Hydraulically lifted multi- gradient drilling pipe string, drilling system and drilling method

Abstract

The application provides a hydraulic lifting multi-gradient drilling pipe column, a drilling system and a drilling method. The multi-gradient drilling pipe column comprises a multi-channel drill rod, a fluid injection adaptation system and a downhole lifting power system. The multi-channel drill rod has a power fluid inflow channel, a power fluid outflow channel and a drilling fluid channel. The fluid injection adaptation system is installed at the upper end of the multi-channel drill rod. The downhole lifting power system is installed on the multi-channel drill rod and is in communication with the annular space or the drilling fluid channel. The power fluid injected by the fluid injection adaptation system can flow into the downhole lifting power system through the power fluid inflow channel, and return to the fluid injection adaptation system through the power fluid outflow channel. The downhole lifting power system can be driven by the power fluid to operate and pressurize the drilling fluid, thereby solving the technical problems of difficult prediction of formation pressure, complex pressure system, high safety risk and long operation period in land and marine complex formation drilling operations.

Description

Technical Field

[0001] This invention relates to the technical field of oil and gas drilling and completion and natural gas hydrate drilling and production, and particularly to a hydraulic lift multi-gradient drilling string, drilling system and drilling method. Background Technology

[0002] As oil and gas exploration and development continue to deepen, drilling is increasingly moving towards new regions, depths, strata, and environments. The unknown and complex nature of the formations is further increasing, leading to greater challenges in wellbore safety control 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 encountered formations. Multiple pressure systems may exist within the same open-hole section, resulting in an extremely narrow safe density window. Similarly, in some offshore drilling operations, the weak cementation of seafloor formations also contributes to the problem of a narrow safe density window.

[0003] Under complex pressure systems, the coexistence of overflows and leaks is a frequent problem, which has become a bottleneck restricting the safe and efficient development of onshore and offshore oil and gas fields. When drilling encounters large fractures or karst caves, high-density drilling fluid is prone to causing severe leakage. When drilling encounters high-pressure gas or water layers, abnormal formation pressure is prone to causing overflows and well kicks. Severe overflows or improper handling of well leakage can lead to secondary and complex accidents such as well collapse, stuck pipe, well kicks, and blowouts, resulting in casualties and economic losses.

[0004] To address the challenges of wellbore safety control caused by complex formations, current research focuses on developing solutions such as bottom-hole constant pressure controlled drilling technology and dual-gradient drilling technology.

[0005] Existing bottom-hole constant pressure controlled 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 pressure of the wellbore fluid column and cannot be adjusted downwards based on it. A single annulus pressure gradient system may face a dilemma under complex formation conditions with multiple pressures.

[0006] Existing dual-gradient drilling technologies mainly include: low-density medium injection dual-gradient drilling, subsea pump lift dual-gradient drilling, and riserless mud level control dual-gradient drilling. Low-density medium injection dual-gradient drilling primarily involves injecting a low-density medium into the annulus and mixing it with conventional drilling fluid to reduce the fluid column pressure in certain well sections. This method is further divided into: hollow microsphere injection, gas injection, and low-density liquid injection. Subsea pump lift dual-gradient drilling mainly achieves the dual-gradient drilling effect by using a subsea pump to lift the returned mud, while simultaneously using a fluid with a density similar to seawater in the riser. Riserless mud level control dual-gradient drilling achieves closed-loop circulation of the drilling fluid and precise control of the bottom hole pressure by installing a subsea pump and adjusting the drilling fluid level inside the riser.

[0007] Existing dual-gradient drilling schemes are based on marine environments, occupy a large downhole space, and are basically unsuitable for onshore drilling environments. Furthermore, they can only adjust the wellbore pressure profile to achieve two gradients, resulting in low flexibility and difficulty in guaranteeing reliability.

[0008] Therefore, in drilling operations under complex geological conditions, existing technologies face technical bottlenecks and environmental and cost constraints, and there is an urgent need to develop new technologies and methods to support drilling operations to achieve faster drilling and reduce costs while increasing efficiency. Summary of the Invention

[0009] The purpose of this invention is to provide a hydraulic lift multi-gradient drilling string, drilling system and drilling method to solve the technical problems of unpredictable formation pressure, complex pressure system, high safety risk and long operation cycle in drilling operations in complex formations on land and at sea.

[0010] The above-mentioned objectives of the present invention can be achieved by the following technical solutions:

[0011] This invention provides a hydraulic lift multi-gradient drilling string, comprising:

[0012] Multi-channel drill pipe, which has a power fluid inlet channel, a power fluid outlet channel and a drilling fluid channel;

[0013] A fluid injection adapter system is installed at the upper end of the multi-channel drill pipe;

[0014] At least one downhole lifting power system;

[0015] The downhole lifting power system is installed on the multi-channel drill pipe and is connected to the annulus or the drilling fluid flow channel; the power fluid injected by the fluid injection adapter system can flow into the downhole lifting power system through the power fluid inflow channel, and after flowing through the downhole lifting power system, return to the fluid injection adapter system through the power fluid outflow channel; and the downhole lifting power system can be driven by the power fluid to pressurize the drilling fluid as it flows through the downhole lifting power system.

[0016] In a preferred embodiment, the downhole lifting power system includes a system fluid inlet and a system fluid outlet communicating with the annulus. The drilling fluid in the annulus can be drawn in by the downhole lifting power system through the system fluid inlet and discharged into the annulus through the system fluid outlet.

[0017] In a preferred embodiment, the hydraulic lift multi-gradient drilling string includes an annular isolation system, which is installed outside the downhole lift power system and is used to isolate the annulus. The system fluid inlet and the system fluid outlet are respectively located on the upper and lower sides of the annular isolation system.

[0018] In a preferred embodiment, the multi-channel drill pipe includes multiple drill pipe sections, and the downhole lifting power system is disposed between two adjacent drill pipe sections.

[0019] In a preferred embodiment, the multi-channel drill pipe includes a central tube, a first arc-shaped plate, and a second arc-shaped plate. The drilling fluid flow channel is disposed inside the central tube. Both the first arc-shaped plate and the second arc-shaped plate are disposed outside the central tube. The first arc-shaped plate and the central tube form the inflow channel for the power fluid, and the second arc-shaped plate and the central tube form the outflow channel for the power fluid.

[0020] In a preferred embodiment, the first arc-shaped plate and the second arc-shaped plate are two parts of a single tube; the multi-channel drill rod includes a partition for separating the power fluid inflow channel from the power fluid outflow channel.

[0021] In a preferred embodiment, the multi-channel drill pipe includes a central tube, a middle tube, and an outer tube, and the drilling fluid flow channel is disposed inside 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.

[0022] In a preferred embodiment, the downhole lifting power system includes a system drive device and an annular lifting device; the system fluid inlet and the system fluid outlet are both located in the annular lifting device; the power fluid inflow channel and the power fluid outflow channel are both connected to the system drive device, and the system drive device can be driven by the power fluid to operate and drive the annular lifting device to operate.

[0023] In a preferred embodiment, the system drive device includes a first turbine mechanism.

[0024] In a preferred embodiment, the annular lifting device includes a second turbine mechanism.

[0025] In a preferred embodiment, the system drive device includes a screw mechanism.

[0026] In a preferred embodiment, the annular lifting device includes a worm gear mechanism.

[0027] In a preferred embodiment, 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, and the power fluid discharge channel is connected to the system drive device through the power fluid outflow channel.

