CN115387746A - Pressure control drilling device and method for semi-submersible drilling platform - Google Patents

Abstract

The invention discloses a pressure control drilling device and a pressure control drilling method for a semi-submersible drilling platform, wherein the pressure control drilling device comprises a flow guide device, a spherical joint, a three-section type telescopic short section, a rotary control head, an adapter, a marine riser, a blowout preventer stack, a casing, a PWD (pulse width device) pressure measurement while drilling tool and a drill bit which are sequentially arranged from the top of a drill rod downwards; the top end of the three-section type telescopic short section is connected with the flow guide device through a spherical joint, and the bottom end of the three-section type telescopic short section is connected with a filament-planting flange at the top of the shell of the rotary control head; the bottom end of the shell of the rotary control head is connected with the marine riser through a conversion joint; a wellhead annulus closed and pressurizable drilling fluid circulating system is formed by the drill rod, the rotary assembly of the rotary control head and the shell; several outlets of the shell of the rotary control head are respectively connected with a hydraulic flat valve, one hydraulic flat valve is connected with a main return pipeline, the main return pipeline is connected with a pressure control flow dividing device, and the pressure control flow dividing device is connected with a pressure control throttle manifold system to realize the adjustment and control of the bottom hole pressure.

Description

Pressure control drilling device and method for semi-submersible drilling platform

Technical Field

The invention relates to the technical field of deep sea oil and gas exploration and development, in particular to a pressure control drilling device and method of a semi-submersible drilling platform.

Background

At present, with the increasing of exploration and development of deep-sea oil and gas resources in China, the continuous requirements of corresponding safe and efficient drilling technologies and technologies, especially for key exploration wells in deep-sea areas, are high in temperature, narrow in pressure window, more severe in operation environment, frequent in complex conditions such as overflow and leakage, and the like, and the development of pressure-controlled drilling technologies and technological researches of ultra-high temperature, high pressure and narrow pressure window is urgently needed.

Patent CN2022211223450 discloses a ring-shaped hydraulic locking type rotary control head device. The structure of the hydraulic locking device comprises a shell, a rotating assembly and an annular hydraulic locking system. The device has changed traditional rotary assembly and casing, and anti-overflow pipe assembly and casing installation fixed mode, and rotary assembly is through adopting a plurality of coplanar equidistance and receive hydraulic cylinder and the locking claw of long-range hydraulic pressure station control, realizes that the locking claw stretches out or withdraws to realize rotary assembly's installation and take out, changed the installation connected mode of staple bolt formula before. The shell can be simultaneously connected with the rotary assembly and the anti-overflow pipe assembly without mutual interference, so that during field construction, the procedure of replacing the rotary control head assembly is reduced, the non-production time is greatly saved, the safety risk of high-altitude operation is reduced, and the environmental protection safety risk caused by leakage of slurry formed by frequently disassembling the anti-overflow pipe is reduced. The rotary control head device provides technical support for establishing a set of safe and efficient under-balance and pressure-controlled drilling process technology of the offshore drilling platform.

However, the existing drilling platform semi-submersible type drilling platform for deepwater cannot meet the requirements of pressure-controlled drilling technology and process, and the main reasons are as follows: firstly, the compressive capacity of the existing marine riser telescopic short section and the spherical joint is not enough, so that the existing rotary control head for sealing the wellhead annulus cannot be arranged at the upper part of the existing marine riser telescopic short section and the spherical joint to apply pressure to the wellhead for pressure-controlled drilling; second, the structure of the flexible nipple joint of current two segmentation marine riser causes and can't realize installing the rotation control head on the tension ring, carries out the accuse and presses the well drilling.

Disclosure of Invention

The invention aims to provide a pressure control drilling device and a pressure control drilling method for a semi-submersible drilling platform, aiming at the problems of the existing wellhead device of the semi-submersible drilling platform and the lack of corresponding pressure control drilling equipment.

