A deep water managed pressure drilling bottom hole pressure control system and deep water block drilling well site

Abstract

The application provides a deep water pressure control drilling well bottom pressure control system, which comprises: a riser gas treatment system located below a tension ring and entirely below the water surface, and composed of an upper joint, a rotary control head, an annular blowout preventer, a flow guide cross and a lower joint from top to bottom; a surface manifold system connected with a slurry return pipeline and composed of a shunt manifold, a filter manifold and a throttle manifold connected in sequence; and a pressure measurement system for measuring real-time pressures at the subsea blowout preventer, the flow guide cross, the shunt manifold and the throttle manifold, respectively. The application proposes a fluid circulation double U-shaped pipe principle based on the drilling fluid circulation U-shaped pipe principle and in combination with the riser gas treatment system, and the power source for the drilling fluid pumping of the deep water pressure control drilling has two, namely, a drilling pump and an injection pump, so that the fluid circulation double U-shaped pipe is realized to meet the process requirements of the pressure control drilling, the pressure control stand connection and the riser safe exhaust.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of deepwater managed pressure drilling, in particular to a deepwater managed pressure drilling bottom hole pressure control system and a deepwater block drilling well site. BACKGROUND

[0002] Deepwater formations are different from land formations, because seawater replaces overburden, which makes formation fracture pressure or formation leakage pressure significantly lower; China's South China Sea is located at the intersection of three major plates, and diapiric structures are abnormally developed, which makes the formation pressure in this region show the characteristics of abnormally high pressure. Therefore, the outstanding problems of deepwater drilling are narrow safety density window, difficult gas invasion treatment and difficult bottom hole pressure control.

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

[0004] In the prior art, the common and difficult engineering problem encountered in deepwater drilling is the leakage and overflow problem under the condition of narrow density window of the formation. When dealing with the above problems by using conventional deepwater drilling technology, since there is no accurate real-time pressure consumption data of each section of the circulation pipeline as a data basis, the existing technology has the problems of high complex failure, long processing cycle and high well control risk.

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

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

[0007] A riser gas treatment system located below the tension ring, which is located below the water surface as a whole, and is composed of an upper connector, a rotary control head, an annular blowout preventer, a flow guide cross, and a lower connector from top to bottom;

[0008] A surface manifold system connected with the slurry return pipeline, which is composed of a shunt manifold, a filter manifold, and a throttling manifold connected in sequence;

[0009] A pressure measurement system for measuring the real-time pressure at the subsea blowout preventer, the flow guide cross, the shunt manifold, and the throttling manifold, respectively.

[0010] According to one embodiment of the present application, the upper joint is connected with a drilling pump; one end of the rotary control head is connected with the upper joint, and the other end is connected with the annular blowout preventer; the flow guide cross is connected with the annular blowout preventer, the upper end of the riser, the riser injection side pipe, and the inlet end of the return mud pipeline respectively, wherein the riser injection side pipe is further connected with an injection pump; and the subsea blowout preventer is arranged on the drill string and connected with the lower end of the riser.

[0011] According to one embodiment of the present application, the inlet end of the flow distribution manifold is connected with the outlet end of the return mud pipeline, and the outlet end is connected with the inlet end of the filter manifold; the outlet end of the filter manifold is connected with the inlet end of the choke manifold, and the outlet end is connected with the circulating tank.

[0012] According to one embodiment of the present application, the power source for the deepwater managed pressure drilling drilling fluid pumping has two, which are the drilling pump and the injection pump respectively, 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 surface manifold system, and the circulating tank; and the drilling fluid pumped by the injection pump flows through the riser injection side pipe, the subsea blowout preventer, the riser annulus, the riser gas treatment system, the surface manifold system, and the circulating tank.

[0013] According to one embodiment of the present application, the pressure measuring 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 position of the flow guide cross, a third pressure measuring device arranged at the inlet position of the flow distribution manifold, and a fourth pressure measuring device arranged at the inlet position of the choke manifold.

[0014] According to another aspect of the present application, a deepwater block drilling well site is also provided, which comprises the deepwater managed pressure drilling bottom hole pressure control system according to any one of the above.

[0015] According to another aspect of the present application, a deepwater managed pressure drilling bottom hole pressure control method is also provided, which is executed by the control system according to any one of the above, and the method comprises:

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

[0017] In the process of the pressure control drilling in the narrow density window, the drilling fluid with a density less than the lower limit of the safety density window prediction value is used to balance the formation pressure with the bottom hole circulating equivalent density in the circulating process and within the safety density window prediction value.

[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. By adjusting the opening of the throttle valve, the measured casing pressure is made equal to the target casing pressure, thereby achieving bottom hole pressure control.

[0019] When performing stand pressure control, the target stand pressure is calculated based on the measured stand pressure, drilling parameters, drilling fluid rheological properties, and target bottom hole pressure. By adjusting the opening of the throttle valve, the measured stand pressure is made equal to the target stand pressure, thus achieving bottom hole pressure control.

[0020] When performing flow control, the relationship between the inlet and outlet flow rates is determined. When there is a deviation between the inlet and outlet flow rates, the flow control is switched from casing pressure control or vertical pressure control to flow control. The throttle valve is adjusted to balance the inlet and outlet flow rates. Then, the bottom hole pressure when the flow rates are balanced is used as the target bottom hole pressure for casing pressure control or vertical pressure control.

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

[0022] The bottom hole pressure expression for the first U-tube, taking the inner side of the drill string as the object, is:

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

[0024] In the formula: P BH P represents the bottom hole pressure, in MPa. cs P represents the drilling pump circulation riser pressure, in MPa. fd The internal circulation pressure loss of the drill string is expressed in MPa; P fb P represents the drill bit pressure drop, measured in MPa. dsm The hydrostatic pressure inside the drill string is MPa.

[0025] The bottom hole pressure expression for the first U-tube, taking the inner side of the annulus as the object, is:

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

[0027] In the formula: P BH P represents the bottom hole pressure, in MPa. cam The hydrostatic pressure inside the casing annulus is measured in MPa; Pfca P is circulating pressure loss in casing annulus, MPa; P ram P is static fluid pressure in casing annulus, MPa; P fra P is circulating pressure loss in casing annulus, MPa; P 地面 P is pressure loss between flow-through cross and choke manifold inlet, MPa; P w1 P is wellhead back pressure, MPa.

