An ultra-deep water ultra-shallow layer complex structure well open drilling wellbore pressure safety control device and method

Abstract

This invention relates to a pressure safety control device and method for open-circuit drilling of complex structure wells in ultra-deepwater and ultra-shallow waters, belonging to the field of offshore oil and gas resource drilling. It includes a real-time monitoring and analysis device and a pressure dynamic control device. The real-time monitoring and analysis device includes a seabed mud control hood, a traction rope, a seabed camera robot, and a computer. The seabed mud control hood is equipped with four drainage holes, each with a drainage control valve. The pressure dynamic control device includes a kill fluid mixing system, a drilling fluid injection pipeline, a No. 1 seabed pipeline, and a No. 2 seabed pipeline. This invention ensures accurate gas intrusion treatment measures and parameter control in open-circuit drilling of complex structure wells in ultra-deepwater and ultra-shallow waters by combining pre-drilling parameter design, real-time monitoring of multiphase flow parameters during drilling, real-time analysis of gas intrusion, and multi-stage throttling safety control on the seabed, providing a guarantee for safe and efficient open-circuit drilling in ultra-deepwater and ultra-shallow waters.

Description

Technical Field

[0001] This invention relates to a device and method for safety control of wellbore pressure in open-circuit drilling of complex structure wells in ultra-deepwater and ultra-shallow waters, belonging to the field of marine oil and gas resource drilling technology. Background Technology

[0002] Currently, my country's dependence on imported oil and gas remains high, posing a significant challenge to energy supply security. Vigorously exploring and developing new oil and gas resource blocks is a crucial way to address this issue. In recent years, my country has made significant progress in deep-water oil and gas exploration and development, successively developing large oil and gas fields such as "Shenhai Yihao" and Kaiping South, and discovering the world's first ultra-deepwater, ultra-shallow gas field, Lingshui 36-1, in the waters off Hainan Island. Located in the Qiongdongnan Basin, the Lingshui 36-1 gas field has an average operating water depth of approximately 1500 meters and an average gas layer burial depth of 210 meters, with proven geological reserves of natural gas exceeding 100 billion cubic meters. "Ultra-shallow" indicates that the gas layer is relatively shallow below the seabed; compared to the burial depth of conventional gas fields, the gas layer in ultra-shallow gas fields is closer to the seabed surface. Ultra-deepwater, ultra-shallow gas fields are characterized by deep water, shallow burial, and complex development technologies, and face challenges such as loose formations and high drilling difficulty.

[0003] To increase single-well production and shorten the investment recovery period in offshore oil and gas development, complex well structures such as branch wells are often used. For drilling ultra-deepwater and ultra-shallow complex well structures, wellbore pressure control faces greater challenges, specifically: Firstly, the drilling fluid density window (mud window) is extremely narrow, mainly due to low fracturing pressure and high uncertainty in pore pressure. In some extreme cases, the pore pressure may even approach or exceed the fracturing pressure, meaning there is no safe density range, making conventional drilling techniques impossible and posing significant difficulties for pressure control. Secondly, ultra-deepwater areas typically exceed 1500 meters in depth, resulting in low-temperature effects on the seabed, which can easily lead to the formation of natural gas hydrates. Furthermore, drilling in ultra-shallow formations often lacks risers and blowout preventers, making it difficult to detect and address issues like gas intrusion during drilling. Additionally, complex structures such as branch wells further complicate pressure control. Strong formation anisotropy and uncertainty mean that complex wells can penetrate multiple formations with different pressure systems, especially in ultra-shallow formations where lateral formation changes are rapid and data from adjacent wells is of limited reference value. This makes predicting pore pressure and fracture pressure more difficult, and pressure control in different branch wells can interfere with each other, further complicating precise pressure control within different branch wells.

[0004] Currently, wellbore pressure control in ultra-deepwater and ultra-shallow drilling processes mainly relies on traditional methods, which suffer from problems such as late detection, slow response, and poor accuracy. There is a lack of a suitable method for safe wellbore pressure control in ultra-deepwater and ultra-shallow wells with complex structures. This problem is a significant factor restricting the safe and efficient drilling of such wells. Therefore, there is an urgent need for a method for safe wellbore pressure control in open-circuit drilling of ultra-deepwater and ultra-shallow wells with complex structures. This invention is proposed to address this need. Summary of the Invention

[0005] To address the shortcomings of existing technologies, particularly the difficulty of safely and efficiently controlling wellbore pressure after gas intrusion in open-circuit drilling of complex structures in ultra-deepwater and ultra-shallow wells, this invention proposes a safe wellbore pressure control device and method for open-circuit drilling of complex structures in ultra-deepwater and ultra-shallow wells. By combining pre-drilling parameter design, real-time monitoring of multiphase flow parameters during drilling and real-time analysis of gas intrusion, and multi-stage throttling safety control on the seabed, accurate gas intrusion treatment measures and parameter control are ensured in open-circuit drilling of complex structures in ultra-deepwater and ultra-shallow wells, providing a guarantee for achieving safe and efficient open-circuit drilling in ultra-deepwater and ultra-shallow wells.

[0006] The present invention adopts the following technical solution:

[0007] A wellbore pressure safety control device for open-circuit drilling of complex structure wells in ultra-deepwater and ultra-shallow water includes a real-time monitoring and analysis device and a pressure dynamic regulation device.

[0008] The real-time monitoring and analysis device includes a seabed mud control hood, a traction rope, a seabed camera robot, and a computer. The seabed mud control hood has four drainage holes, which serve as discharge channels for drilling fluid flowing through the bottom of the well during normal drilling. Each drainage hole is equipped with a drainage hole control valve, which is connected to the computer and can be opened and closed under computer commands. The seabed camera robot is lowered to the vicinity of the four drainage holes via the traction rope to capture real-time images of the return pattern and height of the drilling fluid from the four drainage holes. These images are then transmitted to the computer in real-time. Using image recognition technology, the gas content in the captured drilling fluid return images can be identified.