The invention provides a pressure control drilling device of a semi-submersible drilling platform. The device comprises a flow guide device, a spherical joint, a three-section telescopic short section, a rotary control head, an adapter, a marine riser, a blowout preventer stack, a casing, a PWD (potential pulse detector) while-drilling pressure measuring tool and a drill bit, which are arranged from the top of a drill rod to the bottom in sequence.

The rotary control head is an annular hydraulic locking type rotary control head and structurally comprises a shell, a rotary assembly positioned in the shell and an annular hydraulic locking system positioned on the shell. The detailed structure is described in patent CN 2022211223450.

The three-section telescopic short joint is a three-section telescopic short joint formed by reconstructing an upper short joint of a conventional (or original) two-section telescopic short joint. The telescopic length of the three-section telescopic short section meets the fluctuation height of sea waves, the minimum inner diameter is larger than the maximum outer diameter of a running tool or a rotating assembly of a rotating control head, the top end of the three-section telescopic short section is connected with a flow guide device through a spherical joint, and the bottom end of the three-section telescopic short section is connected with a wire-planting flange at the top of a shell of the rotating control head; the bottom end of the rotary control head is connected with the marine riser; a drilling fluid circulating system which is sealed in the well head annular space and can be pressurized is formed by rotating the control head. And a tensioning ring is arranged on the riser.

Two return outlets of the rotary control head are respectively connected with a hydraulic flat valve, one hydraulic flat valve is connected with a main return outlet pipeline, the main return outlet pipeline is connected with a pressure control flow dividing device, the pressure control flow dividing device is connected with a pressure control throttle manifold system for throttling and pressure control, the outlet of the pressure control throttle manifold system is divided into two pipelines, one pipeline is connected to a liquid-gas separator of a drilling team, gas after liquid-gas separation is prevented from spraying or burning through a blowout prevention pipeline, and liquid flows to a vibrating screen and then returns to a mud tank; the other pipeline is directly connected to a vibrating screen of the drilling team and then returns to the mud tank. And a liquid flowmeter is arranged on the return pipeline to monitor the flow of the return outlet in real time. The other hydraulic flat valve is connected with a grouting pipeline and is connected with a grouting pump of a well team, and the hydraulic flat valve is used for grouting a shaft during conventional drilling; the pressure before the throttle valve, for short, the pressure at the well head is formed by adjusting the opening of the throttle valve of the throttle manifold, so that the adjustment and control of the pressure at the well bottom are realized. And other outlets of the rotary control head can be used as spare return outlets or spare outlets.

Preferably, the bottom end of the casing of the rotating control head is connected with the top end of the marine riser through a conversion joint. The wire-planting flange at the top end of the shell of the rotary control head is connected with the bottom joint of the three-section type telescopic short section through a bolt.

Preferably, the outlet of the pressure control flow dividing device is divided into three pipelines, one pipeline is connected with the pressure control throttle manifold, and the other pipeline is used as a back pressure pipeline to be connected with the back pressure pump and is used for connecting the pressure control pump with a single pipe and tripping the drill in a pressure control mode; one is used as a balance pipeline and is further connected with a throttling pipeline; and the back pressure pump, the back pressure pipeline and the balance pipeline are used for replacing the rotary control head under pressure under the synergistic action.

Preferably, the pressure-control throttle manifold system comprises a throttle manifold, a flowmeter manifold, a hydraulic control system and a PLC data acquisition and control system, and is used for receiving a pressure-control center instruction, automatically opening and closing the opening of the throttle valve, and adjusting and controlling the pressure of a wellhead in real time. And the pressure control center consists of a positive pressure explosion-proof room and a pressure control industrial personal computer.

The method for performing pressure-controlled drilling by adopting the pressure-controlled drilling device of the semi-submersible drilling platform comprises the following steps: in the drilling process, slurry in a slurry tank is pumped to the well bottom through a drill rod by a slurry pump and flows out through a water hole of a downhole drill bit, the slurry with drill cuttings returns to a wellhead rotation control head through an annulus between the drill rod and the well hole, then returns to a pressure control flow dividing device to a pressure control throttle manifold system through a return outlet of the rotation control head and a hydraulic flat valve and a return pipeline, and forms the pressure (wellhead pressure) before a throttle valve by adjusting the valve position opening of the throttle valve of the throttle manifold, so that the adjustment and control of the well bottom pressure are realized.

