Pressure reducing device for reducing downhole annulus pressure

Abstract

The invention discloses a pressure reducing device for reducing downhole annulus pressure, which comprises a shell coaxially arranged in a shaft, the shell is of a hollow structure with an accommodating cavity, a fluid inlet and a fluid outlet of the shell are respectively communicated with an inlet and an outlet of the shaft, and fluid can flow along the axial direction of the shell; the sealing piece is arranged outside the shell to seal an annular space between the shaft and the shell, so that fluid can only flow through the fluid inlet of the shell; the screw motor is arranged in the shell, and the screw motor is configured to convert pressure energy of the fluid into mechanical energy and output torque and rotating speed; and the spiral blade is arranged in the shell at the downstream of the screw motor, and the spiral blade is in transmission connection with the screw motor. The method has remarkable advantages in the aspects of reducing the ECD, expanding the safety density window, prolonging the drilling depth, simplifying underground control, improving the operation reliability and the like, and a brand-new technical solution is provided for economical and efficient drilling of deep wells, ultra-deep wells and narrow-density window stratums.

Description

Technical Field

[0001] The present invention belongs to the technical field of bottom hole pressure reduction, and in particular relates to a pressure reduction device for reducing bottom hole annular pressure based on a screw motor and spiral blades. Background Art

[0002] With the continuous advancement of offshore exploration and development, the difficulty of drilling high-temperature, high-pressure, narrow pressure windows has become increasingly prominent, making drilling fluid loss and even gushing and leaking more likely to occur. In high-temperature, high-pressure wells, controlling annular pressure is key to safe drilling. By controlling the wellbore annular pressure, rapid and safe drilling can be ensured.

[0003] With the continuous improvement of global drilling capabilities, the drilling and research technology for deep oil and gas reservoirs has been greatly improved. There is an increasing amount of research on high-temperature and high-pressure drilling at home and abroad, but most of the research principles and theories for high-temperature and high-pressure well drilling are derived from the extension and comparison of land drilling. In high-temperature and high-pressure wells, reducing the bottomhole pressure difference is the key to safe drilling. The way to reduce the bottomhole pressure difference is usually to reduce the drilling fluid density, but the drilling fluid density must meet the needs of safe drilling. Domestic and foreign researchers have done a lot of research on reducing the bottomhole pressure difference of drilling fluid. While maintaining the static liquid column pressure in the wellbore unchanged, it is necessary to reduce the drilling fluid column pressure on the working surface of the drill bit to achieve the bottomhole pressure difference under the premise of achieving wellbore stability.

[0004] Therefore, the present invention provides a pressure reducing device for reducing the annular pressure at the bottom of a well to solve the problems raised in the above background technology. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a pressure reducing device for reducing the annular pressure at the bottom of a well, thereby achieving a bottomhole pressure of the equivalent circulating drilling fluid close to its hydrostatic pressure, thereby achieving deeper drilling depths.

[0006] To achieve the above-mentioned purpose, the present invention adopts the following technical solutions: a pressure reducing device for reducing the annular space pressure at the bottom of a well, comprising: a shell, coaxially arranged in the wellbore and with an annulus between the shell and the wellbore, the shell being a hollow structure with a cavity, the fluid inlet of the shell being connected to the wellbore inlet, the fluid outlet of the shell being connected to the wellbore outlet, and the fluid being able to flow axially along the shell; a seal, arranged outside the shell to seal the annulus between the wellbore and the shell, so that the fluid can only flow through the fluid inlet of the shell; a screw motor, arranged in the shell, the screw motor being configured to convert the pressure energy of the fluid into mechanical energy and output torque and speed; a spiral blade, arranged in the shell downstream of the screw motor, and the spiral blade being transmission-connected to the screw motor for pumping fluid when the fluid is returned.

[0007] Preferably, the screw motor includes a stator and a rotor, wherein the stator is a bushing and the rotor is a screw with a spiral surface. The stator and the rotor mesh with each other to form a plurality of sealed cavities. When the fluid flows into the stator, the rotor is pushed to rotate in the stator. As the rotor rotates in the stator, the sealed cavity moves along the axial direction of the stator, continuously being generated and disappeared, completing its energy conversion, thereby converting the pressure energy of the fluid into mechanical energy.

[0008] Preferably, the ratio of the number of heads of the rotor to the number of heads of the stator is 1:2, 3:4, 5:6, 7:8 or 9:10, the number of heads of the rotor is an odd number, and the number of heads of the stator is 1 greater than the number of heads of the rotor.