[0009] The pressure dynamic control device includes a kill fluid mixing system, a drilling fluid injection pipeline, a No. 1 subsea pipeline, and a No. 2 subsea pipeline. The kill fluid mixing system is used to obtain kill fluid that meets the requirements and then injects it into the drill pipe through the drilling fluid injection pipeline and the platform wellhead. After flowing through the drill bit at the bottom of the well, it enters the annulus. The drilling fluid injection pipeline is equipped with a platform pipeline data monitoring sub and a platform pipeline control valve.

[0010] One end of each of the No. 1 and No. 2 subsea pipelines is connected to the annulus, and the other end leads to seawater. Both the No. 1 and No. 2 subsea pipelines are equipped with data monitoring sections and pipeline control valves. The data monitoring sections of the platform pipelines and the No. 1 and No. 2 subsea pipelines are all connected to a computer, transmitting the monitored data to the computer in real time. The platform pipeline control valves and pipeline control valves are also connected to the computer, receiving control commands from the computer to achieve real-time and efficient control of wellbore pressure.

[0011] Preferably, the subsea mud control cover includes a circular end face and a circular annular wall, the circular annular wall is fixed to the cementing sheath, and the circular end face has a through hole at its center for drilling the drill pipe;

[0012] A Doppler signal generator is installed on one side of the annular wall of the subsea mud control hood, and a Doppler signal receiver is installed on the opposite side. The Doppler signal receiver is connected to an ultrasonic Doppler monitor, which processes and analyzes the changes in ultrasonic signals and transmits them to a computer. The computer receives data transmitted from the subsea camera robot and the ultrasonic Doppler monitor, and by analyzing the images and ultrasonic data returned from the drainage hole, it obtains data on the changes in gas content in the drilling fluid, and analyzes whether gas invasion has occurred at the bottom of the well and the severity of the gas invasion.

[0013] The flow state within the drilling fluid is measured using the Doppler ultrasonic effect. After gas intrusion, the movement of air bubbles in the drilling fluid causes a Doppler frequency shift in the sound waves. By filtering, the frequency characteristics of the ultrasonic waves in the gas-filled drilling fluid are reflected, obtaining the correspondence between gas content and sound wave frequency change, thus allowing real-time monitoring of the gas content in the drilling fluid. Based on this, the presence of gas intrusion can be determined. When the gas content is >0, it indicates the presence of gas intrusion, and a higher gas content indicates a more severe gas intrusion.

[0014] Preferably, the No. 1 and No. 2 submarine pipelines have the same structure and are symmetrically distributed on both sides of the submarine mud control cover. The No. 1 and No. 2 submarine pipelines pass through the annular wall of the submarine mud control cover and communicate with the annular space.

[0015] The inner diameters of the No. 1 and No. 2 submarine pipelines are divided into three levels, decreasing progressively. The inner diameter decreases as the distance from the annulus increases. This avoids a sudden and sharp reduction in the flow channel, which could result in an excessive throttling pressure drop and allow for better application of wellhead back pressure at the submarine wellhead.

[0016] Preferably, the kill fluid mixing system includes a mixer, a pump, and a pumping line. The pump draws seawater through the pumping line into the mixer to mix with the weighted mud from the weighted mud storage tank to obtain a kill fluid that meets the requirements.

[0017] A method for operating the above-mentioned safety control device for wellbore pressure in open-circuit drilling of ultra-deepwater and ultra-shallow complex structure wells includes:

[0018] (1) Based on the formation data of adjacent wells and the design principle of safe drilling in deep water shallow open-loop drilling, design drilling parameters including drilling fluid density and displacement to provide a basis for safe drilling;

[0019] (2) Combining the images captured by the underwater camera robot and the ultrasonic Doppler monitoring data, we can analyze the real-time changes in the gas content in the annulus of open-circuit drilling, determine whether gas intrusion occurs at the bottom of the well during open-circuit drilling and the extent of gas intrusion, and provide a basis for the control of wellbore pressure.

[0020] (3) When gas invasion occurs, close the control valves of the four drainage holes and open the pipeline control valves of Submarine Pipeline No. 1 and Submarine Pipeline No. 2, so that the drilling fluid in the annulus can flow into the seawater through Submarine Pipeline No. 1 and Submarine Pipeline No. 2. At the same time, based on the gas invasion situation and the formation situation of different drilling sections obtained by real-time monitoring and analysis, optimize the key parameters such as the density, flow rate and valve opening of the kill fluid required for different stages of open-circuit drilling, and inject the prepared kill fluid into the bottom of the well and into the annulus as needed to achieve the purpose of wellbore pressure safety control.

[0021] Preferably, in step (1), during the drilling parameter design process, it is necessary to combine the formation data of adjacent wells (including formation pressure, fracture pressure, formation lithology, etc.) and consider the impact of the existing wells on the drilling of complex structure wells at different stages of drilling (drilling the main well and drilling different branch wells), optimize the design of drilling parameters for open-path drilling of ultra-shallow complex structure wells, and provide a basis for safe drilling.

[0022] When drilling a horizontal main well, only the safety of the main well needs to be considered when designing drilling parameters. Based on the formation pore pressure and formation fracturing pressure of the main well formation, the bottom hole pressure needs to meet the condition of being greater than the formation pore pressure and less than the formation fracturing pressure. From this, the drilling fluid density required for open-circuit drilling can be obtained:

[0023] (1)

[0024] In the formula, P k Formation pore pressure, Pa; P jd ρ is the bottom hole pressure, Pa; s The density of seawater is kg / m³. 3 g is the acceleration due to gravity, m / s² 2 h s Seawater depth, in meters (m); h z ρ represents the vertical drilling depth in the formation, in meters (m); z Density of drilling fluid, kg / m³ 3 ;P p The formation fracture pressure is expressed in Pa.

