Deepwater pressure-controlled drilling well bottom pressure control system and deepwater block drilling well site

Abstract

The invention provides a deepwater pressure control drilling well bottom pressure control system which comprises a marine riser gas treatment system which is located below a tension ring, integrally located below the water surface and composed of an upper connector, a rotary control head, an annular blowout preventer, a flow guide four-way joint and a lower connector from top to bottom. The ground manifold system is connected with the slurry return pipeline and consists of a shunting manifold, a filtering manifold and a throttling manifold which are connected in sequence; and the pressure measuring system is used for measuring the real-time pressure of the seabed blowout preventer, the flow guide four-way joint, the flow dividing manifold and the throttling manifold. On the basis of the drilling fluid circulation U-shaped pipe principle and in combination with a marine riser gas treatment system, the fluid circulation double-U-shaped pipe principle is innovatively provided, the number of power sources for pumping deep water pressure control drilling fluid is two, the two power sources are the drilling pump and the augmented injection pump respectively, and the fluid circulation double-U-shaped pipe principle is achieved; therefore, the process requirements of pressure-controlled drilling, pressure-controlled connection of the stand column and safe exhaust of the marine riser are met.

Description

Technical Field

[0001] The present invention relates to the technical field of deepwater controlled pressure drilling, and in particular to a deepwater controlled pressure drilling bottom hole pressure control system and a deepwater block drilling well site. Background Art

[0002] Deepwater formations are different from terrestrial formations. As seawater replaces the overlying rock formations, the formation fracture pressure or formation leakage pressure is significantly reduced. The South China Sea is located at the intersection of three major plates, and the diapir structure is abnormally developed, making the formation pressure in this area abnormally high. Therefore, the outstanding problems of deepwater drilling are narrow safety density window, difficulty in dealing with gas invasion, and difficulty in controlling bottom hole pressure.

[0003] During the drilling process, the inner hole of the drill string in the well forms a connected system with the annulus through the drill bit water hole, just like a U-shaped tube. Under any working conditions, once the bottom hole pressure is less than the formation pore pressure, the formation product will flow into the wellbore and overflow will occur; when the bottom hole pressure is greater than the formation pore pressure, once it exceeds the formation fracture pressure or loss pressure, the drilling fluid will leak into the formation and well leakage will occur.

[0004] In the existing technology, the common and thorny engineering problem encountered in deepwater drilling is the leakage and overflow problem under the condition of narrow formation density window. When using conventional deepwater drilling technology to deal with the above problems, there is no accurate real-time data of pressure loss of each section of the circulation pipeline as the data basis, which makes the existing technology complex and prone to failure, long processing cycle and high well control risk.

[0005] In view of the problems of the prior art, the present invention provides a deepwater controlled pressure drilling bottom hole pressure control system and a deepwater block drilling well site. Summary of the invention

[0006] In order to overcome the defects of the prior art, the purpose of the present invention is to provide a deepwater managed pressure drilling bottom hole pressure control system, the control system comprising:

[0007] The riser gas handling system is located below the tension ring and below the water surface. From top to bottom, it consists of an upper joint, a rotating control head, an annular blowout preventer, a diversion spool, and a lower joint.

[0008] The ground manifold system is connected to the return slurry pipeline and is composed of a diversion manifold, a filter manifold, and a throttling manifold connected in sequence;

[0009] The pressure measurement system is used to measure the real-time pressure at the seabed blowout preventer, the diversion spool, the diverter manifold, and the throttling manifold respectively.

[0010] According to one embodiment of the present invention, the upper joint is connected to the drilling pump; one end of the rotating control head is connected to the upper joint, and the other end is connected to the annular blowout preventer; the flow guide four-way is respectively connected to the annular blowout preventer, the upper end of the riser, the riser injection side pipe, and the inlet end of the return slurry pipeline, wherein the riser injection side pipe is also connected to the injection pump; the subsea blowout preventer is arranged on the drill string, and the upper end is connected to the lower end of the riser.

[0011] According to one embodiment of the present invention, the inlet end of the diversion manifold is connected to the outlet end of the return slurry pipeline, and the outlet end is connected to the inlet end of the filtration manifold; the outlet end of the filtration manifold is connected to the inlet end of the throttling manifold, and the outlet end is connected to the circulation tank.

[0012] According to one embodiment of the present invention, there are two power sources for pumping drilling fluid in deepwater controlled pressure drilling, namely the drilling pump and the boosting pump, wherein the drilling fluid pumped by the drilling pump flows through the platform riser manifold, the drill string, the drill bit, the wellbore annulus below the mud line, the subsea blowout preventer, the riser annulus, the riser gas treatment system, the ground manifold system, and the circulation tank; the drilling fluid pumped by the boosting pump flows through the riser injection side pipe, the subsea blowout preventer, the riser annulus, the riser gas treatment system, the ground manifold system, and the circulation tank.

[0013] According to one embodiment of the present invention, the pressure measurement system includes: a first pressure measuring device arranged at the position of the subsea blowout preventer, a second pressure measuring device arranged at the outlet of the diversion spool, a third pressure measuring device arranged at the inlet of the diversion manifold, and a fourth pressure measuring device arranged at the inlet of the throttling manifold.

[0014] According to another aspect of the present invention, a deepwater block drilling site is also provided, and the drilling site comprises a deepwater controlled pressure drilling bottom hole pressure control system as described in any one of the above items.

[0015] According to another aspect of the present invention, there is also provided a method for controlling bottom hole pressure in deepwater managed pressure drilling, which is executed by a control system as described in any one of the above items, and the method comprises:

[0016] Based on the geologically predicted formation pressure, the safety density window is predicted to obtain the predicted value of the safety density window;

[0017] During the controlled pressure drilling process in a narrow density window, a drilling fluid having a density less than the lower limit of the predicted value of the safety density window is used to achieve a bottom hole circulating equivalent density balance formation pressure during the circulation process and within the predicted value of the safety density window;

[0018] When performing casing pressure control, the target casing pressure is calculated based on the measured casing pressure, drilling parameters, drilling fluid rheological properties and target bottom hole pressure. The throttle valve opening is adjusted to make the measured casing pressure equal to the target casing pressure, thus achieving bottom hole pressure control.

[0019] When performing vertical pressure control, the target vertical pressure is calculated based on the measured vertical pressure, drilling parameters, drilling fluid rheological properties and target bottom hole pressure. The measured vertical pressure is equal to the target vertical pressure by adjusting the throttle valve opening to achieve bottom hole pressure control.

[0020] When performing flow control, the size relationship of the inlet flow is determined. When the inlet and outlet flows deviate, the casing pressure control or the vertical pressure control is converted to the flow control, and the throttle valve is adjusted to balance the inlet and outlet flows. Then, the casing pressure control or the vertical pressure control is performed based on the bottom hole pressure at the time of flow balance as the target bottom hole pressure.

