Hydraulic lifting multi-gradient drilling string, drilling system, and drilling method

Abstract

A hydraulic lifting multi-gradient drilling string, a drilling system, and a drilling method. In the multi-gradient drilling string, a multi-passage drill rod (1) is provided with a power fluid inflow passage (12), a power fluid outflow passage (13), and a drilling fluid flow passage (11); a fluid injection adaptation system (2) is mounted at the upper end of the multi-passage drill rod; a downhole lifting power system (3) is mounted on the multi-passage drill rod (1) and is communicated with an annulus or the drilling fluid flow passage; a power fluid injected by the fluid injection adaptation system (2) can flow into the downhole lifting power system (3) through the power fluid inflow passage (12) and returns to the fluid injection adaptation system (2) through the power fluid outflow passage (13); and the downhole lifting power system (3) can be driven by the power fluid to operate so as to pressurize a drilling fluid. Thus, the technical problems that in the drilling operation of complex terrestrial and marine formations, the formation pressure is difficult to predict and the pressure system is complex, the safety risk is high, and the operation cycle is long are solved.

Description

Hydraulic lift multi-gradient drilling string, drilling system and drilling method

[0001] Related applications

[0002] This application claims priority to the Chinese invention patent with patent application number 202310760030.1, application date June 26, 2023, and invention name “Hydraulic lift multi-gradient drilling string, drilling system and drilling method”. Technical Field

[0003] The present invention relates to the technical field of oil and natural gas drilling and completion and natural gas hydrate drilling and production, and in particular to a hydraulic lift multi-gradient drilling string, a drilling system and a drilling method. Background Art

[0004] As oil and gas exploration and development continue to deepen, drilling is increasingly moving into new areas, depths, formations, and environments. This has led to an increase in the uncertainty and complexity of the formations, making wellbore safety control increasingly difficult during drilling in some onshore and offshore oil and gas fields. In some onshore areas, oil and gas exploration and development face complex geological conditions, making it difficult to accurately predict the pressure of the formations encountered, and the possibility of multiple pressure systems within the same openhole section, resulting in an extremely narrow safe density window. In some offshore drilling operations, the weak cementation of the seabed formations also contributes to a narrow safe density window.

[0005] In complex pressure systems, the coexistence of spills and leaks has become a bottleneck hindering the safe and efficient development of onshore and offshore oil and gas fields. When drilling into large fractures or caves, high-density drilling fluids can easily lead to significant losses. When drilling into high-pressure gas and water zones, abnormal formation pressures can easily trigger spills and kicks. Improper handling of these spills or lost circulation can lead to secondary, complex accidents such as well collapse, stuck pipe, kicks, and blowouts, resulting in casualties and economic losses.

[0006] In order to cope with the difficulties in wellbore safety control caused by complex formations, the current research and development mainly focuses on coping methods such as bottom hole constant pressure managed pressure drilling technology and dual gradient drilling technology.

[0007] The existing downhole constant pressure managed drilling technology mainly achieves precise control of the entire wellbore annulus pressure profile through wellhead throttling and surface pressure replenishment. However, this technology is limited by the hydrostatic column pressure of the wellbore fluid and cannot achieve downward adjustment based on it. A single annular pressure gradient system may face a dangerous "dilemma" under complex formation conditions with multiple pressures.

[0008] Existing dual-gradient drilling technologies mainly include: dual-gradient drilling with low-density medium injection, dual-gradient drilling with seabed pump lifting, and dual-gradient drilling without riser to control mud level. Among them, dual-gradient drilling with low-density medium injection is mainly achieved by injecting low-density medium into the wellbore annulus and mixing it with conventional drilling fluid to reduce the pressure of the liquid column in some sections of the well. Specifically, it is divided into: hollow microsphere injection method, gas injection method and low-density liquid injection method. Dual-gradient drilling with seabed pump lifting mainly uses a seabed pump to lift the return mud, while using a fluid with a density close to seawater in the riser to achieve a dual-gradient drilling effect. Dual-gradient drilling without riser to control mud level is achieved by installing a seabed pump and adjusting the drilling fluid level inside the riser to achieve closed-loop circulation of the drilling fluid and precise control of bottom hole pressure.

[0009] The existing dual-gradient drilling solution, based on marine environment applications, occupies a large amount of downhole space and is basically unsuitable for terrestrial drilling environments. Furthermore, the adjustment of the wellbore pressure profile can only achieve two gradients, resulting in low flexibility and difficult reliability.

[0010] Therefore, in drilling operations under complex geological conditions, existing technologies face technical bottlenecks and environmental and cost constraints. There is an urgent need to develop new technologies and methods to support drilling operations more quickly and achieve cost reduction and efficiency improvement.

[0011] Summary of the Invention

[0012] The purpose of the present invention is to provide a hydraulic lift multi-gradient drilling string, a drilling system and a drilling method to solve the technical problems of difficult to predict formation pressure, complex pressure system, high safety risk and long operation cycle in drilling operations in complex formations on land and sea.

[0013] The above-mentioned purpose of the present invention can be achieved by adopting the following technical solutions:

[0014] The present invention provides a hydraulic lift multi-gradient drilling string, comprising:

[0015] A multi-channel drill pipe having a power fluid inlet flow channel, a power fluid outflow flow channel, and a drilling fluid flow channel;

[0016] a fluid injection adapter system mounted on the upper end of the multi-channel drill pipe;

[0017] at least one downhole lifting power system;

[0018] The downhole lifting power system is installed on the multi-channel drill pipe and is connected to the annulus; the power fluid injected by the fluid injection adapter system can flow into the downhole lifting power system through the power fluid inlet channel, and return to the fluid injection adapter system through the power fluid outflow channel after flowing through the downhole lifting power system, and the downhole lifting power system can be driven by the power fluid to operate to increase the pressure of the drilling fluid when it flows through the downhole lifting power system.

[0019] The present invention provides a hydraulic lift multi-gradient drilling system, comprising: a wellhead manifold system; the above-mentioned hydraulic lift multi-gradient drilling string, wherein the wellhead manifold system is connected to the power fluid inlet flow channel, power fluid outflow flow channel, drilling fluid flow channel and wellhead device in the hydraulic lift multi-gradient drilling string.

[0020] The present invention provides a hydraulic lift multi-gradient drilling method, which adopts the above-mentioned hydraulic lift multi-gradient drilling string; the downhole lift power system is driven by power fluid and increases the pressure of the drilling fluid when it flows through the downhole lift power system.

[0021] The characteristics and advantages of the present invention are:

[0022] The hydraulic lift multi-gradient drilling string, drilling system, and drilling method provided by the present invention achieve multi-stage regulation of the pressure gradient of the returning drilling fluid during the drilling process through hydraulic lift. This solves the coexisting problems of spills and leaks caused by multiple formation pressure systems and a narrow drilling fluid density window during oil and gas drilling. Under multiple pressure systems, wellbore pressure can be rapidly regulated to achieve a balance between preventing leaks and balancing high formation pressures. The present invention offers several advantages, including a small footprint, rapid and stable pressure regulation, and high integration with conventional drilling operations.

[0023] Moreover, the flow energy of the returning drilling fluid, originally provided by the surface drilling pump, is partially shared by the downhole lifting power system. Therefore, when the downhole lifting power system is started, the bottomhole pressure and the drilling pump pressure both decrease, which reduces the risk of bottomhole leakage and the workload of the surface drilling pump. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The following drawings are intended only to illustrate and explain the present invention, and are not intended to limit the scope of the present invention.