[0028] According to one embodiment of the present application, the second U-shaped pipe is constituted by the riser injection side pipe, the subsea blowout preventer, the riser annulus, and the riser gas treatment system annulus, and a well bottom pressure balance relationship is established on both sides of the second U-shaped pipe, so as to establish a relationship among the standpipe pressure, the well bottom pressure, and the casing pressure, wherein:

[0029] The well bottom pressure with the one side in the annulus as the object comprises a second U-shaped pipe constituted by the riser injection side pipe and the riser annulus, and the well bottom pressure expression of the second U-shaped pipe with the one side in the riser injection side pipe as the object is:

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

[0031] In the formula, P bh is circulating well bottom pressure of the second U-shaped pipe, MPa; P bcs is circulating standpipe pressure of the injection pump, MPa; P fbl is circulating pressure loss in the riser injection side pipe, MPa; P bsm is static fluid pressure in the riser injection side pipe, MPa;

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

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

[0034] In the formula, P bh is circulating well bottom pressure of the second U-shaped pipe, MPa; P ram is static fluid pressure in the riser annulus, MPa; P fra1 is circulating pressure loss in the riser annulus, only the injection displacement, MPa; P 地面1 is pressure loss between the flow-through cross and the choke manifold inlet, only the injection pump displacement, MPa; P w2 P is wellhead back pressure, MPa.

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

[0036] The subsea blowout preventer stack and the riser joint are sequentially lowered, and when the last riser joint is lowered, a working chuck of the riser gas treatment system is installed to connect the riser gas treatment system with the lowered riser, and the return flow line connected to the flow spool and the electrically and hydraulically controlled lines are connected above the water surface, so that the riser gas treatment system is finally connected to the tension ring of the drilling platform.

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

[0038] The surface manifold system is arranged on the deck of the drilling platform in a planar manner or in a tower stack manner, and the return flow line connected to the flow spool is connected to the flow distribution manifold, and the outlet of the choke manifold is connected to the liquid-gas separator of the drilling platform.

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

[0040] According to the readings of the six-speed viscometer of the drilling fluid, a rheological model suitable for the drilling fluid is selected on a shear rate-shear stress graph;

[0041] The shape, size, height span, and right-angle bend of the pipeline in the surface manifold system are considered to establish a flow passage model;

[0042] For the right-angle bend, the right-angle bend is equivalently processed according to the inner diameter of the pipe;

[0043] The circulating pressure loss under different displacement and different return flow passages is measured by using the pressure measurement system, and the pressure loss calculation model of the surface manifold system is corrected.

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

[0045] When suspected gas invasion occurs, the drilling circulation is stopped, the measured standpipe pressure is taken as the standpipe pressure target value, and constant bottom hole pressure gas discharge is performed for standpipe pressure control;

[0046] When suspected overflow occurs, the drilling circulation is stopped, the measured standpipe pressure is taken as the standpipe pressure target value for standpipe pressure control; the flow rate change curve is observed, if the flow rate shows a continuously increasing trend, the flow rate control is implemented, the opening degree of the choke valve is adjusted to balance the inlet and outlet flow rates, a new standpipe pressure target value is obtained at this time, and the constant bottom hole pressure overflow discharge is performed by using the standpipe pressure target value for standpipe pressure control;

[0047] After the constant bottom hole pressure blowout is carried out, the casing pressure control is converted, if the casing pressure value is higher than the set value at this time, the drilling fluid density needs to be improved to reduce the casing pressure, and then the pressure control drilling operation under the casing pressure control is implemented.

[0048] According to another aspect of the application, there is also provided a storage medium containing a series of instructions for carrying out the method steps of any of the above.

[0049] The application provides a deep water pressure control drilling bottom hole pressure control system and a deep water block drilling well site.

[0050] 1) The rotary control head is installed below the tension ring, so that the maximum pressure control of the deep water pressure control drilling bottom hole pressure control system provided by the application is not limited by the pressure bearing capacity of the extension joint in the platform riser system.

[0051] 2) The application is based on the drilling fluid circulation U-shaped pipe principle and innovatively proposes the fluid circulation double U-shaped pipe principle in combination with the riser gas treatment system, the power source for the drilling fluid pump-in of the deep water pressure control drilling has two, which are the drilling pump and the injection pump, the fluid circulation double U-shaped pipe is realized, so as to meet the process requirements of pressure control drilling, pressure control stand connection and riser safe exhaust.

[0052] 3) Through the pressure measuring system and by mainly using the first pressure measuring device at the subsea blowout preventer, the pressure consumption of each section of the circulation pipeline is realized in real time, and more accurate data sources are provided for the bottom hole pressure calculation.

[0053] 4) The bottom hole pressure control method is based on the drilling fluid circulation U-shaped pipe principle and innovatively proposes the double U-shaped pipe principle in combination with the riser gas treatment system, the bottom hole pressure balance relationship is established from the pipe and the annulus for the two U-shaped pipes existing in the deep water pressure control drilling, so as to meet the process requirements of pressure control drilling, pressure control stand connection and riser safe exhaust;

[0054] 5) The bottom hole pressure control method depends on the pressure measuring system, so as to check the numerical simulation results of the hydrodynamic calculation software and the circulation pressure consumption of each pipeline;

[0055] 6) The bottom hole pressure control method includes casing pressure control, stand pressure control and flow control, and can solve the deep water drilling technical problems including narrow density window safe drilling, gas invasion riser exhaust, constant bottom hole pressure drilling of strata with unclear formation pressure and constant bottom hole pressure stand connection.

[0056] Additional features and advantages of the present application will be set forth in the description that follows, and in part will be apparent from the description, or can be learned by practice of the application. The objectives and other advantages of the present application will be realized and attained by the structure particularly pointed out in the description and claims. BRIEF DESCRIPTION OF DRAWINGS

[0057] The accompanying drawings are included to provide a further understanding of the present application and are incorporated in and constitute a part of this specification, illustrate embodiments of the present application and together with the description serve to explain the present application. In the drawings:

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

[0059] Figure 2 shows a wellbore fluid circulation double U-shaped pipe schematic diagram according to an embodiment of the present application;

[0060] Figure 3 shows a step flow chart of a deepwater managed pressure drilling bottom hole pressure control method according to an embodiment of the present application;

[0061] Figure 4 shows a deepwater managed pressure drilling bottom hole pressure control system installation and a step flow chart of a deepwater managed pressure drilling bottom hole pressure control method according to an embodiment of the present application.

