Heat preservation coiled tubing drilling system for polar region cold sea drilling

Abstract

The invention relates to the technical field of petroleum drilling, in particular to a heat preservation coiled tubing drilling system for polar region cold sea drilling, and can solve the problems of pipeline freezing, equipment low-temperature embrittlement and heat energy loss in polar region drilling to a certain extent. The heat preservation coiled tubing drilling system for polar region cold sea drilling comprises a coiled tubing distributed electric heating system, a wellhead device integrated heat preservation skid-mounted system and a heat recycling and reusing method. According to the electric heating system, efficient and controllable heating of the continuous pipe is achieved through spiral winding of a nickel-chromium alloy metal wire, a double-layer insulation design and a segmented heating unit; the heat preservation skid-mounted system maintains the temperature of a wellhead device and a pipeline through an aerogel heat preservation layer, a stainless steel protection shell and a waste heat recovery module. The heat recovery system improves the energy utilization rate through waste heat collection, a heat storage device and a heat exchange technology. Equipment performance is optimized, energy consumption is reduced, and safe and efficient operation of polar region cold sea drilling operation is guaranteed.

Description

Technical Field

[0001] The present application relates to the field of oil drilling technology, and in particular to an insulated continuous tubing drilling system for polar cold sea drilling. Background Art

[0002] As global energy demand continues to rise, the rich oil and gas resources in the polar cold sea region have become the focus of international oil companies. In-depth research on the challenges faced by polar cold sea drilling technology and the current status of key technologies is of great significance to promoting the advancement of drilling technology in this region and achieving efficient development of oil and gas resources.

[0003] The extremely harsh polar cold sea environment presents numerous challenges for coiled tubing drilling operations. The document "Technical Challenges and Key Technologies for Polar Cold Sea Drilling" points out that the harsh operating environment, long-distance logistical support, and stringent environmental requirements are the primary challenges facing polar cold sea oil and gas exploration and development. In this environment, conventional coiled tubing drilling systems frequently encounter problems. According to the "Application Status and Key Technology Analysis of Polar Marine Engineering Equipment," deck machinery and piping systems in polar marine equipment are exposed to low temperatures, leading to frequent equipment freezing and icing. This is also a prominent issue in coiled tubing drilling systems. Frozen drilling fluid can cause pipeline blockages, preventing the equipment from operating normally. Frequent failures not only interrupt drilling operations but also significantly increase operation time and costs.

[0004] The impact of low temperatures on the performance of coiled tubing itself should not be underestimated. Relevant research has shown that the toughness and fatigue resistance of coiled tubing are significantly reduced in low-temperature environments. For example, drilling practices in some cold regions have found that low temperatures make coiled tubing more susceptible to damage such as cracks and fractures. This not only shortens the service life of the coiled tubing, but can also cause serious safety accidents, greatly affecting the safety and continuity of drilling operations.

[0005] At the same time, in the polar cold sea environment, the drilling fluid loses heat too quickly. It's difficult to maintain a suitable bottomhole temperature, severely impacting the performance of drilling tools and rock-breaking efficiency. From an energy transfer perspective, the low temperature acts as a massive heat sink, continuously absorbing heat from the drilling fluid. This makes bottomhole temperatures difficult to meet ideal drilling requirements, thus reducing overall drilling efficiency.

[0006] In addition, in order to cope with low temperature environments, existing continuous tubing drilling systems often need to consume a large amount of additional energy, whether it is used to maintain equipment operation or to heat drilling fluid. Excessive energy consumption leads to low energy utilization and a significant increase in operating costs, which undoubtedly brings a heavy economic burden to the development of polar cold sea oil and gas.

[0007] In summary, the existing continuous tubing drilling system has exposed many drawbacks in the polar cold sea environment, and innovative technologies and equipment are urgently needed to overcome these difficulties in order to achieve efficient and safe development of polar cold sea oil and gas resources. Summary of the Invention

[0008] In order to solve the problem that the existing continuous tubing drilling system has exposed many disadvantages in the polar cold sea environment, innovative technologies and equipment are urgently needed to overcome these difficulties and realize the efficient and safe development of polar cold sea oil and gas resources. This application provides an insulated continuous tubing drilling system for polar cold sea drilling.

[0009] The embodiment of the present application is implemented as follows:

[0010] In a first aspect, the present application provides an insulated coiled tubing drilling system for polar cold sea drilling, comprising:

[0011] The coiled tubing distributed electric heating device, consisting of spirally wound nickel-chromium alloy wire, segmented heating units, and a double-layer insulation structure, can controllably heat the air section, seawater section, and shallow seabed section of the coiled tubing to prevent freezing and low-temperature embrittlement of the pipeline.

[0012] The wellhead integrated insulation skid consists of a steel skid, an aerogel insulation layer, and a stainless steel protective shell. It integrates the wellhead and blowout preventer, and is quickly connected via phenolic foam insulated pipelines. It is combined with the shipboard generator waste heat recovery module to maintain temperature stability.

[0013] Heat recovery and reuse equipment, through waste heat collection pipelines, metal hydride heat storage devices and heat exchanger networks, converts waste heat from engines and generators and drilling fluid into supplementary heat sources for coiled tubing heating, skid-mounted container insulation and maintaining the supercritical state of carbon dioxide;

[0014] The three devices work together to dynamically adjust the heating power through the PID algorithm, control the waste heat flow through the PLC, and distribute the heat-carrying fluid through the circulation pump, thereby achieving stable drilling fluid flow, controllable equipment temperature, and improved energy utilization in polar low-temperature environments.