[0025] FIG1 is a schematic diagram of a working state of an embodiment of a hydraulic lift multi-gradient drilling string provided by the present invention;

[0026] FIG2 is a schematic structural diagram of a fluid injection adaptation system in a hydraulic lift multi-gradient drilling string shown in FIG1 ;

[0027] FIG3 is a schematic structural diagram of a multi-channel drill pipe in the hydraulic lift multi-gradient drilling string shown in FIG1 ;

[0028] FIG3A is a cross-sectional view of FIG3 ;

[0029] FIG4 is a schematic structural diagram of a downhole lifting power system in the hydraulic lift multi-gradient drilling string shown in FIG1 ;

[0030] FIG5 is a schematic diagram of the working state of the annulus isolation system in the hydraulic lift multi-gradient drilling string shown in FIG1;

[0031] FIG6 is a diagram showing the pressure distribution of the multi-gradient drilling wellbore of the hydraulic lift multi-gradient drilling string shown in FIG1 ;

[0032] FIG7 is a schematic diagram of the working state of an embodiment of a hydraulic lift multi-gradient drilling string provided by the present invention;

[0033] FIG8 is a schematic structural diagram of the fluid injection adaptation system in the hydraulic lift multi-gradient drilling string shown in FIG7 ;

[0034] FIG9 is a schematic structural diagram of a multi-channel drill pipe in the hydraulic lift multi-gradient drilling string shown in FIG7 ;

[0035] FIG9A is a cross-sectional view of FIG3 ;

[0036] FIG10 is a schematic structural diagram of a downhole lifting power system in the hydraulic lift multi-gradient drilling string shown in FIG7 ;

[0037] FIG11 is a schematic diagram of the working state of the annulus isolation system in the hydraulic lift multi-gradient drilling string shown in FIG7 ;

[0038] FIG12 is a diagram showing the pressure distribution of the multi-gradient drilling wellbore of the hydraulic lift multi-gradient drilling string shown in FIG7 . DETAILED DESCRIPTION

[0039] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific embodiments of the present invention are now described with reference to the accompanying drawings. In the description of the present invention, unless otherwise specified, the meaning of "multiple" is two or more.

[0040] Option 1

[0041] The present invention provides a hydraulic lift multi-gradient drilling string, as shown in Figures 1 to 12, the hydraulic lift multi-gradient drilling string includes: a multi-channel drill pipe 1, a fluid injection adapter system 2 and at least one downhole lifting power system 3, the multi-channel drill pipe 1 has a power fluid inlet channel 12, a power fluid outflow channel 13 and a drilling fluid channel 11; the fluid injection adapter system 2 is installed at the upper end of the multi-channel drill pipe 1; the downhole lifting power system 3 is installed on the multi-channel drill pipe 1 and is connected to the annulus; the power fluid injected by the fluid injection adapter system 2 can flow into the downhole lifting power system 3 through the power fluid inlet channel 12, and return to the fluid injection adapter system 2 through the power fluid outflow channel 13 after flowing through the downhole lifting power system 3, and the downhole lifting power system 3 can be driven by the power fluid to operate to increase the pressure of the drilling fluid when it flows through the downhole lifting power system 3.

[0042] When downhole lift power system 3 is driven by the power fluid, the drilling fluid in the annulus or drilling fluid flow channel 11 receives additional driving force from downhole lift power system 3, thereby assisting in the lift and returning to the surface. The pressure distribution of the returned drilling fluid changes from the original unilinear distribution to a multilinear distribution with downhole lift power system 3 as the dividing point. The pressure gradient of the returned drilling fluid can be equivalent to a multi-level pressure gradient with downhole lift power system 3 as the dividing point.

[0043] The hydraulic lift multi-gradient drilling string provided by this invention achieves multi-stage adjustment of the pressure gradient of the returning drilling fluid during drilling through hydraulic lift. This solves the coexisting problems of spills and leaks caused by multiple formation pressure systems and a narrow drilling fluid density window during oil and gas drilling. Under multiple pressure systems, it achieves a balance between preventing leakage and balancing high formation pressures.

[0044] Moreover, the flow energy of the upward drilling fluid originally provided by the surface drilling pump is partially shared by the downhole lifting power system 3. Therefore, when the downhole lifting power system 3 is started, the bottom hole pressure and the drilling pump pressure both decrease, which reduces the risk of bottom hole pressure leakage and the workload of the surface drilling pump.

[0045] In conventional drilling, drilling fluid is injected from the surface into the drill string, flows through the drill string to the drill bit 53, then exits through the flow channel of the drill bit 53 and returns to the surface through the wellbore annulus formed by the drill string and the wellbore wall or casing. This flow pattern of drilling fluid is called positive circulation. During positive circulation, drilling fluid flows downward from the multi-channel drill pipe 1 to the drill bit 53 and returns to the surface through the wellbore annulus. The downhole lift power system 3 is connected to the annulus and can be driven by the power fluid to increase the pressure of the drilling fluid in the annulus.

[0046] As shown in Figures 4 and 10, the downhole lifting power system 3 includes a system fluid suction port 31 and a system fluid discharge port 32. The system fluid suction port 31 and the system fluid discharge port 32 are respectively connected to the annulus. The drilling fluid in the annulus can be sucked into the downhole lifting power system 3 through the system fluid suction port 31 and discharged to the annulus through the system fluid discharge port 32.

[0047] In some embodiments, the hydraulic lift multi-gradient drilling string includes an annulus isolation system 4, which is installed outside the downhole lifting power system 3 and is used to isolate the annulus. The system fluid suction port 31 and the system fluid discharge port 32 are respectively arranged on the upper and lower sides of the annulus isolation system 4. The annulus isolation system 4 is installed at the downhole lifting power system 3 to achieve a fluid barrier effect. By isolating the system fluid suction port 31 and the system fluid discharge port 32 of the downhole lifting power system 3, the drilling fluid is prevented from being discharged from the system fluid discharge port 32 of the downhole lifting power system 3 and then being re-absorbed by the system fluid suction port 31 to form a short-circuit, thereby preventing the short-circuit of drilling fluid from affecting the lifting efficiency, thereby improving the lifting performance and efficiency of the drilling fluid.

[0048] The annulus isolation system 4 may include a rubber plug 41 or a plastic baffle 42 , which can cooperate with the well wall or casing to block the annulus fluid.

[0049] In one embodiment, the annulus isolation system 4 includes a rubber plug 41, as shown in Figure 5. The rubber plug 41 is expandable and can be opened and closed by pressure. When the pressure exceeds the expansion pressure of the rubber plug 41, the rubber plug 41 expands and opens, isolating the annulus. When the pressure falls below the release pressure of the rubber plug 41, the rubber plug contracts and closes, releasing the annulus isolation. Preferably, the rubber plug 41 contains materials such as wear-resistant particles or coarse fibers to improve its wear resistance and maintain a certain level of isolation performance during reciprocating friction with the wellbore wall.

[0050] In another embodiment, the annular isolation system 4 includes a plastic baffle 42, as shown in Figure 11. The plastic baffle 42 is pressure-controlled. When the pressure exceeds the baffle extension pressure, the baffle extends, isolating the annulus. When the pressure falls below the baffle extension pressure, the baffle retracts, releasing the annular isolation. The plastic baffle 42 is shaped to approximate the wellbore diameter and can be made of hard plastic. Preferably, wear-resistant particles or coarse fibers are added to the plastic baffle 42 to improve its wear resistance, thereby maintaining a certain level of isolation performance during reciprocating friction with the wellbore wall.

[0051] Furthermore, the features of the annulus isolation system 4 may include: (1) the annulus isolation system 4 comprises one or more shaped or expandable isolation components with a certain strength that can block the annulus fluid. The isolation component may be a rubber plug 41 or a plastic baffle 42, and the maximum isolation size of the isolation component is approximately the wellbore diameter; (2) the isolation component material has a certain wear resistance and impact resistance, and has a certain ability to withstand reciprocating friction with the well wall and drill string vibration; (3) the annulus isolation system 4 can be controlled by manual ground intervention, and the opening and closing of the isolation component can be controlled by mechanical or hydraulic methods. It is closed in conventional drilling to avoid interfering with the flow of annular drilling fluid, and is opened in multi-gradient drilling to block the short-distance circulation of annular fluid.