[0062] In the drawings, the same components have the same reference numerals. In addition, the drawings are not drawn according to the actual proportions.

[0063] In the drawings, the meanings of the respective reference numerals are as follows: 1 - inside the drill string; 2 - annulus below the mud line; 3 - subsea blowout preventer; 4 - riser annulus; 5 - riser augmenter side pipe; 6 - flow guide cross; 7 - annular blowout preventer; 8 - rotary control head; 9 - returns line; 10 - flow divider manifold; 11 - filter manifold; 12 - choke manifold; 13 - drilling pump; 14 - augmenter pump; 15 - first pressure measuring device; 16 - second pressure measuring device; 17 - third pressure measuring device; 18 - fourth pressure measuring device. DETAILED DESCRIPTION

[0064] In order to make the objects, technical solutions and advantages of the present application clearer, the following further describes the embodiments of the present application with reference to the drawings.

[0065] Managed pressure drilling technology is an adaptive drilling technology for precisely controlling the annular pressure profile of the entire wellbore. The purpose is to determine the downhole pressure environment limit and control the annular pressure profile of the wellbore. Deepwater managed pressure drilling can be divided into two types of pressure control and liquid level control in terms of pressure control means. In the prior art, the deepwater managed pressure drilling technology represented by pressure control adopts a managed pressure drilling RGH system based on the platform riser system to form a closed pressure-bearing drilling fluid circulation path, which can realize various forms of bottom hole pressure control methods. Some of the rotary control heads in the managed pressure drilling RGH system of foreign oil service companies are installed on the tension ring. The maximum pressure control value of the rotary 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 more than 500 psi), and the pressure control value in the actual application process is often greater than the pressure-bearing capacity of the expansion joint. The underwater core equipment of the deepwater managed pressure drilling technology represented by liquid level control is mainly a riser pump, which adjusts the liquid level in the riser to adjust the liquid column pressure and the bottom hole pressure, and is a non-closed pressure-bearing circulation path.

[0066] Currently, deepwater managed pressure drilling at home and abroad mainly uses pressure control means for managed 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, the bottom hole pressure does not need to be adjusted, and outside this range, the method of adjusting casing pressure or adjusting drilling fluid density is used to restore the hydrocarbon substances to the set range. However, the bottom hole pressure control method described in the prior art is a method for treating downhole invasion, and the given expected range proposes a treatment method. The disadvantage is that for deepwater drilling, the operation risk and challenge are much greater than land and shallow water drilling. It is necessary to timely detect, effectively suppress and control the invasion of invasion, rather than maintaining in a certain expected range.

[0067] The control method described in the prior art (application number: 201811286680.2) uses drilling fluid static column pressure, annular hydraulic friction, and throttling pressure, and gives a pressure safety fluctuation range. After checking the circulation pressure consumption by the while-drilling pressure measurement device, the casing pressure of the wellbore is controlled. However, the application scenario of this prior art is more in land drilling and shallow water drilling operations, and the pressure control is mainly casing pressure control. For deepwater drilling using floating platforms, the drilling fluid circulation process is significantly different from land and shallow water drilling. In addition to annular friction, the long-distance return slurry pipeline internal circulation friction and the difference between the managed pressure drilling manifold system and the return slurry port are also worth considering.

[0068] In summary, a common and challenging engineering problem encountered in deepwater drilling under narrow formation density windows is leakage and overflow. Conventional deepwater drilling technologies face high complexity, long processing cycles, and high well control risks when addressing these issues. Precisely controlling the balance between bottom hole pressure and formation pressure under narrow density windows is crucial to the success of deepwater drilling. Deepwater pressure-controlled drilling technology, relying on deepwater pressure-controlled drilling processes, equipment, automatic control systems, and real-time hydraulic calculation software, can achieve precise bottom hole pressure control, constant bottom hole pressure connection to the drilling column, and gas overflow venting from the riser during drilling. This reduces complexity, time constraints, and well control risks, thereby improving the drilling success rate of deepwater drilling.

[0069] To address the complex engineering challenges of high temperature, high pressure, and narrow safety density windows encountered in deepwater drilling, this invention proposes a double U-shaped pipe structure for deepwater pressure-controlled drilling. Combining the principles of the U-shaped pipe with the characteristics of deepwater pressure-controlled drilling equipment, it presents a bottom-hole pressure control system, a deepwater drilling site, and a control method. Based on the readings of the established pressure measurement system, the circulating pressure loss can be directly obtained, and the pressure loss calculation model of the surface manifold system can be corrected. For different situations, accurate bottom-hole pressure control is achieved through different control objectives. Depending on the downhole conditions, casing pressure control, standpipe pressure control, flow control, or a combination of these control methods can be correctly selected to achieve bottom-hole pressure control.

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

[0071] A bottomhole pressure control system for deepwater controlled pressure drilling includes: a riser gas treatment system, a surface manifold system, and a pressure measurement system.

[0072] like Figure 1 As shown, in one embodiment, the water-proof gas treatment system is located below the tension ring, and the entire system is below the water surface, starting from the upper connector (…). Figure 1 (Not shown in the image), rotary control head 8, annular blowout preventer 7, flow guide four-way valve 6, lower connector ( Figure 1 (Not shown in the text) consists of...

[0073] Specifically, the riser gas treatment system includes: upper and lower connectors, a rotary control head 8, an annular blowout preventer 7, and a flow guide four-way connector 6. Further, the upper connector is connected to the drilling pump 13. One end of the rotary control head 8 is connected to the upper connector, and the other end is connected to the annular blowout preventer 7. The flow guide four-way connector 6 is 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 line 9, respectively. The riser injection side pipe 5 is also connected to the injection pump 14.

[0074] Furthermore, the riser gas treatment system is connected to the riser of the floating platform through upper and lower connecting joints; the riser gas treatment system is located below the tension ring and the whole system is located below the water surface; the riser gas treatment system consists of an upper joint, a rotary control head 8, an annular blowout preventer 7, a flow guide four-way connector 6, and a lower joint from top to bottom.