[0015] In one possible implementation, the nickel-chromium alloy wire of the continuous tube distributed electric heating device is spirally wound around the outer wall of the continuous tube at a pitch of 5-10 mm, the length of a single coil is 1-2 m, and adjacent coils are connected by insulating joints;

[0016] The continuous tube distributed electric heating device has a double-layer insulation structure, with the inner layer being a 0.1-0.3 mm thick polyimide film and the outer layer being a 2-5 mm thick nano-aerogel composite material;

[0017] The heating unit is set up every 50-100m and is powered by a series-parallel hybrid circuit. The single-section voltage is ≤100V and the current is ≤15A.

[0018] The temperature control system based on PID algorithm dynamically adjusts the heating power through temperature sensors and IGBT switches.

[0019] In one possible implementation, the steel skid in the integrated insulation skid-mounted wellhead is filled with an aerogel insulation layer and covered with a stainless steel protective shell. The wellhead and blowout preventer are integrated on the skid, and the pipelines are skid-mounted separately and covered with a phenolic foam insulation layer. The waste heat from the ship's generator is heated by a plate heat exchanger in the thermal oil circulation system, and the waste heat flow is controlled by a PLC to adjust the temperature.

[0020] In one possible implementation, the heat recovery and reuse device further includes:

[0021] The waste heat collection module collects heat from the engine and generator through heat-conducting pipes;

[0022] The metal hydride thermal storage device stores heat and distributes it to the skid-mounted box and coiled tubing equipment through a circulation pump;

[0023] The carbon dioxide heating and pressurizing box uses an electric heating wire combined with a heat conduction oil bath to ensure that the carbon dioxide is in a supercritical state when it enters the coiled tubing;

[0024] The heat exchanger in the drilling fluid circulation pipeline transfers waste heat to carbon dioxide and reduces the drilling fluid temperature.

[0025] In a possible implementation, the outer diameter of the coiled tube ranges from 19.1 mm to 88.9 mm, the wall thickness is determined by calculating the stress formula of a thin-walled cylinder, and a wall thickness margin is added to withstand the operating load.

[0026] In one possible implementation, the thermal oil circulation system exchanges heat with the air in the skid-mounted box through a serpentine coil heat exchanger, and the PLC adjusts the speed of the circulation pump based on feedback from the temperature sensor.

[0027] In one possible implementation, the carbon dioxide heating and pressurizing box is equipped with a pressure sensor, an electric regulating valve and a compressor. When the pressure is lower than 7.38 MPa, pressurization is started and the temperature is raised to above 31.26°C.

[0028] In a possible implementation, the cold end of the heat exchanger of the drilling fluid circulation pipeline is connected to the carbon dioxide delivery pipeline to ensure that the temperature and pressure of the carbon dioxide remain in a supercritical state during the entire circulation process.

[0029] The technical solution provided by this application can achieve at least the following beneficial effects:

[0030] The insulated coiled tubing drilling system for polar cold sea drilling provided in this application has the following advantages:

[0031] Optimizing equipment performance and extending its lifespan: The distributed electric heating system for coiled tubing maintains a suitable temperature even at low temperatures, reducing damage such as cracks and breakages and lowering replacement costs. The wellhead and pipeline insulation skid integrates the wellhead and blowout preventer into a custom-made steel skid. The skid utilizes an aerogel insulation layer and stainless steel protective shell to withstand harsh environments, stabilize temperatures, reduce the probability of equipment failure, and ensure stable operation of the wellhead.

[0032] Efficient energy utilization and cost reduction: The coiled tubing distributed electric heating system improves heating efficiency and reduces energy waste through a unique circuit design, high-frequency alternating current, double-layer insulation, and high-efficiency thermal insulation. The wellhead assembly and pipeline insulation skid introduce waste heat from the ship's generator as a supplemental heat source, and the temperature is precisely adjusted using a plate heat exchanger and PLC control system. The heat recovery and reuse system incorporates a waste heat collection system to recover and store various types of waste heat, accurately distribute heat, and comprehensively improve energy utilization while reducing external energy consumption.

[0033] Improved operational efficiency and quality assurance: The distributed electric heating system for coiled tubing, along with the wellhead assembly and pipeline insulation skid, ensures stable fluid flow, avoids pumping obstructions, and reduces the risk of wellbore freezing. A heat recovery and reuse system heats the skid, reducing the risk of equipment failure and ensuring that carbon dioxide enters the coiled tubing in a supercritical state. This improves drilling efficiency and quality, ensuring smooth drilling operations. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0035] Figure 1 This is a schematic structural diagram of an insulated coiled tubing drilling system for polar cold sea drilling, shown in an exemplary embodiment of the present application;

[0036] Figure 2 1 is a schematic structural diagram of an integrated thermal insulation skid-mounted device for a wellhead device according to an exemplary embodiment of the present application;

[0037] Figure 3 1 is a schematic structural diagram of a coiled tube distributed electric heating device according to an exemplary embodiment of the present application;

[0038] Figure 41 is a schematic structural diagram of a heating layer shown in an exemplary embodiment of the present application;

[0039] Figure 5 1 is a schematic structural diagram of a horizontal and vertical section of an electrically heated coiled tubing according to an exemplary embodiment of the present application;

[0040] Figure 6 It is a flow chart of a heat recovery and reuse device shown in an exemplary embodiment of the present application.