[0052] The downward delivery and upward return of the power fluid are both achieved through the multi-channel drill pipe 1. In one embodiment, the power fluid outflow channel 13 and the power fluid inflow channel 12 of the multi-channel drill pipe 1 are respectively connected to the downhole lift power system 3. The power fluid flows into the downhole lift power system 3 through the power fluid inflow channel 12, flows through the downhole lift power system 3, and then enters the power fluid outflow channel 13.

[0053] In another embodiment, the multi-channel drill pipe 1 includes multiple drill pipe sections 10, and the downhole lifting power system 3 is arranged between two adjacent drill pipe sections 10. As shown in Figures 1, 3, 7 and 9, the drill pipe sections 10 and the downhole lifting power system 3 are distributed longitudinally, and the upper and lower ends of the downhole lifting power system 3 are respectively connected to the drill pipe sections 10; each drill pipe section 10 is respectively provided with a power fluid inlet channel 12, a power fluid outlet channel 13 and a drilling fluid channel 11, and the flow channels of the drill pipe section 10 are connected to the corresponding flow channels in the downhole lifting power system 3. The power fluid inlet channel 12 of each drill pipe section 10 is connected through the corresponding flow channel in the downhole lifting power system 3, the power fluid outflow channel 13 of each drill pipe section 10 is also connected through the corresponding flow channel in the downhole lifting power system 3, and the drilling fluid flow channel 11 of each drill pipe section 10 is also connected through the corresponding flow channel in the downhole lifting power system 3. For example, the downhole lift power system 3 is designed with its own flow channel. After the power fluid drives one downhole lift power system 3, it can continue to flow downward through its own designed flow channel to the flow channel of the drill pipe section 10 and enter the next downhole lift power system 3, thus achieving downward flow of the power fluid. When the multi-gradient drilling string has multiple downhole lift power systems 3, as shown in Figures 1 and 7, the drill pipe sections 10 and downhole lift power systems 3 can be arranged alternately in the longitudinal direction and connected end to end.

[0054] The structural form of the multi-channel drill rod 1 is not limited to one.

[0055] In one embodiment, a multi-channel drill pipe 1 includes a center pipe 14, a first curved plate 151, and a second curved plate 152. As shown in Figures 3 and 3A, a drilling fluid flow channel 11 is disposed within the center pipe 14; both the first curved plate 151 and the second curved plate 152 are disposed outside the center pipe 14. A power fluid inlet channel 12 is formed between the first curved plate 151 and the center pipe 14, and a power fluid outlet channel 13 is formed between the second curved plate 152 and the center pipe 14. In another embodiment, a power fluid inlet channel 12 is formed between the second curved plate 152 and the center pipe 14, and a power fluid outlet channel 13 is formed between the first curved plate 151 and the center pipe 14. When the multi-channel drill pipe 1 includes multiple drill pipe sections 10, each drill pipe section 10 is provided with a corresponding center pipe 14, first curved plate 151, and second curved plate 152.

[0056] Furthermore, the first curved plate 151 and the second curved plate 152 are two parts of a single tubular body; the multi-channel drill pipe 1 includes a partition 153 for separating the power fluid inflow channel 12 from the power fluid outflow channel 13. Preferably, as shown in FIG3A , the first curved plate 151 and the second curved plate 152 are integral, forming a circular tube. The partition 153 is disposed between the circular tube and the center tube 14 to separate the independent power fluid inflow channel 12 and the power fluid outflow channel 13.

[0057] In another embodiment, a multi-channel drill pipe 1 includes a central tube 14, a middle tube 161, and an outer tube 162. A drilling fluid flow channel 11 is disposed within the central tube 14. A power fluid outflow channel 13 and a power fluid inflow channel 12 are constructed between the middle tube 161 and the central tube 14, and between the middle tube 161 and the outer tube 162. Specifically, the power fluid outflow channel 13 is constructed between the middle tube 161 and the central tube 14, and the power fluid inflow channel 12 is constructed between the middle tube 161 and the outer tube 162. Alternatively, as shown in Figures 9 and 9A, the power fluid inflow channel 12 is constructed between the middle tube 161 and the central tube 14, and the power fluid outflow channel 13 is constructed between the middle tube 161 and the outer tube 162.

[0058] The main function of the multi-channel drill pipe 1 is to realize the separated flow of power fluid and drilling fluid, and to provide independent flow channels for the power fluid and the drilling fluid respectively, thereby preventing the two fluid systems from mixing.

[0059] Features of the multi-channel drill pipe 1 may include:

[0060] (1) The multi-channel drill pipe 1 has three or more flow channels. The power fluid inlet flow channel 12, the power fluid outlet flow channel, and the drilling fluid flow channel 11 are separated from each other and do not interfere with each other. The power fluid can complete a closed downhole circulation through the inlet and outlet flow channels without mixing with the drilling fluid.

[0061] (2) The drill pipe sections 10 can be connected to each other by threads or joints, and can be connected to the drilling top drive 52 device or the kelly 51 at the wellhead through the fluid injection adapter system 2;

[0062] (3) The drill pipe section 10 can be connected to the downhole lifting power system 3 underground. The power fluid flows into the downhole lifting power system 3 from the power fluid inflow channel 12, drives the downhole lifting power system 3, and then flows into the power fluid outflow channel 13.

[0063] In one embodiment, the downhole lifting power system 3 includes a system driving device 34 and an annulus lifting device 33; the system fluid suction port 31 and the system fluid discharge port 32 are both arranged on the annulus lifting device 33; the power fluid inlet channel 12 and the power fluid outlet channel 13 are both connected to the system driving device 34, and the system driving device 34 can be driven by the power fluid to operate and drive the annulus lifting device 33 to operate.

[0064] The structural forms of the system drive device 34 and the annular space lifting device 33 are not limited to one. For example, the system drive device 34 can be a first turbine mechanism 341 or a screw mechanism 342, and the annular space lifting device 33 can be a second turbine mechanism 331 or a worm mechanism 332.

[0065] In one embodiment, the system driving device 34 includes a first turbine mechanism 341. As shown in Figure 4, the annulus lifting device 33 includes a second turbine mechanism 331. The first turbine mechanism 341 and the second turbine mechanism 331 constitute a downhole lifting pump.

[0066] In another embodiment, the system driving device 34 includes a screw mechanism 342. As shown in Figure 10, the annulus lifting device 33 includes a worm mechanism 332, and the screw mechanism 342 and the worm mechanism 332 constitute a downhole lifting pump.

[0067] Downhole lift power system 3 provides lifting power for the annular drilling fluid. Driven by hydraulic power, it converts fluid energy into system mechanical energy, driving the annular fluid flow and further converting it into annular fluid kinetic energy. When the system drive device 34 is in operation, it drives the annular lift device 33 via the power transmission device 35.

[0068] Furthermore, the features of the downhole lifting power system 3 may include:

[0069] (1) The downhole lifting power system 3 also includes a system housing and a sealing assembly, wherein the system housing is a protective shell of the system, and its main functions are to provide installation space for other components, withstand the fluid pressure inside and outside the system, prevent other components of the system from being damaged by impact, and provide a flow channel suction port and discharge port for the system drive device and the annular lifting device; the sealing assembly mainly functions to ensure the fluid sealing of the system flow channel inlet and outlet, as well as the sealing between the system housing and the system drive device, and between the system housing and the annular lifting device, maintain fluid pressure, and avoid leakage of power fluid and drilling fluid;

[0070] (2) The main function of the system drive device is to receive the energy of the power fluid. The power fluid flows into the system drive device from the power fluid flow channel of the multi-channel drill pipe 1, driving it to operate and converting the fluid kinetic energy into mechanical energy of the system drive device;

[0071] (3) The main function of the annular lifting device is to output the system mechanical energy into the annular fluid kinetic energy. When it is running, the annular fluid is sucked into the annular lifting device from the system fluid suction port 31, and is discharged from the system fluid discharge port 32 after obtaining additional flow rate and pressure, thereby achieving the effect of lifting the annular drilling fluid.