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

[0076] In existing controlled-pressure drilling systems, the rotary control head is mounted 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 exceeding 500 psi). In actual applications, the controlled pressure value often exceeds the pressure-bearing capacity of the expansion joint. In this invention, the rotary control head 8 is mounted below the tension ring, so that the maximum controlled pressure of the deep-water controlled-pressure drilling bottomhole pressure control system provided by this invention is not limited by the pressure-bearing capacity of the expansion joint in the platform riser system, making it suitable for use in deep-water drilling environments encountering high temperatures and high pressures.

[0077] like Figure 1 As shown, in one embodiment, the ground manifold system is connected to the return slurry line 9 and consists of a branch manifold 10, a filter manifold 11, and a throttling manifold 12 connected in sequence. Specifically, the inlet end of the branch manifold 10 is connected to the outlet end of the return slurry line 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 (Not shown in the image) 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 flow guide four-way 6, the diversion manifold 10, and the throttling manifold 12, respectively. Specifically, the pressure measurement system includes: a first pressure measuring device 15 located at the subsea blowout preventer 3, a second pressure measuring device 16 located at the outlet of the flow guide four-way 6, a third pressure measuring device 17 located at the inlet of the diversion manifold 10, and a fourth pressure measuring device 18 located at the inlet of the throttling manifold 12.

[0079] Furthermore, in the pressure measurement system, the pressure P1 measured by the first pressure measuring device 15 represents the hydrostatic pressure P in the annulus 4 above that point. ram Circulation pressure loss (P) within the annulus 4 of the riser pipe fra P fra1 ), the circulating pressure loss (P) between the return slurry outlet of the guide four-way 6 and the drilling fluid inlet of the choke manifold 12. 地面 P 地面1 ), which is the sum of the three.

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

[0081] The difference in readings P2-P3 between the second pressure measuring device 16 and the third pressure measuring device 17 represents the circulating pressure loss in the flowline 9 between the two devices. Specifically, the difference in readings P2-P3 between the second pressure measuring device 16 and the third pressure measuring device 17 represents the sum of the hydrostatic pressure and the frictional resistance between the two devices.

[0082] The difference in readings P3-P4 between the third pressure measuring device 17 and the fourth pressure measuring device 18 represents the circulating pressure loss in the flowline between the two devices. Specifically, the difference in readings P3-P4 between the third pressure measuring device 17 and the fourth pressure measuring device 18 represents the sum of the hydrostatic pressure and the frictional resistance between the two devices.

[0083] Further, in actual applications, the relative height difference between the flow-through cross 6 and the inlet of the shunt manifold 10 will be affected by the up-and-down heave of the floating platform; the frictional resistance between the inlet of the shunt manifold 10 and the inlet of the throttle manifold 12 is affected by the shape, size, and angle of the manifold pipes and the relative height between the manifolds.

[0084] In the prior art, the common and difficult engineering problem encountered in deepwater drilling is the loss and overflow under the condition of narrow density window of the stratum. When dealing with the above problem by using conventional deepwater drilling technology, since there is no accurate real-time data of the pressure loss of each section of the circulating pipeline as a data basis, the prior art has the problems of high complex failure, long processing period, and high well control risk.

[0085] The pressure measuring system provided by the method can monitor and obtain the pressure value at the set position in real time, and the circulating pressure loss between different positions can be obtained through the pressure difference. The first pressure measuring device 15 provided at the subsea blowout preventer 3 can reflect the circulating pressure loss from the flow-through cross 6 to the throttle manifold 12, and the pressure value at this position can be used as an accurate reference data for the calculation of the bottom hole pressure. Moreover, the deepwater managed pressure drilling ground pipeline is long, and the circulating pressure loss cannot be ignored as in land or shallow water drilling. The pressure loss measuring system (pressure measuring system) of the ground manifold pipeline provided by the present application can provide more accurate data source for the calculation of the bottom hole pressure and provide data basis for the judgment of the loss and overflow conditions.

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

[0087] In the application, the power source of the drilling fluid pumped in the deep water managed pressure drilling is two, which are the drilling pump 13 and the augmented injection pump 14, wherein the drilling fluid pumped in by the drilling pump 13 flows through the platform riser manifold, the drill string 1, the drill bit, the annulus 2 below the mud line, the subsea blowout preventer 3, the riser annulus 4, the riser gas processing system, the ground manifold system and the circulating tank. The drilling fluid pumped in by the augmented injection pump 14 flows through the riser augmented injection side pipe 5, the subsea blowout preventer 3, the riser annulus 4, the riser gas processing system, the ground manifold system and the circulating tank.

[0088] Specifically, in the application, the first U-shaped pipe is composed of the drill string 1, the drill bit and the annulus 2 below the mud line; the second U-shaped pipe is composed of the riser augmented injection side pipe 5, the subsea blowout preventer 3, the riser annulus 4 and the annulus of the riser gas processing system. Further, the drilling fluid in the riser annulus 4 of the second U-shaped pipe participated by the augmented injection pump 14 is the drilling fluid in the original circulating tank and the drilling fluid containing cuttings in the annulus 2 below the mud line.

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

[0090] Different from the land and shallow water managed pressure drilling, the deep water managed pressure drilling bottom hole pressure control system provided by the application has two U-shaped pipes in the drilling fluid circulation process. The application proposes the fluid circulation double U-shaped pipe principle based on the drilling fluid circulation U-shaped pipe principle and in combination with the riser gas processing system, the power source of the drilling fluid pumped in the deep water managed pressure drilling is two, which are the drilling pump 13 and the augmented injection pump 14, realizing the fluid circulation double U-shaped pipe, so as to meet the process requirements of the managed pressure drilling, the managed pressure stand building and the riser safe gas discharge, and to solve the outstanding problems of the narrow safety density window, the great gas invasion treatment difficulty and the great bottom hole pressure control difficulty of the deep water drilling to a certain extent.

[0091] According to another aspect of the application, a deep water block drilling well site is also provided, which comprises the deep water managed pressure drilling bottom hole pressure control system provided by the application.