[0028] In a preferred embodiment, the hydraulic lift multi-gradient drilling string includes a data monitoring system, which includes downhole measurement tools disposed on the downhole portion of the multi-channel drill pipe.

[0029] The present invention provides a hydraulic lift multi-gradient drilling system, comprising: a wellhead manifold system; the aforementioned hydraulic lift multi-gradient drilling string, wherein the wellhead manifold system is connected to the power fluid inflow channel, power fluid outflow channel, drilling fluid channel and wellhead device in the hydraulic lift multi-gradient drilling string.

[0030] This invention provides a hydraulic lift multi-gradient drilling method, employing the aforementioned hydraulic lift multi-gradient drilling string; the downhole lift power system is driven by the power fluid and pressurizes the drilling fluid as it flows through the downhole lift power system.

[0031] In a preferred embodiment, the hydraulic lift multi-gradient drilling string includes multiple downhole lift power systems, and the lift performance of each downhole lift power system may be the same or different.

[0032] The features and advantages of this invention are:

[0033] The hydraulic lift multi-gradient drilling string, drilling system, and drilling method provided by this invention achieve multi-level adjustment of the pressure gradient of the drilling fluid returning during the drilling process through hydraulic lift. This solves the problem of simultaneous leakage and overflow caused by multiple formation pressure systems and narrow drilling fluid density windows encountered during oil and gas drilling. Under a multi-pressure system, wellbore pressure can be quickly adjusted to prevent leakage and balance high formation pressure. This invention has several advantages, including small footprint, rapid and stable pressure adjustment, and high integration with conventional drilling operations.

[0034] Moreover, the flow energy of the drilling fluid that was 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, both the bottom hole pressure and the drilling pump pressure decrease, which reduces the risk of bottom hole formation leakage and also reduces the workload of the surface drilling pump. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 A schematic diagram of the working state of an embodiment of the hydraulic lift multi-gradient drilling string provided by the present invention;

[0037] Figure 2 for Figure 1 The diagram shows the structure of the fluid injection adaptation system in a hydraulic lift multi-gradient drilling string.

[0038] Figure 3 for Figure 1 The diagram shows the structure of a multi-channel drill pipe in a hydraulic lift multi-gradient drilling string.

[0039] Figure 3A for Figure 3 A cross-section;

[0040] Figure 4 for Figure 1 The diagram shows the structure of the downhole lifting power system in a hydraulic lift multi-gradient drilling string.

[0041] Figure 5 for Figure 1 The diagram shows the working state of the annulus isolation system in a hydraulic lift multi-gradient drilling string.

[0042] Figure 6 for Figure 1The diagram shown is a multi-gradient drilling wellbore pressure distribution diagram for a hydraulic lift multi-gradient drilling string.

[0043] Figure 7 A schematic diagram of the working state of an embodiment of the hydraulic lift multi-gradient drilling string provided by the present invention;

[0044] Figure 8 for Figure 7 The diagram shows the structure of the fluid injection adaptation system in a hydraulic lift multi-gradient drilling string.

[0045] Figure 9 for Figure 7 The diagram shows the structure of a multi-channel drill pipe in a hydraulic lift multi-gradient drilling string.

[0046] Figure 9A for Figure 3 A cross-section;

[0047] Figure 10 for Figure 7 The diagram shows the structure of the downhole lifting power system in a hydraulic lift multi-gradient drilling string.

[0048] Figure 11 for Figure 7 The diagram shows the working state of the annulus isolation system in a hydraulic lift multi-gradient drilling string.

[0049] Figure 12 for Figure 7 The diagram shows the pressure distribution in a multi-gradient drilling wellbore using a hydraulic lift multi-gradient drilling string.

[0050] Explanation of icon numbers:

[0051] 1. Multi-channel drill pipe; 10. Drill pipe sections;

[0052] 11. Drilling fluid flow channel; 12. Power fluid inflow channel; 13. Power fluid outflow channel;

[0053] 14. Central tube;

[0054] 151. First curved plate; 152. Second curved plate; 153. Partition;

[0055] 161. Middle tube; 162. Outer tube;

[0056] 2. Fluid injection adapter system;

[0057] 21. Power fluid injection channel; 22. Power fluid discharge channel;

[0058] 23. Drilling fluid flow channels;

[0059] 24. Rotary flow channel inlet; 25. Central flow channel inlet;

[0060] 3. Downhole lifting power system; 301. First-stage downhole lifting power system; 302. Second-stage downhole lifting power system; 303. Third-stage downhole lifting power system;

[0061] 31. System fluid inlet; 32. System fluid outlet;

[0062] 33. Circular lifting device; 331. Second turbine mechanism; 332. Worm gear mechanism;

[0063] 34. System drive unit; 341. First turbine mechanism; 342. Screw mechanism;

[0064] 35. Power transmission device;

[0065] 4. Annular isolation system;

[0066] 41. Rubber stopper; 42. Plastic baffle;

[0067] 51. Square drill pipe; 52. Top drive; 53. Drill bit; 54. Wellhead assembly;

[0068] 6. Wellhead manifold system;

[0069] 61. Drilling mud pump; 62. Drilling fluid solids control system;

[0070] 63. Drilling the platform;

[0071] 7. Data monitoring system; 71. Downhole measurement tools. Detailed Implementation

[0072] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0073] Option 1

[0074] This invention provides a hydraulic lift multi-gradient drilling string, such as... Figures 1-12As shown, 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 lift power system 3. The multi-channel drill pipe 1 has a power fluid inflow 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 lift 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 lift power system 3 through the power fluid inflow channel 12, and after flowing through the downhole lift power system 3, it returns to the fluid injection adapter system 2 through the power fluid outflow channel 13. Furthermore, the downhole lift power system 3 can be driven by the power fluid to pressurize the drilling fluid as it flows through the downhole lift power system 3.

[0075] When the downhole lifting power system 3 is driven by the power fluid, the drilling fluid in the annulus or drilling fluid channel 11 receives additional driving force at the downhole lifting power system 3, thereby returning to the surface with the assistance of the lifting action. The pressure distribution of the returning drilling fluid changes from the original unilinear distribution to a multilinear distribution with the downhole lifting power system 3 as the dividing point. The pressure gradient of the returning drilling fluid can be equivalent to a multi-level pressure gradient with the downhole lifting power system 3 as the dividing point.

[0076] The hydraulic lift multi-gradient drilling string provided by this invention achieves multi-level adjustment of the pressure gradient of the drilling fluid returning during drilling through hydraulic lift; it can solve the problem of leakage and overflow caused by multiple formation pressure systems and narrow drilling fluid density windows encountered during oil and gas drilling. Under the multi-pressure system, it achieves the reconciliation of preventing leakage and balancing high formation pressure.

[0077] Moreover, the flow energy of the 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, both the bottom hole pressure and the drilling pump pressure decrease, which reduces the risk of bottom hole formation leakage and also reduces the workload of the surface drilling pump.

[0078] In conventional drilling, drilling fluid is injected into the drill string cavity from the surface, flows through the drill string cavity to the drill bit 53, and then flows out from the drill bit 53 flow channel, returning to the surface through the annulus formed by the drill string and the wellbore 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 then returns to the surface through the annulus. The downhole lifting power system 3 is connected to the annulus and can be driven by the power fluid to pressurize the drilling fluid in the annulus.