[0021] According to one embodiment of the present invention, the first U-shaped tube is formed by the drill string, the drill bit, and the annulus below the mudline, and a bottom hole pressure balance relationship is established on both sides of the first U-shaped tube, thereby establishing a relationship between the standpipe pressure, the bottom hole pressure, and the casing pressure, wherein:

[0022] The bottom hole pressure expression of the first U-shaped tube with one side of the drill string as the object is:

[0023] P BH =P cs -P fd -P fb +P dsm

[0024] Where: P BH is the bottom hole pressure, MPa; P cs is the drilling pump circulation standpipe pressure, MPa; P fd is the circulating pressure loss in the drill string, MPa; P fb is the drill bit pressure drop, MPa; P dsm is the hydrostatic pressure in the drill string, MPa;

[0025] The bottom hole pressure expression of the first U-shaped tube with one side in the annulus as the object is:

[0026] P BH =P cam +P fca +P ram +P fra +P 地面 +P w1

[0027] Where: P BH is the bottom hole pressure, MPa; P cam is the static pressure in the casing annulus, MPa; Pfca is the circulating pressure loss in the casing annulus, MPa; P ram is the hydrostatic pressure in the riser annulus, MPa; P fra is the circulation pressure loss in the riser annulus, MPa; P 地面 is the pressure loss between the diversion spool and the inlet of the throttling manifold, which is the sum of the displacement of the drilling pump and the displacement of the injection pump, MPa; P w1 is the wellhead back pressure, MPa.

[0028] According to one embodiment of the present invention, the second U-shaped tube is composed of the riser injection side tube, the subsea blowout preventer, the riser annulus, and the riser gas processing system annulus. The bottom hole pressure balance relationship is established on both sides of the second U-shaped tube, thereby establishing a relationship between the riser pressure, the bottom hole pressure, and the casing pressure, wherein:

[0029] The bottom hole pressure expressed with one side of the annulus as the object includes the second U-shaped tube composed of the riser injection side tube and the riser annulus. The bottom hole pressure expression of the second U-shaped tube with one side of the riser injection side tube as the object is:

[0030] P bh =P bcs -P fbl +P bsm

[0031] Where: P bh is the bottom hole pressure of the second U-tube circulation, MPa; P bcs is the circulation standpipe pressure of the booster pump, MPa; P fbl P is the circulating pressure loss in the riser injection pipe, MPa; bsm The static pressure of the water in the riser side pipe, MPa;

[0032] The bottom hole pressure expression of the second U-shaped tube with one side in the annulus as the object is:

[0033] P bh =P ram +P fra1 +P 地面1 +P w2

[0034] Where: P bh is the bottom hole pressure of the second U-tube circulation, MPa; P ram is the hydrostatic pressure of the riser annulus, MPa; P fra1 P is the pressure loss of the inner circulation of the riser annulus, which is only the injection displacement, MPa; 地面1 is the pressure loss between the diversion cross and the throttling manifold inlet, which is only the displacement of the injection pump, MPa; P w2 is the wellhead back pressure, MPa.

[0035] According to one embodiment of the present invention, the method further comprises a riser gas handling system installation step, wherein:

[0036] The subsea blowout preventer group and riser pipes are lowered in sequence. When the last riser pipe is lowered, the working chuck of the riser gas handling system is installed to connect the riser gas handling system with the lowered riser pipe. The riser gas handling system is slowly lowered to connect the return slurry pipeline and the electric and hydraulic control pipelines at the diversion four-way above the water surface, and finally the riser gas handling system is connected to the tension ring of the drilling platform.

[0037] According to one embodiment of the present invention, the method further comprises a surface manifold system installation step, wherein:

[0038] The surface manifold system is deployed on the drilling platform deck in a planar arrangement or tower stacking manner and pipelines are connected. The return slurry pipeline connected to the diversion manifold is connected to the diversion manifold, and the throttling manifold outlet is connected to the liquid-gas separator of the drilling platform.

[0039] According to one embodiment of the present invention, the method further comprises a surface manifold system pressure loss evaluation step, wherein:

[0040] According to the reading of the six-speed viscometer of the drilling fluid, select the rheological model suitable for the drilling fluid on the shear rate-shear stress chart;

[0041] Considering the shape, size, height span, and right-angle bend of the pipelines in the ground manifold system, a flow channel model is established;

[0042] For right-angle bends, the right-angle bends are treated equivalently according to the inner diameter of the pipe;

[0043] The pressure measurement system is used to measure the circulation pressure loss under different displacements and different return slurry flow channels, and the pressure loss calculation model of the ground manifold system is calibrated.

[0044] According to one embodiment of the present invention, the method further comprises a bottom hole pressure control step when suspected gas invasion or overflow occurs, wherein:

[0045] When suspected gas invasion occurs, stop drilling and use the measured vertical pressure as the vertical pressure target value to perform constant bottom hole pressure exhaust with vertical pressure control;

[0046] When suspected overflow occurs, stop drilling and use the measured vertical pressure as the vertical pressure target value for vertical pressure control; observe the flow change curve. If the flow shows a trend of continuous increase, implement flow control and reduce the throttle valve opening to balance the inlet and outlet flows. At this time, a new vertical pressure target value is obtained, and vertical pressure control is performed based on this vertical pressure target value to discharge overflow at a constant bottom hole pressure;

[0047] After the constant bottom hole pressure overflow is completed, it is switched to casing pressure control. If the casing pressure value is higher than the set value at this time, it is necessary to increase the density of the drilling fluid to reduce the casing pressure, and then implement the pressure controlled drilling operation under the casing pressure control.

[0048] According to another aspect of the present invention, a storage medium is provided, which contains a series of instructions for executing the method steps as described in any one of the above.

[0049] The present invention provides a deepwater controlled pressure drilling bottom hole pressure control system and a deepwater block drilling well site, which has the following advantages over the prior art:

[0050] 1) The rotating control head is installed under the tension ring, so that the maximum pressure control value of the deepwater controlled pressure drilling bottom hole pressure control system provided by the present invention is not limited by the pressure bearing capacity of the expansion joint in the platform riser system.

[0051] 2) The present invention is based on the U-tube principle for drilling fluid circulation and combines the riser gas treatment system to innovatively propose a double U-tube principle for fluid circulation. There are two power sources for pumping drilling fluid into deepwater controlled pressure drilling, namely the drilling pump and the booster pump, realizing the double U-tube for fluid circulation, thereby meeting the process requirements of controlled pressure drilling, controlled pressure connection of columns, and safe exhaust of risers.

[0052] 3) By setting up a pressure measurement system and focusing on the first pressure measuring device at the seabed blowout preventer, the pressure consumption of each section of the circulation pipeline can be obtained in real time, providing a more accurate data source for bottom hole pressure calculation.

[0053] 4) The bottom hole pressure control method is based on the U-shaped tube principle of drilling fluid circulation and combines the double U-shaped tube principle with the riser gas treatment system. For the two U-shaped tubes in deepwater controlled pressure drilling, the bottom hole pressure balance relationship is established from the inside of the tube and the annulus respectively, so as to meet the process requirements of controlled pressure drilling, controlled pressure connection column, and safe exhaust of the riser;

[0054] 5) The bottom hole pressure control method relies on the pressure measurement system to verify the numerical simulation results of the hydraulic calculation software and the circulating pressure loss of each pipeline;

[0055] 6) Bottom hole pressure control methods include casing pressure control, stand pressure control, and flow control. The deepwater drilling technical problems that can be solved include: safe drilling in a narrow density window, venting of gas-invaded risers, constant bottom hole pressure drilling in formations with unclear formation pressure, and constant bottom hole pressure column connection.