[0092] The present application can effectively solve the problem of drilling in deep water narrow density window, reduce the complex time limit, reduce the well control risk, and improve the success rate of deep water drilling. The present application provides a deep water pressure control underwater key equipment (deep water pressure control drilling bottom hole pressure control system) and a bottom hole pressure control method (deep water pressure control drilling bottom hole pressure control method). According to the different process requirements of deep water pressure control drilling, a fluid circulation double U-shaped pipe mode is provided. On the basis of conventional hydraulic calculation, through the set pressure measuring system and by mainly using the first pressure measuring device 15 at the blowout preventer 3, the pressure consumption of each section of the circulating pipeline is realized in real time, and more accurate data sources are provided for bottom hole pressure calculation.

[0093] The present application is based on the principle of pressure control drilling U-shaped pipe for bottom hole pressure calculation; combined with the characteristics of floating platform and deep water pressure control drilling equipment, pressure measuring devices are installed at the blowout preventer group 3, the slurry return port of the flow guide cross 6, the slurry inlet port of the flow distribution manifold 10, and the slurry inlet port of the choke manifold 12; according to the well structure, the drilling tool assembly, the drilling fluid performance, the drilling fluid rheological mode, the drilling displacement, the pipe diameter and deployment mode of the pressure control drilling manifold system, the circulating pressure consumption of each section is calculated, and the pressure difference between each pressure measuring device is used as the standard for checking; the bottom hole pressure control method can use casing pressure control, standpipe pressure control, and flow control, and can use the control method according to the downhole situation.

[0094] Figure 3 A step flow chart of a deep water pressure control drilling bottom hole pressure control method according to an embodiment of the present application is shown.

[0095] As Figure 3 shown, in step S301, a 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) is:

[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) , that is, narrow density window.

[0098] As Figure 3As shown, in step S302, the bottom hole circulating equivalent density balances the formation pressure during the circulation process and remains within the predicted safe density window. Specifically, during controlled-pressure drilling with a narrow density window, drilling fluid with a density lower than the lower limit of the predicted safe density window is used to achieve bottom hole circulating equivalent density balance of the formation pressure during circulation and remain within the predicted safe density window. Further, the pump shutdown corresponds to the stand-up drilling operation. To achieve constant bottom hole pressure, back pressure compensation is achieved through the second U-shaped pipe circulation path, via the injection pump 14 and the controlled-pressure drilling manifold system by adjusting the choke valve opening. This is casing pressure control. The applied back pressure equivalent drilling fluid density is the predicted formation pressure equivalent drilling fluid density plus 0.02 g / cm³. 3 This is a method for controlling the pressure of the sleeve in narrow-density window column connection operations.

[0099] like Figure 3 As shown, in step S303, casing pressure control is performed. Specifically, during 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. By adjusting the opening of the choke valve, the measured casing pressure is made equal to the target casing pressure, thus achieving bottom hole pressure control. Furthermore, the actuators for bottom hole pressure control are all choke valves; however, the control targets are casing pressure, riser pressure, and outlet flow rate.

[0100] like Figure 3 As shown, in step S304, stand pressure control is performed. Specifically, when performing stand pressure control, the target stand pressure (predicted formation pressure) is calculated based on the measured stand pressure, drilling parameters, drilling fluid rheological properties, and target bottom hole pressure. By adjusting the opening of the throttle valve, the measured stand pressure is made equal to the target stand pressure, thereby achieving bottom hole pressure control.

[0101] like Figure 3 As shown, in step S305, flow control is performed. Specifically, when performing flow control, the relationship between the inlet and outlet flow rates is determined. When there is a deviation between the inlet and outlet flow rates, the flow control is switched from casing pressure control or vertical pressure control to flow control. The throttle valve is adjusted to balance the inlet and outlet flow rates. Then, the bottom hole pressure at the point of flow balance is used as the target bottom hole pressure for casing pressure control or vertical pressure control.

[0102] Casing pressure control is applied to controlled-pressure drilling operations and stand-up connection operations using low-density drilling fluids under narrow safety density windows and when the annulus is not affected by oil and gas. It can also be applied to pressure control during the circulation and weighting of drilling fluid. Flow control is used to determine whether there is a blowout in the well. This control method can obtain the true target bottom hole pressure. Stand-up pressure control is applied to formations where the annulus is affected by oil and gas or high-pressure formations. After flow control is completed, the target stand-up pressure is calculated based on the target bottom hole pressure to achieve constant bottom hole pressure blowout operation.

[0103] In this invention, the double U-shaped tube structure and principle of deepwater pressure controlled drilling are as follows: The first U-shaped tube consists of the drill string (1), drill bit, and annulus below the mudline (2); the second U-shaped tube consists of the riser injection side pipe (5), subsea blowout preventer (3), riser annulus (4), and riser gas treatment system annulus. The principle of the U-shaped tube can be briefly described as follows: the target of interest is bottom hole pressure. A bottom hole pressure balance relationship is established on both sides of the U-shaped tube, thereby establishing a relationship between riser pressure, bottom hole pressure, and casing pressure.

[0104] In one embodiment, the first U-shaped tube is formed by the drill string inner 1, the drill bit, and the annulus 2 below the mudline. A bottom hole pressure balance relationship is established on both sides of the first U-shaped tube, thereby establishing a relationship between the riser pressure, bottom hole pressure, and casing pressure, wherein:

[0105] The expression for the bottom hole pressure of the first U-tube, taking the inside of the drill string as the object, is:

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

[0107] In the formula: P BH P represents the bottom hole pressure, in MPa. cs P is the drilling pump circulation riser pressure, in MPa; fd The internal circulation pressure loss of the drill string is expressed in MPa; P fb P represents the drill bit pressure drop, measured in MPa. dsm The hydrostatic pressure inside the drill string is MPa.

[0108] The bottom hole pressure expression for the first U-tube, taking the inner side of the annulus as the object, is:

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

[0110] In the formula: P BH P represents the bottom hole pressure, in MPa. cam The hydrostatic pressure inside the casing annulus is measured in MPa; P fca The pressure loss during internal circulation in the casing annulus is measured in MPa; P ram P represents the hydrostatic pressure within the annulus of the riser pipe, in MPa; fra The pressure loss during internal circulation of the riser pipe annulus is measured in MPa; P 地面 The pressure loss between the flow guide four-way valve and the choke manifold inlet is given by P, which is the sum of the drilling pump displacement and the injection pump displacement, expressed in MPa. w1 The wellhead back pressure is measured in MPa.