[0025] During drilling, the flow of drilling fluid generates friction, which increases the bottom hole pressure. Therefore, the drilling fluid discharge rate cannot be too high to prevent formation damage and avoid well leakage, well kick, or blowout accidents. Based on the bottom hole pressure balance requirements, the drilling fluid discharge rate can be obtained from the following formula:

[0026] (2)

[0027] (3)

[0028] In the formula, △P fhk The frictional resistance of the fluid flow in the annulus is Pa; f is the friction coefficient, which is dimensionless; Q L For drilling fluid displacement, m 3 / min;d hk The diameter of the annular flow section is in meters (m).

[0029] When drilling branch wells after the main well is completed, the design of branch well drilling parameters must not only ensure the safety of the well currently being drilled, but also consider the safety of the wells already drilled. Based on the formation pore pressure and formation fracturing pressure in both the well being drilled and the wells already drilled, the bottom hole pressure in the well being drilled must simultaneously meet the condition of being greater than the formation pore pressure in both the well being drilled and the wells already drilled, and less than the formation fracturing pressure in both the well being drilled and the wells already drilled. Based on this, the required drilling fluid density for the well being drilled can be obtained.

[0030] (4)

[0031] In the formula, P k1 ,P k2 ,P k3 ,……,P kn For formation pore pressures in different wells, Pa; P p1 ,P p2 ,P p3 ,……,P pn For different wells, the formation fracture pressure is given in Pa.

[0032] At the same time, the above conditions must also be met when designing the drilling fluid discharge rate for post-drilled branch wells. The drilling fluid discharge rate can be obtained according to the following formula:

[0033] (5).

[0034] Preferably, in step (2), based on the real-time footage captured by the underwater camera robot of the drilling fluid return during the open-circuit drilling process, image recognition technology is used to analyze the changes in key parameters such as the morphology and gas content of the returned drilling fluid; combined with the drilling fluid return parameters during normal drilling without gas invasion, when the gas content E in the returned drilling fluid is found to be... gA value greater than 0 indicates gas intrusion during open-circuit drilling, and the severity of gas intrusion can be determined by the gas content. The higher the gas intrusion flow rate, the more severe the gas intrusion.

[0035] When there is no air invasion:

[0036] (6)

[0037] When air intrusion occurs:

[0038] (7)

[0039] Air intrusion flow rate:

[0040] (8)

[0041] In the formula, v g v is the velocity of gas in the drilling fluid. m v is the mixing velocity of the returning drilling fluid. l E represents the liquid phase flow rate in the drilling fluid. g denoted as the gas content of the cross section; A represents the cross-sectional area of ​​the annulus.

[0042] Preferably, in step (2), during the ultrasonic Doppler monitoring process, when gas invasion occurs in the annulus, the movement of bubbles in the drilling fluid within the annulus will cause a Doppler frequency shift in the sound waves. By filtering, the frequency variation characteristics of the ultrasonic waves in the drilling fluid containing bubbles can be reflected, and thus the correspondence between the gas content and the Doppler frequency shift can be obtained, thereby realizing real-time monitoring of the gas content change in the drilling fluid. Based on this, it is possible to determine in real time whether gas invasion exists in the annulus and the degree of gas invasion.

[0043] Preferably, a Doppler signal generator fixed to the annular wall of the seabed mud control hood emits ultrasonic waves of a fixed frequency into the drilling fluid flowing within the annulus. When these waves encounter solid particles (rock cuttings) or air bubbles in the drilling fluid, they are reflected, deviating from the emitted frequency. A Doppler signal receiver fixed to the other end of the annular wall of the seabed mud control hood receives the reflected waves. After signal processing and spectral analysis, the velocity of the reflecting objects within the cross-section can be calculated. Finally, the Doppler frequency shift is obtained. :

[0044] (9)

[0045] In the formula, This indicates the frequency of the ultrasonic waves emitted by the Doppler signal generator; This indicates the frequency of the ultrasonic wave received by the Doppler signal receiver; Indicates the velocity of the particle; This indicates the angle between the ultrasonic beam and the axis of the seabed mud control cover; Indicates the speed of sound in a fluid;

[0046] By analyzing the correlation between Doppler frequency shift and gas content, the gas content in the drilling fluid can be monitored in real time to determine whether gas invasion exists. When the gas content is >0, it indicates that gas invasion exists, and the higher the gas content, the more severe the gas invasion.

[0047] When combining images captured by underwater camera robots and ultrasonic Doppler monitoring data to determine the extent of air intrusion, the result with the greatest severity shall prevail.

[0048] Preferably, in step (3), when gas invasion occurs, the drilling fluid in the annulus flows to the seawater through the No. 1 and No. 2 subsea pipelines with gradually decreasing inner diameters, thereby increasing the resistance of fluid outflow in the annulus, which is similar to applying a back pressure at the wellhead of the subsea, thereby increasing the bottom pressure, which is more conducive to quickly controlling the bottom gas invasion and the subsequent well control process.

[0049] After obtaining the formation conditions following gas invasion, it is necessary to first design reasonable well control parameters such as well control fluid density and well control fluid displacement, and immediately implement wellbore pressure control measures. The design of well control fluid density and well control fluid displacement must consider the influence of other drilled wells and must meet the following requirements:

[0050] (10)

[0051] In the formula, P hy The back pressure at the seabed wellhead is Pa; ρ m The density of the kill fluid in the annulus, kg / m³ 3 ;

[0052] During the well control process, well control is achieved by injecting kill fluid and controlling the opening of pipeline control valves on Subsea Pipeline 1 and Subsea Pipeline 2. The opening of the pipeline control valves can be adjusted to change the back pressure at the subsea wellhead. At the same time, the drilling fluid return images captured by the subsea robot and ultrasonic Doppler monitoring data can be used to analyze the bottom hole gas intrusion control and whether secondary gas intrusion has occurred in real time until the well control is successful. Well control is considered successful only when the gas content is zero for a certain period of time (at least the time it takes for the fluid to flow from the bottom of the well through the annulus to the wellhead).

[0053] For any details not covered in this invention, please refer to the prior art.