[0056] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0058] Figure 1 A schematic structural diagram of a deepwater managed pressure drilling bottom hole pressure control system according to an embodiment of the present invention is shown;

[0059] Figure 2 A schematic diagram of a double U-shaped pipe for wellbore fluid circulation according to an embodiment of the present invention is shown;

[0060] Figure 3 A flowchart showing the steps of a method for controlling bottom hole pressure in deep water managed pressure drilling according to an embodiment of the present invention is shown;

[0061] Figure 4 A flowchart showing the steps of installing a deepwater managed pressure drilling bottom hole pressure control system and a deepwater managed pressure drilling bottom hole pressure control method according to an embodiment of the present invention is shown.

[0062] In the accompanying drawings, the same reference numerals are used for the same components. In addition, the accompanying drawings are not drawn according to the actual scale.

[0063] The meanings of the various reference numerals in the accompanying drawings are as follows: 1-inside the drill string; 2-wellbore annulus below the mud line; 3-subsea blowout preventer; 4-rise annulus; 5-rise injection side pipe; 6-diversion spool; 7-annular blowout preventer; 8-rotating control head; 9-return slurry pipeline; 10-diversion manifold; 11-filtration manifold; 12-throttling manifold; 13-drilling pump; 14-injection pump; 15-first pressure measuring device; 16-second pressure measuring device; 17-third pressure measuring device; 18-fourth pressure measuring device. DETAILED DESCRIPTION

[0064] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

[0065] Managed pressure drilling technology is an adaptive drilling technology used to accurately control the pressure profile of the entire wellbore annulus. Its purpose is to determine the downhole pressure environment limit and thereby control the wellbore annulus pressure profile. Deepwater controlled pressure drilling can be divided into two types based on the means of controlling pressure: pressure control and liquid level control. In the prior art, deepwater controlled pressure drilling process technology represented by pressure control adopts a controlled pressure drilling RGH system based on a platform riser system to construct a closed, pressurized drilling fluid circulation path, which can realize various forms of bottom hole pressure control methods. Some of the rotating control heads in the controlled pressure drilling RGH systems of foreign oil service companies are installed on the tension ring. The maximum pressure control value of the rotating control head installed on the tension ring is limited by the pressure-bearing capacity of the expansion joint in the platform riser system (generally not exceeding 500psi). The pressure control value in actual application is often greater than the pressure-bearing capacity of the expansion joint. The deepwater pressure-controlled drilling technology represented by liquid level control mainly has a riser pump as its underwater core equipment. The liquid column pressure and bottom hole pressure are regulated by adjusting the liquid level in the riser, and it is a non-closed pressurized circulation path.

[0066] At present, deepwater controlled pressure drilling at home and abroad mostly uses pressure control means to carry out controlled pressure drilling operations. The control method described in the prior art (application number: 202010911736.X) can be summarized as setting the content range of downhole hydrocarbon substances. Within this range, there is no need to adjust the bottom hole pressure. If it is not within this range, the hydrocarbon substances are restored to the set range by adjusting the casing pressure or adjusting the drilling fluid density. However, the bottom hole pressure control method described in the prior art is a method for dealing with downhole well intrusions, which gives an expected range and proposes a treatment method. The disadvantage is that for deepwater drilling, the operational risks and challenges are greater than those for land and shallow water drilling. The invasion of well intrusions should be discovered in time, effectively suppressed and handled, and effectively controlled, rather than maintained within a certain expected range.

[0067] The control method described in the prior art (application number: 201811286680.2) utilizes the static column pressure of the drilling fluid, the annulus hydraulic friction, and the throttling pressure, and assigns a pressure safety fluctuation range. After the circulating pressure loss is verified by the downhole pressure measuring device, the casing pressure of the wellbore is controlled. However, the application scenarios of this prior art are more in land drilling and shallow water drilling operations, and the pressure control is mainly based on casing pressure control. For deepwater drilling using floating platforms, the drilling fluid circulation process is significantly different from that of land and shallow water drilling. In addition to the annulus friction, the circulation friction in the long-distance return slurry pipeline and the height difference between the pressure-controlled drilling manifold system and the return slurry port are also worth considering.

[0068] In summary, in the existing technology, the common and difficult engineering problems encountered in deepwater drilling are the leakage and overflow problems under the conditions of narrow density windows of formations. The conventional deepwater drilling technology has high complexity and failure rate, long processing cycle and high well control risk when dealing with the above problems. How to accurately control the balance between bottom hole pressure and formation pressure under narrow density window conditions has become the key to the success of deepwater drilling. Deepwater controlled pressure drilling technology relies on deepwater controlled pressure drilling technology, deepwater controlled pressure drilling equipment, automatic control system and real-time hydraulic calculation software. It can achieve precise control of bottom hole pressure during drilling, constant bottom hole pressure connection column, and gas intrusion and overflow discharge of watertight pipe, thereby reducing the complexity, timeliness and well control risks, and improving the success rate of deepwater drilling.

[0069] In view of the complex engineering problems encountered in deepwater drilling such as high temperature, high pressure and narrow safety density window, the present invention proposes a double U-tube structure for deepwater controlled pressure drilling and combines the U-tube principle and the characteristics of deepwater controlled pressure drilling equipment to propose a deepwater controlled pressure drilling bottom hole pressure control system, a deepwater block drilling site and a control method; the circulating pressure loss can be directly obtained according to the reading of the set pressure measurement system and the pressure loss calculation model of the ground manifold system can be corrected; according to different situations, accurate control of the bottom hole pressure is achieved through different control targets, and the casing pressure control, vertical pressure control, flow control or a combination of the above control methods are correctly selected according to the downhole situation to achieve bottom hole pressure control.

[0070] Figure 1 A schematic structural diagram of a deepwater managed pressure drilling bottom hole pressure control system according to an embodiment of the present invention is shown.

[0071] A deepwater controlled pressure drilling bottom hole pressure control system comprises: a watertight pipe gas processing system, a surface manifold system and a pressure measurement system.

[0072] like Figure 1 As shown, in one embodiment, the watertight pipe gas handling system is located below the tension ring and is located below the water surface as a whole. Figure 1 Not shown), rotating control head 8, annular blowout preventer 7, flow guide spool 6, lower joint ( Figure 1 Not shown) composition.

[0073] Specifically, the riser gas handling system includes: upper and lower joints, a rotary control head 8, an annular blowout preventer 7, and a flow guide spool 6. Further, the upper joint is connected to the drilling pump 13. One end of the rotary control head 8 is connected to the upper joint, and the other end is connected to the annular blowout preventer 7. The flow guide spool 6 is respectively connected to the annular blowout preventer 7, the upper end of the riser 4, the riser injection side pipe 5, and the inlet end of the return slurry pipeline 9, wherein the riser injection side pipe 5 is also connected to the injection pump 14.

[0074] Furthermore, the riser gas handling system is connected to the floating platform riser through upper and lower connecting joints; the riser gas handling system is located below the tension ring and is located below the water surface as a whole; the riser gas handling system is composed of an upper joint, a rotating control head 8, an annular blowout preventer 7, a diversion spool 6, and a lower joint from top to bottom.