[0041] In the figure: 1. Continuous tube metal tube body, 2. Polyimide film insulation layer, 3. Thermal insulation and weight reduction filling layer, 4. External protective layer, 5. Distributed electric heating metal winding, 6. Power supply copper core live wire, 7. Power supply copper core neutral wire, 8. Distributed temperature sensor, 9. Sensor power line, 10. Sensor data line. DETAILED DESCRIPTION

[0042] In order to make the purpose, implementation methods and advantages of the present application clearer, the exemplary implementation methods of the present application will be clearly and completely described below in conjunction with the drawings in the exemplary embodiments of the present application. Obviously, the described exemplary embodiments are only part of the embodiments of the present application, not all of the embodiments. It should be understood that the specific embodiments described here are only used to explain the present application and are not used to limit the present application.

[0043] It should be noted that the brief descriptions of terms in this application are only for the purpose of facilitating the understanding of the embodiments described below, and are not intended to limit the embodiments of this application. Unless otherwise specified, these terms should be understood according to their ordinary and usual meanings.

[0044] In the specification and claims of this application and the accompanying drawings, the terms "first," "second," "third," etc. are used to distinguish similar or similar objects or entities, and are not necessarily intended to limit a particular order or sequence, unless otherwise noted. It should be understood that the terms used in this manner are interchangeable under appropriate circumstances.

[0045] The terms "comprise," "include," and "have," and any variations thereof, are intended to cover but not exclude inclusion; for example, a product or device comprising a list of components is not necessarily limited to all the components expressly listed but may include other components not expressly listed or inherent to such product or device.

[0046] Before explaining the insulated continuous tubing drilling system for polar cold sea drilling provided by the embodiment of the present application, the application scenario and implementation environment of the embodiment of the present application are first introduced.

[0047] As global energy demand continues to rise, the rich oil and gas resources in the polar cold sea region have become the focus of international oil companies. In-depth research on the challenges faced by polar cold sea drilling technology and the current status of key technologies is of great significance to promoting the advancement of drilling technology in this region and achieving efficient development of oil and gas resources.

[0048] The extremely harsh polar cold sea environment presents numerous challenges for coiled tubing drilling operations. The document "Technical Challenges and Key Technologies for Polar Cold Sea Drilling" points out that the harsh operating environment, long-distance logistical support, and stringent environmental requirements are the primary challenges facing polar cold sea oil and gas exploration and development. In this environment, conventional coiled tubing drilling systems frequently encounter problems. According to the "Application Status and Key Technology Analysis of Polar Marine Engineering Equipment," deck machinery and piping systems in polar marine equipment are exposed to low temperatures, leading to frequent equipment freezing and icing. This is also a prominent issue in coiled tubing drilling systems. Frozen drilling fluid can cause pipeline blockages, preventing the equipment from operating normally. Frequent failures not only interrupt drilling operations but also significantly increase operation time and costs.

[0049] The impact of low temperatures on the performance of coiled tubing itself should not be underestimated. Relevant research has shown that the toughness and fatigue resistance of coiled tubing are significantly reduced in low-temperature environments. For example, drilling practices in some cold regions have found that low temperatures make coiled tubing more susceptible to damage such as cracks and fractures. This not only shortens the service life of the coiled tubing, but can also cause serious safety accidents, greatly affecting the safety and continuity of drilling operations.

[0050] At the same time, in the polar cold sea environment, the drilling fluid loses heat too quickly. It's difficult to maintain a suitable bottomhole temperature, severely impacting the performance of drilling tools and rock-breaking efficiency. From an energy transfer perspective, the low temperature acts as a massive heat sink, continuously absorbing heat from the drilling fluid. This makes bottomhole temperatures difficult to meet ideal drilling requirements, thus reducing overall drilling efficiency.

[0051] In addition, in order to cope with low temperature environments, existing continuous tubing drilling systems often need to consume a large amount of additional energy, whether it is used to maintain equipment operation or to heat drilling fluid. Excessive energy consumption leads to low energy utilization and a significant increase in operating costs, which undoubtedly brings a heavy economic burden to the development of polar cold sea oil and gas.

[0052] In summary, the existing continuous tubing drilling system has exposed many drawbacks in the polar cold sea environment, and innovative technologies and equipment are urgently needed to overcome these difficulties in order to achieve efficient and safe development of polar cold sea oil and gas resources.

[0053] Based on this, the present application provides an insulated coiled tubing drilling system for polar cold sea drilling, comprising a distributed electric heating system for the coiled tubing, an integrated insulation skid-mounted system for the wellhead assembly, and a heat recovery and reuse method. The electric heating system achieves efficient and controllable heating of the coiled tubing through spirally wound nickel-chromium alloy wire, a double-layer insulation design, and a segmented heating unit. The insulation skid-mounted system maintains the temperature of the wellhead assembly and pipeline through an aerogel insulation layer, a stainless steel protective shell, and a waste heat recovery module. The heat recovery system improves energy utilization through waste heat collection, heat storage devices, and heat exchange technology. This invention optimizes equipment performance, reduces energy consumption, and ensures safe and efficient operation of polar cold sea drilling operations.