[0054] The beneficial effects of this invention are as follows:

[0055] This invention addresses the unique characteristics of open-circuit drilling in ultra-deepwater and ultra-shallow complex well structures. It proposes optimizing key parameters such as drilling fluid density and flow rate at different stages of the open-circuit drilling process to provide a foundation for safe drilling. Simultaneously, by combining images captured by a subsea camera robot and ultrasonic Doppler monitoring data, it analyzes and determines in real-time whether gas intrusion occurs at the wellbore bottom and the extent of such intrusion. Once gas intrusion is detected at the wellbore bottom, considering the mutual influence among multiple wells in complex well structures, it combines well-killing fluid injection and backpressure control at the subsea wellhead to achieve rapid and successful well control. This provides theoretical and technical support for safe and efficient open-circuit drilling in ultra-deepwater and ultra-shallow complex well structures. Attached Figure Description

[0056] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute an undue limitation of this application.

[0057] Figure 1 This is a schematic diagram of the overall structure of the wellbore pressure safety control device for open-circuit drilling of ultra-deepwater and ultra-shallow complex structure wells according to the present invention.

[0058] Figure 2 This is a top view of the seabed mud control cover of the present invention;

[0059] In the diagram, 1-computer, 2-weighted mud tank, 3-mixer, 4-water pump, 5-pumping pipeline, 6-platform pipeline data monitoring sub, 7-platform pipeline control valve, 8-drilling fluid injection pipeline, 9-platform wellhead, 10-drill pipe, 11-traction rope, 12-subsea camera robot, 13-pipeline control valve B, 14-data monitoring sub A, 15-pipeline control valve A, 16-drain hole No. 1, 17-drain hole No. 1 control valve, 18-Doppler signal receiver, 19-drain hole No. 2, 20-drain hole No. 2 21-Pipeline control valve, 22-Data monitoring sub-section B, 23-Pipeline control valve D, 24-Doppler signal generator, 25-Subsea mud control cover, 26-Cementing sheath, 27-Bottom hole drill bit, 28-Main horizontal well, 29-Branch well A, 30-Branch well B, 31-Branch well C, 32-Branch well D, 33-Subsea pipeline No. 1, 34-Subsea pipeline No. 2, 35-Drain hole No. 3, 36-Drain hole No. 4, 37-Ultrasonic Doppler monitor, 38-Subsea formation, 39-Seawater. Detailed Implementation

[0060] To enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. However, this is not the only description; all aspects not described in detail herein are based on conventional techniques in the art.

[0061] Example 1

[0062] A safety control device for wellbore pressure in open-circuit drilling of complex structures in ultra-deepwater and ultra-shallow water wells, such as Figure 1 As shown, it includes a real-time monitoring and analysis device and a pressure dynamic control device;

[0063] The real-time monitoring and analysis device includes a seabed mud control hood 25, a traction rope 11, a seabed camera robot 12, and a computer 1. The seabed mud control hood 25 has four drainage holes: drainage hole 16, drainage hole 29, drainage hole 35, and drainage hole 46. These four drainage holes are located on the seabed mud control hood 25 and serve as discharge channels for drilling fluid flowing through the bottom of the well during normal drilling. Each drainage hole is equipped with a drainage hole control valve, such as... Figure 1 As shown, a control valve 17 for drain hole 16 is installed on drain hole 1, and a control valve 20 for drain hole 2 is installed on drain hole 29. Each drain hole control valve is connected to computer 1 and can be closed and opened under the command of computer 1. The underwater camera robot 12 is lowered to the vicinity of the four drain holes by a traction rope 11 to capture images of the return shape and height of the drilling fluid returning from the four drain holes in real time, and transmits the captured images to computer 1 in real time. Using image recognition technology, the gas content in the captured drilling fluid return images can be identified.

[0064] The pressure dynamic control device includes a kill fluid mixing system, a drilling fluid injection line 8, a subsea No. 1 pipeline 33, and a subsea No. 2 pipeline 34. The kill fluid mixing system is used to obtain kill fluid that meets the requirements and then injects it into the drill pipe 10 through the drilling fluid injection line 8 and the platform wellhead 9. After flowing through the drill bit 27 at the bottom of the well, it enters the annulus. The drilling fluid injection line 8 is equipped with a platform pipeline data monitoring sub 6 and a platform pipeline control valve 7.

[0065] Both Submarine Pipeline 1 (33) and Submarine Pipeline 2 (34) are connected at one end to the annulus and at the other end to seawater (39); both Submarine Pipeline 1 (33) and Submarine Pipeline 2 (34) are equipped with data monitoring sections and pipeline control valves, such as... Figure 1Data monitoring sub-section A14, pipeline control valve A15, and pipeline control valve B13 are installed on subsea pipeline 1 (33). Data monitoring sub-section B22, pipeline control valve C21, and pipeline control valve D23 are installed on subsea pipeline 2 (34). Platform pipeline data monitoring sub-section 6, data monitoring sub-section A14 on subsea pipeline 1 (33), and data monitoring sub-section B22 on subsea pipeline 2 (34) are all connected to computer 1, transmitting the monitored data to computer 1 in real time. Platform pipeline control valves 7, A15, B13, C21, and D23 are all connected to computer 1, receiving control commands from computer 1 to achieve real-time and efficient control of wellbore pressure.

[0066] Example 2

[0067] A wellbore pressure safety control device for open-circuit drilling of complex structure wells in ultra-deep water and ultra-shallow water, as described in Example 1, is different in that the seabed mud control cover 25 includes a circular end face and a circular annular wall. The circular annular wall is fixed on the cementing sheath 26, and a through hole is provided in the center of the circular end face for drilling of the drill pipe 10.

[0068] A Doppler signal generator 24 is installed on one side of the annular wall of the seabed mud control hood 25, and a Doppler signal receiver 18 is installed on the opposite side. The Doppler signal receiver 18 is connected to an ultrasonic Doppler monitor 37. The ultrasonic Doppler monitor 37 is used to process and analyze the changes in ultrasonic signals and transmit them to the computer 1. The computer 1 receives the data transmitted by the seabed camera robot 12 and the ultrasonic Doppler monitor 37, and by analyzing the images and ultrasonic data returned from the drainage hole, it obtains the data on the changes in gas content in the drilling fluid, and analyzes whether gas invasion has occurred at the bottom of the well and the severity of the gas invasion.