[0079] like Figure 4 and Figure 10As shown, the downhole lifting power system 3 includes a system fluid inlet 31 and a system fluid outlet 32. The system fluid inlet 31 and the system fluid outlet 32 ​​are respectively connected to the annulus. The drilling fluid in the annulus can be drawn into the downhole lifting power system 3 through the system fluid inlet 31 and discharged into the annulus through the system fluid outlet 32.

[0080] In some embodiments, the hydraulic lift multi-gradient drilling string includes an annular isolation system 4, which is installed outside the downhole lift power system 3 and is used to isolate the annulus. A system fluid inlet 31 and a system fluid outlet 32 ​​are respectively located on the upper and lower sides of the annular isolation system 4. The annular isolation system 4 installed at the downhole lift power system 3 achieves fluid isolation, preventing drilling fluid from being discharged from the system fluid outlet 32 ​​and then re-inhaled through the system fluid inlet 31, thus avoiding short-range circulation and preventing the short-range circulation of drilling fluid from affecting the lift efficiency. This improves the lifting performance and efficiency of the drilling fluid.

[0081] The annular packing system 4 may include a rubber plug 41 or a plastic baffle 42, which can cooperate with the wellbore or casing to block annular fluid.

[0082] In one embodiment, the annular sealing system 4 includes a rubber stopper 41, such as Figure 5 As shown, the rubber plug 41 is expandable and can be opened and closed by pressure. When the pressure is greater than the expansion pressure of the rubber plug 41, the rubber plug 41 expands and opens, sealing the annulus; when the pressure is less than the unsealing pressure of the rubber plug 41, the rubber plug contracts and closes, releasing the annulus seal. Preferably, the rubber plug 41 contains wear-resistant particles or coarse fibers to improve the wear resistance of the material and maintain a certain sealing performance during reciprocating friction with the well wall downhole.

[0083] In another embodiment, the annular containment system 4 includes a plastic baffle 42, such as Figure 11 As shown, the plastic baffle 42 can be controlled by pressure. When the pressure is greater than the baffle extension pressure, the baffle extends to seal the annulus; when the pressure is less than the baffle extension pressure, the baffle retracts to release the annulus seal. The plastic baffle 42 is a fixed shape, and its size is approximately the same as the well diameter. It can be made of rigid plastic. Preferably, the plastic baffle 42 contains wear-resistant particles or coarse fibers to improve its wear resistance, thus maintaining a certain sealing performance during reciprocating friction with the well wall downhole.

[0084] Furthermore, the annular sealing system 4 may include the following features: (1) The annular sealing system 4 comprises one or more fixed or expandable sealing components with a certain strength that can block annular fluid. The sealing components may be rubber plugs 41 or plastic baffles 42. The maximum sealing size of the sealing components is approximately the same as the wellbore diameter; (2) The sealing 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 annular sealing system 4 can be controlled by artificial ground intervention. The opening and closing of the sealing components can be controlled by mechanical or hydraulic methods. It can be closed in conventional drilling to avoid interfering with the flow of annular drilling fluid, and opened in multi-gradient drilling to block short-range circulation of annular fluid.

[0085] 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 lifting power system 3. The power fluid flows into the downhole lifting power system 3 through the power fluid inflow channel 12, and then enters the power fluid outflow channel 13 after passing through the downhole lifting power system 3.

[0086] In another embodiment, the multi-channel drill pipe 1 includes multiple drill pipe sections 10, and the downhole lifting power system 3 is disposed between two adjacent drill pipe sections 10, such as... Figure 1 , Figure 3 , Figure 7 and Figure 9 As shown, the drill pipe section 10 and the downhole lifting power system 3 are distributed longitudinally. The upper and lower ends of the downhole lifting power system 3 are connected to the drill pipe section 10, respectively. Each drill pipe section 10 is provided with a power fluid inflow channel 12, a power fluid outflow channel 13, and a drilling fluid flow channel 11. 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 inflow channels 12 of each drill pipe section 10 are connected through the corresponding flow channels in the downhole lifting power system 3. The power fluid outflow channels 13 of each drill pipe section 10 are also connected through the corresponding flow channels in the downhole lifting power system 3. The drilling fluid flow channels 11 of each drill pipe section 10 are also connected through the corresponding flow channels in the downhole lifting power system 3. For example, the downhole lifting power system 3 itself is designed with flow channels. After the power fluid drives one downhole lifting power system 3, it can continue to flow downwards through its own designed flow channels to the flow channels of the drill pipe section 10, and then enter the next downhole lifting power system 3, realizing the downward flow of the power fluid. When this multi-gradient drilling string has multiple downhole lifting power systems 3, such as Figure 1 and Figure 7 As shown, the drill pipe section 10 and the downhole lifting power system 3 can be arranged alternately along the longitudinal direction and connected end to end.

[0087] The structure of the multi-channel drill pipe 1 is not limited to one type.

[0088] In one embodiment, the multi-channel drill pipe 1 includes a central tube 14, a first arc-shaped plate 151, and a second arc-shaped plate 152, as shown below. Figure 3 and Figure 3A As shown, the drilling fluid flow channel 11 is disposed inside the central tube 14; the first arc-shaped plate 151 and the second arc-shaped plate 152 are both disposed outside the central tube 14. A power fluid inflow channel 12 is constructed between the first arc-shaped plate 151 and the central tube 14, and a power fluid outflow channel 13 is constructed between the second arc-shaped plate 152 and the central tube 14. In another embodiment, a power fluid inflow channel 12 is constructed between the second arc-shaped plate 152 and the central tube 14, and a power fluid outflow channel 13 is constructed between the first arc-shaped plate 151 and the central tube 14. When the multi-channel drill pipe 1 includes multiple drill pipe sections 10, each drill pipe section 10 is respectively provided with a cooperating central tube 14, a first arc-shaped plate 151, and a second arc-shaped plate 152.

[0089] Furthermore, the first arc-shaped plate 151 and the second arc-shaped plate 152 are two parts of a single tube; 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... Figure 3A As shown, the first arc plate 151 and the second arc plate 152 are integral, and the first arc plate 151 and the second arc plate 152 are combined into a circular tube. The partition plate 153 is disposed between the circular tube and the central tube 14 to separate the independent power fluid inflow channel 12 and power fluid outflow channel 13.

[0090] In another embodiment, the 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, a power fluid outflow channel 13 is constructed between the middle tube 161 and the central tube 14, and a power fluid inflow channel 12 is constructed between the middle tube 161 and the outer tube 162; or, as... Figure 9 and Figure 9A As shown, a power fluid inflow channel 12 is constructed between the middle pipe 161 and the central pipe 14, and a power fluid outflow channel 13 is constructed between the middle pipe 161 and the outer pipe 162.

[0091] The main function of the multi-channel drill pipe 1 is to achieve the separation of power fluid and drilling fluid flow, providing independent flow channels for power fluid and drilling fluid respectively, and avoiding the mixing of the two fluid systems.

[0092] The features of the multi-channel drill pipe 1 may include:

[0093] (1) The multi-channel drill pipe 1 has three or more flow channels. The power fluid inflow channel 12, the power fluid outflow 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 the downhole closed circulation through the inflow and outflow channels and does not mix with the drilling fluid.

[0094] (2) The drill pipe sections 10 can be connected to each other by threads or joints, and can be connected to the top drive 52 device or square drill pipe 51 at the wellhead by the fluid injection adapter system 2.

[0095] (3) The drill pipe section 10 can be connected to the downhole lifting power system 3 downhole. The power fluid flows into the downhole lifting power system 3 through the power fluid inflow channel 12, drives the downhole lifting power system 3, and then flows into the power fluid outflow channel 13.