[0075] like Figure 1 As shown, in one embodiment, a subsea blowout preventer 3 is disposed on a drill string, and an upper end thereof is connected to a lower end of a riser 4 .

[0076] In the prior art controlled pressure drilling system, the rotary control head is installed on the tension ring, and its maximum controlled pressure is limited by the pressure bearing capacity of the expansion joint in the platform riser system (generally not more than 500psi). The controlled pressure value in actual application is often greater than the pressure bearing capacity of the expansion joint. In the present invention, the rotary control head 8 is installed under the tension ring, so that the maximum controlled pressure of the deepwater controlled pressure drilling bottom hole pressure control system provided by the present invention is not limited by the pressure bearing capacity of the expansion joint in the platform riser system, and is suitable for application in high temperature and high pressure environments encountered in deepwater drilling.

[0077] like Figure 1 As shown, in one embodiment, the surface manifold system is connected to the return slurry pipeline 9, and is composed of a shunt manifold 10, a filter manifold 11, and a throttling manifold 12 connected in sequence. Specifically, the inlet end of the shunt manifold 10 is connected to the outlet end of the return slurry pipeline 9, and the outlet end is connected to the inlet end of the filter manifold 11; the outlet end of the filter manifold 11 is connected to the inlet end of the throttling manifold 12, and the outlet end is connected to the circulation tank ( Figure 1 ) connection.

[0078] like Figure 1 As shown, in one embodiment, the pressure measurement system is used to measure the real-time pressure at the subsea blowout preventer 3, the diversion spool 6, the flow manifold 10, and the choke manifold 12. Specifically, the pressure measurement system includes: a first pressure measuring device 15 arranged at the subsea blowout preventer 3, a second pressure measuring device 16 arranged at the outlet of the diversion spool 6, a third pressure measuring device 17 arranged at the inlet of the flow manifold 10, and a fourth pressure measuring device 18 arranged at the inlet of the choke manifold 12.

[0079] Furthermore, in the pressure measurement system, the pressure P1 measured by the first pressure measuring device 15 represents the hydrostatic column pressure P in the riser annulus 4 above the point. ram , Circulation pressure loss in the riser annulus 4 (P fra , P fra1 ), the circulation pressure loss between the return slurry outlet of the diversion spool 6 and the drilling fluid inlet of the throttling manifold 12 (P 地面 , P 地面1 ), which is the sum of the three.

[0080] The difference P1-P2 between the readings of the first pressure measuring device 15 and the second pressure measuring device 16 represents the sum of the hydrostatic column hydraulic pressure and the circulating pressure loss between the two.

[0081] The pressure difference P2-P3 measured by the second pressure measuring device 16 and the third pressure measuring device 17 represents the circulating pressure loss in the return slurry pipeline 9 between the two devices. Specifically, the reading difference P2-P3 between the second pressure measuring device 16 and the third pressure measuring device 17 represents the sum of the static liquid column pressure and the friction resistance along the way.

[0082] The pressure difference P3-P4 measured by the third pressure measuring device 17 and the fourth pressure measuring device 18 represents the circulating pressure loss in the pipeline of the ground manifold system between the two devices. Specifically, the reading difference P3-P4 between the third pressure measuring device 17 and the fourth pressure measuring device 18 represents the sum of the hydrostatic column hydraulic pressure and the friction resistance along the way between the two.

[0083] Furthermore, in practical applications, the relative height difference between the diversion spool 6 and the slurry inlet of the diversion manifold 10 will be affected by the up and down heave of the floating platform; the friction along the way between the slurry inlet of the diversion manifold 10 and the slurry inlet of the throttling manifold 12 is affected by the shape, size, pipe turning angle of each manifold pipe and the relative height between the manifolds.

[0084] In the existing technology, the common and thorny engineering problem encountered in deepwater drilling is the leakage and overflow problem under the condition of narrow formation density window. When using conventional deepwater drilling technology to deal with the above problems, there is no accurate real-time data of pressure loss of each section of the circulation pipeline as the data basis, which makes the existing technology complex and prone to failure, long processing cycle and high well control risk.

[0085] This method can monitor and obtain the pressure value at the setting position in real time through the pressure measurement system, and can obtain the circulating pressure loss between different positions through the pressure difference. Make full use of the first pressure measuring device 15 set at the seabed blowout preventer 3. On the one hand, it can reflect the circulating pressure loss from the diversion four-way 6 to the throttling manifold 12, and on the other hand, the pressure value there can be used as an accurate reference data for the calculation of the bottom hole pressure. In addition, the ground pipeline of deep-water pressure-controlled drilling is long, and the circulating pressure loss cannot be ignored like land or shallow water drilling. The present invention establishes a pressure loss measurement system (pressure measurement system) in the ground manifold pipeline, which can provide a more accurate data source for the calculation of the bottom hole pressure and provide a data basis for the judgment of leakage and overflow.

[0086] Figure 2 A schematic diagram of a double U-shaped pipe for wellbore fluid circulation according to an embodiment of the present invention is shown.

[0087] In the present invention, there are two power sources for pumping drilling fluid into deepwater controlled pressure drilling, namely, drilling pump 13 and booster pump 14, wherein the drilling fluid pumped by drilling pump 13 flows through the platform riser manifold, drill string 1, drill bit, wellbore annulus 2 below mudline, subsea blowout preventer 3, riser annulus 4, riser gas treatment system, surface manifold system, and circulation tank. The drilling fluid pumped by booster pump 14 flows through riser booster side pipe 5, subsea blowout preventer 3, riser annulus 4, riser gas treatment system, surface manifold system, and circulation tank.

[0088] Specifically, in the present invention, the first U-shaped tube is composed of the drill string 1, the drill bit, and the annulus 2 below the mudline; the second U-shaped tube is composed of the watertight pipe injection side pipe 5, the seabed blowout preventer 3, the watertight pipe annulus 4, and the watertight pipe gas treatment system annulus. Further, the drilling fluid components in the watertight pipe annulus 4 of the second U-shaped tube participated by the injection pump 14 are the drilling fluid in the original circulation tank and the cuttings-containing drilling fluid in the wellbore annulus 2 below the mudline.

[0089] In the drilling process of the prior art, the inner hole of the drill string in the well forms a connected system with the annulus through the drill bit water hole, like a U-shaped tube. Under any working conditions, once the bottom hole pressure is less than the formation pore pressure, the formation product will flow into the wellbore and overflow will occur; when the bottom hole pressure is greater than the formation pore pressure, once it exceeds the formation fracture pressure or loss pressure, the drilling fluid will leak into the formation and well leakage will occur.

[0090] Different from controlled pressure drilling on land and in shallow water, the deepwater controlled pressure drilling bottom hole pressure control system provided by the present invention has two U-shaped tubes in the drilling fluid circulation process. The present invention is based on the principle of U-shaped tubes for drilling fluid circulation and combines the riser gas treatment system to innovatively propose the principle of double U-shaped tubes for fluid circulation. There are two power sources for pumping drilling fluid into deepwater controlled pressure drilling, namely the drilling pump 13 and the booster pump 14, realizing the double U-shaped tubes for fluid circulation, thereby meeting the process requirements of controlled pressure drilling, controlled pressure connection columns, and safe exhaust of risers, and can to a certain extent solve the outstanding problems of narrow safety density window, difficult gas invasion treatment, and difficult bottom hole pressure control in deepwater drilling.