The equation for bottom hole pressure is as follows:

bottom hole pressure = mud liquid column pressure + annulus friction + wellhead pressure

Wherein:

slurry column pressure: the mud column pressure = mud density x gravitational acceleration x vertical depth of the borehole, and is generally a relatively stable value when the mud density and the vertical depth of the borehole are fixed.

Annular friction resistance: the annular friction is related to pump displacement, mud density, mud performance, well bore structure, drill pipe combination and other factors, and generally under the condition that drilling parameters and mud performance are determined, the annular friction is a relatively stable value.

Pressure at the well head: it is the only pressure that can carry out adjustment and control in real time according to the actual drilling operating mode in scene. The basic control principle of the system is that a target bottom hole pressure value is set, then a measured value of a downhole pressure measurement while drilling PWD tool or a bottom hole pressure value calculated by a hydraulic model is compared with the set target bottom hole pressure value in real time, the system automatically calculates a wellhead pressure setting value, and the opening size of a throttle valve is adjusted by an automatic throttle control system until the actual wellhead pressure is basically consistent with the wellhead pressure setting value, so that the purposes of adjusting and controlling the bottom hole pressure to be consistent with the set target bottom hole pressure value, keeping the opening size of the throttle valve, maintaining the wellhead pressure to be stable and realizing the pressure-controlled drilling construction of the semi-submersible type marine drilling platform are achieved.

Compared with the prior art, the invention has the advantages that:

(1) The pressure-controlled drilling device changes the state that the traditional wellhead is not closed and can not be pressurized, and the pressure-controlled drilling device is characterized in that an inner cylinder of a traditional two-section type telescopic short section is transformed into a three-section type telescopic short section, and an annular hydraulic locking type rotary control head is arranged between an outer cylinder of the original two-section type telescopic short section and the three-section type telescopic short section to form a wellhead annular closed and pressurizable drilling fluid circulating system.

(2) The pressure-controlled drilling device provided by the invention is characterized in that a pressure-controlled automatic throttling manifold system is connected to the return pipeline, and the pressure at the wellhead can be adjusted and controlled in real time according to the actual underground condition, so that the pressure-controlled drilling technology and process are realized.

(3) The pressure-controlled drilling device provided by the invention has the advantages that the state of the traditional return pipeline no-flow monitoring device is changed, the flow meter is connected on the return pipeline, the outlet flow can be monitored in real time, the overflow and leakage software system of the industrial personal computer compares and judges the drilling parameters and the outlet and inlet flows acquired by the PLC in real time, the overflow or leakage is found as soon as possible and the alarm is given, the traditional monitoring of the change of the liquid level of the mud tank to find the overflow or leakage is changed, the well control safety is improved, and the production risk is reduced.

(4) The pressure-controlled drilling device of the semi-submersible type drilling platform fills the blank of the pressure-controlled drilling technology and process of the semi-submersible type drilling platform (or deepwater drilling platform) in China in order to establish a set of safe and efficient underbalance and pressure-controlled drilling technology and process of the semi-submersible type deepwater drilling platform.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.

Drawings

FIG. 1 is a schematic structural diagram of a pressure control drilling device of a semi-submersible drilling platform.

FIG. 2 is a schematic structural diagram of a pressure control manifold system.

Fig. 3, controlled pressure drilling or circulation flow chart.

FIG. 4 is a flow chart of pressure control tripping and single drill connection.

Fig. 5, a conventional drill-out flow chart.

Fig. 6, conventional drill-down flow chart.

FIG. 7 is a flow chart of the pressure control belt pressure replacement rotary assembly.

FIG. 8 is a flow chart of pressure-control throttling circulation sewage discharge.