[0072] (4) The power transmission device 35 is mainly used to connect the system drive device and the annular lifting device, and transmit the mechanical energy of the system drive device after hydraulic drive to the annular lifting device through the transmission structure, so that the annular lifting device can operate. The power transmission device 35 may include a transmission rod or a transmission sleeve and other structures. The system drive device and the annular lifting device are connected by the power transmission device 35 to realize the transmission of system mechanical energy;

[0073] (5) Both ends of the downhole lifting power system 3 can be connected to the ordinary drill pipe or multi-channel drill pipe 1 through a conversion joint, and its drilling fluid flow channel 11 can be connected to the drilling fluid flow channel of the ordinary drill pipe or multi-channel drill pipe 1;

[0074] (6) The downhole lifting power system 3 can be installed in multiple stages at different well depths, and the working effects of different downhole lifting power systems 3 can be superimposed to achieve the effects of multi-stage lifting and multi-gradient drilling.

[0075] In one embodiment, the fluid injection adapter system 2 is provided with a power fluid injection channel 21 and a power fluid discharge channel 22. The power fluid injection channel 21 is connected to the system drive device 34 via the power fluid inlet channel 12, and the power fluid discharge channel 22 is connected to the system drive device 34 via the power fluid outlet channel 13. For example, the fluid injection adapter system 2 is provided with a rotating injection channel, a rotating discharge channel, and a dynamic seal, and is divided into an inner and outer housing. During injection, the outer housing does not rotate, while the inner housing rotates with the drill string.

[0076] The power fluid injection channel 21 and the power fluid discharge channel 22 are respectively provided with a rotary flow channel opening 24, as shown in Figures 2 and 8, wherein one rotary flow channel opening 24 serves as the power fluid injection port, and the other rotary flow channel opening 24 serves as the power fluid discharge port. The two flow channel openings can be connected inwardly to the annular flow channel of the multi-channel drill pipe 1, and can be connected outwardly to the wellhead manifold system 6 to realize the inflow and discharge of the power fluid. The fluid injection adapter system 2 can adopt a dynamic seal pressure-bearing design, which can keep the drill string rotating during the drilling process. The power fluid is injected through the rotary flow channel opening 24 and enters the multi-channel drill pipe 1. Finally, after the circulation, it is returned to the other rotary flow channel opening 24 by the multi-channel drill pipe 1 for discharge. The two rotary flow channel openings 24 are arranged relative to each other or arranged on both sides.

[0077] The fluid injection adapter system 2 is also provided with a central flow channel opening 25 serving as the inlet of the drilling fluid circulation channel. The drilling fluid can flow into the central flow channel opening 25 from the upper top drive 52 device and flow into the well through the inner cavity of the multi-channel drill pipe 1 connected below; alternatively, the drilling fluid can flow into the central flow channel opening 25 from the inner cavity of the upper square drill pipe 51 and flow into the well through the inner cavity of the multi-channel drill pipe 1 connected below.

[0078] The fluid injection adapter system 2 has excellent sealing performance and can be installed at the top drive 52, above the drill floor 63, and adjust its height as the top drive 52 rises and falls. The fluid injection adapter system 2 can also be installed at the wellhead, below the drill floor 63, and adjust its height as the kelly 51 is tripped and carried. The fluid injection adapter system 2 can be set between the top drive 52 and the multi-channel drill pipe 1. During drilling, it gradually moves downward with the top drive 52 as drilling progresses, and moves upward with it when the drill is tripped.

[0079] The fluid injection adapter system 2 separates the power fluid and the drilling fluid, and can provide independent injection channels for the two fluid systems respectively. It can also realize the continuous closed circulation of the power fluid and the drilling fluid in common drilling conditions such as rotation, tripping, and stopping of ordinary drill pipes or the above-mentioned multi-channel drill pipes 1.

[0080] Further features of the fluid injection adapter system 2 may include:

[0081] (1) The fluid injection adapter system 2 includes a system housing and a rotating core assembly. The system housing mainly includes a power fluid injection port, a power fluid flow channel, and a power fluid discharge port. The injection port and the discharge port can be matched with the flow channel of the rotating core assembly. The rotating core assembly mainly includes a drilling fluid flow channel 11, a power fluid injection flow channel 21, and a power fluid discharge flow channel 22, which can be assembled with the system housing;

[0082] (2) A bearing assembly is installed at the end of the rotating core assembly, which can limit the upward and downward range of the rotating core assembly while maintaining the relative rotation function between it and the system housing;

[0083] (3) The fluid injection adapter system 2 also includes a high-pressure sealing assembly, which mainly includes a bearing seal and a flow channel seal, which is used to maintain the bearing seal, the flow seal of the power fluid and the drilling fluid during operation;

[0084] (4) The fluid injection adapter system 2 can be installed above the wellhead blowout preventer group or below the top drive 52. One end can be connected to the drilling top drive 52 device or the kelly drill pipe 51, and the other end can be connected to the ordinary drill pipe or the multi-channel drill pipe 1 through a conversion joint;

[0085] (5) The drilling fluid flow channel 23 of the fluid injection adapter system 2 can provide a connection for the drilling fluid flow channel 23 between the top drive 52 and the multi-channel drill pipe 1, and between the square drill pipe 51 and the multi-channel drill pipe 1, so as to maintain the continuous injection of the drilling fluid; the injection port, injection flow channel, discharge port and discharge flow channel of the power fluid can maintain the continuous injection and discharge of the power fluid.

[0086] In one embodiment, the hydraulic lift multi-gradient drilling string includes a data monitoring system 7, which includes a downhole measuring tool 71 arranged in the downhole part of the multi-channel drill pipe 1, for monitoring and recording downhole parameters, obtaining accurate bottom hole pressure, temperature and other parameters, providing evaluation for construction operation results, and guiding the adjustment of ground construction parameters.

[0087] Furthermore, the data monitoring system 7 includes a surface component, primarily composed of pressure sensors, flow meters, temperature sensors, and a control computer. This component monitors and records surface operation parameters, including the injection rate, pressure, and temperature of the power and drilling fluids, as well as the discharge rate, pressure, and temperature, and wellhead back pressure. This surface component monitors and records surface operation parameters, providing a foundation for software module calculations, real-time data optimization, and operational condition analysis and assessment.

[0088] The wellhead device 54 installed at the upper end of the multi-channel drill pipe 1 is connected to the annulus outside the multi-channel drill pipe 1, and the drilling fluid can circulate through the multi-channel drill pipe 1 and the wellhead device 54. Specifically, the ground part of the data monitoring system 7 can be connected to the outlet of the power fluid output device, the outlet of the drilling mud pump 61, the wellhead manifold, and the wellhead device 54 to measure fluid flow, pressure, and temperature. The downhole measurement tool 71 serves as the downhole part of the data monitoring system 7. It mainly monitors and records downhole parameters including downhole pressure and downhole temperature. The downhole part is connected to a conventional drill pipe or a multi-channel drill pipe 1 to measure downhole pressure and temperature. The data monitoring system 7 can interact with the control computer and transmit the monitored and recorded data to the computer for storage and data processing.

[0089] To prevent mixing of the power fluid driving the downhole lift power system 3 with the drilling fluid, thereby eliminating fluid contamination and pressure interference and reducing the burden on surface equipment, some embodiments of the hydraulic lift multi-gradient drilling string provided by the present invention utilize a method of separating the power fluid from the drilling fluid to achieve multi-gradient drilling. The drilling fluid is the operating fluid used in conventional drilling operations to balance formation pressure and carry cuttings, while the power fluid is the fluid system driving the downhole lift power system 3.