[0069] The flow state within the drilling fluid is measured using the Doppler ultrasonic effect. After gas intrusion, the movement of air bubbles in the drilling fluid causes a Doppler frequency shift in the sound waves. By filtering, the frequency characteristics of the ultrasonic waves in the gas-filled drilling fluid are reflected, obtaining the correspondence between gas content and sound wave frequency change, thus allowing real-time monitoring of the gas content in the drilling fluid. Based on this, the presence of gas intrusion can be determined. When the gas content is >0, it indicates the presence of gas intrusion, and a higher gas content indicates a more severe gas intrusion.

[0070] Example 3

[0071] A wellbore pressure safety control device for open-circuit drilling of complex structure wells in ultra-deepwater and ultra-shallow waters, as described in Example 2, differs in that the No. 1 subsea pipeline 33 and the No. 2 subsea pipeline 34 have the same structure and are symmetrically distributed on both sides of the subsea mud control hood 25. The No. 1 subsea pipeline 33 and the No. 2 subsea pipeline 34 pass through the annular wall of the subsea mud control hood and communicate with the annulus. Setting up two pipelines can increase the adjustable range, and when one pipeline is damaged, the other pipeline can be used as a backup.

[0072] The inner diameters of Subsea Pipeline 1 (33) and Subsea Pipeline 2 (34) are divided into three levels and decrease progressively. The inner diameter decreases as the distance from the annulus increases. This avoids a sudden and sharp reduction in the flow channel, which would result in an excessive throttling pressure drop and allow for better application of wellhead back pressure at the subsea wellhead.

[0073] Example 4

[0074] A wellbore pressure safety control device for open-circuit drilling of complex structure wells in ultra-deep water and ultra-shallow water, as described in Example 3, differs in that the kill fluid mixing system includes a mixer 3, a water pump 4, and a water pumping pipeline 5. The water pump 4 pumps seawater 39 into the mixer 3 through the water pumping pipeline 5 to mix with the weighted mud from the weighted mud storage tank 2 to obtain a kill fluid that meets the requirements.

[0075] Example 5

[0076] A method for operating the wellbore pressure safety control device for open-circuit drilling of ultra-deepwater and ultra-shallow complex structure wells according to Embodiment 4 includes:

[0077] (1) Based on the formation data of adjacent wells and the design principle of safe drilling in deep water shallow open-loop drilling, design drilling parameters including drilling fluid density and displacement to provide a basis for safe drilling;

[0078] (2) Combining the images captured by the underwater camera robot and the ultrasonic Doppler monitoring data, we can analyze the real-time changes in the gas content in the annulus of open-circuit drilling, determine whether gas intrusion occurs at the bottom of the well during open-circuit drilling and the extent of gas intrusion, and provide a basis for the control of wellbore pressure.

[0079] (3) When gas invasion occurs, close the control valves of the four drainage holes and open the pipeline control valves of Submarine Pipeline No. 1 and Submarine Pipeline No. 2, so that the drilling fluid in the annulus can flow into the seawater through Submarine Pipeline No. 1 and Submarine Pipeline No. 2. At the same time, based on the gas invasion situation and the formation situation of different drilling sections obtained by real-time monitoring and analysis, optimize the key parameters such as the density, flow rate and valve opening of the kill fluid required for different stages of open-circuit drilling, and inject the prepared kill fluid into the bottom of the well and into the annulus as needed to achieve the purpose of wellbore pressure safety control.

[0080] Example 6

[0081] The working method of a wellbore pressure safety control device for open-circuit drilling of ultra-deepwater and ultra-shallow complex structure wells is as described in Example 5. The difference is that in step (1), during the drilling parameter design process, it is necessary to combine the formation data of adjacent wells (including formation pressure, fracture pressure, formation lithology, etc.) and consider the impact of the drilling of wells already drilled at different stages of drilling of complex structure wells (drilling the main well and drilling different branch wells) on the drilling to be drilled, and optimize the design of drilling parameters for open-circuit drilling of ultra-shallow complex structure wells to provide a basis for safe drilling.

[0082] When drilling a horizontal main well, only the safety of the main well needs to be considered when designing drilling parameters. Based on the formation pore pressure and formation fracturing pressure of the main well formation, the bottom hole pressure needs to meet the condition of being greater than the formation pore pressure and less than the formation fracturing pressure. From this, the drilling fluid density required for open-circuit drilling can be obtained:

[0083] (1)

[0084] In the formula, P k Formation pore pressure, Pa; P jd ρ is the bottom hole pressure, Pa; s The density of seawater is kg / m³. 3 g is the acceleration due to gravity, m / s² 2 h s Seawater depth, in meters (m); h z ρ represents the vertical drilling depth in the formation, in meters (m); z Density of drilling fluid, kg / m³ 3 ;P p The formation fracture pressure is expressed in Pa.

[0085] During drilling, the flow of drilling fluid generates friction, which increases the bottom hole pressure. Therefore, the drilling fluid discharge rate cannot be too high to prevent formation damage and avoid well leakage, well kick, or blowout accidents. Based on the bottom hole pressure balance requirements, the drilling fluid discharge rate can be obtained from the following formula:

[0086] (2)

[0087] (3)

[0088] In the formula, △P fhk The frictional resistance of the fluid flow in the annulus is Pa; f is the friction coefficient, which is dimensionless; Q L For drilling fluid displacement, m 3 / min;d hk The diameter of the annular flow section is in meters (m).

[0089] When drilling branch wells after completing the main horizontal well 28, the design of branch well drilling parameters must not only ensure the safety of the current well being drilled, but also consider the safety of the wells already drilled, such as... Figure 1 As shown, in this embodiment, the branch wells in the seafloor formation 38 include branch well A 29, branch well B 30, branch well C 31, and branch well D 32. Based on the formation pore pressure and formation fracture pressure in the drilling and existing wells, the bottom hole pressure in the drilling well needs to simultaneously satisfy the condition of being greater than the formation pore pressure in the drilling and existing wells and less than the formation fracture pressure in the drilling and existing wells. Therefore, the required drilling fluid density in the drilling well can be obtained.