[0054] Next, the technical solution of the present application and how the technical solution of the present application solves the above-mentioned technical problems will be described in detail through embodiments and in combination with the accompanying drawings. The various embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments.

[0055] Figure 1 It is a structural schematic diagram of an insulated coiled tubing drilling system for polar cold sea drilling, shown as an exemplary embodiment of the present application.

[0056] In an exemplary embodiment, Figure 1 As shown, a thermal insulation coiled tubing drilling system for polar cold sea drilling is provided. In this embodiment, the system may include:

[0057] The coiled tubing distributed electric heating device, consisting of spirally wound nickel-chromium alloy wire, segmented heating units, and a double-layer insulation structure, can controllably heat the air section, seawater section, and shallow seabed section of the coiled tubing to prevent freezing and low-temperature embrittlement of the pipeline.

[0058] The wellhead integrated insulation skid consists of a steel skid, an aerogel insulation layer, and a stainless steel protective shell. It integrates the wellhead and blowout preventer, and is quickly connected via phenolic foam insulated pipelines. It is combined with the shipboard generator waste heat recovery module to maintain temperature stability.

[0059] Heat recovery and reuse equipment, through waste heat collection pipelines, metal hydride heat storage devices and heat exchanger networks, converts waste heat from engines and generators and drilling fluid into supplementary heat sources for coiled tubing heating, skid-mounted container insulation and maintaining the supercritical state of carbon dioxide;

[0060] The three devices work together to dynamically adjust the heating power through the PID algorithm, control the waste heat flow through the PLC, and distribute the heat-carrying fluid through the circulation pump, thereby achieving stable drilling fluid flow, controllable equipment temperature, and improved energy utilization in polar low-temperature environments.

[0061] Figure 2 This is a schematic structural diagram of an integrated thermal insulation skid-mounted device for a wellhead device according to an exemplary embodiment of the present application. Figure 3 : is a schematic structural diagram of a coiled tube distributed electric heating device according to an exemplary embodiment of the present application. Figure 4 is a schematic structural diagram of a heating layer shown in an exemplary embodiment of the present application. Figure 5 : is a schematic structural diagram of a horizontal and vertical section of a coiled tube according to an exemplary embodiment of the present application. Figure 6 It is a flow chart of a heat recovery and reuse device shown in an exemplary embodiment of the present application.

[0062] In a possible implementation, the specific implementation structure of the drilling system is as follows:

[0063] 1. Coiled tube distributed electric heating device

[0064] like Figure 3 As shown, some embodiments of the present application provide a distributed electric heating system for coiled tubing, which combines electric heating technology with thermal insulation coatings to achieve efficient and controllable heating of coiled tubing in multiple environments such as air sections, seawater sections, and shallow seabed sections.

[0065] The heating layer design features a non-contact nested coiled tubing and riser. The wire, made of nickel-chromium alloy, is spirally wound around the outer wall of the coiled tubing, with a tight spacing of 5-10mm. This ensures excellent corrosion resistance in complex marine environments while maintaining suitable electrical resistance. This spacing also ensures uniform heating. The length of each coil segment is designed to be 1-2m, ensuring effective heating in each segment without compromising the overall mechanical strength of the coiled tubing. Adjacent coils are connected by specially designed insulating joints to prevent electrical leakage and ensure safe system operation.

[0066] like Figure 4 As shown, to prevent electrical leakage and enhance thermal insulation, the outer layer of the metal wire utilizes a double-layer insulation design. The inner layer tightly wraps the metal wire with a 0.1-0.3mm thick polyimide film. Polyimide film can withstand temperatures up to 300°C, significantly reducing the risk of electrical leakage. The outer layer is coated with a nano-aerogel composite material, sprayed to a thickness of 2-5mm. This nano-aerogel composite material not only boasts a thermal conductivity of less than 0.02W / m·K, offering excellent thermal insulation, but also provides mechanical protection for the internal structure, resisting the physical impact of the complex deep-sea environment.

[0067] like Figure 5As shown, referring to the API SPEC 5ST specification, coiled tubing utilizes a hollow metal tube structure with an outer diameter range of 0.750 in (19.1 mm) to 3 1 / 2 in (88.9 mm). Different outer diameters correspond to different wall thicknesses. For example, the maximum outer diameter of 3 1 / 2 in corresponds to a maximum wall thickness of 0.30 in (7.6 mm), and the latest wall thickness is 0.156 in (4.0 mm). Considering the drilling flow rate requirements, equipment space limitations, and the required flexibility of the coiled tubing, a coiled tubing with an appropriate outer diameter is selected. The maximum wall thickness of the coiled tubing is then determined by calculation based on actual operating loads such as pressure and tension. For example, using the thin-walled cylinder stress formula for internal pressure as an example, is used (where is the hoop stress (in MPa), is the internal pressure (in MPa), is the coiled tubing outer diameter (in mm), and is the wall thickness (in mm). Furthermore, by combining the allowable stress [ ] (in MPa) of the selected coiled tubing material, a wall thickness calculation formula can be derived by modifying the formula. In actual operation, the coiled tubing also bears other loads such as tension, so a certain wall thickness margin needs to be considered. Usually, based on experience or relevant standards, a certain wall thickness margin is added to ultimately determine the maximum wall thickness of the coiled tubing and the thickness of the coating in this patent.