[0090] The power fluid and drilling fluid have independent fluid systems. The drilling fluid is configured based on actual drilling requirements on site. The power fluid can use the same or different fluid systems as the drilling fluid. The two fluids are driven by a surface hydraulic pump and a drilling mud pump 61, respectively. The drilling fluid and power fluid have separate surface manifolds, and the fluid injection adapter system 2 enables independent circulation during the drilling process. This system supports various drilling operations, including drill string rotation, lifting and lowering, and pressurized circulation.

[0091] After being injected into the wellbore via the fluid injection adapter system 2, the power fluid and drilling fluid enter the multi-channel drill pipe 1. The multi-channel drill pipe 1 provides independent flow paths for the two fluids, allowing the power fluid and drilling fluid to flow independently and without interfering with each other. The power fluid then flows through the multi-channel drill pipe 1 to the downhole lift power system 3. The components within this system convert the kinetic energy of the power fluid into mechanical energy, driving the downhole lift power system 3.

[0092] The drilling fluid flows through the multi-channel drill pipe 1 or ordinary drill pipe to the drill bit 53, enters the annulus through the water hole or nozzle of the drill bit 53, and carries the cuttings back up along the annulus of the wellbore. After the downhole lifting power system 3 is started, the annular drilling fluid enters the suction port of the downhole lifting power system 3 during the upward return process. The mechanical energy of the internal components of the downhole lifting power system 3 is converted into kinetic energy of the annular drilling fluid. After the annular drilling fluid obtains additional kinetic energy, it flows out of the discharge port of the downhole lifting power system 3. At the same time, an annular isolation system 4 is installed at the downhole lifting power system 3 to achieve a fluid barrier effect, preventing the drilling fluid flowing out of the system fluid discharge port 32 of the downhole lifting power system 3 from being re-absorbed, causing a short-range circulation of the annular drilling fluid and affecting the lifting efficiency.

[0093] The downhole lifting power system 3 can be installed in multiple stages at different designed well depths, and is uniformly driven by the power fluid to perform multi-stage lifting of the annular drilling fluid to achieve multi-gradient pressure changes. Multiple downhole lifting power systems 3 can be connected in series or in parallel. When connected in series, the power fluid flows through one downhole lifting power system 3 and drives its system drive device 34, and then continues to flow downward to the next downhole lifting power system 3. When connected in parallel, a portion of the power fluid flows through one downhole lifting power system 3 and drives its system drive device 34; the other portion of the power fluid only flows through the downhole lifting power system 3 (through an independent flow channel) but does not drive its system drive device 34. This portion of the power fluid flows downward to the next downhole lifting power system 3.

[0094] After driving the downhole lift power system 3, the power fluid returns to the surface through the multi-channel drill pipe 1 flow channel, exits the fluid injection adapter system 2, and enters the wellhead manifold. After being lifted by the downhole lift power system 3, the annular drilling fluid also returns to the surface through the multi-channel drill pipe 1 flow channel, flowing through the wellhead manifold system 6 into the drilling fluid treatment system, completing the drilling fluid circulation. The treated power fluid and drilling fluid can repeat this process, achieving fluid circulation and maintaining continuous operation of hydraulic lift multi-gradient drilling.

[0095] In order to strengthen the exploration and development of terrestrial and marine oil and gas resources, fill the gaps in the current wellbore pressure control technology system, and break through the existing technical equipment to deal with the complexity of the wellbore, especially the situation where the drilling fluid static liquid column pressure is limited in the event of sudden leakage, it is necessary to fully combine the actual conditions of drilling in complex formations and well control safety considerations. In response to the problems of high safety risks and difficulty in handling in complex formations on land and in the ocean, at least some implementation methods of the hydraulic lift multi-gradient drilling string provided by the present invention can achieve multi-level two-way adjustment of the overall and local pressure gradients of the wellbore pressure based on the static liquid column pressure by means of hydraulic lift, and can solve the coexistence of overflow and leakage caused by multiple formation pressure systems and narrow drilling fluid density windows during oil and gas drilling. Under multiple pressure systems, it can achieve the reconciliation of preventing leakage and balancing high formation pressure. The present invention is also applicable to pressure control of drilling in complex formations on land and in the ocean, and can achieve safe and efficient drilling under complex geological conditions.

[0096] For ease of understanding, FIG1 to FIG5 show a specific embodiment.

[0097] As shown in FIG1 , during the construction of an oil well driven by a top drive 52, a corresponding specific hydraulic lift multi-gradient drilling string is used. The drilling string comprises a fluid injection adapter system 2 installed at the top drive 52, a multi-channel drill pipe 1 having three channels, a downhole lift power system 3 comprising a turbine, and an annulus isolation system 4 made of wear-resistant rubber. The fluid injection adapter system 2 is coupled to the top drive 52, and the multi-channel drill pipe 1 is connected to the fluid injection adapter system 2. A three-stage downhole lift power system 3 is employed, all of which are connected to the multi-channel drill pipe 1. The annulus isolation system 4 is also installed in conjunction with the downhole lift power system 3. The inflow and outflow of power fluid and drilling fluid are both controlled by a wellhead manifold system 6, which is connected to the drilling equipment system through which the fluid flows, including the wellhead assembly 54, a drilling mud pump 61, the top drive 52, the fluid injection adapter system 2, and a drilling fluid solid phase control system 62.

[0098] As shown in Figure 2, the fluid injection adapter system 2 used is a mechanical device with good sealing performance installed at the top drive 52 position, located above the drill floor 63. The device has two rotating flow channel openings 24 and a central flow channel opening 25. The central flow channel opening 25 is the entrance of the drilling fluid circulation channel. The drilling fluid can flow in from the upper top drive 52 device and flow into the well through the inner cavity of the multi-channel drill pipe 1 connected below. The rotating flow channel openings 24 are located on the side of the fluid injection adapter system 2 and are arranged relative to each other. One of them serves as the power fluid injection port and the other serves as the power fluid discharge port. The two flow channel openings can be connected inwardly to the annular flow channel of the multi-channel drill pipe 1 and can be connected outwardly to the wellhead manifold system 6 to realize the inflow and discharge of the power fluid.

[0099] The fluid injection adapter system 2 utilizes a dynamic seal and pressure-bearing design to maintain drill string rotation during drilling. Power fluid is injected through the rotating flow channel 24 and enters the multi-channel drill pipe 1. After circulation, it is returned to the multi-channel drill pipe 1 and discharged through another rotating flow channel 24. The fluid injection adapter system 2 can adjust its height as the top drive 52 rises and falls.

[0100] The fluid injection adapter system 2 installed at the top drive 52 is only an example of combining the concept of the hydraulic lift multi-gradient drilling method with site needs. By changing the flow channel shape, adding flow channel inlets or adjusting the flow channel angle, other similar structures can also be obtained to achieve the same or similar hydraulic lift multi-gradient drilling functions.

[0101] As shown in Figures 3 and 3A, the multi-channel drill pipe 1 used is a downhole circulation multi-channel drill pipe 1 with three channels. The difference between the multi-channel drill pipe 1 and the conventional double-wall drill pipe is that the annulus of the multi-channel drill pipe 1 is divided into two arc-shaped annuli on the left and right, thus having three independent flow channels. The two annular flow channels serve as the power fluid inflow channel and the discharge channel respectively. After the power fluid is injected into the arc-shaped annulus on one side, it passes through the downhole lifting power system 3 and then returns through the arc-shaped annulus on the other side. The middle circular flow channel is the drilling fluid injection channel, which is connected to the inner cavity of the downhole lifting power system 3, which can ensure that the drilling fluid flows to the drill bit 53 and is discharged from the water hole of the drill bit 53.