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

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

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

[0114] In the formula, P is the circulating bottom hole pressure of the second U-shaped tube, Mpa; P is the circulating standpipe pressure of the injection pump, Mpa; P is the circulating pressure loss in the riser injection side pipe, Mpa; P is the hydrostatic pressure in the riser injection side pipe, Mpa; P is the circulating pressure loss in the riser annulus, Mpa; P is the pressure loss from the flow-through cross to the choke manifold inlet, Mpa; and P is the wellhead back pressure, Mpa. bh bcs fbl bsm

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

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

[0117] In the formula, P is the circulating bottom hole pressure of the second U-shaped tube, Mpa; P is the hydrostatic pressure in the riser annulus, Mpa; P is the circulating pressure loss in the riser annulus, which is only the injection displacement, Mpa; P is the pressure loss from the flow-through cross to the choke manifold inlet, which is only the injection pump displacement, Mpa; and P is the wellhead back pressure, Mpa. bh ram fra1 地面1 w2

[0118] Figure 4 A step flow chart of the installation of the deepwater managed pressure drilling bottom hole pressure control system and the deepwater managed pressure drilling bottom hole pressure control method according to one embodiment of the present application is shown.

[0119] As Figure 4 ​​​​​​​​​As shown, in step S401, the riser gas treatment system is installed. Specifically, the subsea blowout preventer assembly and individual risers are lowered sequentially. When the last individual riser is lowered, the working chuck for lowering the riser gas treatment system is installed, connecting the riser gas treatment system to the lowered riser. The system is then slowly lowered, and above the water surface, the return slurry line 9 at the guide cross 6, as well as the electrical and hydraulic control lines, are connected, ultimately connecting the riser gas treatment system to the tension ring of the drilling (floating) platform.

[0120] like Figure 4 As shown, in step S402, the surface manifold system is installed. Specifically, the surface manifold system is deployed on the drilling (floating) platform deck in a planar or tower-stacking manner and the pipelines are connected. The return slurry line 9 from the flow guide four-way 6 is connected to the diversion manifold 10, 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 surface manifold system is evaluated. Specifically, after the riser gas treatment system and the surface manifold system are installed in place, functional tests are conducted. The circulating pressure loss under different discharge rates and circulation paths is tested according to the pressure loss evaluation process within the surface manifold pipeline. Further, based on the drilling fluid six-speed viscometer readings, a suitable rheological model for the drilling fluid is selected on the shear rate-shear stress chart. Considering the shape, size, height span, and right-angle bends of the pipelines in the surface manifold system, a flow channel model is established. For right-angle bends, equivalent treatment is performed based on the pipe's inner diameter. Using a pressure measurement system, the circulating pressure loss under different discharge rates and different return flow paths is measured, and the pressure loss calculation model of the surface manifold system in conventional hydraulic calculation software is corrected.

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

[0123] like Figure 4As shown, in step S405, the well bottom pressure control when suspected gas invasion or overflow occurs. Specifically, when suspected gas invasion occurs, stop drilling circulation, take the measured stand pressure as the stand pressure target value, and perform constant well bottom pressure exhaust under stand pressure control; when suspected overflow occurs, stop drilling circulation, take the measured stand pressure as the stand pressure target value, and perform stand pressure control; observe the flow change curve, if the flow shows a continuously increasing trend, implement flow control, and reduce the opening degree of the throttle valve to balance the import and export flow, at this time a new stand pressure target value is obtained, and the stand pressure control is performed under the stand pressure target value to perform constant well bottom pressure overflow exhaust; after the constant well bottom pressure overflow exhaust is performed, the sleeve pressure control is converted, and if the sleeve pressure value is higher than the set value at this time, the drilling fluid density needs to be increased to reduce the sleeve pressure, and then the pressure control drilling operation under the sleeve pressure control is implemented.

[0124] The application discloses a deep water pressure control drilling well bottom pressure control method, and establishes a deep water pressure control drilling double U-shaped pipe well bottom pressure balance relationship formula according to deep water pressure control drilling equipment and pressure control drilling U-shaped pipe principles. Through a pressure measuring system, the pressure value at a set position can be monitored and obtained in real time, the circulation pressure consumption between different positions can be obtained through a pressure difference, and the hydraulic calculation result can be corrected by means of the pressure measuring system; the first pressure measuring device 15 arranged at the blowout preventer 3 is fully utilized, on one hand, the circulation pressure consumption from the flow guide cross 6 to the choke manifold 12 can be corrected, and on the other hand, the pressure value at the position can be taken as an accurate reference point for well bottom pressure calculation. The application considers that the ground pipeline of the deep water pressure control drilling is long, and the circulation pressure consumption cannot be ignored like land or shallow water drilling, and establishes a pressure consumption evaluation process in the ground manifold pipeline. The application describes in detail the pressure control drilling well bottom pressure control method corresponding to the situations of narrow safety density window and suspected gas invasion or overflow.

[0125] The deep water pressure control drilling well bottom pressure control system and the deep water block drilling well site provided by the application can also be matched with a computer readable storage medium, the computer program is stored on the storage medium, and the computer program is executed to run a deep water pressure control drilling well bottom pressure control method.

[0126] The computer program can run computer instructions, the computer instructions include computer program codes, and the computer program codes can be in the form of source code, object code, an executable file or some intermediate form.

[0127] The computer readable storage medium can include any entity or device capable of carrying computer program codes, recording media, U disks, mobile hard disks, magnetic disks, optical disks, computer memories, read-only memories (ROM), random access memories (RAM), electric carrier signals, telecommunication signals and software distribution media.

[0128] It should be noted that the contents contained in the computer-readable storage medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction, for example, in some jurisdictions, according to legislation and patent practice, the computer-readable storage medium does not include electrical carrier signals and telecommunication signals.

[0129] In summary, the present application provides a deep water managed pressure drilling bottom hole pressure control system and a deep water block drilling well site, which has the following advantages compared with the prior art:

[0130] 1) The rotary control head is installed below the tension ring, so that the maximum pressure control value of the deep water managed pressure drilling bottom hole pressure control system provided by the present application is not limited by the pressure bearing capacity of the extension joint in the platform riser system.