[0068] To meet the heating needs of long-distance coiled tubing, the distributed electric heating system features a heating unit every 50-100 meters. Adjacent units utilize a series-parallel hybrid circuit. This unique circuit design ensures that the voltage in a single section remains ≤100V and the current ≤15A, optimizing power transmission and heating efficiency while ensuring safety. Power is supplied via cables connected to the surface power supply; all heating unit and control unit cables enter the coiled tubing only through the top entrance.

[0069] Regarding the monitoring and feedback system, distributed temperature sensors with an accuracy of ±0.5°C are installed throughout the coiled tubing to monitor the fluid temperature. The collected temperature data is transmitted via cables to the control system. Based on this temperature data, the control system uses a PID algorithm to adjust the IGBT switching frequency, dynamically adjusting the heating power to ensure stable coiled tubing temperature. The PID controller's output consists of a proportional term (P), an integral term (I), and a differential term (D). The formula is: where , , and are the proportional, integral, and differential coefficients, respectively. is the error signal, representing the difference between the actual and setpoint temperatures. This continuous adjustment controls the heating power, keeping the coiled tubing temperature as close to the setpoint as possible, achieving precise temperature control.

[0070] 2. Coiled tubing wellhead insulation skid-mounted device

[0071] like Figure 2As shown in the figure, the wellhead assembly and the blowout preventer are integrated into a steel skid. The steel skid has high strength and stability and can adapt to the harsh polar environmental conditions, such as strong winds and low temperatures. The skid is filled with an aerogel insulation layer. Aerogel is a material with extremely low thermal conductivity, which can be as low as 0.013W / (m·K), which can effectively prevent heat from being lost from the inside of the skid to the outside. The outside is covered with a stainless steel protective shell. Stainless steel has good corrosion resistance and mechanical properties, which can protect the internal aerogel insulation layer from damage by the external environment and extend the service life of the insulation skid.

[0072] The pipelines are individually skid-mounted and quickly connected via flanges. This design facilitates on-site installation and removal, improving operational efficiency. The pipelines are covered with a phenolic foam insulation layer. The phenolic foam's thermal insulation properties effectively reduce heat loss from the fluid within the pipe, maintaining a stable fluid temperature and ensuring normal drilling operations. Furthermore, the phenolic foam's flame retardant properties prevent the spread of fire along the pipeline in the event of a fire, ensuring safety throughout the entire operating area.

[0073] Waste heat from the ship's generators is introduced as a supplemental heat source, and the thermal oil circulation system is heated via a plate heat exchanger. The plate heat exchanger boasts efficient heat transfer performance, quickly transferring waste heat from the ship's generators to the thermal oil. The thermal oil then transfers heat to the insulation skid via coils, maintaining the temperature within the skid within an appropriate range. The PLC adjusts the waste heat flow based on temperature information fed back by the PT100 sensor, achieving precise control of equipment and pipeline temperatures. When the temperature is below the set point, the PLC increases the waste heat flow, increasing heating power. When the temperature is above the set point, the PLC reduces the waste heat flow to avoid overheating, thereby maintaining stable equipment and pipeline temperatures and ensuring the normal operation of the wellhead equipment and pipelines.

[0074] 3. Heat recovery and reuse device

[0075] like Figure 6 As shown, a waste heat collection system is built on a drilling vessel or platform. Heat pipes are arranged to closely fit the heat dissipation areas of major heat source equipment, such as engines and generators, capturing excess heat generated during operation. A heat exchanger then transfers the collected heat to thermal oil. After absorbing the heat, the oil flows into a metal hydride thermal storage device, storing a large amount of thermal energy and achieving stable heat storage.

[0076] During the heat distribution process, powered by a circulating pump, the heat-carrying fluid flows from the heat storage device and, along different branch pipes, precisely delivers heat to the relevant equipment on the platform's continuous pipes, providing them with a suitable operating temperature environment and reducing the risk of equipment failure due to low temperatures. Multiple sets of serpentine coil heat exchangers are installed inside the skid-mounted box. As the heat-carrying fluid flows through the coils, it exchanges heat with the air inside the skid-mounted box through the coil walls, thereby raising the temperature inside the box. To achieve precise temperature control, multiple high-precision temperature sensors are installed inside the skid-mounted box to monitor the temperature inside the box in real time and feed the collected data back to the programmable logic controller. Based on the pre-set temperature value, the PLC precisely controls the flow of the heat-carrying fluid by adjusting the speed of the circulating pump, thereby maintaining a stable temperature inside the skid-mounted box, creating a good operating environment for the equipment inside the box, and reducing the risk of equipment failure due to low temperatures.