[0102] The multi-channel drill pipe 1 with three channels is only an example of combining the concept of the hydraulic lift multi-gradient drilling method with site needs. By modifying the multi-channel drill pipe 1 to have more than three channels, adjusting the flow channel cross-section or adjusting the size of the multi-channel drill pipe 1, other forms of structures can be obtained to achieve the same or similar hydraulic lift multi-gradient drilling functions.

[0103] As shown in Figure 4, the downhole lifting power system 3 used is a downhole lifting pump composed of two turbines, which has a certain pressure-bearing and sealing performance. The system drive device and annulus lifting device of this system are both composed of turbines and are connected to each other through a mechanical power transmission device 35. The flow channels and cavities of the two components are independent, and there is no exchange of power fluid and drilling fluid. Fluid discharge ports and suction ports are distributed at equal intervals at a certain angle on the upper and lower parts of the annulus lifting device, providing a lifting channel for the drilling fluid. During operation, drilling fluid flows into the inner cavity of the upper drill pipe and flows through the inner cavity of the downhole lifting power system 3 to the bottomhole drill bit 53. After the power fluid is injected into the pump body from the curved annulus on one side of the multi-channel drill pipe 1, it drives the turbine in the system drive device to rotate, and then returns to the curved annulus on the other side of the multi-channel drill pipe 1 through the bottom flow channel.

[0104] The turbine of the system drive unit rotates, and the mechanical structure of the power transmission device 35 transmits torque to the turbine of the annular lift unit, driving the turbine blades to rotate and generate fluid driving force. The annular drilling fluid located below the annular lift unit is drawn into the fluid intake port. The rotating turbine blades transmit the mechanical power of the power transmission device 35 to the annular drilling fluid, pushing the annular drilling fluid upward and out of the fluid outlet.

[0105] The downhole lifting power system 3 composed of a turbine is only an example of combining the concept of the hydraulic lift multi-gradient drilling method with on-site needs. By adjusting the turbine size and number of stages, changing the overall structure size, changing the structure shape, replacing the system drive device and the annular lifting device type, other forms of structure can be obtained to achieve the same or similar hydraulic lift multi-gradient drilling function.

[0106] As shown in Figure 5, the annular isolation system 4 employed is an expandable annular isolation device made of wear-resistant rubber. This device is designed with a rubber plug 41 that can be opened and closed by pressure. When the pressure exceeds the expansion pressure of rubber plug 41, rubber plug 41 expands and opens, isolating the annulus. When the pressure is less than the release pressure of rubber plug 41, the rubber contracts and closes, releasing the annular isolation. This device is installed between the fluid intake and discharge ports at the bottom of the downhole lifting power system 3 to block any short-circuit fluid circulation that may occur between the intake and discharge ports. Wear-resistant particles or coarse fibers are added to the wear-resistant rubber to improve the material's wear resistance, allowing it to maintain a certain level of isolation performance during reciprocating friction with the wellbore wall.

[0107] The annular space isolation system 4 made of wear-resistant rubber is only an example of combining the concept of the hydraulic lift multi-gradient drilling method with site needs. By adopting other isolation materials, or by adjusting the size, changing the opening and closing methods, etc., other forms of structures or materials can be obtained to achieve the same or similar hydraulic lift multi-gradient drilling functions.

[0108] In one embodiment, based on the aforementioned system configuration, multi-gradient drilling wellbore pressure control is performed, employing a three-stage downhole lift power system 3 for annular fluid lift. As shown in Figure 6, these three systems comprise a first-stage downhole lift power system 301, a second-stage downhole lift power system 302, and a third-stage downhole lift power system 303. After initiating multi-gradient drilling, if the actual lifting performance of each downhole lift system is the same, the wellbore annular pressure distribution will shift from the original OG line to an OF-ED-CB-AK line. Pressure mutation points E, C, and A can be connected by a straight line, resulting in an approximate dual-gradient distribution of the wellbore annular equivalent pressure, represented by the OA-AK line. In the process of starting up the first-level downhole lifting power system 301 to the third-level downhole lifting power system 303 in sequence, the bottom hole pressure decreases from point G to points I, J, and K in sequence. When one or all of the downhole lifting power systems are shut down, the bottom hole pressure increases accordingly and eventually returns to point G. This embodiment formed based on the method concept and system composition of the present invention can effectively achieve accurate control of the bottom hole pressure.

[0109] 7 to 11 show another specific embodiment.

[0110] As shown in FIG7 , in an oil well construction operation using rotary drilling, a corresponding specific hydraulic lift multi-gradient drilling method and system is adopted. The system comprises a fluid injection adapter system 2 installed at the wellhead position, a multi-channel drill pipe 1 with double annuli, a downhole lift power system 3 consisting of a screw mechanism 342 and a worm mechanism 332, and an annulus isolation system 4 made of wear-resistant plastic. Among them, the fluid injection adaptation system 2 is coordinated with the wellhead device 54 and the square drill pipe 51, the multi-channel drill pipe 1 is connected to the fluid injection adaptation system 2, and a three-level downhole lifting power system 3 is adopted, all of which are connected to the multi-channel drill pipe 1, and an annulus isolation system 4 is installed in conjunction with the downhole lifting power system 3. The inflow and discharge of power fluid and drilling fluid are controlled by the wellhead manifold system 6, and the wellhead manifold system 6 is connected to the drilling equipment system through which the fluid flows, such as the wellhead device 54, the drilling mud pump 61, the square drill pipe 51, the fluid injection adaptation system 2 and the drilling fluid solid phase control system 62.

[0111] As shown in Figure 8, the fluid injection adapter system 2 used is a mechanical device with good sealing performance installed at the wellhead position, located below the drill floor 63. The device has two rotating flow channel openings 24 and a central flow channel opening 25. The central flow channel opening 25 is the entrance of the drilling fluid circulation channel. The drilling fluid can flow in from the inner cavity of the upper square drill pipe 51 and flow into the well through the inner cavity of the multi-channel drill pipe 1 connected below. The rotating flow channel openings 24 are located at the bottom of the fluid injection adapter system 2 and are arranged on both sides, one of which serves as the power fluid injection port and the other as the power fluid discharge port. The two flow channel openings can be connected inwardly to the annular flow channel of the multi-channel drill pipe 1, and can be connected outwardly to the wellhead manifold system 6 to realize the inflow and discharge of the power fluid.

[0112] The fluid injection adapter system 2 utilizes a dynamic seal and pressure-bearing design to maintain drill string rotation during drilling. Power fluid is injected through the rotating flow channel 24 and enters the multi-channel drill pipe 1. After circulation, it is returned to the multi-channel drill pipe 1 and discharged through another rotating flow channel 24. The fluid injection adapter system 2 can adjust its height as the kelly 51 is carried in and out of the well.

[0113] The fluid injection adapter system 2 installed at the wellhead position is only an example of combining the concept of the hydraulic lift multi-gradient drilling method with on-site needs. By changing the flow channel shape, adding flow channel inlets or adjusting the flow channel angle, other forms of structures can be obtained to achieve the same or similar hydraulic lift multi-gradient drilling functions.

[0114] As shown in Figures 9 and 9A, the multi-channel drill pipe 1 used is a downhole circulation drill pipe with a double annulus. This multi-channel drill pipe 1 is a specially made three-wall drill pipe. In addition to the central circular flow channel, the multi-channel drill pipe 1 also has two layers of annular flow channels, thus having three independent flow channels. The two annular flow channels serve as the power fluid inflow channel and discharge channel, respectively. The power fluid is injected through one layer of the annular flow channel, passes through the downhole lifting power system 3, and then returns through the other layer of the annular flow channel. The central circular flow channel is the drilling fluid injection channel, which is connected to the inner cavity of the downhole lifting power system 3, ensuring that the drilling fluid flows to the drill bit 53 and is discharged through the drill bit 53 water hole.