[0009] Preferably, the screw motor and the spiral blade are connected via two universal joint couplings and three anti-drop assemblies, that is, the two universal joint couplings are connected via one anti-drop assembly, and the two universal joint couplings are connected to the screw motor and the spiral blade respectively via one anti-drop assembly.

[0010] Preferably, the universal joint coupling includes a first universal joint housing, a second universal joint housing and a connecting shaft, and the first universal joint housing and the second universal joint housing are provided with bending direction marking grooves and bending angle marking grooves arranged along the circumferential direction, so as to quickly and accurately locate the bending direction and bending angle of the universal joint coupling during assembly, phase alignment and operation monitoring.

[0011] Preferably, the sealing member is an NBR nitrile rubber sealing ring.

[0012] Preferably: the anti-drop assembly includes an anti-drop joint, an anti-drop nut and an anti-drop connecting rod, the anti-drop joint is a shell-shaped connecting component, a support step is formed inside it; the anti-drop pull rod connects the anti-drop nut and the rotor of the screw motor to transmit tension; the anti-drop nut is a core force-bearing component, when the shell of the screw drill tool below the anti-drop assembly is broken or disengaged due to abnormal reasons, the anti-drop nut can be seated on the support step of the anti-drop joint to achieve mechanical locking, thereby bringing out the lower part of the rotor to avoid falling objects in the well.

[0013] The present invention has the following advantages due to the adoption of the above technical solution: 1. Effectively reduce equivalent circulating drilling fluid density (ECD) The present invention converts the hydraulic energy in the circulating fluid into mechanical energy through a screw motor, driving the second-stage spiral blades to actively suck the circulating fluid in the annulus, thereby forming a controllable negative pressure difference below the seal, so that the bottom hole pressure significantly approaches the hydrostatic pressure, thereby reducing ECD to the lowest level without reducing the density of the drilling fluid, avoiding risks such as well leakage and pressure differential sticking.

[0014] 2. Expand the safe drilling depth window Since ECD is effectively reduced, the margin between the fracture pressure and the bottomhole pressure increases, and drilling operations can be safely carried out at higher formation pressure gradients or deeper well sections. Theoretically, the drillable depth of a single well can be extended by 5%-20%, significantly reducing the number of staged drilling and casing running times, and saving drilling costs.

[0015] 3. No need for active speed regulation, system matching is simple and reliable The screw motor and the spiral blades of the present invention are rigidly mechanically connected, and the displacement / speed of the two are naturally matched, without the need for complex frequency conversion speed regulation devices or ground intervention, thereby reducing control elements and electronic devices, and improving the reliability, high temperature and high pressure resistance and service life of downhole tools.

[0016] 4. Integration of sealing and rotating functions to reduce friction and wear The annulus seal of the present invention is supported on bearings and remains stationary relative to the casing when the drill string rotates, ensuring that all return fluid and rock cuttings are forced to flow through the spiral blades, while avoiding relative rotation between the seal and the casing, significantly reducing the risk of seal wear, torque loss and casing damage.

[0017] 5. Fully mechanical hydraulic drive, suitable for high temperature and high pressure well conditions The entire energy conversion and pumping process of the present invention is driven by drilling fluid hydraulics, has no electronic components, can withstand temperatures above 200°C, and can withstand pressure differentials above 70 MPa, making it particularly suitable for harsh working conditions such as deep wells, ultra-deep wells, and geothermal wells. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present invention. Throughout the drawings, the same reference numerals are used to denote the same components. In the drawings: Figure 1 A schematic diagram of the overall structure of a pressure reducing device for reducing the annular pressure at the bottom of a well provided by one embodiment of the present invention; Figure 2 A schematic structural diagram of a universal joint coupling provided in one embodiment of the present invention; Figure 3A schematic structural diagram of a screw motor provided in one embodiment of the present invention; Figure 4 A schematic structural diagram of a spiral blade provided in one embodiment of the present invention; Figure 5 A schematic structural diagram of an anti-drop assembly provided in one embodiment of the present invention.