[0090] (4)

[0091] In the formula, P k1 ,P k2 ,P k3 ,……,P kn For formation pore pressures in different wells, Pa; P p1 ,P p2 ,P p3 ,……,P pn For different wells, the formation fracture pressure is given in Pa.

[0092] At the same time, the above conditions must also be met when designing the drilling fluid discharge rate for post-drilled branch wells. The drilling fluid discharge rate can be obtained according to the following formula:

[0093] (5).

[0094] Example 7

[0095] A working method for a wellbore pressure safety control device for open-circuit drilling of complex structure wells in ultra-deep water and ultra-shallow layers, as described in Example 6, except that in step (2), based on the real-time shooting of the drilling fluid return during the open-circuit drilling process by the seabed camera robot, image recognition technology is used to analyze the changes in key parameters such as the morphology and gas content of the returned drilling fluid.

[0096] In the captured returned images, the colors of gas, liquid, and solid are different. By analyzing and processing the images, the proportion of gas can be determined, thus yielding the gas content. Combined with the drilling fluid return parameters during normal drilling without gas intrusion, when the gas content E in the returned drilling fluid is found... g A value greater than 0 indicates gas intrusion during open-circuit drilling. The severity of gas intrusion can be determined by the gas content; the higher the gas intrusion flow rate, the more severe the gas intrusion. Real-time image analysis can yield the gas content in the drilling fluid. Furthermore, by combining the drilling fluid injection rate and liquid phase velocity, the change in gas velocity in the drilling fluid can be obtained.

[0097] When there is no air invasion:

[0098] (6)

[0099] When air intrusion occurs:

[0100] (7)

[0101] Air intrusion flow rate:

[0102] (8)

[0103] In the formula, v g v is the velocity of gas in the drilling fluid. m v is the mixing velocity of the returning drilling fluid. l E represents the liquid phase flow rate in the drilling fluid. g denoted as the gas content of the cross section; A represents the cross-sectional area of ​​the annulus.

[0104] Example 8

[0105] A working method for a wellbore pressure safety control device for open-circuit drilling of complex structure wells in ultra-deep water and ultra-shallow water is described in Example 7. The difference is that in step (2), during the ultrasonic Doppler monitoring process, when gas invasion occurs in the annulus, the movement of air bubbles in the drilling fluid in the annulus will cause the sound waves to undergo Doppler frequency shift. By filtering, the frequency variation characteristics of ultrasonic waves in drilling fluid containing air bubbles can be reflected, and the correspondence between gas content and Doppler frequency shift can be obtained, thereby realizing real-time monitoring of changes in gas content in drilling fluid. Based on this, it is possible to determine in real time whether gas invasion exists in the annulus and the degree of gas invasion.

[0106] A Doppler signal generator fixed to the annular wall of the seabed mud control hood emits ultrasonic waves of a fixed frequency into the drilling fluid flowing within the annulus. When these waves encounter solid particles (rock cuttings) or air bubbles in the drilling fluid, they are reflected, deviating from the emitted frequency. A Doppler signal receiver fixed to the other end of the annular wall of the seabed mud control hood receives the reflected waves. After signal processing and spectral analysis, the velocity of the reflecting objects within the cross-section can be calculated. Finally, the Doppler frequency shift is obtained. :

[0107] (9)

[0108] In the formula, This indicates the frequency of the ultrasonic waves emitted by the Doppler signal generator; This indicates the frequency of the ultrasonic wave received by the Doppler signal receiver; Indicates the velocity of the particle; This indicates the angle between the ultrasonic beam and the axis of the seabed mud control cover; Indicates the speed of sound in a fluid;

[0109] By analyzing the correlation between Doppler frequency shift and gas content, the gas content in the drilling fluid can be monitored in real time to determine whether gas invasion exists. When the gas content is >0, it indicates that gas invasion exists, and the higher the gas content, the more severe the gas invasion.

[0110] In this embodiment, when combining images captured by a subsea camera robot and ultrasonic Doppler monitoring data to determine gas intrusion, the result with the highest severity is used. Existing technologies that rely solely on drilling fluid return images captured by a subsea camera robot or ultrasonic Doppler monitoring data to determine overflow are subject to objective factors, such as the influence of seabed organisms or returned rock cuttings during filming. Similarly, the use of ultrasonic methods is affected by rock cuttings or additives in the drilling fluid, leading to inherent errors in both methods. Combining these two methods results in more accurate gas intrusion monitoring and better guidance for well control fluid parameter design.

[0111] Example 9

[0112] The working method of a wellbore pressure safety control device for open-circuit drilling of ultra-deep water and ultra-shallow complex structure wells is as described in Example 8. The difference is that in step (3), when gas invasion occurs, the drilling fluid in the annulus flows to the seawater through the No. 1 and No. 2 subsea pipelines with gradually decreasing inner diameters, thereby increasing the resistance of fluid outflow in the annulus, which is similar to applying a back pressure at the wellhead of the seabed, thereby increasing the bottom pressure, which is more conducive to quickly controlling the bottom gas invasion and the subsequent well killing process.