[0115] The multi-channel drill pipe 1 with double annuli is only an example of combining the concept of the hydraulic lift multi-gradient drilling method with site needs. By increasing the number of annuli of the multi-channel drill pipe 1, adjusting the flow channel cross-section or adjusting the size of the multi-channel drill pipe 1, other forms of structures can be obtained to achieve the same or similar hydraulic lift multi-gradient drilling functions.

[0116] As shown in Figure 10, the downhole lift power system 3 employed is a downhole lift pump comprised of a screw mechanism 342 and a worm mechanism 332, exhibiting a certain degree of pressure-bearing and sealing properties. The system's drive unit comprises the screw mechanism 342, and the annular lift unit comprises the worm mechanism 332. These are connected via a mechanical power transmission mechanism. The two components have independent flow paths and cavities, preventing exchange of power fluid and drilling fluid. Fluid outlets and intakes are equidistantly spaced at regular angles on the upper and lower portions of the annular lift unit, providing a lifting channel for the drilling fluid. During operation, drilling fluid flows from the upper multi-channel drill pipe 1 through the inner cavity of the downhole lift power system 3 to the bottomhole drill bit 53. After the power fluid is injected into the pump body through one annular channel of the multi-channel drill pipe 1, it rotates the screw in the system drive unit and then returns from the bottom through two side channels to the other annular channel of the multi-channel drill pipe 1.

[0117] The screw of the system drive unit rotates, and the mechanical structure of the power transmission unit transmits torque to the worm of the annular lift unit, driving the worm to rotate and generate fluid driving force. The annular drilling fluid located below the annular lift unit is drawn into the fluid intake port. The rotating worm transmits the mechanical power of the power transmission unit to the annular drilling fluid, pushing the annular drilling fluid upward and out the fluid outlet.

[0118] The downhole lifting power system 3 composed of the screw mechanism 342 and the worm mechanism 332 is only an example of combining the concept of the hydraulic lift multi-gradient drilling method with on-site needs. By adjusting the size of the screw or worm, changing the overall structure size, changing the structure shape, replacing the system drive device and the annulus lifting device type, other forms of structure can be obtained to achieve the same or similar hydraulic lift multi-gradient drilling function.

[0119] As shown in FIG11 , the annulus isolation system 4 used is an annulus isolation device made of wear-resistant plastic. The device is designed with a plastic baffle 42 that is approximately the same size as the wellbore and can be controlled by pressure. When the pressure is greater than the baffle extension pressure, the baffle extends to isolate the annulus; when the pressure is less than the baffle extension pressure, the baffle retracts to release the annulus isolation.

[0120] The device is installed between the fluid suction port and the discharge port at the bottom of the downhole lifting power system 3 to block the possible short-range circulation of the fluid between the suction port and the discharge port. Wear-resistant particles or coarse fibers and other materials are added to the wear-resistant plastic to improve the wear resistance of the material, which can maintain a certain sealing performance during the reciprocating friction between the downhole and the well wall.

[0121] The annular space isolation system 4 made of wear-resistant plastic is only an example of combining the concept of the hydraulic lift multi-gradient drilling method with site needs. By adopting other isolation materials, or by adjusting the size, changing the opening and closing methods, other forms of structures or materials can be obtained to achieve the same or similar hydraulic lift multi-gradient drilling functions.

[0122] In one embodiment, based on the aforementioned system configuration, multi-gradient drilling wellbore pressure control is performed, employing a three-stage downhole lift power system 3 for annular fluid lift. As shown in Figure 12, these three systems comprise a first-stage downhole lift power system 301, a second-stage downhole lift power system 302, and a third-stage downhole lift power system 303. After initiating multi-gradient drilling, if the various downhole lift systems have different lift performance, the wellbore annular pressure distribution will shift from the original OG line to an OF-ED-CB-AK line. Pressure mutation points E, C, and A can be connected by a broken line, resulting in an approximate four-gradient distribution of the wellbore annular equivalent pressure, namely, the OE, EC, CA, and AK lines.

[0123] In the process of starting up the first-level downhole lifting power system 301 to the third-level downhole lifting power system 303 in sequence, the bottom hole pressure decreases from point G to points I, J, and K in sequence. When one or all of the downhole lifting power systems are shut down, the bottom hole pressure increases accordingly and eventually returns to point G. This embodiment formed based on the method concept and system composition of the present invention can effectively achieve accurate control of the bottom hole pressure.

[0124] Based on the method concept and system composition of the present invention, various other implementation schemes can be flexibly formed in combination with on-site conditions and needs.

[0125] Wellbore annulus pressure is the basis for ensuring the mechanical balance between the wellbore and the formation, the core of safe drilling, and a major problem that has not been effectively solved for a long time. In particular, as oil and gas exploration continues to deepen into complex formations, the uncertainty and complexity of formation pressure are becoming increasingly prominent. A single annulus pressure gradient can no longer meet the safety construction requirements of complex working conditions such as the increasing number of spills and leaks. The present invention proposes a hydraulic lift multi-gradient drilling string, which is different from the dual-gradient drilling technology and can be applied to both land and marine environments. The present invention can achieve a multi-gradient distribution of wellbore annulus pressure and can simultaneously perform bidirectional pressure regulation of the wellbore annulus as a whole and locally. The pressure can be increased or decreased, providing a new safe operation method adapted to land conditions for drilling and completion in complex formations.

[0126] The hydraulic lift multi-gradient drilling string proposed in the present invention can quickly adjust the wellbore pressure under a multi-pressure system to achieve the reconciliation of preventing leakage and balancing high formation pressure; and has many advantages such as small space occupation, fast and stable pressure adjustment, and high integration with conventional drilling operations. It provides a more flexible drilling process concept for drilling in complex formations on land and at sea. General designers and R&D personnel in the oil and gas industry can, based on the method concept and system composition of the present invention, form a matching multi-gradient drilling technology according to actual field conditions, which can provide a feasible solution for on-site resolution of accidents such as well collapse, stuck drill, well kick, blowout, and co-existence of leakage and blowout in complex formations, and provide technical support for the safe and efficient development of oil and gas on land and at sea.

[0127] Option 2

[0128] The present invention provides a hydraulic lift multi-gradient drilling system, comprising a wellhead manifold system 6 and the aforementioned hydraulic lift multi-gradient drilling string. The wellhead manifold system 6 is connected to the power fluid inlet flow channel 12, the power fluid outlet flow channel 13, and the drilling fluid flow channel 11 in the hydraulic lift multi-gradient drilling string. The primary function of the wellhead manifold system 6 is to transport fluid, providing fluid pathways between various devices and systems in the hydraulic lift multi-gradient drilling string. This hydraulic lift multi-gradient drilling system shares the technical features and effects of the aforementioned hydraulic lift multi-gradient drilling string, which will not be further elaborated here.

[0129] Furthermore, the features of the wellhead manifold system 6 include: (1) the wellhead manifold system 6 can be connected to node equipment of the fluid flow system such as the fluid injection adapter system 2, the power fluid output device, the drilling mud pump 61, the wellhead device 54, the top drive 52, the drilling fluid solid phase control system 62, etc. to carry out fluid transportation; the wellhead manifold system 6 can withstand a certain fluid pressure and has good connection sealing under the condition of fluid pressure flow; (2) the wellhead manifold system 6 is mainly composed of soft and hard pipelines, manifold joints, manifold connectors and control valves. The wellhead manifold system 6 is installed with multiple control valves, which can open and close the manifold, control the fluid flow and provide emergency pressure relief under high pressure conditions; (3) the main body of the wellhead manifold system 6 is composed of multiple sections of hard pipelines and soft hoses connected to each other, and the manifold connection position is connected by the manifold joints and manifold connectors, which is easy to disassemble and install.