[0131] 2) The present application innovatively proposes the fluid circulation double U-shaped pipe principle based on the drilling fluid circulation U-shaped pipe principle and in combination with the riser gas treatment system, the power source for the drilling fluid pump-in of the deep water managed pressure drilling has two, which are the drilling pump and the injection pump, the fluid circulation double U-shaped pipe is realized, so as to meet the process requirements of managed pressure drilling, managed pressure stand connection and riser safe exhaust.

[0132] 3) Through the pressure measuring system and by mainly using the first pressure measuring device at the subsea blowout preventer, the pressure consumption of each section of the circulation pipeline is realized in real time, and more accurate data sources are provided for the bottom hole pressure calculation.

[0133] 4) The bottom hole pressure control method innovatively proposes the double U-shaped pipe principle based on the drilling fluid circulation U-shaped pipe principle and in combination with the riser gas treatment system, the bottom hole pressure balance relationship is established from the pipe and the annulus for the two U-shaped pipes existing in the deep water managed pressure drilling, so as to meet the process requirements of managed pressure drilling, managed pressure stand connection and riser safe exhaust;

[0134] 5) The bottom hole pressure control method depends on the pressure measuring system, so as to verify the numerical simulation results of the hydraulics calculation software and the circulation pressure consumption of each pipeline;

[0135] 6) The bottom hole pressure control method includes three methods of casing pressure control, stand pressure control and flow control, and can solve the deep water drilling technical problems including narrow density window safe drilling, gas invasion riser exhaust, constant bottom hole pressure drilling of strata with unclear formation pressure and constant bottom hole pressure stand connection.

[0136] It should be understood that the embodiments disclosed in the present application are not limited to the specific structures, processing steps or materials disclosed herein, but should be extended to the equivalent alternatives of these features understood by those skilled in the related art. It should also be understood that the terms used herein are only for the purpose of describing the specific embodiments and do not mean limitation.

[0137] In the description of the application, unless otherwise specified and limited, the terms "a plurality of" means two or more; the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail" and the like indicate the orientation or positional relationship shown in the drawings based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the application. In addition, the terms "first", "second", "third" and the like are only for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0138] In the description of the application, it should be noted that, unless otherwise specified and limited, the terms "connected", "connected" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in the application can be understood according to the specific circumstances.

[0139] Certain terms are used throughout this application to refer to particular system components. As one skilled in the art will appreciate, the same component can be referred to by different names and can not be referred to as such throughout this application. In this application, 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", "essentially" or "approximately" that can be used herein relate to the industry-accepted tolerance for the corresponding term. As the term "coupled" can be used in this document, it includes direct coupling and indirect coupling via another component, element, circuit, or module, wherein for indirect coupling, the intervening component, element, circuit, or module does not change the information of the signal but can adjust the current level, voltage level, and / or power level of the signal. The inferred coupling (e.g., where one element is coupled to another element by inference) includes direct and indirect coupling between the two elements in the same way as "coupled".

[0140] The phrase "one embodiment" or "an embodiment" appearing in the specification means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the application. Therefore, the phrase "one embodiment" or "an embodiment" appearing throughout the specification does not necessarily refer to the same embodiment.

[0141] Embodiments of the application are presented by way of example and description only, and are not intended to limit the application to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. Embodiments are chosen and described in order to best explain the principles of the application and its practical application, and to thereby enable others skilled in the art to best utilize the application in various embodiments and with various modifications as are suited to the particular use contemplated.

[0142] Although the present application has been disclosed with reference to the embodiments described above, it is not the intention to limit the application to what has been disclosed. Any modifications and variations that are obvious to those skilled in the art are considered to be within the scope of the present application. The scope of the patent protection is defined by the appended claims.

Claims

1. A method of deepwater managed pressure drilling bottom hole pressure control, characterized by, The method is executed by a deep water managed pressure drilling bottom hole pressure control system, and the method comprises: The safety density window is predicted based on the predicted formation pressure, and a safety density window prediction value is obtained; in the process of the narrow density window managed pressure drilling, drilling fluid with a density less than the lower limit of the safety density window prediction value is used to balance the formation pressure with the bottom hole circulating equivalent density in the circulation process and within the safety density window prediction value; in the process of casing pressure control, the target casing pressure is calculated according to the measured casing pressure, drilling parameters, drilling fluid rheological properties and the target bottom hole pressure, the measured casing pressure is equal to the target casing pressure by adjusting the opening degree of the choke valve, and the bottom hole pressure control is realized; in the process of standpipe pressure control, the target standpipe pressure is calculated according to the measured standpipe pressure, drilling parameters, drilling fluid rheological properties and the target bottom hole pressure, the measured standpipe pressure is equal to the target standpipe pressure by adjusting the opening degree of the choke valve, and the bottom hole pressure control is realized; in the process of flow control, the size relationship of the inlet flow is judged, when the inlet and outlet flow deviates, the flow control is switched from the casing pressure control or the standpipe pressure control, the choke valve is adjusted to balance the inlet and outlet flow, and then the bottom hole pressure at the flow balance is taken as the target bottom hole pressure for the casing pressure control or the standpipe pressure control; The system comprises: a riser gas treatment system located below a tension ring, located entirely below the water surface, and composed of an upper joint, a rotary control head, an annular blowout preventer, a flow guide cross, and a lower joint from top to bottom; a surface manifold system connected with a slurry return pipeline and composed of a shunt manifold, a filter manifold, and a throttle manifold connected in sequence; and a pressure measurement system for measuring the real-time pressure at the subsea blowout preventer, the flow guide cross, the shunt manifold, and the throttle manifold, respectively. The bottom hole pressure control steps when suspected gas invasion or overflow occur comprise: when suspected gas invasion occurs, drilling is stopped and circulation is performed, the measured standpipe pressure is taken as the standpipe target value, and constant bottom hole pressure gas discharge is performed by standpipe pressure control; when suspected overflow occurs, drilling is stopped and circulation is performed, the measured standpipe pressure is taken as the standpipe target value, and constant bottom hole pressure overflow discharge is performed by standpipe pressure control; the flow change curve is observed, if the flow shows a continuously increasing trend, the flow control is implemented, the opening degree of the choke valve is reduced to balance the inlet and outlet flow, a new standpipe target value is obtained at this time, and the constant bottom hole pressure overflow discharge is performed by standpipe pressure control with the standpipe target value; after the constant bottom hole pressure overflow discharge is performed, the casing pressure control is switched, if the casing pressure value is higher than the set value at this time, the drilling fluid density needs to be increased to reduce the casing pressure, and then the managed pressure drilling operation under the casing pressure control is implemented.