[0113] After obtaining the formation conditions following gas invasion, it is necessary to first design reasonable well control parameters such as well control fluid density and well control fluid displacement, and immediately implement wellbore pressure control measures. The design of well control fluid density and well control fluid displacement must consider the influence of other drilled wells and must meet the following requirements:

[0114] (10)

[0115] In the formula, P hy The back pressure at the seabed wellhead is Pa; ρ m The density of the kill fluid in the annulus, kg / m³ 3 ;

[0116] During well control, well control is achieved through the injection of kill fluid and the control of the opening of the pipeline control valves on Subsea Pipeline 1 and Subsea Pipeline 2. Adjusting the opening of the pipeline control valves alters the back pressure at the wellhead, thereby applying back pressure to the subsea mud control hood and controlling the multiphase flow pressure in the wellbore. A smaller valve opening results in a more pronounced throttling effect, meaning greater resistance to flow and thus a higher back pressure at the wellhead. The specific adjustment depends on the site conditions. When the bottom hole pressure is insufficient to control gas intrusion, the throttling valve opening must be reduced to apply greater back pressure. Simultaneously, analysis of drilling fluid return images captured by the subsea robot and ultrasonic Doppler monitoring data allows for real-time analysis of bottom hole gas intrusion control and the occurrence of secondary gas intrusion until well control is successful. Well control is considered successful only when the gas content remains zero for a certain period (at least the time it takes for fluid to flow from the bottom hole through the annulus to the wellhead).

[0117] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for operating a wellbore pressure safety control device for open-circuit drilling of complex structure wells in ultra-deepwater and ultra-shallow water, characterized in that, The wellbore pressure safety control device for open-circuit drilling of complex structure wells in ultra-deepwater and ultra-shallow water includes a real-time monitoring and analysis device and a dynamic pressure control device. The real-time monitoring and analysis device includes a seabed mud control hood, a traction rope, a seabed camera robot, and a computer. The seabed mud control hood is equipped with four drainage holes, each with a drainage hole control valve connected to the computer. The seabed camera robot is lowered to the vicinity of the four drainage holes by the traction rope to capture images of drilling fluid returning from the four drainage holes in real time and transmits the captured images to the computer in real time. The pressure dynamic control device includes a kill fluid mixing system, a drilling fluid injection pipeline, a No. 1 subsea pipeline, and a No. 2 subsea pipeline. The kill fluid mixing system is used to obtain kill fluid that meets the requirements and then injects it into the drill pipe through the drilling fluid injection pipeline and the platform wellhead. After flowing through the drill bit at the bottom of the well, it enters the annulus. The drilling fluid injection pipeline is equipped with a platform pipeline data monitoring sub and a platform pipeline control valve. One end of each of the No. 1 and No. 2 subsea pipelines is connected to the annulus, and the other end leads to seawater. Both the No. 1 and No. 2 subsea pipelines are equipped with data monitoring sections and pipeline control valves. The platform pipeline data monitoring sections and the No. 1 and No. 2 subsea pipeline data monitoring sections are all connected to a computer to transmit the monitored data to the computer in real time. The platform pipeline control valves and pipeline control valves are also connected to the computer to receive control commands from the computer, thereby realizing real-time control of wellbore pressure. The subsea mud control cover includes a circular end face and a circular annular wall. The circular annular wall is fixed to the cementing sheath, and the circular end face has a through hole at its center for drilling the drill pipe. A Doppler signal generator is installed on one side of the annular wall of the subsea mud control hood, and a Doppler signal receiver is installed on the opposite side. The Doppler signal receiver is connected to an ultrasonic Doppler monitor. The ultrasonic Doppler monitor is used to process and analyze the changes in ultrasonic signals and transmit them to a computer. The computer receives data transmitted from the subsea camera robot and the ultrasonic Doppler monitor. By analyzing the images and ultrasonic data returned from the drainage hole, it obtains data on the changes in gas content in the drilling fluid and analyzes whether gas invasion has occurred at the bottom of the well and the severity of the gas invasion. The No. 1 and No. 2 submarine pipelines have the same structure and are symmetrically distributed on both sides of the submarine mud control cover. The No. 1 and No. 2 submarine pipelines pass through the annular wall of the submarine mud control cover and communicate with the annular space. The inner diameters of the No. 1 and No. 2 submarine pipelines are divided into three levels, decreasing progressively, with the inner diameter decreasing the further away from the annulus. The operating method of the wellbore pressure safety control device for open-circuit drilling of ultra-deepwater and ultra-shallow complex structure wells is characterized by comprising: (1) Based on the formation data of adjacent wells and the design principle of safe drilling in deep water shallow open-loop drilling, design drilling parameters including drilling fluid density and displacement to provide a basis for safe drilling; (2) Combine the images captured by the underwater camera robot and the ultrasonic Doppler monitoring data to analyze the real-time changes in the gas content in the annulus of the open-circuit drilling, determine whether gas invasion occurs at the bottom of the well during the open-circuit drilling process and the degree of gas invasion, and provide a basis for the control of wellbore pressure; when combining the images captured by the underwater camera robot and the ultrasonic Doppler monitoring data to jointly determine the gas invasion situation, the result with the greatest severity shall prevail. (3) When gas invasion occurs, close the control valves of the four drainage holes and open the pipeline control valves of Submarine Pipeline 1 and Submarine Pipeline 2, so that the drilling fluid in the annulus flows to the seawater through Submarine Pipeline 1 and Submarine Pipeline 2; at the same time, based on the gas invasion situation and formation conditions of different drilling sections obtained by real-time monitoring and analysis, optimize the density, flow rate and valve opening of the kill fluid required for different stages of open-circuit drilling, and inject the prepared kill fluid into the bottom of the well and into the annulus as needed to achieve the purpose of wellbore pressure safety control; In step (1), during the drilling parameter design process, it is necessary to combine the formation data of adjacent wells and consider the impact of existing wells at different stages of drilling of complex structure wells on the drilling of the wells to be drilled, and optimize the drilling parameters of open-circuit drilling of ultra-shallow complex structure wells to provide a basis for safe drilling. When drilling a horizontal main well, only the safety of the main well needs to be considered when designing drilling parameters. Based on the formation pore pressure and formation fracturing pressure of the main well formation, the bottom hole pressure needs to meet the condition of being greater than the formation pore pressure and less than the formation fracturing pressure. Based on this, the drilling fluid density required for open-circuit drilling can be obtained. （1） In the formula, P k Formation pore pressure, Pa; P jd ρ is the bottom hole pressure, Pa; s The density of seawater is kg / m³. 3 g is the acceleration due to gravity, m / s² 2 h s Seawater depth, in meters (m); h z ρ represents the vertical drilling depth in the formation, in meters (m); z Density of drilling fluid, kg / m³ 3 ;P p The formation fracture pressure is expressed in Pa. During drilling, friction is generated during drilling fluid flow, which increases the bottom hole pressure. Therefore, the drilling fluid discharge rate cannot be too high. Based on the bottom hole pressure balance requirement, the drilling fluid discharge rate can be obtained from the following formula: （2） （3） In the formula, △P fhk The frictional resistance of the fluid flow in the annulus is Pa; f is the friction coefficient, which is dimensionless; Q L For drilling fluid displacement, m 3 / min;d hk The diameter of the annular flow section is in meters (m). When drilling branch wells after the main well is completed, the design of branch well drilling parameters must not only ensure the safety of the well currently being drilled, but also consider the safety of the wells already drilled. Based on the formation pore pressure and formation fracturing pressure in both the well being drilled and the wells already drilled, the bottom hole pressure in the well being drilled must simultaneously meet the condition of being greater than the formation pore pressure in both the well being drilled and the wells already drilled, and less than the formation fracturing pressure in both the well being drilled and the wells already drilled. Based on this, the required drilling fluid density for the well being drilled is obtained. （4） In the formula, P k1 ,P k2 ,P k3 ,……,P kn For formation pore pressures in different wells, Pa; P p1 ,P p2 ,P p3 ,……,P pn For different wells, the formation fracture pressure is given in Pa. Meanwhile, the drilling fluid displacement can be obtained according to the following formula: （5）； In step (3), when gas invasion occurs, the drilling fluid in the annulus flows to the seawater through the No. 1 and No. 2 subsea pipelines with progressively smaller inner diameters, thereby increasing the resistance to fluid outflow from the annulus. Given the formation conditions after gas invasion, the first step is to design a reasonable kill fluid density and displacement rate, and immediately implement wellbore pressure control measures. The design of the kill fluid density and displacement rate must consider the influence of other drilled wells and must meet the following requirements: （10） In the formula, P hy The back pressure at the seabed wellhead is Pa; ρ m The density of the kill fluid in the annulus, kg / m³ 3 ; During the well control process, well control is achieved by injecting kill fluid and controlling the opening of pipeline control valves on Subsea Pipeline 1 and Subsea Pipeline 2. The opening of the pipeline control valves can be adjusted to change the back pressure at the subsea wellhead. At the same time, the drilling fluid return images captured by the subsea robot and ultrasonic Doppler monitoring data can be analyzed in real time to determine the control of gas invasion at the bottom of the well and whether secondary gas invasion has occurred, until the well control is successful.