[0077] For the carbon dioxide injected into the coiled tubing, a dedicated heating and pressurization box is installed before it enters the top of the coiled tubing. This heating and pressurization box uses a heating method that combines electric heating wires with a heat transfer oil bath. The electric heating wires are evenly distributed around the heating chamber, and the heat transfer oil fills the entire heating chamber to ensure the uniformity of the heating process. The heating and pressurization box is also equipped with a pressure regulation module consisting of a high-precision pressure sensor, an electric control valve, and a compressor. When the carbon dioxide gas enters the heating and pressurization box, the pressure sensor monitors the pressure in real time. Once the pressure drops below 7.38MPa, the electric control valve opens, and the compressor starts to pressurize the carbon dioxide. At the same time, the heating system raises the temperature of the carbon dioxide to above 31.26°C based on the information fed back by the temperature sensor, thereby ensuring that the carbon dioxide is in a supercritical state when it enters the coiled tubing.

[0078] In addition, during the circulation of drilling fluid, the high-temperature drilling fluid returning to the ground from the bottom of the well contains a large amount of heat. A heat exchanger is installed on the pipeline for the drilling fluid to return to the ground, and the cold end of the heat exchanger is connected to the carbon dioxide transmission pipeline. The heat in the drilling fluid can be transferred to the carbon dioxide, further helping the carbon dioxide to maintain a supercritical state. At the same time, the temperature of the drilling fluid when it returns to the ground is reduced, reducing the thermal shock to the ground equipment, and achieving a drilling fluid temperature of more than 31.26°C and a pressure of more than 7.38MPa in the entire flow channel, ensuring that the carbon dioxide is always in a supercritical state during the entire circulation process.

[0079] It can be seen that this application has the following advantages over the prior art:

[0080] (1) Equipment performance optimization and life extension: The distributed electric heating system of the coiled tubing keeps the coiled tubing at a suitable temperature at low temperatures, reducing damage such as cracks and breakages, and reducing replacement costs; the wellhead device and pipeline insulation skid integrates the wellhead device and the blowout preventer into a special steel skid, using an aerogel insulation layer and a stainless steel protective shell to withstand harsh environments, stabilize the temperature, reduce the probability of equipment failure, and ensure stable operation of the wellhead device.

[0081] (2) Efficient energy utilization and cost reduction: The continuous tube distributed electric heating system improves heating efficiency and reduces energy waste through unique circuit design, high-frequency alternating current, double-layer insulation and high-efficiency thermal insulation design; the wellhead device and pipeline insulation skid introduce the waste heat of the ship's generator as a supplementary heat source, and accurately adjusts the temperature with the help of plate heat exchangers and PLC control systems; the heat recovery and reuse system builds a waste heat collection system to recover and store various types of waste heat, accurately distribute heat, and comprehensively improve the comprehensive energy utilization rate and reduce external energy consumption.

[0082] (3) Improved operational efficiency and quality assurance: The design of the distributed electric heating system for coiled tubing, the wellhead device, and the pipeline insulation skid ensures stable fluid flow, avoids pumping obstruction, and reduces the risk of wellbore freezing; the heat recovery and reuse system provides heat for the skid-mounted box, reduces the risk of equipment failure, ensures that carbon dioxide is in a supercritical state when it enters the coiled tubing, improves drilling efficiency and quality, and ensures the smooth progress of drilling operations.

[0083] In a possible implementation, the specific implementation process of the drilling system arrangement is as follows:

[0084] (1) Coiled Tube Distributed Electric Heating System

[0085] S1 coiled tubing specifications: Refer to API SPEC 5ST and select the coiled tubing outer diameter based on comprehensive considerations of drilling flow, equipment space, and flexibility requirements.

[0086] When determining the outer diameter, simulation tests are conducted on coiled tubing with different outer diameters to compare their performance under different working conditions.

[0087] Then, based on the operating load (such as internal pressure calculated using the thin-walled cylinder stress formula), combined with the allowable stress of the material, and considering the wall thickness allowance, the maximum wall thickness and coating thickness are determined.

[0088] The wall thickness allowance is determined with reference to industry standards and past project experience. Finite element analysis software is used to simulate and evaluate the mechanical properties of the coiled tubing under different wall thickness allowances to ensure that the wall thickness meets actual usage requirements.

[0089] S2 Heating Layer Wire Winding: Nickel-chromium alloy wire is spirally wound around the outer wall of the coiled tubing at a pitch of 5-10mm. In actual operation, the appropriate pitch can be flexibly selected based on the site environment and heating requirements.

[0090] The length of a single coil segment is controlled at 1-2 meters, and adjacent coils are connected using specially designed insulating joints. During the connection process, professional testing tools are used to test the insulation performance of each joint to ensure that the insulation resistance meets safety standards, ensuring heating uniformity and system safety.

[0091] S3 double-layer insulation treatment: The inner layer of the metal wire is tightly wrapped with a 0.1-0.3mm thick polyimide film, which can withstand high temperatures of 300°C and reduce the risk of leakage.

[0092] When wrapping, professional winding equipment is used to ensure that the film fits tightly to the metal wire without wrinkles or bubbles.

[0093] The outer layer is covered with a 2-5mm thick nano-aerogel composite material through a spraying process. Its thermal conductivity is less than 0.02W / m·K, which has both thermal insulation and mechanical protection functions.

[0094] Before spraying, the surface of the coiled tubing is cleaned and pretreated to enhance material adhesion; during the spraying process, the spraying pressure, temperature and spray gun movement speed are strictly controlled to ensure uniform coating thickness.

[0095] S4 heating unit layout: To meet the requirements of long-distance coiled tubing heating, a heating unit is set up every 50-100 meters. Adjacent units adopt a series-parallel hybrid circuit to ensure that the single-segment voltage is ≤100V and the current is ≤15A, ensuring safety and optimizing power transmission and heating efficiency.