2. The method of claim 1, wherein, The upper joint is connected with a drilling pump; one end of the rotary control head is connected with the upper joint, and the other end is connected with the annular blowout preventer; the flow guide cross is connected with the annular blowout preventer, the upper end of the riser, the riser injection side pipe, and the inlet end of the slurry return pipeline, respectively; the subsea blowout preventer is arranged on the drill string and connected with the lower end of the riser.

3. A method of deepwater managed pressure drilling bottom hole pressure control as defined in claim 2, wherein, The inlet end of the flow divider manifold is connected with the outlet end of the return slurry pipeline, and the outlet end is connected with the inlet end of the filter manifold; the outlet end of the filter manifold is connected with the inlet end of the throttle manifold, and the outlet end is connected with the circulating tank.

4. The method of claim 3, wherein, The power source for pumping the drilling fluid in the deep water managed pressure drilling includes two parts, namely, the drilling pump and the injection pump, wherein the drilling fluid pumped by the drilling pump flows through the platform riser manifold, the drill string, the drill bit, the annulus below the mud line, the subsea blowout preventer, the riser annulus, the riser gas treatment system, the surface manifold system and the circulating tank; the drilling fluid pumped by the injection pump flows through the riser injection side pipe, the subsea blowout preventer, the riser annulus, the riser gas treatment system, the surface manifold system and the circulating tank.

5. The method of claim 1, wherein, The pressure measuring system comprises a first pressure measuring device arranged at the position of the subsea blowout preventer, a second pressure measuring device arranged at the position of the outlet of the flow guide cross, a third pressure measuring device arranged at the inlet of the flow divider manifold and a fourth pressure measuring device arranged at the inlet of the throttle manifold.

6. A method of deepwater managed pressure drilling bottom hole pressure control as defined in claim 1, wherein, The first U-shaped pipe is composed of the drill string, the drill bit and the annulus below the mud line, and the bottom hole pressure balance relationship is established on both sides of the first U-shaped pipe, so as to establish the relationship among the riser pressure, the bottom hole pressure and the casing pressure, wherein: The bottom hole pressure expression of the first U-shaped pipe with the drill string on one side as the object is: ； where: P BH is the bottom hole pressure, MPa; P cs is the circulating standpipe pressure of the drilling pump, MPa; P fd is the circulating pressure loss in the drill string, MPa; P fb is the bit pressure drop, MPa; P dsm is the static liquid pressure in the drill string, MPa; The bottom hole pressure expression of the first U-shaped pipe with the annulus on one side as the object is: ； wherein: P BH is the bottom hole pressure, MPa; P cam is the hydrostatic 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 circulating pressure loss in the riser annulus, MPa; P 地面 is the pressure loss between the flow-through cross and the choke inlet, is the sum of the drilling pump displacement and the augmented pump displacement, MPa; P w1 is the wellhead back pressure, MPa.

7. A method of deepwater managed pressure drilling bottom hole pressure control as defined in claim 6, wherein, The second U-shaped pipe is composed of the riser injection side pipe, the subsea blowout preventer, the riser annulus and the riser gas treatment system annulus, and the bottom hole pressure balance relationship is established on both sides of the second U-shaped pipe, so as to establish the relationship among the riser pressure, the bottom hole pressure and the casing pressure, wherein: The bottom hole pressure expression of the second U-shaped pipe with the riser injection side pipe on one side as the object is: ； wherein: P bh P is the second U-shaped tube circulating bottom hole pressure, MPa; P bcs P is the circulating standpipe pressure of the injection pump, MPa; P fbl P is the circulating pressure loss in the riser injection side pipe, MPa; P bsm P is the static liquid pressure in the riser injection side pipe, MPa; The bottom hole pressure expression of the second U-shaped pipe with the annulus on one side as the object is: ； wherein: P bh P is the second U-shaped tube circulating bottom hole pressure, MPa; P ram P is the annulus static liquid pressure of the riser, MPa; P fra1 P is the annulus internal circulating pressure consumption of the riser, only for the injection displacement, MPa; P 地面1 P is the pressure consumption between the flow guide four-way valve and the choke manifold inlet, only for the injection pump displacement, MPa; P w2 P is the wellhead back pressure, MPa.

8. The method of bottom hole pressure control for managed pressure drilling in deep water of claim 1, wherein, The method further comprises a riser gas treatment system installation step, wherein: The subsea blowout preventer group and the riser joint are sequentially lowered, when the last riser joint is lowered, a working chuck of the riser gas treatment system is installed, the riser gas treatment system is connected with the lowered riser, the return slurry pipeline and the electric control and liquid control pipelines are connected at the flow guide cross on the water surface, and finally the riser gas treatment system is connected with the tension ring of the drilling platform.

9. The method of claim 1, wherein, The method further comprises a surface manifold system installation step, wherein: The surface manifold system is arranged on the deck of the drilling platform in a planar arrangement or a tower stacking manner, and the pipeline connection is performed, the return slurry pipeline connected to the flow guide cross is connected with the flow divider manifold, and the outlet of the throttle manifold is connected with the liquid and gas separator of the drilling platform.

10. A method of deepwater managed pressure drilling bottom hole pressure control according to any one of claims 1 to 9 wherein, The method further comprises a surface manifold system pressure consumption evaluation step, wherein: According to the reading of the six-speed viscosity meter of the drilling fluid, a rheological model suitable for the drilling fluid is selected on a shear rate-shear stress graph. A flow channel model is established considering the shape, size, height span, right-angle bend of the pipeline in the ground manifold system; For the right-angle bend, the right-angle bend is equivalently treated according to the inner diameter of the pipe; The pressure measurement system is used to measure the circulating pressure loss under different displacement and different slurry return flow channels, and a pressure loss calculation model of the ground manifold system is corrected.

11. A storage medium, characterized by It comprises a series of instructions for performing the method steps as claimed in any one of claims 1-10.

12. A deep water block drilling rig site, characterized by, The drilling well site comprises the system, and the system performs a deepwater managed pressure drilling bottom hole pressure control method as claimed in any one of claims 1-10.

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