2. The working method of the wellbore pressure safety control device for open-circuit drilling of ultra-deepwater and ultra-shallow complex structure wells according to claim 1, characterized in that, The kill fluid mixing system includes a mixer, a pump, and a pumping line. The pump draws seawater through the pumping line into the mixer to mix with the weighted mud from the weighted mud storage tank to obtain a kill fluid that meets the requirements.

3. The working method of the wellbore pressure safety control device for open-circuit drilling of ultra-deepwater and ultra-shallow complex structure wells according to claim 2, characterized in that, In step (2), based on the real-time footage captured by the underwater camera robot of the drilling fluid return during the open-circuit drilling process, image recognition technology is used to analyze the morphology and gas content changes of the returned drilling fluid; combined with the drilling fluid return parameters during normal drilling without gas invasion, when the gas content E in the returned drilling fluid is found to be... g A value greater than 0 indicates gas intrusion during open-circuit drilling, and the severity of gas intrusion is determined by the gas content. The higher the gas intrusion flow rate, the more severe the gas intrusion. When there is no air invasion: （6） When air intrusion occurs: （7） Air intrusion flow rate: （8） In the formula, v g v is the velocity of gas in the drilling fluid. m v is the mixing velocity of the returning drilling fluid. l E represents the liquid phase flow rate in the drilling fluid. g denoted as the gas content of the cross section; A represents the cross-sectional area of ​​the annulus.

4. The working method of the wellbore pressure safety control device for open-circuit drilling of ultra-deepwater and ultra-shallow complex structure wells according to claim 3, characterized in that, In step (2), during ultrasonic Doppler monitoring, when gas invasion occurs in the annulus, the movement of air bubbles in the drilling fluid within the annulus causes a Doppler frequency shift in the sound waves. By filtering, the frequency variation characteristics of the ultrasonic waves in drilling fluid containing air bubbles can be reflected, thereby obtaining the correspondence between the gas content and the Doppler frequency shift, thus realizing real-time monitoring of changes in the gas content in the drilling fluid. Based on this, it is possible to determine in real time whether gas invasion exists in the annulus and the degree of gas invasion.

5. The working method of the wellbore pressure safety control device for open-circuit drilling of ultra-deepwater and ultra-shallow complex structure wells according to claim 4, characterized in that, A Doppler signal generator fixed to the annular wall of the seabed mud control hood emits ultrasonic waves of a fixed frequency into the drilling fluid flowing within the annulus. When these waves encounter solid particles or bubbles in the drilling fluid, they are reflected, deviating from the emitted frequency. A Doppler signal receiver fixed to the other end of the annular wall of the seabed mud control hood receives the reflected waves. After signal processing and spectral analysis, the velocity of the reflecting objects within the cross-section can be calculated. Finally, the Doppler frequency shift is obtained. : （9） In the formula, This indicates the frequency of the ultrasonic waves emitted by the Doppler signal generator; This indicates the frequency of the ultrasonic wave received by the Doppler signal receiver; Indicates the velocity of the particle; This indicates the angle between the ultrasonic beam and the axis of the seabed mud control cover; Indicates the speed of sound in a fluid; By observing the correlation between Doppler frequency shift and gas content, the gas content in drilling fluid can be monitored in real time to determine whether gas intrusion exists. When the gas content is greater than 0, it indicates that gas invasion exists, and the higher the gas content, the more severe the gas invasion.

Images