Reference numbers in the figures:

the device comprises a mud pump 1, a riser 2, a drill rod 3, a PWD pressure measurement while drilling tool 4, a drill bit 5, a flow guide device 6, a spherical joint 7, a three-section telescopic short section 8, a rotary control head 9, a conversion joint 10, a top joint 11 of an outer cylinder of the telescopic short section of the riser, a tension ring 12, a riser 13, a downhole blowout preventer stack 14, a casing 15, a hydraulic flat valve 16, a return pipeline 17, a pressure control flow divider 18, a pressure control throttle manifold system 19, a pressure control center 20, a logging house industrial personal computer 21, a mud tank outlet pipeline 22, a liquid separator outlet pipeline 23, a liquid separator 24, a liquid separator liquid outlet pipeline 25, a liquid separator gas outlet pipeline 26, a back pressure pump 27, a back pressure pipeline 28, a grouting pump 29, a grouting pipeline 30, a hydraulic flat valve 31, a kill pipeline 32, a throttle pipeline 33, a balance pipeline 34, a team throttle manifold 35, a throttle pipe 19.1, a flow measurement system 19.2, a PLC data acquisition and control system 19.4, a data line 20.1 and a data line 20.2.

Detailed Description

The preferred embodiments of the present invention will be described in conjunction with the accompanying drawings, and it will be understood that they are described herein for the purpose of illustration and explanation and not limitation.

As shown in fig. 1 to 7, the pressure-controlled drilling device of the semi-submersible drilling platform provided by the invention comprises a slurry pump 1, a riser 2, a drill rod 3, a PWD pressure-while-drilling tool 4, a drill bit 5, a flow guiding device 6, a spherical joint 7, a three-section type telescopic short section 8, a rotary control head 9, a conversion joint 10, a riser top joint 11, a tension ring 12, a riser 13, an underground blowout preventer stack 14, a casing 15, a return outlet hydraulic flat valve 16, a return outlet pipeline 17, a pressure-controlled flow dividing device 18, a pressure-controlled throttle manifold system 19, a pressure-controlled control center 20, a logging house 21, a mud tank outlet pipeline 22, a liquid-gas separator outlet pipeline 23, a liquid industrial personal computer 24, a liquid-gas separator outlet pipeline 25, a liquid-gas separator gas outlet pipeline 26, a return pump 27, a return pressure pipeline 28, a grouting pump 29, a grouting pipeline 30, a hydraulic grouting pipe flat valve 31, a well control pipeline 32, a throttling pipeline 33, a balance pipeline 34 and a well team throttling manifold 35. The rotary control head 9 refers in particular to an annular hydraulic locking type rotary control head of patent CN 2022211223450.

The mud pump 1 can be provided with a plurality of mud pumps, and the operation of a single mud pump or the simultaneous operation of a plurality of mud pumps can be realized by arranging a valve switch among the plurality of mud pumps. The mud pump 1 is connected with a drill rod 3 through a vertical pipe 2, and a valve, a pressure gauge and a pressure sensor are arranged on a connecting pipeline. Mud pump 1 is also connected to kill line 32.

The three-section telescopic short section 8 is a necessary device and a fluid channel for returning mud out of a wellhead when a rotary assembly is removed in conventional drilling or underbalanced drilling and pressure control drilling. The minimum inner diameter of the three-section telescopic short section 8 is larger than the maximum outer diameter of a rotary assembly or a running tool, so that the three-section telescopic short section 8 is not required to be disassembled and assembled when the rotary assembly is disassembled and assembled, the running tool can be installed or taken out of the rotary assembly through the three-section telescopic short section 8 inner cylinder, and the telescopic length of the rotary assembly meets the fluctuation height of sea waves. The top end of the three-section type telescopic short section 8 is connected with a drilling crew flow guide device 6 through a spherical joint 7, and the flow guide device 6 is provided with a flow guide device outlet to a mud tank. The bottom end of the three-section type telescopic short section 8 is connected with a wire-planting flange at the top of the shell of the rotary control head 9 through a flange.