[0091] According to another aspect of the present invention, a deepwater block drilling well site is provided, which includes a deepwater controlled pressure drilling bottom hole pressure control system provided by the present invention.

[0092] The present invention can effectively solve the problem of deepwater narrow density window drilling; reduce complexity and timeliness, reduce well control risks; and improve the success rate of deepwater drilling. The present invention provides deepwater pressure-controlled underwater key equipment (deepwater pressure-controlled drilling bottom hole pressure control system) and a bottom hole pressure control method (deepwater pressure-controlled drilling bottom hole pressure control method). In view of the different process requirements of deepwater pressure-controlled drilling, a double U-tube mode for fluid circulation is proposed. On the basis of conventional hydraulic calculations, by setting up a pressure measurement system and focusing on the use of the first pressure measuring device 15 at the seabed blowout preventer 3, the pressure consumption of each section of the circulation pipeline can be acquired in real time, providing a more accurate data source for bottom hole pressure calculation.

[0093] The present invention calculates the bottom hole pressure based on the principle of the U-shaped tube of the controlled pressure drilling; in combination with the characteristics of the floating platform and the deep-water controlled pressure drilling equipment, the pressure measuring devices are installed on the seabed blowout preventer group 3, the return slurry port of the diversion spool 6, the slurry inlet of the diversion manifold 10, and the slurry inlet of the throttling manifold 12; the circulation pressure consumption of each section is calculated according to the wellbore structure, the drilling tool assembly, the drilling fluid performance, the rheological mode of the drilling fluid, the drilling displacement, the pipe diameter and the deployment mode of the controlled pressure drilling manifold system, and the pressure difference between the pressure measuring devices is used as the standard for verification; the bottom hole pressure control method can adopt casing pressure control, vertical pressure control, flow control, and the control method can be used in combination according to the downhole situation.

[0094] Figure 3 A flowchart of the steps of a method for controlling bottom hole pressure in deepwater managed pressure drilling according to an embodiment of the present invention is shown.

[0095] like Figure 3 As shown, in step S301, the safety density window prediction value is obtained. Specifically, based on the geologically predicted formation pressure, the safety density window is predicted to obtain the safety density window prediction value. Further, based on the geologically predicted formation pressure, the predicted safety density window Δρ 安全密度窗口(预测) for:

[0096] Δρ 安全密度窗口(预测) =(max{ρ 坍塌压力系数 , ρ 孔隙压力系数},min{ρ 漏失压力系数 , ρ 破裂压力系数})

[0097] If Δρ 循环压耗 >Δρ 安全密度窗口(预测) , i.e., a narrow density window.

[0098] like Figure 3As shown, in step S302, the bottom hole circulating equivalent density is balanced to achieve the formation pressure in the circulation process and is within the predicted value of the safety density window. Specifically, in the pressure controlled drilling process of the narrow density window, a drilling fluid with a density less than the lower limit of the predicted value of the safety density window is used to achieve the bottom hole circulating equivalent density balanced to achieve the formation pressure in the circulation process and is within the predicted value of the safety density window. Furthermore, stopping the pump and keeping it stationary corresponds to the column connection operation. In order to achieve a constant bottom hole pressure, a second U-shaped pipe circulation passage is required. The booster pump 14 and the pressure controlled drilling manifold system adjust the throttle valve opening to achieve back pressure compensation. This is casing pressure control. The back pressure equivalent drilling fluid density applied is the predicted formation pressure equivalent drilling fluid density plus 0.02g / cm 3 , which is a casing pressure control method for narrow density window column connection operations.

[0099] like Figure 3 As shown, in step S303, casing pressure control is performed. Specifically, when performing casing pressure control, the target casing pressure (predicted formation pressure) is calculated based on the measured casing pressure, drilling parameters, drilling fluid rheological properties and target bottom hole pressure, and the measured casing pressure is equal to the target casing pressure by adjusting the throttle valve opening to achieve bottom hole pressure control. Furthermore, the actuators for bottom hole pressure control are all throttle valves, but the control targets of interest are casing pressure, riser pressure and outlet flow.

[0100] like Figure 3 As shown, in step S304, the vertical pressure is controlled. Specifically, when performing the vertical pressure control, the target vertical pressure (predicted formation pressure) is calculated based on the measured vertical pressure, drilling parameters, drilling fluid rheological properties and target bottom hole pressure, and the throttle valve opening is adjusted so that the measured vertical pressure is equal to the target vertical pressure to achieve bottom hole pressure control.

[0101] like Figure 3 As shown, in step S305, flow control is performed. Specifically, when performing flow control, the magnitude relationship of the inlet flow is determined, and when the inlet and outlet flow rates deviate, the casing pressure control or the vertical pressure control is converted to the flow control, and the throttle valve is adjusted to balance the inlet and outlet flow rates, and then the casing pressure control or the vertical pressure control is performed based on the bottom hole pressure when the flow rate is balanced as the target bottom hole pressure.

[0102] Casing pressure control is used in pressure controlled drilling operations and column connection operations under narrow safety density windows using low-density drilling fluid and when the annulus is not invaded by oil and gas. It can also be used for pressure control in the process of circulating weighted drilling fluid; flow control is used to determine whether there is overflow in the well, and this control method can obtain the actual target bottom hole pressure; standpipe pressure control is used when the annulus is invaded by oil and gas or in high-pressure formations. After flow control is completed, the target bottom hole pressure is calculated based on the target standpipe pressure to achieve constant bottom hole pressure overflow discharge operations with constant standpipe pressure.

[0103] In the present invention, the double U-shaped tubes for deepwater pressure-controlled drilling and the U-shaped tube principle are as follows: the first U-shaped tube is composed of the drill string 1, the drill bit, and the annulus 2 below the mudline; the second U-shaped tube is composed of the water-receiving pipe 5, the seabed blowout preventer 3, the water-receiving pipe annulus 4, and the water-receiving pipe gas treatment system annulus. The U-shaped tube principle is briefly described as the target of concern is the bottom hole pressure, and the bottom hole pressure balance relationship is established on both sides of the U-shaped tube, thereby establishing a relationship between the riser pressure, the bottom hole pressure, and the casing pressure.

[0104] In one embodiment, the first U-shaped tube is formed by the drill string 1, the drill bit, and the annulus 2 below the mudline. The bottom hole pressure balance relationship is established on both sides of the first U-shaped tube, so as to establish a relationship between the standpipe pressure, the bottom hole pressure, and the casing pressure, wherein:

[0105] The bottom hole pressure expression of the first U-shaped tube with one side of the drill string as the object is:

[0106] P BH =P cs -P fd -P fb +P dsm

[0107] Where: P BH is the bottom hole pressure, MPa; P cs is the drilling pump circulation standpipe pressure, MPa; P fd is the circulating pressure loss in the drill string, MPa; P fb is the drill bit pressure drop, MPa; P dsm is the hydrostatic pressure in the drill string, MPa;

[0108] The bottom hole pressure expression of the first U-shaped tube with one side in the annulus as the object is:

[0109] P BH =P cam +P fca +P ram +P fra +P 地面 +P w1

[0110] Where: P BH is the bottom hole pressure, MPa; P cam is the static pressure in the casing annulus, MPa; P fca is the circulating pressure loss in the casing annulus, MPa; P ram is the hydrostatic pressure in the riser annulus, MPa; P fra is the circulation pressure loss in the riser annulus, MPa; P 地面 is the pressure loss between the diversion spool and the inlet of the throttling manifold, which is the sum of the displacement of the drilling pump and the displacement of the injection pump, MPa; P w1 is the wellhead back pressure, MPa.