[0096] In one embodiment, the downhole lifting power system 3 includes a system drive device 34 and an annular lifting device 33; the system fluid inlet 31 and the system fluid outlet 32 ​​are both located in the annular lifting device 33; the power fluid inflow channel 12 and the power fluid outflow channel 13 are both connected to the system drive device 34, and the system drive device 34 can be driven by the power fluid to operate and drive the annular lifting device 33 to operate.

[0097] The structural forms of the system drive unit 34 and the annular lifting device 33 are not limited to one type. For example, the system drive unit 34 can be a first turbine mechanism 341 or a screw mechanism 342, and the annular lifting device 33 can be a second turbine mechanism 331 or a worm gear mechanism 332.

[0098] In one embodiment, the system drive unit 34 includes a first turbine mechanism 341. For example... Figure 4 As shown, the annular lifting device 33 includes a second turbine mechanism 331, and the first turbine mechanism 341 and the second turbine mechanism 331 constitute a downhole lifting pump.

[0099] In another embodiment, the system drive unit 34 includes a screw mechanism 342. For example... Figure 10 As shown, the annular lifting device 33 includes a worm gear mechanism 332, and the screw mechanism 342 and the worm gear mechanism 332 constitute a downhole lifting pump.

[0100] The downhole lifting power system 3 provides lifting power to the annular drilling fluid. Driven by hydraulics, it can convert fluid energy into mechanical energy, propelling the annular fluid flow and further converting it into annular fluid kinetic energy. When the system drive unit 34 is operating, it can drive the annular lifting device 33 through the power transmission device 35.

[0101] Furthermore, the features of the downhole lifting power system 3 may include:

[0102] (1) The downhole lifting power system 3 also includes a system housing and sealing components. The system housing is the protective shell of the system. Its main functions are to provide installation space for other components, withstand the pressure of fluids inside and outside the system, prevent other components of the system from being damaged by impact, and provide the flow channel inlet and outlet for the system drive device and the annular lifting device. The sealing components mainly function 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 the system housing and the annular lifting device, maintain fluid pressure, and prevent leakage of power fluid and drilling fluid.

[0103] (2) The main function of the system drive device is to receive the power fluid energy to drive it. The power fluid flows into the system drive device from the power fluid flow channel of the multi-channel drill pipe 1, drives it to operate, and converts the fluid kinetic energy into the mechanical energy of the system drive device.

[0104] (3) The main function of the annular lifting device is to convert the mechanical energy of the system into the kinetic energy of the annular fluid. When it is in operation, the annular fluid is drawn into the annular lifting device through the system fluid inlet 31, and after gaining additional velocity and pressure, it is discharged through the system fluid outlet 32, thereby achieving the effect of lifting the annular drilling fluid.

[0105] (4) The main function of the power transmission device 35 is to connect the system drive device and the ring lift device, and to transmit the mechanical energy of the system drive device after hydraulic drive to the ring lift device through the transmission structure, so that the ring lift device can operate. The power transmission device 35 may include a transmission rod or transmission sleeve, etc. The system drive device and the ring lift device are connected by the power transmission device 35 to realize the transmission of system mechanical energy;

[0106] (5) Both ends of the downhole lifting power system 3 can be connected to the ordinary drill pipe or the multi-channel drill pipe 1 through conversion joints, and its drilling fluid flow channel 11 can be connected to the drilling fluid flow channel of the ordinary drill pipe or the multi-channel drill pipe 1.

[0107] (6) The downhole lifting power system 3 can be installed in multiple stages at different well depths. The working effects of different downhole lifting power systems 3 can be superimposed to achieve the functions of multi-stage lifting and multi-gradient drilling.

[0108] 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 through the power fluid inflow channel 12, and the power fluid discharge channel 22 is connected to the system drive device 34 through the power fluid outflow channel 13. For example, the fluid injection adapter system 2 is provided with a rotary injection channel, a rotary discharge channel, and a dynamic seal, and has inner and outer shells. During injection, the outer shell does not rotate, while the inner shell rotates with the drill string.

[0109] The power fluid injection channel 21 and the power fluid discharge channel 22 are each provided with a rotating channel port 24, such as Figure 2 and Figure 8 As shown, one rotary flow channel 24 serves as the power fluid injection port, and the other rotary flow channel 24 serves as the power fluid discharge port. Both ports can connect internally to the annular flow channel of the multi-channel drill pipe 1, and externally to the wellhead manifold system 6 to facilitate the inflow and outflow of power fluid. This fluid injection adapter system 2 can employ a dynamic seal pressure-bearing design, maintaining drill string rotation during drilling. Power fluid is injected through the rotary flow channel 24, enters the multi-channel drill pipe 1, and finally circulates back through the multi-channel drill pipe 1 to be discharged through the other rotary flow channel 24. The two rotary flow channels 24 can be arranged opposite each other or on opposite sides.

[0110] The fluid injection adapter system 2 is also provided with a central flow port 25 as the inlet of the drilling fluid circulation channel. The drilling fluid can flow into the central flow port 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; or, the drilling fluid can flow into the central flow port 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.

[0111] The fluid injection adapter system 2 has good sealing performance and can be installed at the top drive 52 position, above the drill platform 63, and its height can change with the rise and fall of the top drive 52. Alternatively, the fluid injection adapter system 2 can be installed at the wellhead position, below the drill platform 63, and its height can change with the tripping and pulling of the kelly 51. The fluid injection adapter system 2 can be positioned between the top drive 52 and the multi-channel drill pipe 1. During drilling, it gradually moves downwards with the top drive 52 as drilling progresses, and it moves upwards with the top drive 52 during tripping.

[0112] The fluid injection adapter system 2 separates the power fluid and drilling fluid, providing independent injection channels for the two fluid systems. It can also achieve continuous closed-loop circulation of power fluid and drilling fluid in common drilling conditions such as rotation, tripping, and stopping of ordinary drill pipe or the aforementioned multi-channel drill pipe 1.

[0113] Furthermore, the fluid injection adapter system 2 may include the following features:

[0114] (1) The fluid injection adapter system 2 includes a system housing and a rotating core component. 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 discharge port can be matched with the flow channel of the rotating core component. The rotating core component 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.

[0115] (2) A bearing assembly is installed at the end of the rotating core assembly. The bearing assembly can limit the vertical movement range of the rotating core assembly while maintaining its relative rotation function with respect to the system housing.

[0116] (3) The fluid injection adapter system 2 also includes a high-pressure sealing assembly, which mainly includes bearing seals and flow channel seals, used to maintain bearing sealing and flow sealing of power fluid and drilling fluid during operation.

[0117] (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 square drill pipe 51, and the other end can be connected to the ordinary drill pipe or the multi-channel drill pipe 1 through the conversion connector.

[0118] (5) The drilling fluid flow channel 23 of the fluid injection adaptation system 2 can provide connection 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 drilling fluid; the injection port, injection channel, discharge port and discharge channel of the power fluid can maintain the continuous injection and discharge of the power fluid.

[0119] In one embodiment, the hydraulic lift multi-gradient drilling string includes a data monitoring system 7, which includes a downhole measuring tool 71 installed on the downhole portion of the multi-channel drill pipe 1 to monitor and record downhole parameters, obtain accurate bottom hole pressure, temperature and other parameters, provide evaluation of the construction operation effect, and guide the adjustment of surface construction parameters.