The shell bottom flange of the rotating control head 9 is connected with the riser top joint 11 through a crossover joint 10. The rotating assembly of the rotating control head 9 is seated in the housing and secured by an annular hydraulic locking system. The drill pipe 3, the shell and the rotating assembly form a closed and pressurizable wellhead. Two outlets on the shell of the rotary control head 9 are provided with hydraulic flat valves. Wherein the hydraulic flat valve 16 is connected with the main return pipeline 17, and the hydraulic flat valve 31 is connected with the grouting pipeline 30. The other two outlets are respectively used as a spare return outlet or a spare outlet.

The return pipeline 17 is connected with a pressure control flow dividing device 18. And then connected into the pressure control manifold system 19. The pressure control flow divider 18 is composed of a four-way joint and four valves. The four interfaces of the four-way joint are respectively connected with a return pipeline 17, a pressure control throttle manifold system 19, a back pressure pipeline 28 and a balance pipeline 34, and valves are arranged near the interfaces.

The pressure control throttling manifold system 19 comprises a throttling manifold 19.1, a flow measuring system 19.2, a hydraulic control system 19.3 and a PLC data acquisition and control system 19.4. The return liquid in the return pipeline enters the pressure-control throttle manifold system 19 after passing through the pressure-control flow dividing device, and firstly enters the throttle manifold 19.1. As shown in fig. 2, the throttle manifold 19.1 comprises an inlet composed of a valve M1 and a four-way joint D, a pressure sensor C is mounted on the four-way joint D, an outlet of the four-way joint D is divided into three passages, two throttle passages (one for each) and a straight-through passage, and one throttle passage is composed of a valve M2, a throttle valve a, a valve M3, an angle passage E, a tee joint F and a tee joint G; the other throttling channel consists of a valve M5, a throttling valve B, a valve M6 and a tee joint G; and the straight-through channel consists of a valve M4, a tee joint F and a tee joint G. The flow measuring system 19.2 comprises an inlet three-way joint H, a flow measuring channel, a bypass channel and an outlet joint K; the measuring channel consists of a three-way joint H, a valve M7, a flowmeter L, an angle joint I, an angle joint J, a valve M8 and a three-way joint K; the bypass channel consists of a three-way joint H, a valve M9 and a three-way joint K. Installing front and rear pressure sensors C of the flow meter on the three-way joint H and the three-way joint K; the remaining outlet of the three-way joint K is used as an outlet. The pressure sensor C, the mass flow meter L, the throttle valve A valve position sensor and the throttle valve B valve position sensor which are arranged on the four-way joint D, the three-way joint H and the three-way joint K are all connected with a PLC data acquisition and control system 19.4 through a junction box.

The outlet of the pressure-controlled throttle manifold system 19 is divided into two paths, one path 22 to the mud tank, the other path 23 to the liquid-gas separator 24, the liquid outlet 25 of the liquid-gas separator 24 to the mud tank, and the gas outlet 26 to the blowout preventer or torch. The pressure-control throttling manifold system 19 is an actuating mechanism of an automatic throttling control system, and has the functions of monitoring and acquiring pressure-control drilling parameters, receiving an instruction of an industrial personal computer, adjusting the opening of a throttling valve A or a throttling valve B, and adjusting and controlling the pressure of a wellhead in real time, so that the control of the pressure of a well bottom is finally achieved.

The pressure control center 20 is internally provided with a pressure control industrial control unit (comprising a pressure control software system), is connected with a PLC data acquisition and control system 19.4 of a pressure control throttling manifold system 19 through a data line 20.1, is connected with a logging room industrial control computer 21 through a data line 20.2, stores acquired pressure control drilling parameters in a database of the pressure control industrial control unit, automatically calculates a wellhead pressure control pressure parameter setting value through the pressure control software system, sends a command to the PLC data acquisition and control system 19.4, switches a throttling valve A or B of the throttling manifold 19.1 through a control hydraulic control system 19.3, adjusts and controls wellhead pressure, and when the actual wellhead pressure is consistent with the set wellhead pressure value, the system keeps the wellhead pressure stable, so that the pressure control drilling technology and process are realized, as shown in figure 1. The pressure control industrial control unit comprises data acquisition, display, calculation, analysis, judgment, alarm and instruction issuing, and is a foundation and guarantee for implementing the pressure control drilling technology. The pressure control center also comprises a positive pressure explosion-proof room which provides a safe explosion-proof working environment and an equipment environment.