[0111] In one embodiment, the second U-shaped tube is composed of the riser injection side tube 5, the subsea blowout preventer 3, the riser annulus 4, and the riser gas processing system annulus. The bottom hole pressure balance relationship is established on both sides of the second U-shaped tube, so as to establish a relationship between the riser pressure, the bottom hole pressure, and the casing pressure, wherein:

[0112] The bottom hole pressure expressed with one side of the annulus as the object includes the second U-shaped tube composed of the riser injection side tube 5 and the riser annulus 4. The bottom hole pressure expression of the second U-shaped tube with one side of the riser injection side tube as the object is:

[0113] P bh =P bcs -P fbl +P bsm

[0114] Where: P bh is the bottom hole pressure of the second U-tube circulation, MPa; P bcs is the circulation standpipe pressure of the booster pump, MPa; P fbl P is the circulating pressure loss in the riser injection pipe, MPa; bsm The static pressure of the water in the riser side pipe, MPa;

[0115] The bottom hole pressure expression of the second U-shaped tube with one side in the annulus as the object is:

[0116] P bh =P ram +P fra1 +P 地面1 +P w2

[0117] Where: P bh is the bottom hole pressure of the second U-tube circulation, MPa; P ram is the hydrostatic pressure of the riser annulus, MPa; P fra1 P is the pressure loss of the inner circulation of the riser annulus, which is only the injection displacement, MPa; 地面1 is the pressure loss between the diversion cross and the throttling manifold inlet, which is only the displacement of the injection pump, MPa; P w2 is the wellhead back pressure, MPa.

[0118] Figure 4 A flowchart showing the steps of installing a deepwater managed pressure drilling bottom hole pressure control system and a deepwater managed pressure drilling bottom hole pressure control method according to an embodiment of the present invention is shown.

[0119] like Figure 4As shown, in step S401, the riser gas handling system is installed. Specifically, the subsea blowout preventer group and the riser are lowered in sequence, and when the last riser is lowered, the working chuck of the riser gas handling system is installed, so that the riser gas handling system is connected to the lowered riser, and the riser gas handling system is slowly lowered, and the return slurry pipeline 9 at the diversion spool 6 and the electric control and hydraulic control pipelines are connected above the water surface, and finally the riser gas handling system is connected to the tension ring of the drilling (floating) platform.

[0120] like Figure 4 As shown, in step S402, the ground manifold system is installed. Specifically, the ground manifold system is deployed on the deck of the drilling (floating) platform in a planar arrangement or tower stacking manner and the pipelines are connected, the return slurry pipeline 9 connected to the diversion manifold 10 is connected, and the outlet of the throttling manifold 12 is connected to the liquid-gas separator of the drilling platform.

[0121] like Figure 4 As shown, in step S403, the pressure loss of the ground manifold system is evaluated. Specifically, after the watertight pipe gas treatment system and the ground manifold system are installed in place, a functional test is carried out, and the circulating pressure loss under different displacements and different circulation path conditions is tested according to the pressure loss evaluation process in the ground manifold pipeline. Furthermore, according to the reading of the six-speed viscometer of the drilling fluid, a rheological model suitable for the drilling fluid is selected on the shear rate-shear stress chart; considering the shape, size, height span, and right-angle bend of the pipeline in the ground manifold system, a flow channel model is established; for right-angle bends, the right-angle bends are equivalently treated according to the inner diameter of the pipe; a pressure measurement system is used to measure the circulating pressure loss under different displacements and different return slurry flow channels, and the pressure loss calculation model of the ground manifold system in the conventional hydraulic calculation software is corrected.

[0122] like Figure 4 As shown, in step S404, the bottom hole pressure of deepwater pressure controlled drilling is controlled. Specifically, the following is adopted: Figure 3 The deepwater managed pressure drilling bottom hole pressure control method shown is used to control the bottom hole pressure.

[0123] like Figure 4As shown, in step S405, bottom hole pressure control is performed when suspected gas invasion or overflow occurs. Specifically, when suspected gas invasion occurs, the drilling cycle is stopped, and the measured vertical pressure is used as the vertical pressure target value to perform constant bottom hole pressure exhaust under vertical pressure control; when suspected overflow occurs, the drilling cycle is stopped, and the measured vertical pressure is used as the vertical pressure target value to perform vertical pressure control; observe the flow change curve, if the flow shows a trend of continuous increase, implement flow control, adjust the throttle valve opening to balance the inlet and outlet flows, and then obtain a new vertical pressure target value, and use this vertical pressure target value to perform vertical pressure control and perform constant bottom hole pressure overflow; after the constant bottom hole pressure overflow is completed, it is converted to casing pressure control. If the casing pressure value is higher than the set value at this time, it is necessary to increase the density of the drilling fluid to reduce the casing pressure, and then implement pressure-controlled drilling operations under casing pressure control.

[0124] The present invention discloses a bottom hole pressure control method for deepwater controlled pressure drilling, and establishes a bottom hole pressure balance relationship of a double U-shaped tube for deepwater controlled pressure drilling according to the deepwater controlled pressure drilling equipment and the principle of controlled pressure drilling U-shaped tube. Through the set pressure measurement system, the pressure value at the set position can be monitored and obtained in real time, the circulating pressure loss between different positions can be obtained through the pressure difference, and the hydraulic calculation result can be corrected with the help of the pressure measurement system; the first pressure measuring device 15 set at the submarine blowout preventer 3 is fully utilized, on the one hand, the circulating pressure loss from the diversion four-way 6 to the throttling manifold 12 can be corrected, and on the other hand, the pressure value there can be used as an accurate reference point for bottom hole pressure calculation. The present invention takes into account that the ground pipeline of deepwater controlled pressure drilling is long, and the circulating pressure loss cannot be ignored like land or shallow water drilling, and establishes a pressure loss evaluation process in the ground manifold pipeline. The present invention describes in detail the corresponding bottom hole pressure control method for controlled pressure drilling for narrow safety density windows and suspected gas invasion or overflow.

[0125] The deepwater controlled pressure drilling bottom hole pressure control system and deepwater block drilling well site provided by the present invention can also be used in conjunction with a computer-readable storage medium, on which a computer program is stored, and the computer program is executed to run a deepwater controlled pressure drilling bottom hole pressure control method.

[0126] A computer program can run computer instructions, which include computer program code. The computer program code may be in source code form, object code form, executable file, or some intermediate form.

[0127] Computer-readable storage media may include: any entity or device that can carry computer program code, recording media, USB flash drives, mobile hard disks, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc.