[0130] After the drilling fluid returns to the surface through the wellbore annulus, it eventually flows into the drilling fluid multi-stage solid phase control system and re-enters the circulation system after solid phase control treatment.

[0131] Fluid injection adapter system 2, multi-channel drill pipe 1, downhole lifting power system 3, annulus isolation system 4, data monitoring system 7, wellhead manifold system 6. The above components are additional adaptation parts under the conditions of existing conventional drilling well sites and equipment.

[0132] Option 3

[0133] The present invention provides a hydraulic lift multi-gradient drilling method that utilizes the aforementioned hydraulic lift multi-gradient drilling string and drilling system. A downhole lift power system 3 is driven by a power fluid and increases the pressure of the drilling fluid as it flows through the downhole lift power system 3. This hydraulic lift multi-gradient drilling method relies on downhole fluid lift to achieve multi-gradient regulation of the wellbore fluid pressure distribution. It also shares the technical features and effects of the aforementioned hydraulic lift multi-gradient drilling string, which will not be further elaborated here.

[0134] Furthermore, the hydraulic lift multi-gradient drilling string includes multiple downhole lift power systems 3, and the lifting performance of each downhole lift power system 3 is the same or different. At the pre-designed corresponding downhole position, one or more downhole lift power systems 3 are installed. The system is driven by hydraulic power. When the system is not started, the wellbore annulus pressure gradient is a single gradient, and the pressure distribution is a unilinear distribution, which is the same as the conventional drilling situation. When the system is started, the annulus fluid obtains additional driving force at the system, thereby returning to the ground under the action of assisting lifting. The wellbore annulus pressure distribution changes from the original unilinear distribution to a multilinear distribution with the downhole lift power system 3 as the dividing point. The wellbore annulus pressure gradient can be equivalent to a multi-level pressure gradient with the downhole lift power system 3 as the dividing point.

[0135] The equivalent pressure gradient distribution characteristics vary with the performance parameters of the downhole lifting power system 3. When the downhole lifting power systems 3 used have the same lift, the equivalent pressure distribution of each fluid segment above the bottommost downhole lifting power system 3 is a linear distribution with the same slope. When the downhole lifting power systems 3 used have different lifts, the equivalent pressure distribution of each fluid segment above the bottommost downhole lifting power system 3 is a multi-segment linear distribution with different slopes. The number of pressure gradients depends on the number of downhole lifting power systems 3 used. The more downhole lifting power systems 3 used, the more pressure gradients can be adjusted. The annulus isolation system 4 is installed in multiple stages to match the number of downhole lifting power systems 3.

[0136] Since the wellbore fluid flow energy originally provided by the surface drilling pump is partially shared by the downhole lifting power system 3, when the system is started, the bottomhole pressure and the drilling pump pressure both decrease, which not only reduces the risk of bottomhole pressure leakage, but also reduces the workload of the surface drilling pump.

[0137] The above description is only an illustrative embodiment of the present invention and is not intended to limit the scope of the present invention. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principle of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A hydraulic lift multi-gradient drilling string, wherein: include: A multi-channel drill pipe having a power fluid inflow channel, a power fluid outflow channel and a drilling fluid flow channel; a fluid injection adapter system mounted on the upper end of the multi-channel drill pipe; at least one downhole lifting power system; The downhole lifting power system is installed on the multi-channel drill pipe and is connected to the annulus; the power fluid injected by the fluid injection adapter system can flow into the downhole lifting power system through the power fluid inlet channel, and return to the fluid injection adapter system through the power fluid outflow channel after flowing through the downhole lifting power system, and the downhole lifting power system can be driven by the power fluid to increase the pressure of the drilling fluid when it flows through the downhole lifting power system.

2. The hydraulic lift multi-gradient drilling string according to claim 1, wherein: The downhole lifting power system comprises a system fluid suction port and a system fluid discharge port connected to the annulus. The drilling fluid in the annulus can be sucked into the downhole lifting power system through the system fluid suction port and discharged into the annulus through the system fluid discharge port.

3. The hydraulic lift multi-gradient drilling string according to claim 2, wherein: The hydraulic lift multi-gradient drilling string includes an annulus isolation system, which is installed outside the downhole lift power system and is used to isolate the annulus. The system fluid suction port and the system fluid discharge port are respectively arranged on the upper and lower sides of the annulus isolation system.

4. The hydraulic lift multi-gradient drilling string according to claim 3, wherein: The multi-channel drill pipe includes a plurality of drill pipe sections, and the downhole lifting power system is arranged between two adjacent drill pipe sections.

5. The hydraulic lift multi-gradient drilling string according to any one of claims 1 to 4, wherein: The multi-channel drill pipe comprises a central tube, a first curved plate and a second curved plate, and the drilling fluid flow channel is arranged in the central tube; The first curved plate and the second curved plate are both arranged outside the central tube, the power fluid inflow channel is constructed between the first curved plate and the central tube, and the power fluid inflow channel is constructed between the second curved plate and the central tube. The power fluid flows out of the flow passage.

6. The hydraulic lift multi-gradient drilling string according to claim 5, wherein: The first arc plate and the second arc plate are two parts of a tube body; the multi-channel drill pipe includes a partition plate for separating the power fluid inflow channel and the power fluid outflow channel.

7. The hydraulic lift multi-gradient drilling string according to any one of claims 1 to 4, wherein: The multi-channel drill pipe comprises a central tube, a middle tube and an outer tube, and the drilling fluid flow channel is arranged in the central tube; The power fluid outflow channel and the power fluid inflow channel are constructed between the middle tube and the central tube and between the middle tube and the outer tube.

8. The hydraulic lift multi-gradient drilling string according to claim 2, wherein: The downhole lifting power system includes a system driving device and an annular lifting device; The system fluid suction port and the system fluid discharge port are both arranged on the annular lifting device; The power fluid inflow channel and the power fluid outflow channel are both connected to the system driving device, and the system driving device can be driven by the power fluid to operate and drive the annulus lifting device to operate.

9. The hydraulic lift multi-gradient drilling string according to claim 8, wherein: The system drive device includes a first turbine mechanism.

10. The hydraulic lift multi-gradient drilling string according to claim 8 or 9, wherein: The annulus lift device includes a second turbine mechanism.

11. The hydraulic lift multi-gradient drilling string according to claim 8, wherein: The system driving device includes a screw mechanism.

12. The hydraulic lift multi-gradient drilling string according to claim 8 or 11, wherein: The annulus lifting device comprises a worm gear mechanism.

13. The hydraulic lift multi-gradient drilling string according to claim 8, wherein: The fluid injection adapter system is provided with a power fluid injection channel and a power fluid discharge channel. The power fluid injection channel is connected to the system drive device through the power fluid inflow channel. The power fluid discharge flow channel is communicated with the system drive device through the power fluid outflow flow channel.

14. The hydraulic lift multi-gradient drilling string according to claim 1, wherein: The hydraulic lift multi-gradient drilling string includes a data monitoring system, which includes a downhole measurement tool arranged in the downhole portion of the multi-channel drill pipe.

15. A hydraulic lift multi-gradient drilling system, wherein: include: Wellhead manifold system; The hydraulic lift multi-gradient drilling string according to any one of claims 1 to 14, wherein the wellhead manifold system is connected to the power fluid inlet flow channel, the power fluid outflow flow channel and the drilling fluid flow channel in the hydraulic lift multi-gradient drilling string.

16. A hydraulic lift multi-gradient drilling method, wherein: A hydraulic lift multi-gradient drilling string according to any one of claims 1 to 14; The downhole lifting power system is driven by the power fluid to operate, and is pressurized when the drilling fluid flows through the downhole lifting power system.

17. The hydraulic lift multi-gradient drilling method according to claim 16, wherein: The hydraulic lift multi-gradient drilling string includes a plurality of downhole lift power systems, and the lifting performances of the downhole lift power systems are the same or different.

Images