[0019] The reference numerals in the figures are as follows: 1-wellbore outlet; 2-fluid outlet; 3-spiral blade; 4-housing; 5-universal joint coupling; 6-anti-drop assembly; 7-seal; 8-stator; 9-rotor; 10-fluid inlet; 11-wellbore inlet; 12-first universal joint housing; 13-second universal joint housing; 14-connecting shaft; 15-anti-drop joint; 16-anti-drop connecting rod; 17-anti-drop nut; 18-wellbore. DETAILED DESCRIPTION

[0020] To make the objectives, technical solutions, and advantages of the present invention more apparent, specific embodiments of the present invention are further described below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. Rather, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0021] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0022] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature identified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means more than two, unless otherwise specifically defined.

[0023] In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connect," "fixed," etc. should be understood broadly. For example, they may refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0024] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0025] In the description of this specification, the reference terms "one embodiment," "some embodiments," "example," "specific example," or "some examples" mean that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0026] The present invention provides a pressure-reducing device for reducing bottomhole annular pressure, comprising: a housing coaxially disposed within the wellbore, the housing being a hollow structure having a cavity, the fluid inlet and outlet of the housing being connected to the wellbore inlet and outlet, respectively, allowing fluid to flow axially along the housing; a seal disposed on the exterior of the housing to seal the annular space between the wellbore and the housing, so that fluid can only flow through the fluid inlet of the housing; a screw motor disposed within the housing, the screw motor being configured to convert the pressure energy of the fluid into mechanical energy and output torque and rotational speed; and spiral blades disposed within the housing downstream of the screw motor, the spiral blades being transmission-connected to the screw motor. The present invention exhibits significant advantages in reducing ECD, expanding the safe density window, extending drilling depth, simplifying downhole control, and improving operational reliability, providing a new technical solution for economical and efficient drilling of deep wells, ultra-deep wells, and formations with narrow density windows.

[0027] Hereinafter, a pressure reducing device for reducing the annular pressure at the bottom of a well provided by an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0028] See also Figure 1 A pressure reducing device for reducing the annular space pressure at the bottom of a well provided in an embodiment of the present invention includes: a shell 4, which is coaxially arranged in the wellbore and has an annulus between the shell 4 and the wellbore, the shell 4 is a hollow structure with a cavity, the fluid inlet 2 of the shell 4 is connected with the wellbore inlet 1, and the fluid outlet 10 of the shell 4 is connected with the wellbore outlet 11, and the fluid can flow axially along the shell 4; a seal 7, which is arranged outside the shell 4 to seal the annulus between the wellbore and the shell 4, so that the fluid can only flow through the fluid inlet 2 of the shell 4; a screw motor, which is arranged in the shell 4, and the screw motor is configured to convert the pressure energy of the fluid into mechanical energy and output torque and speed; a spiral blade 3, which is arranged in the shell 4 downstream of the screw motor, and the spiral blade 3 is transmission-connected to the screw motor for sucking fluid when the fluid is returned.

[0029] In the above embodiment, preferably, please refer to Figure 3 The screw motor includes a stator 8 and a rotor 9. The stator 8 is a sleeve and the rotor 9 is a screw with a spiral surface. The stator 8 and the rotor 9 mesh with each other to form a number of sealed cavities. When the fluid flows into the stator 8, it pushes the rotor 9 to rotate in the stator 8. As the rotor 9 rotates in the stator 8, the sealed cavity moves along the axial direction of the stator 9, constantly generating and disappearing, completing its energy conversion, thereby converting the pressure energy of the fluid into mechanical energy.

[0030] In the above embodiment, preferably, the ratio of the number of heads of the rotor 9 to the number of heads of the stator 8 is generally 1:2, 3:4, 5:6, 7:8 or 9:10, the number of heads of the rotor 9 is an odd number, and the number of heads of the stator 8 is 1 greater than the number of heads of the rotor 9.

[0031] In the above embodiment, preferably, please refer to Figure 1 、 Figure 2 The screw motor and spiral blade 3 are connected by two universal joints 5 and three anti-drop assemblies 6. Specifically, the two universal joints 5 are connected to each other by an anti-drop assembly 6, and the two universal joints 5 are connected to the screw motor and spiral blade 3 by an anti-drop assembly 6 respectively. The function of the universal joints 5 is to convert the planetary motion of the screw motor into shaft rotation and transmit it to the spiral blade 3. Then, through the spiral blade 3 and the drive shaft, it is transmitted to the rotary head, thereby transmitting the torque and speed generated by the screw motor to the drill bit.