[0128] It should be noted that the content contained in computer-readable storage media can be appropriately increased or decreased based on the requirements of legislation and patent practices in the jurisdiction. For example, in some jurisdictions, based on legislation and patent practices, computer-readable storage media do not include electrical carrier signals and telecommunications signals.

[0129] In summary, the present invention provides a deepwater controlled pressure drilling bottom hole pressure control system and a deepwater block drilling well site, which have the following advantages compared with the prior art:

[0130] 1) The rotating control head is installed under the tension ring, so that the maximum pressure control value of the deepwater controlled pressure drilling bottom hole pressure control system provided by the present invention is not limited by the pressure bearing capacity of the expansion joint in the platform riser system.

[0131] 2) The present invention is based on the U-tube principle for drilling fluid circulation and combines the riser gas treatment system to innovatively propose a double U-tube principle for fluid circulation. There are two power sources for pumping drilling fluid into deepwater controlled pressure drilling, namely the drilling pump and the booster pump, realizing the double U-tube for fluid circulation, thereby meeting the process requirements of controlled pressure drilling, controlled pressure connection of columns, and safe exhaust of risers.

[0132] 3) By setting up a pressure measurement system and focusing on the first pressure measuring device at the seabed blowout preventer, the pressure consumption of each section of the circulation pipeline can be obtained in real time, providing a more accurate data source for bottom hole pressure calculation.

[0133] 4) The bottom hole pressure control method is based on the U-shaped tube principle of drilling fluid circulation and combines the double U-shaped tube principle with the riser gas treatment system. For the two U-shaped tubes in deepwater controlled pressure drilling, the bottom hole pressure balance relationship is established from the inside of the tube and the annulus respectively, so as to meet the process requirements of controlled pressure drilling, controlled pressure connection column, and safe exhaust of the riser;

[0134] 5) The bottom hole pressure control method relies on the pressure measurement system to verify the numerical simulation results of the hydraulic calculation software and the circulating pressure loss of each pipeline;

[0135] 6) Bottom hole pressure control methods include casing pressure control, stand pressure control, and flow control. The deepwater drilling technical problems that can be solved include: safe drilling in a narrow density window, venting of gas-invaded risers, constant bottom hole pressure drilling in formations with unclear formation pressure, and constant bottom hole pressure column connection.

[0136] It should be understood that the embodiments disclosed in the present invention are not limited to the specific structures, processing steps or materials disclosed herein, but should be extended to equivalent substitutions of these features understood by ordinary technicians in the relevant field. It should also be understood that the terms used herein are only used for the purpose of describing specific embodiments and are not meant to be limiting.

[0137] In the description of the present invention, unless otherwise specified, "plurality" means two or more than two; the orientations or positional relationships indicated by the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail", etc. are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0138] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0139] Certain terms are used throughout this application document to indicate specific system components. As those skilled in the art will recognize, different names can usually be used to indicate the same components, so this application document is not intended to distinguish those components that are only different in name but not in function. In this application document, the terms "comprise", "include" and "have" are used in an open form, and therefore should be interpreted as meaning "including but not limited to...". In addition, the terms "substantially", "substantially" or "approximately" that may be used in this article relate to the tolerances of the corresponding terms accepted by the industry. The term "coupling" as may be used in this article includes direct coupling and indirect coupling via other components, elements, circuits, or modules, wherein for indirect coupling, the components, elements, circuits, or modules between them do not change the information of the signal but can adjust its current level, voltage level, and / or power level. Inferred coupling (for example, one of the elements is coupled to another element by inference) includes direct and indirect coupling between two elements in the same way as "coupling".

[0140] The "one embodiment" or "embodiment" mentioned in the specification means that the specific features, structures or characteristics described in conjunction with the embodiment are included in at least one embodiment of the present invention. Therefore, the phrases "one embodiment" or "embodiment" appearing in various places throughout the specification do not necessarily refer to the same embodiment.

[0141] The embodiments of the present invention are given for the purpose of illustration and description, and are not intended to be exhaustive or to limit the invention to the disclosed forms. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiments are selected and described in order to better illustrate the principles and practical applications of the present invention and to enable those of ordinary skill in the art to understand the present invention and thereby design various embodiments with various modifications suitable for specific uses.

[0142] Although the embodiments disclosed in the present invention are as above, the contents described are only embodiments adopted for facilitating the understanding of the present invention and are not intended to limit the present invention. Any technician in the technical field to which the present invention belongs can make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed in the present invention, but the patent protection scope of the present invention shall still be subject to the scope defined in the attached claims.

Claims

1. A deepwater managed pressure drilling bottom hole pressure control system, characterized in that: The control system comprises: The riser gas handling system is located below the tension ring and below the water surface. From top to bottom, it consists of an upper joint, a rotating control head, an annular blowout preventer, a diversion spool, and a lower joint. The ground manifold system is connected to the return slurry pipeline and is composed of a diversion manifold, a filter manifold, and a throttling manifold connected in sequence; The pressure measurement system is used to measure the real-time pressure at the seabed blowout preventer, the diversion spool, the diverter manifold, and the throttling manifold respectively.

2. A deepwater managed pressure drilling bottom hole pressure control system according to claim 1, characterized in that: The upper joint is connected to the drilling pump; one end of the rotating control head is connected to the upper joint, and the other end is connected to the annular blowout preventer; the flow guide spool is respectively connected to the annular blowout preventer, the upper end of the riser, the riser injection side pipe, and the inlet end of the return slurry pipeline, wherein the riser injection side pipe is also connected to the injection pump; the subsea blowout preventer is arranged on the drill string, and the upper end is connected to the lower end of the riser.

3. A deepwater managed pressure drilling bottom hole pressure control system as claimed in claim 2, characterized in that: The inlet end of the diversion manifold is connected to the outlet end of the return slurry pipeline, and the outlet end is connected to the inlet end of the filter manifold; the outlet end of the filter manifold is connected to the inlet end of the throttling manifold, and the outlet end is connected to the circulation tank.

4. A deepwater managed pressure drilling bottom hole pressure control system as claimed in claim 3, characterized in that: There are two power sources for pumping drilling fluid in deepwater controlled pressure drilling, namely the drilling pump and the boosting pump, wherein the drilling fluid pumped by the drilling pump flows through the platform riser manifold, the drill string, the drill bit, the wellbore annulus below the mud line, the subsea blowout preventer, the riser annulus, the riser gas handling system, the ground manifold system, and the circulation tank; the drilling fluid pumped by the boosting pump flows through the riser injection side pipe, the subsea blowout preventer, the riser annulus, the riser gas handling system, the ground manifold system, and the circulation tank.

5. A deepwater managed pressure drilling bottom hole pressure control system according to any one of claims 1 to 4, characterized in that: The pressure measurement system comprises: a first pressure measuring device arranged at the position of the subsea blowout preventer, a second pressure measuring device arranged at the outlet of the diversion spool, a third pressure measuring device arranged at the inlet of the diversion manifold, and a fourth pressure measuring device arranged at the inlet of the throttling manifold.

6. A deepwater drilling well site, characterized in that: The drilling well site comprises a deep-water managed pressure drilling bottom hole pressure control system as described in any one of claims 1-5.