[0120] Furthermore, the data monitoring system 7 includes a surface component, mainly composed of pressure sensors, flow meters, temperature sensors, and a control computer. This component monitors and records surface construction parameters, including the injection flow rate, injection pressure, injection temperature, discharge flow rate, discharge pressure, discharge temperature, and wellhead back pressure of the power fluid and drilling fluid. The surface component monitors and records these parameters, providing a foundation for software module calculations, real-time data optimization, and operational condition analysis.

[0121] The wellhead device 54, installed on the upper end of the multi-channel drill pipe 1, communicates with the annulus outside the multi-channel drill pipe 1, allowing drilling fluid to circulate through the multi-channel drill pipe 1 and the wellhead device 54. Specifically, the surface portion 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 rate, pressure, and temperature. The downhole measuring tool 71, as the downhole portion of the data monitoring system 7, primarily monitors and records downhole parameters including downhole pressure and temperature. This downhole portion connects to the conventional drill pipe or the multi-channel drill pipe 1 to measure downhole pressure and temperature. The data monitoring system 7 can interact with a control computer, transmitting monitored and recorded data to the computer for storage and processing.

[0122] To avoid mixing of the power fluid driving the downhole lifting power system 3 with the drilling fluid, thus eliminating fluid contamination and pressure interference problems, and reducing the burden on surface equipment, some embodiments of the hydraulic lift multi-gradient drilling string provided by this invention achieve multi-gradient drilling by separating the power fluid from the drilling fluid. The drilling fluid is the working fluid used in conventional drilling operations to balance formation pressure and carry cuttings, while the power fluid is the fluid system that drives the downhole lifting power system 3.

[0123] The power fluid and drilling fluid have independent fluid systems. The drilling fluid is configured according to the actual drilling requirements on site, while the power fluid can use the same or different fluid system 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 their own independent surface manifolds, and their independent circulation during drilling is achieved by the fluid injection adaptation system 2. The fluid injection adaptation system 2 can maintain various operating modes during drilling, such as drill string rotation, raising and lowering, and pressurized circulation.

[0124] After being injected into the wellbore via the fluid injection adaptation system 2, the power fluid and drilling fluid enter the multi-channel drill pipe 1. The multi-channel drill pipe 1 provides independent flow channels for the two fluids, allowing them to flow independently without interference. Specifically, the power fluid flows through the multi-channel drill pipe 1 to the downhole lifting power system 3. Under the action of the internal components of this system, the kinetic energy of the power fluid is first converted into mechanical energy to drive the operation of the downhole lifting power system 3.

[0125] Drilling fluid flows through the multi-channel drill pipe 1 or a regular drill pipe to the drill bit 53, where it enters the annulus through the water inlet or nozzle, carrying cuttings upwards along the annulus. After the downhole lifting power system 3 starts operating, the annulus drilling fluid enters the suction port of the downhole lifting power system 3 during its upward return. The mechanical energy of the internal components of the downhole lifting power system 3 is converted into the kinetic energy of the annulus drilling fluid. After gaining additional kinetic energy, the annulus drilling fluid flows out from the discharge port of the downhole lifting power system 3. Simultaneously, an annulus isolation system 4 is installed at the downhole lifting power system 3 to achieve fluid isolation, preventing the drilling fluid flowing out of the system fluid discharge port 32 of the downhole lifting power system 3 from being re-inhaled, thus avoiding short-range circulation of the annulus drilling fluid and affecting the lifting efficiency.

[0126] The downhole lifting power system 3 can be installed in multiple stages at different designed well depths, driven uniformly by a power fluid, to lift the annular drilling fluid in multiple stages, achieving multi-gradient pressure changes. Multiple downhole lifting power systems 3 can be connected in series or parallel. In series, the power fluid flows through one downhole lifting power system 3 and drives its system drive device 34 before continuing downwards into the next downhole lifting power system 3. In parallel, a portion of the power fluid flows through one downhole lifting power system 3 and drives its system drive device 34; another portion flows only through that downhole lifting power system 3 (through an independent flow channel) but does not drive its system drive device 34, flowing downwards into the next downhole lifting power system 3.

[0127] After the power fluid drives the downhole lifting power system 3, it returns to the surface through the multi-channel drill pipe 1 and flows out from the fluid injection adapter system 2 into the wellhead manifold. The annular drilling fluid, after being lifted by the downhole lifting power system 3, also returns to the surface through the multi-channel drill pipe 1 and flows into the drilling fluid treatment system through the wellhead manifold system 6, achieving drilling fluid circulation. The treated power fluid and drilling fluid can repeat the above process to achieve fluid circulation and maintain continuous operation of hydraulic lift multi-gradient drilling.

[0128] To enhance the exploration and development of onshore and offshore oil and gas resources, fill the gaps in current wellbore pressure control technology, and overcome the limitations imposed by existing technologies and equipment on complex downhole conditions, particularly during sudden leakage due to the constraints of drilling fluid hydrostatic pressure, it is necessary to fully consider the actual conditions of drilling in complex formations and well control safety. Addressing the high safety risks and difficulties in handling complex onshore and offshore formation drilling, this invention provides at least a partial implementation of a hydraulic lift multi-gradient drilling string. Through hydraulic lift, it achieves multi-level, bidirectional adjustment of the overall and local pressure gradients in the wellbore, based on hydrostatic pressure. This solves the problem of simultaneous leakage and overflow caused by multiple formation pressure systems and narrow drilling fluid density windows encountered during oil and gas drilling. Under multi-pressure systems, it achieves a balance between preventing leakage and balancing high formation pressure. This invention is applicable to pressure control in both onshore and offshore complex formation drilling, enabling safe and efficient drilling under complex geological conditions.

[0129] For ease of understanding, Figures 1-5 A specific embodiment is shown.

[0130] like Figure 1As shown, in an oil well operation using a top drive 52, a suitable hydraulic lift multi-gradient drilling string is employed. This drilling string comprises a fluid injection adapter system 2 installed at the top drive 52, a multi-channel drill pipe 1 with three channels, a downhole lift power system 3 composed of a turbine, and an annular seal system 4 made of wear-resistant rubber. The fluid injection adapter system 2 works in conjunction with the top drive 52, the multi-channel drill pipe 1 is connected to the fluid injection adapter system 2, and the three-stage downhole lift power system 3 is connected to the multi-channel drill pipe 1. The annular seal system 4 is installed in conjunction with the downhole lift power system 3. The inflow and outflow of both the power fluid and drilling fluid are controlled by the wellhead manifold system 6. The wellhead manifold system 6 is connected to the wellhead device 54, drilling mud pump 61, top drive 52, fluid injection adapter system 2, and drilling fluid solids control system 62, among other drilling equipment systems through which fluids flow.

[0131] like Figure 2 As shown, the fluid injection adapter system 2 is a well-sealed mechanical device installed at the top drive 52 position, located above the drill platform 63. This device has two rotary flow ports 24 and one central flow port 25. The central flow port 25 is the inlet for the drilling fluid circulation channel, allowing drilling fluid to flow in from the upper top drive 52 and into the well via the inner cavity of the multi-channel drill pipe 1 connected below. The rotary flow ports 24 are located on the side of the fluid injection adapter system 2, arranged opposite each other. One serves as the power fluid injection port, and the other as the power fluid discharge port. Both flow ports can connect inward to the annular flow channel of the multi-channel drill pipe 1, and outward to the wellhead manifold system 6 to achieve the inflow and outflow of power fluid.