[0032] In the above embodiment, preferably, the universal joint coupling 5 includes a first universal joint housing 12, a second universal joint housing 13 and a connecting shaft 14, and the first universal joint housing 12 and the second universal joint housing 13 are provided with bending direction marking grooves and bending angle marking grooves arranged along the circumferential direction, so as to quickly and accurately locate the bending direction and bending angle of the universal joint coupling 5 during assembly, phase alignment and operation monitoring.

[0033] In the above embodiment, preferably, the sealing member 7 is made of NBR nitrile rubber sealing ring. The NBR nitrile rubber sealing ring is suitable for use in media such as petroleum hydraulic oil, glycol hydraulic oil, diester lubricating oil, gasoline, water, silicone grease, silicone oil, etc., and is currently the most widely used and lowest-cost rubber seal.

[0034] In the above embodiment, preferably, please refer to Figure 4 The anti-drop assembly 6 includes an anti-drop joint 15, an anti-drop connecting rod 16, and an anti-drop nut 17. The anti-drop joint 15 is a shell-shaped connecting component with a support step formed inside. The anti-drop pull rod 16 connects the anti-drop nut 17 to the screw motor's rotor 9 to transmit tension. The anti-drop nut 17 is a core load-bearing component. If the shell of the screw drill below the anti-drop assembly 6 breaks or disengages due to abnormal reasons, the anti-drop nut 17 can seat on the support step of the anti-drop joint 15 to achieve mechanical locking, thereby pulling the lower part of the rotor 9 out of the well to prevent falling objects.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A pressure reducing device for reducing the annular pressure at the bottom of a well, characterized in that: include: a housing coaxially disposed within the wellbore with an annulus formed therebetween; the housing being a hollow structure having a cavity; a fluid inlet of the housing communicating with the wellbore inlet; a fluid outlet of the housing communicating with the wellbore outlet; and fluid being able to flow axially along the housing; a seal disposed on the exterior of the housing to seal an annulus between the wellbore and the housing so that fluid can only flow through a fluid inlet of the housing; a screw motor disposed in the housing, the screw motor being configured to convert the pressure energy of the fluid into mechanical energy and output torque and rotational speed; The spiral blade is arranged in the housing downstream of the screw motor and is in driving connection with the screw motor for sucking fluid when the fluid is returned.

2. The pressure reducing device according to claim 1, characterized in that: The screw motor includes a stator and a rotor, wherein the stator is a bushing and the rotor is a screw with a spiral surface. The stator and the rotor mesh with each other to form a plurality of sealed cavities. When the fluid flows into the stator, the rotor is pushed to rotate in the stator. As the rotor rotates in the stator, the sealed cavity moves along the axial direction of the stator, continuously generating and disappearing, completing its energy conversion, thereby converting the pressure energy of the fluid into mechanical energy.

3. The pressure reducing device according to claim 2, characterized in that: The ratio of the number of heads of the rotor to the number of heads of the stator is 1:2, 3:4, 5:6, 7:8 or 9:10, the number of heads of the rotor is an odd number, and the number of heads of the stator is 1 greater than the number of heads of the rotor.

4. The pressure reducing device according to claim 1, characterized in that: The screw motor and the spiral blade are connected through two universal joint couplings and three anti-drop assemblies, that is, the two universal joint couplings are connected through one anti-drop assembly, and the two universal joint couplings and the screw motor and the spiral blade are respectively connected through one anti-drop assembly.

5. The pressure reducing device according to claim 4, characterized in that: The universal joint coupling includes a first universal joint housing, a second universal joint housing and a connecting shaft, and the first universal joint housing and the second universal joint housing are provided with bending direction marking grooves and bending angle marking grooves arranged along the circumferential direction, so as to quickly and accurately locate the bending direction and bending angle of the universal joint coupling during assembly, phase alignment and operation monitoring.

6. The pressure reducing device according to claim 1, characterized in that: The sealing element is an NBR nitrile rubber sealing ring.

7. The pressure reducing device according to claim 2, characterized in that: The anti-drop assembly includes an anti-drop joint, an anti-drop nut and an anti-drop connecting rod. The anti-drop joint is a shell-shaped connecting component with a support step formed inside. The anti-drop pull rod connects the anti-drop nut and the rotor of the screw motor to transmit tension. The anti-drop nut is a core force-bearing component. When the shell of the screw drill tool below the anti-drop assembly breaks or disengages due to abnormal reasons, the anti-drop nut can be seated on the support step of the anti-drop joint to achieve mechanical locking, thereby bringing out the lower part of the rotor to avoid falling objects in the well.

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