The Research Of Improving The Drilling Problem On Bit Weight By Using New Thruster

With the development of unconventional oil and gas resources,the application of horizontal well drilling technology has been increasing,among which the problem of drilling weight on the bit is one of those that must be solved.In this paper,the new booster is designed to improve the problem of drilling weight on the bit that is hard to be exerted and the high-level resistance between the coiled tubing and borehole wall so as to realize efficient drilling,to increase production as well as to save cost.Owing to the increasing difficulty of drilling,the technology of coiled tubing drilling is proposed to solve the related problem.The application of the technology coiled tubing drilling has great effect on the development of drilling automation.What’s more,it can greatly reduce the cost of drilling operation and improve labor efficiency.So the technology could become the mainstream method of drilling in the future,but there are still some deficiencies in the coiled tubing drilling.The focus of the drilling programs are converting gradually to the deep development and the stratigraphic structure is becoming more and more complex.Meanwhile,because of the small diameter of the coiled tubing,lower flexibility,lower compressive strength of structural characteristics,this may bring about some problems that the increased friction with the borehole wall makes the coiled tubing drilling difficultly,or that the bit weight will be difficult to exerted on the drill bit due to the coiled tubing pressing on surface of wall.Therefore,new equipment and technologies are needed to be used to improve the above problems so as to realize efficient drilling.In order to solve the problem of weight on the bit as well as high-level resistance,this paper is planned to improve the efficiency of the coiled tubing drilling from two aspects.The first aspect is to reduce the friction between the coiled tubing and the borehole wall.On the other hand,the weight on the bit is increased through downhole thruster,and the drill bit is provided with a larger and more stable axial force.Finally,a new booster is designed,which consists of two parts: fluid flowing control device and hydraulic thruster.In the first part,it’s the design of fluid flowing control device.Firstly,the working principle is introduced in detail.Then,the overall design scheme and local structure of flowing control device is put forward,including the power end,hydraulic end and control part.The role of the power end is to provide the power for the realization of reciprocating motion of the actuator in hydraulic end,which can realize inhalation and exclusion of drilling fluid.Besides,the function of the control part is to realize the coordination on the power end and hydraulic end,to interconnect between each other and to achieve expected results.For the design of the power end,mainly includes the design of the structure of the valve and its core as well as its corresponding calculation in size,such as the length of lifting,the speed controlling,and the flowing parameters related to the size of the calculation.Then a check of the overall intensity about the valve is carried on.For the design of the hydraulic end,mainly includes the design of the structure of the hydraulic cylinder and the design of import and export valve as well as the calculation of the corresponding dimensions and parameters,such as the size of diameter,length,thickness,stroke and so on.Control circuit is designed to control the movement of the valve core in the power end,which changes fluid flowing of the power end,then pressure on the left-end of implementation part of hydraulic end will be changed,so as to realize the non-uniform and reciprocating motion of the implementation part.Finally,fluid pulsation in the hydraulic end will be caused,and the signals of the cutoff point about the journey will be given back to control circuit by Hall switch,then triggering circuit switches’ action orderly,which will change the motion in the power end.So a closed control system is set up a to take a control of fluid flowing.The second part of the design is about the hydraulic thruster downhole,the function of which is mainly to exert axial pressure on drill bit under the condition that coiled tubing is pressed on wall closely.The structure design and analysis include the circulation of the one-way valve,the design of the cylinder as well as the calculation of its outside diameter size,length,and the axial thrust.Finally,The stability is verified by mathematical analysis.After determining the structure and parameters of each part,use CAD to draw the two-dimensional engineering graphics and the 3d modeling by SolidWorks,then use ANSYS to analyze the stress of the components that may be easily damaged.Compared the results of mathematical analysis with that of the software analysis,its feasibility will be verified.Finally,the principle of the device is introduced in detail.All in all,On the one hand,the new booster can achieve 3.72 Hz fluid pulsation by flowing control device,and can make the coiled tubing vibrate in the security range,of which the pressure fluctuation amplitude is 1.84 MPa.So it is able to improve the situation when the high-level resistance is encountered in the process of coiled tubing drilling in horizontal Wells,which may lead to a difficulty of laying down the coiled tubing.On the other hand,a axial force,19.33 k N,is able to beexerted on the bit by the downhole hydraulic-compound thruster,which can provide larger weight on the bit as well as avoid the instability caused by long stroke,so as to improve the other situations that the weight on the bit is difficult to be exerted.The improvement of these two aspects has great help to improve the efficiency of the coiled tubing drilling operation,and it can save economic cost to a great extent,and it is extremely economic and has high efficiency.