[0132] The fluid injection adapter system 2 adopts a dynamic seal pressure-bearing design, which can keep the drill string rotating during drilling. The power fluid is injected through the rotating flow port 24 and enters the multi-channel drill pipe 1. After the final circulation, it returns from the multi-channel drill pipe 1 to another rotating flow port 24 for discharge. The fluid injection adapter system 2 can change height as the top drive 52 rises and falls.

[0133] The fluid injection adapter system 2 installed at the top drive 52 position is only one example of the hydraulic lift multi-gradient drilling method concept combined with field needs. By changing the flow channel shape, increasing the flow channel inlet, or adjusting the flow channel angle, other similar structures can be obtained to achieve the same or similar hydraulic lift multi-gradient drilling functions.

[0134] like Figure 3 and Figure 3AAs shown, the multi-channel drill pipe 1 used is a downhole circulation multi-channel drill pipe 1 with three channels. The difference between this 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 annulus on the left and right, thus having three independent flow channels. The two flow channels of the annulus serve as the inflow and outflow channels for the power fluid, respectively. After the power fluid is injected into one arc-shaped annulus, it passes through the downhole lifting power system 3 and then returns through the other arc-shaped annulus. 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, ensuring that the drilling fluid flows to the drill bit 53 and is discharged through the water hole of the drill bit 53.

[0135] The multi-channel drill pipe 1 with three channels is only one example of the hydraulic lift multi-gradient drilling method concept combined with field 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.

[0136] like Figure 4 As shown, the downhole lifting power system 3 is a downhole lifting pump composed of two turbines, possessing a certain degree of pressure-bearing and sealing performance. Both the system drive unit and the annular lifting device are composed of turbines, connected to each other via a mechanical power transmission device 35. The flow channels and cavities of the two components are independent, preventing exchange between the power fluid and drilling fluid. Fluid outlets and inlets are distributed at equal intervals at a certain angle on the upper and lower parts of the annular lifting device, providing lifting channels for the drilling fluid. During operation, the drilling fluid flows in from the inner cavity of the upper drill pipe, through the inner cavity of the downhole lifting power system 3, and towards the bottom hole drill bit 53. The power fluid is injected into the pump body through the arc-shaped annulus on one side of the multi-channel drill pipe 1, driving the turbine located in the system drive unit to rotate, and then returns through the bottom flow channel to the arc-shaped annulus on the other side of the multi-channel drill pipe 1.

[0137] The turbine of the system drive unit rotates, and the torque is transmitted to the turbine of the annular lifting device through the mechanical structure of the power transmission device 35, driving the turbine blades to rotate and generating fluid driving force. The annular drilling fluid located at the bottom of the annular lifting device is drawn in by the fluid inlet, and 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 discharging it from the fluid outlet.

[0138] The downhole lifting power system 3, which consists of turbines, is only one example of the hydraulic lifting multi-gradient drilling method concept combined with field needs. Other forms of structures can be obtained to achieve the same or similar hydraulic lifting multi-gradient drilling functions by adjusting the turbine size and number of stages, changing the overall structural size, changing the structural shape, and changing the system drive device and annular lifting device type.

[0139] like Figure 5As shown, the annular packing system 4 is an expandable annular packing device made of wear-resistant rubber. This device is designed with a pressure-driven rubber plug 41 that can be opened and closed. When the pressure is greater than the expansion pressure of the rubber plug 41, the rubber plug 41 expands and opens, sealing the annulus; when the pressure is less than the release pressure of the rubber plug 41, the rubber contracts and closes, releasing the annular packing. This device is installed between the fluid inlet and outlet at the bottom of the downhole lifting power system 3, blocking possible short-range fluid circulation between the inlet and outlet. The wear-resistant rubber contains wear-resistant particles or coarse fibers to improve its wear resistance, maintaining a certain sealing performance during reciprocating friction with the wellbore.

[0140] The annular packer system 4, made of wear-resistant rubber, is only one example of the hydraulic lift multi-gradient drilling method concept combined with field needs. By using other packer materials, or by adjusting the size, changing the opening and closing method, other forms of structures or materials can be obtained to achieve the same or similar hydraulic lift multi-gradient drilling functions.

[0141] In one embodiment, based on the above system composition, multi-gradient drilling wellbore pressure control is performed, and a three-stage downhole lifting power system 3 is used for annular fluid lifting, such as... Figure 6 As shown, the three stages are the first-stage downhole lifting power system 301, the second-stage downhole lifting power system 302, and the third-stage downhole lifting power system 303. After multi-gradient drilling is initiated, if the actual lifting performance of each stage of the downhole lifting system is the same, the annular pressure distribution in the wellbore will change from the original OG line to the OF-ED-CB-AK line. The pressure abrupt change points E, C, and A can be connected by straight lines, so the equivalent pressure in the annular space can be approximated as a dual-gradient distribution, namely the OA-AK line. During the sequential activation of the first-stage downhole lifting power system 301 to the third-stage downhole lifting power system 303, the bottom hole pressure decreases sequentially from point G to points I, J, and K. 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, based on the methodological concept and system composition of this invention, can effectively achieve accurate control of the bottom hole pressure.

[0142] Figures 7-11 Another specific embodiment is shown.

[0143] like Figure 7As shown, in the construction operation of an oil well using rotary table drilling, a specific hydraulic lift multi-gradient drilling method and system are adopted. The system consists of a fluid injection adapter system 2 installed at the wellhead, a multi-channel drill pipe 1 with double annulus, a downhole lifting power system 3 composed of a screw mechanism 342 and a worm gear mechanism 332, and an annulus sealing system 4 made of wear-resistant plastic. The fluid injection adapter system 2 works in conjunction with the wellhead device 54 and the crisscross drill pipe 51. The multi-channel drill pipe 1 is connected to the fluid injection adapter system 2. A three-stage downhole lifting power system 3 is used, which is connected to the multi-channel drill pipe 1. An annular isolation system 4 is installed in conjunction with the downhole lifting power system 3. The inflow and outflow of power fluid and drilling fluid are controlled by the wellhead manifold system 6. The wellhead manifold system 6 is connected to the drilling equipment system through which the fluid flows, including the wellhead device 54, drilling mud pump 61, crisscross drill pipe 51, fluid injection adapter system 2, and drilling fluid solid phase control system 62.

[0144] like Figure 8 As shown, the fluid injection adapter system 2 is a wellhead-mounted, well-sealed mechanical device located below the drill platform 63. This device has two rotary flow ports 24 and one central flow port 25. The central flow port 25 serves as the inlet for the drilling fluid circulation channel, allowing drilling fluid to flow in from the inner cavity of the upper square drill pipe 51 and then into the well via the inner cavity of the multi-channel drill pipe 1 connected below. The rotary flow ports 24 are located at the bottom of the fluid injection adapter system 2, arranged on both sides. One serves as the power fluid injection port, and the other as the power fluid discharge port. Both flow ports can connect inward to the annular flow channel of the multi-channel drill pipe 1 and outward to the wellhead manifold system 6 to facilitate the inflow and outflow of power fluid.

[0145] The fluid injection adapter system 2 adopts a dynamic sealing pressure-bearing design, which can keep the drill string rotating during drilling. The power fluid is injected through the rotating flow port 24 and enters the multi-channel drill pipe 1. After the final circulation, it returns from the multi-channel drill pipe 1 to another rotating flow port 24 for discharge. The fluid injection adapter system 2 can change height as the angular drill pipe 51 is pulled in and out of the hole.