The pressure control back pressure pump 27 is connected with the pressure control flow dividing device 18 through a back pressure pipeline 28, then is connected with the outlet of the rotary control head through a return pipeline 17, the other path is also connected with the pressure control throttle manifold system 19 through the pressure control flow dividing device 18, and the main function of the pressure control back pressure pump is that fluid is provided for the wellhead rotary control head 9 and the pressure control throttle manifold system 19 when the slurry pump 1 stops pumping, throttling is carried out by the pressure control throttle manifold system 19 to form wellhead pressure, loss of compensation ring empty pressure loss is achieved, and the constant of the bottom hole pressure is kept, such as the working conditions that a pump stops connecting a single heel, and the drilling is started or stopped. The flow chart of pressure control to joint single and pressure control to trip is shown in figure 4.

The balance pipeline 34, the back pressure pump 27, the back pressure pipeline 28, the pressure control flow dividing device 18, the pressure control throttle manifold system 19, the outlet pipelines 22 and 23, the throttle pipeline 33 and the like form a balance wellhead pressure supplementing system. When the rotary assembly is replaced under pressure at the wellhead, the blowout preventer stack 14 needs to be closed, and then the wellhead below the blowout preventer stack 14 is subjected to pressure regulation and control through a balanced wellhead pressure supplementing system. The flow of the pressure-control pressurized replacement rotating assembly is shown in figure 7.

The grouting pump 29, the grouting pipeline 30, the grouting pipeline valve and the like form a grouting system. The grouting line 30 connects the grouting pump 29 to the rotary control head outlet valve 31, and is mainly used for grouting the shaft during conventional tripping after the rotary assembly 19.2 is removed. The conventional tripping procedure is shown in fig. 5. In contrast, FIG. 6 is a conventional drill-down flow chart.

The pressure control throttling manifold system 19 forms a throttling circulation blowdown system with the mud pump 1, the stand pipe 2, the drill rod 3, the closed blowout preventer stack 14, the throttling pipeline 33, the front tee joint of the well team throttling manifold 35, the balance pipeline 34, the pressure control flow dividing device 18, the outlet pipeline 21 or 22 of the pressure control throttling manifold system 19 and the like, and can be used as a standby means for emergency danger elimination, so that the well control safety is improved, and the production risk is reduced. The pressure-control throttling circulation blowdown flow is shown in figure 8.

Although the present invention has been described with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present invention.

Claims (9)

1. The pressure control drilling device of the semi-submersible drilling platform is characterized by comprising a drill rod, wherein the top end of the drill rod is connected with a mud pump, and a flow guide device, a spherical joint, a three-section type telescopic short section, a rotary control head, an adapter, a marine riser, a blowout preventer group, a casing, a PWD (pulse width modulation) while-drilling pressure measuring tool and a drill bit are sequentially arranged from the top of the drill rod to the bottom;

the three-section telescopic short joint is a three-section telescopic short joint reconstructed from an upper short joint of a conventional two-section telescopic short joint, the telescopic length of the three-section telescopic short joint meets the fluctuation height of sea waves, the minimum inner diameter of the three-section telescopic short joint is larger than the maximum outer diameter of a running tool or a rotating assembly of a rotating control head, the top end of the three-section telescopic short joint is connected with a flow guide device through a spherical joint, and the bottom end of the three-section telescopic short joint is connected with a top-end thread-planting flange of a shell of the rotating control head;

the rotary control head is an annular hydraulic locking type rotary control head and structurally comprises a shell, a rotary assembly positioned in the shell and an annular hydraulic locking system positioned on the shell; the top end of the shell of the rotary control head is connected with the three-section type bottom end, and the base of the shell of the rotary control head is connected with the marine riser through the adapter; the rotary assembly of the rotary control head is fixed in the shell through an annular hydraulic locking mechanism, and a wellhead annular closed and pressurizable drilling fluid circulating system is formed through the drill rod, the rotary assembly of the rotary control head and the shell;