7. A method for controlling bottom hole pressure in deepwater pressure-controlled drilling, characterized in that: Executed by a control system according to any one of claims 1 to 5, the method comprises: Based on the geologically predicted formation pressure, the safety density window is predicted to obtain the predicted value of the safety density window; During the controlled pressure drilling process in a narrow density window, a drilling fluid having a density less than the lower limit of the predicted value of the safety density window is used to achieve a bottom hole circulating equivalent density balance formation pressure during the circulation process and within the predicted value of the safety density window; When performing casing pressure control, the target casing pressure is calculated based on the measured casing pressure, drilling parameters, drilling fluid rheological properties and target bottom hole pressure. The throttle valve opening is adjusted to make the measured casing pressure equal to the target casing pressure, thus achieving bottom hole pressure control. When performing vertical pressure control, the target vertical pressure is calculated based on the measured vertical pressure, drilling parameters, drilling fluid rheological properties and target bottom hole pressure. The measured vertical pressure is equal to the target vertical pressure by adjusting the throttle valve opening to achieve bottom hole pressure control. When performing flow control, the size relationship of the inlet flow is determined. When the inlet and outlet flows deviate, the casing pressure control or the vertical pressure control is converted to the flow control, and the throttle valve is adjusted to balance the inlet and outlet flows. Then, the casing pressure control or the vertical pressure control is performed based on the bottom hole pressure at the time of flow balance as the target bottom hole pressure.

8. A method for controlling bottom hole pressure in deep water managed pressure drilling according to claim 7, characterized in that: The first U-shaped tube is composed of the drill string, the drill bit, and the annulus below the mud line. The bottom hole pressure balance relationship is established on both sides of the first U-shaped tube, thereby establishing a relationship between the standpipe pressure, the bottom hole pressure, and the casing pressure, where: The bottom hole pressure expression of the first U-shaped tube with one side of the drill string as the object is: P BH =P cs -P fd -P fb +P dsm Where: P BH is the bottom hole pressure, MPa; P cs is the drilling pump circulation standpipe pressure, MPa; P fd is the circulating pressure loss in the drill string, MPa; P fb is the drill bit pressure drop, MPa; P dsm is the hydrostatic pressure in the drill string, MPa; The bottom hole pressure expression of the first U-shaped tube with one side in the annulus as the object is: P BH =P cam +P fca +P ram +P fra +P 地面 +P w1 Where: P BH is the bottom hole pressure, MPa; P cam is the static pressure in the casing annulus, MPa; P fca is the circulating pressure loss in the casing annulus, MPa; P ram is the hydrostatic pressure in the riser annulus, MPa; P fra is the circulation pressure loss in the riser annulus, MPa; P 地面 is the pressure loss between the diversion spool and the inlet of the throttling manifold, which is the sum of the displacement of the drilling pump and the displacement of the injection pump, MPa; P w1 is the wellhead back pressure, MPa.

9. A method for controlling bottom hole pressure in deep water managed pressure drilling according to claim 8, characterized in that: The second U-shaped pipe is composed of the riser injection side pipe, the subsea blowout preventer, the riser annulus, and the riser gas processing system annulus. The bottom hole pressure balance relationship is established on both sides of the second U-shaped pipe, thereby establishing a relationship between the riser pressure, the bottom hole pressure, and the casing pressure, wherein: The bottom hole pressure expressed with one side of the annulus as the object includes the second U-shaped tube composed of the riser injection side tube and the riser annulus. The bottom hole pressure expression of the second U-shaped tube with one side of the riser injection side tube as the object is: P bh =P bcs -P fbl +P bsm Where: P bh is the bottom hole pressure of the second U-tube circulation, MPa; P bcs is the circulation standpipe pressure of the booster pump, MPa; P fbl P is the circulating pressure loss in the riser injection pipe, MPa; bsm The static pressure of the water in the riser side pipe, MPa; The bottom hole pressure expression of the second U-shaped tube with one side in the annulus as the object is: P bh =P ram +P fra1 +P 地面1 +P w2 Where: P bh is the bottom hole pressure of the second U-tube circulation, MPa; P ram is the hydrostatic pressure of the riser annulus, MPa; P fra1 P is the pressure loss of the inner circulation of the riser annulus, which is only the injection displacement, MPa; 地面1 is the pressure loss between the diversion cross and the throttling manifold inlet, which is only the displacement of the injection pump, MPa; P w2 is the wellhead back pressure, MPa.

10. A method for controlling bottom hole pressure in deep water managed pressure drilling according to any one of claims 7 to 9, characterized in that: The method further comprises the step of installing a riser gas handling system, wherein: The subsea blowout preventer group and riser pipes are lowered in sequence. When the last riser pipe is lowered, the working chuck of the riser gas handling system is installed to connect the riser gas handling system with the lowered riser pipe. The riser gas handling system is slowly lowered to connect the return slurry pipeline and the electric and hydraulic control pipelines at the diversion four-way above the water surface, and finally the riser gas handling system is connected to the tension ring of the drilling platform.

11. A method for controlling bottom hole pressure in deep water managed pressure drilling according to any one of claims 7 to 10, characterized in that: The method further comprises a surface manifold system installation step, wherein: The surface manifold system is deployed on the drilling platform deck in a planar arrangement or tower stacking manner and pipelines are connected. The return slurry pipeline connected to the diversion manifold is connected to the diversion manifold, and the throttling manifold outlet is connected to the liquid-gas separator of the drilling platform.

12. A method for controlling bottom hole pressure in deep water managed pressure drilling according to any one of claims 7 to 11, characterized in that: The method further comprises a surface manifold system pressure loss evaluation step, wherein: According to the reading of the six-speed viscometer of the drilling fluid, select the rheological model suitable for the drilling fluid on the shear rate-shear stress chart; Considering the shape, size, height span, and right-angle bend of the pipelines in the ground manifold system, a flow channel model is established; For right-angle bends, the right-angle bends are treated equivalently according to the inner diameter of the pipe; The pressure measurement system is used to measure the circulation pressure loss under different displacements and different return slurry flow channels, and the pressure loss calculation model of the ground manifold system is calibrated.

13. A method for controlling bottom hole pressure in deep water managed pressure drilling according to any one of claims 7 to 12, characterized in that: The method further comprises a bottom hole pressure control step when suspected gas invasion or overflow occurs, wherein: When suspected gas invasion occurs, stop drilling and use the measured vertical pressure as the vertical pressure target value to perform constant bottom hole pressure exhaust with vertical pressure control; When suspected overflow occurs, stop drilling and use the measured vertical pressure as the vertical pressure target value for vertical pressure control; observe the flow change curve. If the flow shows a trend of continuous increase, implement flow control and reduce the throttle valve opening to balance the inlet and outlet flows. At this time, a new vertical pressure target value is obtained, and vertical pressure control is performed based on this vertical pressure target value to discharge overflow at a constant bottom hole pressure; After the constant bottom hole pressure overflow is completed, it is switched to casing pressure control. If the casing pressure value is higher than the set value at this time, it is necessary to increase the density of the drilling fluid to reduce the casing pressure, and then implement the pressure controlled drilling operation under the casing pressure control.

14. A storage medium, characterized in that: It contains a series of instructions for executing the method steps as claimed in any one of claims 7-13.

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