[0146] The fluid injection adapter system 2 installed at the wellhead is only one example of the hydraulic lift multi-gradient drilling method concept combined with field needs. Other forms of structures can be obtained by changing the flow channel shape, adding flow channel inlets, or adjusting the flow channel angle to achieve the same or similar hydraulic lift multi-gradient drilling functions.

[0147] like Figure 9 and Figure 9AAs shown, the multi-channel drill pipe 1 is a downhole circulation drill pipe with double annulus. This multi-channel drill pipe 1 is a specially designed three-walled 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 inflow and outflow channels for the power fluid, respectively. The power fluid is injected into one annular flow channel, passes through the downhole lifting power system 3, and then returns through the other 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 water hole of the drill bit 53.

[0148] The multi-channel drill pipe 1 with double annulus is only one example of the concept of hydraulic lift multi-gradient drilling combined with field needs. Other forms of structure can be obtained by increasing the number of annulus, adjusting the flow channel cross-section, or adjusting the size of the multi-channel drill pipe 1 to achieve the same or similar hydraulic lift multi-gradient drilling function.

[0149] like Figure 10 As shown, the downhole lifting power system 3 is a downhole lifting pump composed of a screw mechanism 342 and a worm gear mechanism 332, possessing a certain degree of pressure-bearing and sealing performance. The system drive unit is composed of the screw mechanism 342, and the annular lifting device is composed of the worm gear mechanism 332. They are connected to each other through a mechanical power transmission device. The flow channels and cavities of the two components are independent, preventing exchange between the power fluid and drilling fluid. Fluid outlets and inlets are distributed at equal intervals at a certain angle on the upper and lower parts of the annular lifting device, providing lifting channels for the drilling fluid. During operation, the drilling fluid flows in from the inner cavity of the upper multi-channel drill pipe 1, flows through the inner cavity of the downhole lifting power system 3 to the bottom hole drill bit 53. The power fluid is injected into the pump body through one layer of the annular flow channel of the multi-channel drill pipe 1, driving the screw located in the system drive unit to rotate, and then returns from the bottom through the two side flow channels to the other layer of the annular flow channel of the multi-channel drill pipe 1.

[0150] After the screw of the system drive unit rotates, the torque is transmitted to the worm gear of the annular lifting device through the mechanical structure of the power transmission device, driving the worm gear to rotate and generating fluid driving force. The annular drilling fluid located at the bottom of the annular lifting device is drawn in by the fluid inlet, and the rotating worm gear transmits the mechanical power of the power transmission device to the annular drilling fluid, pushing the annular drilling fluid upward and discharging it from the fluid outlet.

[0151] The downhole lifting power system 3, consisting of screw mechanism 342 and worm mechanism 332, is only one example of the hydraulic lifting multi-gradient drilling method concept combined with field needs. Other forms of structures can be obtained to achieve the same or similar hydraulic lifting multi-gradient drilling functions by adjusting the screw or worm size, changing the overall structural size, changing the structural shape, and changing the system drive device and annular lifting device type.

[0152] like Figure 11 As shown, the annular packing system 4 is an annular packing device made of wear-resistant plastic. The device is designed with a plastic baffle 42 that is approximately the diameter of the wellbore and can be controlled by pressure. When the pressure is greater than the baffle extension pressure, the baffle extends to pack the annulus; when the pressure is less than the baffle extension pressure, the baffle retracts to release the annular packing.

[0153] The device is installed between the fluid inlet and outlet at the bottom of the downhole lifting power system 3 to block short-range fluid circulation that may occur between the inlet and outlet. Wear-resistant plastic is made of wear-resistant particles or coarse fibers to improve the wear resistance of the material, and can maintain a certain sealing performance during the reciprocating friction between the downhole and the well wall.

[0154] The annular packing system 4, made of wear-resistant plastic, is only one example of the hydraulic lift multi-gradient drilling method concept combined with field needs. Other forms of structures or materials can be obtained by using other packing materials, or by adjusting the size, changing the opening and closing method, etc., to achieve the same or similar hydraulic lift multi-gradient drilling functions.

[0155] In one embodiment, based on the above system composition, multi-gradient drilling wellbore pressure control is performed, and a three-stage downhole lifting power system 3 is used for annular fluid lifting, such as... Figure 12 As shown, these represent the first-stage downhole lifting power system 301, the second-stage downhole lifting power system 302, and the third-stage downhole lifting power system 303. After initiating multi-gradient drilling, if each stage of the downhole lifting system has different lifting performance, the annular pressure distribution in the wellbore will change from the original OG line to the OF-ED-CB-AK line. The pressure abrupt change points E, C, and A can be connected by a broken line, therefore, the equivalent pressure in the wellbore annulus can be approximately formed into a four-gradient distribution, namely the OE, EC, CA, and AK lines.

[0156] During the process of sequentially starting the first-stage downhole lifting power system 301 to the third-stage downhole lifting power system 303, the bottom hole pressure decreases sequentially from point G to points I, J, and K. 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. Based on the method concept and system composition of this invention, this embodiment can effectively achieve accurate control of the bottom hole pressure.

[0157] Based on the methodological concept and system composition of this invention, various other implementation schemes can be flexibly formed by combining on-site conditions and requirements.

[0158] Annular pressure is fundamental to ensuring the mechanical balance between the wellbore and the formation, is the core of safe drilling, and has long been a major challenge that has not been effectively resolved. Especially as oil and gas exploration delves deeper into complex formations, the uncertainty and complexity of formation pressure become increasingly prominent. A single annular pressure gradient is no longer sufficient to meet the safety requirements of complex operating conditions such as the increasing coexistence of overflows and leaks. This invention proposes a hydraulic lift multi-gradient drilling string, distinct from dual-gradient drilling technology, and applicable to both onshore and offshore environments. This invention enables multi-gradient distribution of annular pressure in the wellbore, and allows for bidirectional pressure regulation of the annular system, both overall and locally. The pressure can be increased or decreased, providing a new and safe operating method adapted to onshore conditions for drilling and completion in complex formations.

[0159] The hydraulic lift multi-gradient drilling string proposed in this invention can rapidly regulate wellbore pressure under a multi-pressure system, achieving a balance between preventing leakage and balancing high formation pressure. It also boasts advantages such as small footprint, rapid and stable pressure regulation, and high integration with conventional drilling operations. This provides a more flexible drilling technology concept for drilling in complex onshore and offshore formations. General designers and R&D personnel in the oil and gas industry can use the methodological concept and system composition based on this invention to develop matching multi-gradient drilling technologies according to actual field conditions. This can provide feasible solutions for resolving accidents such as well collapse, stuck pipe, well kick, blowout, and simultaneous leakage and blowout in complex formations, providing technical support for the safe and efficient development of onshore and offshore oil and gas.

[0160] Option 2

[0161] This 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 inflow channel 12, the power fluid outflow channel 13, and the drilling fluid flow channel 11 within the hydraulic lift multi-gradient drilling string. The main function of the wellhead manifold system 6 is to transport fluid, providing fluid channels between the various devices and systems within the hydraulic lift multi-gradient drilling string. This hydraulic lift multi-gradient drilling system possesses the technical characteristics and effects of the aforementioned hydraulic lift multi-gradient drilling string, which will not be elaborated further here.

[0162] Furthermore, the wellhead manifold system 6 has the following characteristics: (1) The wellhead manifold system 6 can be connected to the fluid flow system node equipment 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, and the drilling fluid solid phase control system 62 to transport fluid; the wellhead manifold system 6 can withstand a certain fluid pressure and has good connection sealing under the condition of fluid pressurized 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 equipped with multiple control valves, which can open and close the manifold, control the fluid flow rate and release pressure in case of high pressure; (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. At the manifold connection position, it is connected by manifold joints and manifold connectors, which are easy to disassemble and install.