several outlets at the lower part of the shell of the rotary control head are respectively connected with a hydraulic flat valve, one hydraulic flat valve is connected with a main return pipeline, the main return pipeline is connected with a pressure control flow dividing device, the pressure control flow dividing device is connected with a pressure control throttle manifold system for throttling and pressure control, the outlet of the pressure-control throttle manifold system is divided into two pipelines, one pipeline is connected to a liquid-gas separator of the drilling team, gas after liquid-gas separation is sprayed or combusted through a spraying-proof pipeline, and liquid flows to a vibrating screen and then returns to a mud tank; the other pipeline directly returns to the mud tank after going to the vibrating screen of the drilling crew; the opening of the throttle valve of the pressure control throttle manifold system is adjusted to form the pressure before the throttle valve, which is called wellhead pressure for short, so that the adjustment and control of the bottom hole pressure are realized; and the other hydraulic flat valve is connected with a grouting pipeline and is connected with a grouting pump of a drilling crew for grouting a shaft during conventional drilling, and other outlets can be used as spare outlets.

The managed pressure rig of claim 1, wherein the bottom end of the housing of the rotating control head is connected to the top end of the riser by an adapter; the wire-planting flange at the top end of the shell of the rotary control head is connected with the bottom joint of the three-section type telescopic short section through a bolt.

2. The managed pressure rig of claim 1, wherein the rotating control head is mounted above the tension ring.

3. The pressure controlled drilling rig of claim 1, wherein the outlet of the pressure controlled splitter is divided into three lines, one connecting the pressure controlled choke manifold system to cooperate with the mud return line for pressure controlled drilling and pressure controlled circulation; one of the pressure control pipelines is used as a back pressure pipeline connected with the back pressure pump, and is used for controlling the pressure of a single pipe and controlling the pressure to drill down under the cooperative action of the back pressure pipeline and the pressure control throttle manifold system; and the rotating assembly is used as a balance pipeline connected with a drilling team throttling pipeline, is cooperated with the back pressure pump, the back pressure pipeline, the balance pipeline and the pressure control throttling manifold system, and is used for replacing the rotating control head under pressure.

4. The pressure-controlled drilling device of the semi-submersible drilling platform as claimed in claim 3, wherein the pressure-controlled throttle manifold system comprises a throttle manifold, a flowmeter manifold, a hydraulic control system, and a PLC data acquisition and control system, and is used for receiving a pressure-controlled control center command, automatically opening and closing the throttle valve, and adjusting and controlling the wellhead pressure in real time.

5. The pressure-controlled drilling rig of the semi-submersible drilling platform as recited in claim 4 wherein the pressure-controlled control center is comprised of a positive pressure explosion-proof house and a pressure-controlled industrial control computer.

6. The pressure controlled drilling rig of claim 1, wherein the other two outlets of the rotary control head housing are connected to hydraulic flat valves respectively as spare return lines or spare outlets.

7. The pressure controlled drilling rig of claim 1, wherein a fluid flow meter is disposed on the return line to monitor the flow rate at the return port in real time.

8. A method for controlled pressure drilling of a semi-submersible rig, characterized in that a controlled pressure drilling rig of a semi-submersible rig according to any of claims 1-7 is used.

9. The pressure-controlled drilling method for the semi-submersible drilling platform as claimed in claim 8, wherein during drilling, mud in a mud tank is pumped to the bottom of the well through a drill stem by a mud pump, flows out through a water hole of a downhole drill bit, returns drill cuttings carried by the mud to a wellhead rotary control head through an annulus between the drill stem and a well hole, then flows to a pressure-controlled flow dividing device to a pressure-controlled throttle manifold system through a return outlet of the rotary control head and a hydraulic flat valve through a return pipeline, and forms pressure before a throttle valve through adjustment of the valve position opening of the throttle valve of the throttle manifold, so that adjustment and control of the bottom pressure are realized.

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