation system is designed.Starting from the principle of RFID technology,the working principle of the bypass valve based on RFID technology is introduced,and the overall structure of the bypass valve is designed.The selection of the internal structure of the technical bypass valve is explained one by one,which proves the feasibility of realizing the dual-circulation drilling systemFinally,the pressure loss model and the lowest annulus return velocity calculation model suitable for different rheological parameters and flow conditions are derived.The software development tool VB is used to develop a calculation software that can solve related parameters such as pressure loss and flow rate of the dual-cycle drilling system.Three cases(ultra-deep wells,slim-hole wells,and extended-reach wells)were used to verify the system,and finally concluded that the dual-cycle drilling system can effectively reduce pressure loss while ensuring the efficiency of rock carryingThe dual-circulation system proposed in this paper has the advantage of reducing the annulus pressure loss,but it also has the disadvantage of reducing the hydraulic energy obtained by the drill bit.Therefore,the work in this paper is a pilot study,which extends the exploration of extended reach wells under extreme conditions.It is of great significance to develop drilling technologies for complex structure wells such as ultra-super well deep drilling and slim-hole narrow annulus clearance.