[0096] After the circuit connection is completed, use professional power testing equipment to measure and debug the circuit parameters to ensure that the circuit operates stably and the heating unit can work normally.

[0097] S5 temperature monitoring and regulation: Temperature sensors with an accuracy of ±0.5°C are distributed throughout the coiled tubing. These sensors collect temperature data and transmit it to the control system. Based on the PID algorithm (a formula consisting of the proportional term P, the integral term I, and the differential term D, based on the difference between the actual and set temperatures), the IGBT switching frequency is adjusted, dynamically adjusting the heating power to stabilize the coiled tubing temperature. During system operation, the temperature sensors are regularly calibrated to ensure accurate measurement data. Furthermore, the PID parameters are optimized based on actual operating conditions to improve temperature control accuracy and response speed.

[0098] (2) Implementation steps for wellhead equipment and pipeline insulation skid

[0099] S1 fabricates the steel skid and designs its structure and dimensions based on the size and layout of the wellhead and BOP, ensuring it can stably support the wellhead and BOP. A support structure is installed within the skid to facilitate subsequent filling with an aerogel insulation layer.

[0100] S2 fills the skid with aerogel insulation, ensuring that the aerogel is evenly distributed to avoid gaps. Once filled, install the stainless steel protective shell and secure it to the skid by welding or bolting.

[0101] S3 For pipelines, according to the on-site installation requirements, prefabricate the phenolic foam insulation material into a pipe sleeve of appropriate length, then put the pipe sleeve on the pipeline, and use glue or steel tape to fix the pipe sleeve firmly.

[0102] S4 installs the ship's generator waste heat recovery system, connects the plate heat exchanger to the generator waste heat outlet and the thermal oil circulation system, and ensures that the connection is well sealed and leak-free.

[0103] The S5 heatsink installs the coil inside the insulation skid and connects the thermal oil circulation system to the coil. A PLC control system and PT100 sensors are also installed, and the sensors are connected to the PLC to enable real-time temperature monitoring and control.

[0104] When S6 installs the wellhead equipment and pipeline insulation skid on site, it first fixes the steel skid in the predetermined position, and then quickly connects the pipeline sections through flanges to ensure a tight connection without leakage.

[0105] Finally, debug the supplementary heat system and set appropriate temperature parameters through PLC according to actual temperature requirements so that the system can automatically adjust the waste heat flow and maintain a stable temperature inside the insulation skid.

[0106] (3) Implementation steps for heat recovery and reuse

[0107] S1 installs the waste heat collection system and plans the direction of the heat transfer pipe to ensure that it fits tightly with heat source equipment such as engines and generators, while avoiding interference with the normal operation of other equipment. When installing the heat exchanger, attention should be paid to its sealing and heat transfer efficiency, and the connecting pipes should be properly insulated to reduce heat loss during transmission.

[0108] S2: Install the heat storage device. Install the device on a stable foundation, taking waterproof and heat-insulating measures to prevent the external environment from affecting the internal heat storage process. Ensure that the connection between the heat storage device and the waste heat collection system is tight and unobstructed, allowing the heat transfer fluid to flow smoothly into the heat storage device for heat storage.

[0109] S3 is equipped with a coiled tubing heating system that connects the heat storage device to the heat exchanger surrounding the coiled tubing. By adjusting the valves on the heat exchanger, the rate and amount of heat transferred to the coiled tubing can be precisely controlled to ensure that the coiled tubing maintains an appropriate temperature under different operating environments.

[0110] In the installation of the skid-mounted box heating system, S4 installs the serpentine coil heat exchanger in the skid-mounted box according to the designed layout, ensuring that the coil is in full contact with the air in the box to achieve efficient heat exchange.

[0111] Install temperature sensors at key locations within the skid-mounted enclosure, taking care to avoid interference from heat sources or airflow. When connecting the sensor to the PLC, shield the wiring to prevent signal interference.

[0112] Connect the PLC to the control end of the circulation pump and debug the program. Set appropriate upper and lower temperature limits according to actual needs to achieve precise control of the temperature inside the skid-mounted box.

[0113] Installation of the S5 carbon dioxide heating and pressurizing box: Install it on the carbon dioxide delivery pipeline in front of the top of the coiled tubing, ensuring that the connection is firm and the seal is good.

[0114] When installing the electric heating wire, be sure to properly insulate it to prevent leakage. Fill the heat transfer oil to the specified level, install the pressure sensor, electric regulating valve, and compressor, and connect the control circuit and power supply.

[0115] After the installation is completed, the entire heating and pressurizing box device is strictly pressure tested and sealed to ensure that it is correct before subsequent debugging.

[0116] S6 is equipped with a drilling fluid heat recovery system. A heat exchanger is installed on the pipeline that returns the drilling fluid to the ground, and the cold end of the heat exchanger is connected to the carbon dioxide transmission pipeline to ensure that heat can be effectively transferred to the carbon dioxide.

[0117] S7 conducts system debugging, starts the waste heat collection system, carefully checks whether the heat transfer pipes and heat exchangers are working properly, and closely observes the temperature changes of the heat storage tank.