[0163] 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 after solid phase control treatment, it re-enters the circulation system.

[0164] The components are: 2. Fluid injection adaptation system; 1. Multi-channel drill pipe; 3. Downhole lifting power system; 4. Annular isolation system; 7. Data monitoring system; 6. Wellhead manifold system. These components are additional adaptation parts under existing conventional drilling site and equipment conditions.

[0165] Option 3

[0166] This invention provides a hydraulic lift multi-gradient drilling method, employing the aforementioned hydraulic lift multi-gradient drilling string and drilling system. The downhole lift power system 3 is driven by the power fluid and pressurizes the drilling fluid flowing through it. This hydraulic lift multi-gradient drilling method relies on downhole fluid lift to achieve multi-gradient adjustment of wellbore fluid pressure distribution, and possesses the technical characteristics and effects of the aforementioned hydraulic lift multi-gradient drilling string, which will not be elaborated further here.

[0167] Furthermore, the hydraulic lift multi-gradient drilling string includes multiple downhole lift power systems 3, each with the same or different lift performance. At pre-designed downhole locations, one or more downhole lift power systems 3 are installed. These systems are hydraulically driven. When the system is not activated, the annular pressure gradient is a single gradient, and the pressure distribution is linear, similar to conventional drilling. When the system is activated, the annular fluid receives additional driving force at this system, thus returning to the surface with assisted lift. The annular pressure distribution changes from a linear distribution to a multilinear distribution divided by the downhole lift power systems 3. The annular pressure gradient can be equivalently represented as a multi-stage pressure gradient divided by the downhole lift power systems 3.

[0168] The equivalent pressure gradient distribution characteristics vary with the performance parameters of the downhole lifting power system 3. When the downhole lifting power system 3 used has the same head, the equivalent pressure distribution of the fluid in each segment above the bottommost downhole lifting power system 3 is a linear distribution with the same slope. When the downhole lifting power system 3 used has different heads, the equivalent pressure distribution of the fluid in each 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 annular isolation system 4 is installed in multiple stages to coordinate with the number of downhole lifting power systems 3.

[0169] Since the wellbore fluid flow energy originally provided by the surface drilling pump is partially shared by the downhole lifting power system 3, both the bottom hole pressure and the drilling pump pressure decrease when the system is started. This reduces the risk of bottom hole formation leakage and also alleviates the workload of the surface drilling pump.

[0170] The above descriptions are merely a few embodiments of the present invention. Those skilled in the art can make various modifications or variations to the embodiments of the present invention based on the content disclosed in the application documents without departing from the spirit and scope of the present invention.

Claims

1. A hydraulic lift multi-gradient drilling string, characterized in that, include: Multi-channel drill pipe, which has a power fluid inlet channel, a power fluid outlet channel and a drilling fluid channel; A fluid injection adapter system is installed at 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 communicates with the annulus; the power fluid injected by the fluid injection adapter system can flow into the downhole lifting power system through the power fluid inflow channel, and after flowing through the downhole lifting power system, it returns to the fluid injection adapter system through the power fluid outflow channel. Furthermore, the downhole lifting power system can be driven by the power fluid to pressurize the drilling fluid as it flows through the downhole lifting power system. The downhole lifting power system includes a system fluid inlet and a system fluid outlet communicating with the annulus. The drilling fluid in the annulus can be drawn into the annulus by the downhole lifting power system through the system fluid inlet and discharged into the annulus through the system fluid outlet. The downhole lifting power system includes a system drive unit and an annular lifting unit; Both the system fluid inlet and the system fluid outlet are located in the annular lifting device; Both the power fluid inflow channel and the power fluid outflow channel are connected to the system drive device, which is driven by the power fluid to operate and drive the annular lifting device to operate.

2. The hydraulic lift multi-gradient drilling string according to claim 1, characterized in that, The hydraulic lift multi-gradient drilling string includes an annular isolation system, which is installed outside the downhole lift power system and is used to isolate the annulus. The system fluid inlet and the system fluid outlet are respectively located on the upper and lower sides of the annular isolation system.

3. The hydraulic lift multi-gradient drilling string according to claim 2, characterized in that, The multi-channel drill pipe includes multiple drill pipe sections, and the downhole lifting power system is located between two adjacent drill pipe sections.

4. The hydraulic lift multi-gradient drilling string according to any one of claims 1-3, characterized in that, The multi-channel drill pipe includes a central tube, a first arc-shaped plate, and a second arc-shaped plate, with the drilling fluid flow channel disposed inside the central tube; Both the first arc-shaped plate and the second arc-shaped plate are disposed outside the central tube. The first arc-shaped plate and the central tube form the power fluid inflow channel, and the second arc-shaped plate and the central tube form the power fluid outflow channel.

5. The hydraulic lift multi-gradient drilling string according to claim 4, characterized in that, The first arc-shaped plate and the second arc-shaped plate are two parts of a single tube; the multi-channel drill rod includes a partition for separating the inflow channel and the outflow channel of the power fluid.

6. The hydraulic lift multi-gradient drilling string according to any one of claims 1-3, characterized in that, The multi-channel drill pipe includes a central tube, a middle tube, and an outer tube, and the drilling fluid flow channel is disposed inside the central tube; The middle tube and the central tube, and the middle tube and the outer tube, form the power fluid outflow channel and the power fluid inflow channel.

7. The hydraulic lift multi-gradient drilling string according to claim 1, characterized in that, The system drive unit includes a first turbine mechanism.

8. The hydraulic lift multi-gradient drilling string according to claim 1 or 7, characterized in that, The annular lifting device includes a second turbine mechanism.

9. The hydraulic lift multi-gradient drilling string according to claim 1, characterized in that, The system drive device includes a screw mechanism.

10. The hydraulic lift multi-gradient drilling string according to claim 1 or 9, characterized in that, The annular lifting device includes a worm gear mechanism.

11. The hydraulic lift multi-gradient drilling string according to claim 1, characterized in that, The fluid injection adapter system is equipped with a power fluid injection channel and a power fluid discharge channel. The power fluid injection channel is connected to the system drive device via the power fluid inflow channel. The power fluid discharge channel is connected to the system drive device through the power fluid outflow channel.

12. The hydraulic lift multi-gradient drilling string according to claim 1, characterized in that, The hydraulic lift multi-gradient drilling string includes a data monitoring system, which includes downhole measurement tools installed on the downhole portion of the multi-channel drill pipe.

13. A hydraulic lift multi-gradient drilling system, characterized in that, include: Wellhead manifold system; The hydraulic lift multi-gradient drilling string according to any one of claims 1-12, wherein the wellhead manifold system is connected to the power fluid inflow channel, the power fluid outflow channel and the drilling fluid channel in the hydraulic lift multi-gradient drilling string.

14. A hydraulic lift multi-gradient drilling method, characterized in that, The hydraulic lift multi-gradient drilling string according to any one of claims 1-12 is adopted; The downhole lifting power system is driven by the power fluid and pressurizes the drilling fluid as it flows through the downhole lifting power system.

15. The hydraulic lift multi-gradient drilling method according to claim 14, characterized in that, The hydraulic lift multi-gradient drilling string includes multiple downhole lift power systems, and the lift performance of each downhole lift power system may be the same or different.

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