Research On Choke Manifold System Of Managed Pressure Drilling

In order to ensure the safety of drilling in the H₂S formation,Chinese oil and gas industry standard "SY/T5087-2005" stipulates the design of density for drilling high sulfur-bearing strata should take the upper limit 0.15g/cm³ with the safe additional density within the specified range 0.07g/cm³-0.15g/cm³,or take the upper limit 5MPa with the additional bottom hole pressure within the specified range 3MPa-5MPa.In the H₂S formation,the conventional drilling process is used to design the drilling fluid density in the state of stopping the pump,adding 5MPa additional pressure.After the pump circulation,Leakage occurs because the bottom hole pressure is greater than the formation fracture pressure.Such formation is defined as a wall with a narrow pressure window containing H₂S,and fine pressure control drilling technology is an effective way to solve this problem,which accurates control borehole annulus pressure profile,and reduces the occurrence of underground complex with reducing the drilling fluid density,adjusting the wellhead back pressure and hydraulic friction and other parameters.Foreign pressure control drilling system mainly includes Halliburton MPD system,Schlumberger DAPC system and Weatherford MFC system.Through the study,due to fine regulation of wellhead back pressure and measurement of drilling parameters,pressure control drilling ground control system and equipment loss is complex ang big,which causes the high cost of pressure control drilling services and limition for promotion and application.This paper will improve pressure control drilling technology and ground control system to reduce the cost and Increase the efficiency on the basis of the safety of drilling H₂S narrow pressure window formation.In order to give full play of the effect of fine pressure control drilling,the H₂S narrow pressure window formation is further divided into two strata with a narrow pressure window,one area and two area.One area means the disparity between the formation fracture pressure and the formation pore pressure is less than 5MPa.Because the pressure window is very narrow,fine pressure control drilling technology must be used for drilling.In this paper,the system of fine pressure control drilling is designed optimizily.The manual throttle valve is used to cooperate with the automatic throttle valve to reduce the erosion of the automatic throttle and improve the working life of the automatic throttle valve.At the same time,automatic shunt device is designed and mud pump is a good substitute of the function of the back pressure pump,to ensure the safety of drilling and reduce the cost of drilling.Two area means the disparity between the formation fracture pressure and the formation pore pressure is more than or equal to 5MPa.A new type of fine pressure controlled drilling technology is designed for this type of formation:when designing drilling fluid density,firstly complete the calculation of the normal drilling state of the annulus pressure,then add a 0?5MPa of additional safety value according to the size of the cycle of pressure drilling fluid density,not adding wellhead back pressure in normal state and adding wellhead back pressure in other states.All kinds of work condition,the bottom hole pressure in the formation should between pore pressure and fracture pressure,and always at least 5MPa greater than the formation pore pressure.Combined with the characteristics of the pressure-controlled drilling process applied in the second zone of the narrow pressure window,the text also designs other ground throttle system.This study is of great significance to promote the application and application of fine pressure control drilling technology because of the universality of the second area in drilling formation.Combined with theoretical research,the fine pressure control drilling wellhead back pressure control system was optimized.The control process of wellhead back pressure is simulated by conventional PID control,cascade PID control and fuzzy PID control.The simulation results of wellhead back pressure under different control methods are obtained.According to the results,the fuzzy PID control has the characteristics of fine regulation,smoothness and accuracy.Therefore,fuzzy PID control is regarded as the control method of wellhead back pressure of fine pressure control drilling,which provides the basis for the optimization of fine pressure control drilling.