[0118] Start the skid-mounted box heating device and carbon dioxide heating and pressurizing box in sequence, monitor the temperature and pressure data in real time, and adjust the control parameters according to the actual measurement results.

[0119] By simulating different working conditions, the stability and reliability of the system are comprehensively tested to ensure that the drilling fluid temperature and pressure in the entire flow channel can meet the requirements of the supercritical state of carbon dioxide under various conditions, so that the entire heat recovery and reuse system can operate stably and efficiently.

[0120] It should be understood that, although the various steps in the flowcharts involved in the above-described embodiments are displayed in sequence according to the instructions, these steps are not necessarily executed in the order indicated. Unless otherwise specified herein, there is no strict order restriction on the execution of these steps, and these steps can be executed in other orders. Moreover, at least a portion of the steps in the flowcharts involved in the above-described embodiments may include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a portion of steps or stages in other steps.

[0121] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0122] The embodiments described above merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. An insulated coiled tubing drilling system for polar cold sea drilling, characterized in that: include: The coiled tubing distributed electric heating device, consisting of spirally wound nickel-chromium alloy wire, segmented heating units, and a double-layer insulation structure, can controllably heat the air section, seawater section, and shallow seabed section of the coiled tubing to prevent freezing and low-temperature embrittlement of the pipeline. The wellhead integrated insulation skid consists of a steel skid, an aerogel insulation layer, and a stainless steel protective shell. It integrates the wellhead and blowout preventer, and is quickly connected via phenolic foam insulated pipelines. It is combined with the shipboard generator waste heat recovery module to maintain temperature stability. Heat recovery and reuse equipment, through waste heat collection pipelines, metal hydride heat storage devices and heat exchanger networks, converts waste heat from engines and generators and drilling fluid into supplementary heat sources for coiled tubing heating, skid-mounted container insulation and maintaining the supercritical state of carbon dioxide; The three devices work together to dynamically adjust the heating power through the PID algorithm, control the waste heat flow through the PLC, and distribute the heat-carrying fluid through the circulation pump, thereby achieving stable drilling fluid flow, controllable equipment temperature, and improved energy utilization in polar low-temperature environments.

2. The insulated coiled tubing drilling system for polar cold sea drilling according to claim 1, characterized in that: The coiled tube distributed electric heating device and nickel-chromium alloy wire are spirally wound on the outer wall of the coiled tube with a pitch of 5-10 mm. The length of a single coil is 1-2 m, and adjacent coils are connected by insulating joints. The continuous tube distributed electric heating device has a double-layer insulation structure, with the inner layer being a 0.1-0.3 mm thick polyimide film and the outer layer being a 2-5 mm thick nano-aerogel composite material; The heating unit is set up every 50-100m and is powered by a series-parallel hybrid circuit. The single-section voltage is ≤100V and the current is ≤15A. The temperature control system based on PID algorithm dynamically adjusts the heating power through temperature sensors and IGBT switches.

3. The insulated coiled tubing drilling system for polar cold sea drilling according to claim 1, characterized in that: The steel skid in the integrated insulation skid-mounted device for the wellhead device is filled with an aerogel insulation layer and covered with a stainless steel protective shell. The wellhead device and blowout preventer are integrated on the skid, and the pipeline is skidded separately and covered with a phenolic foam insulation layer. The waste heat from the generator on board the ship is heated by the plate heat exchanger to heat the thermal oil circulation system, and the waste heat flow is controlled by the PLC to adjust the temperature.

4. The insulated coiled tubing drilling system for polar cold sea drilling according to claim 1, characterized in that: The heat recovery and reuse device further comprises: The waste heat collection module collects heat from the engine and generator through heat-conducting pipes; The metal hydride thermal storage device stores heat and distributes it to the skid-mounted box and coiled tubing equipment through a circulation pump; The carbon dioxide heating and pressurizing box uses an electric heating wire combined with a heat conduction oil bath to ensure that the carbon dioxide is in a supercritical state when it enters the coiled tubing; The heat exchanger in the drilling fluid circulation pipeline transfers waste heat to carbon dioxide and reduces the drilling fluid temperature.

5. The insulated coiled tubing drilling system for polar cold sea drilling according to claim 2, characterized in that: The outer diameter of the continuous pipe ranges from 19.1 mm to 88.9 mm, and the wall thickness is determined by calculating the stress formula of a thin-walled cylinder, and the wall thickness margin is increased to withstand the operating load.

6. The insulated coiled tubing drilling system for polar cold sea drilling according to claim 3, characterized in that: The thermal oil circulation system exchanges heat with the air in the skid-mounted box through a serpentine coil heat exchanger, and the PLC adjusts the speed of the circulation pump based on feedback from the temperature sensor.

7. The insulated coiled tubing drilling system for polar cold sea drilling according to claim 4, characterized in that: The carbon dioxide heating and pressurizing box is equipped with a pressure sensor, an electric regulating valve and a compressor. When the pressure is lower than 7.38MPa, pressurization is started and the temperature is raised to above 31.26°C.

8. The insulated coiled tubing drilling system for polar cold sea drilling according to claim 4, characterized in that: The cold end of the heat exchanger of the drilling fluid circulation pipeline is connected to the carbon dioxide delivery pipeline to ensure that the temperature and pressure of the carbon dioxide remain in a supercritical state during the entire circulation process.

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