CN101492999B - Use of Hydrostatic Bearings for Downhole Applications - Google Patents

Abstract

The invention provides a fluid hydrostatic bearing used for stabilizing a drilling string and operating bottom drilling tool components. The fluid hydrostatic bearing adopts the existing mud stream as bearing fluid. For operation, the bearing can be used between a moveable recoilless pad and stratum to decrease friction. Different fluid hydrostatic bearing pressure can be used for operation selectively. With the same and different fluid hydrostatic bearing pressure selectively adopted, multi-mode (nonlinearity and linearity) operation can be provided. With a plurality of pressure cavities adopted, the bearing can be more resistant against defects in the stratum.

Description

Use of Hydrostatic Bearings for Downhole Applications

technical field

The present invention relates generally to the field of drilling, and more particularly to drill string stabilization and bottom hole assembly handling.

Background technique

Wells drilled with current technology can reach depths of tens of thousands of feet. The well can be non-linear to increase the exposure of the producing zone. The maximum depth is limited by the mechanical strength of the drill pipe. Specifically, this depth is limited by the ability of the drill pipe to withstand compression, tension, torsion, bending and differential pressure forces required to create the borehole. The drill pipe is subjected to torsional forces due to the torque required to overcome friction against the formation and to rotate the drill bit. Due to the extended length of the drill string in deep wells and the friction against the formation, the reduction in torsional stiffness can even lead to a stick-slip effect which, in extreme cases, can lead to spin-off of the drill pipe joint, damage to the drill bit, BHA vibrations and other undesired outcomes. In situations where the surface or intermediate casing is in place, friction between the casing and the drill string can wear through the casing at the pressure point of the bend, causing either formation fluids to enter the well or loss of circulation. The extensive force of the drill pipe against the mudcake wall can cause differential pressure sticking and equipment loss.

It is known to reduce drill string friction by using stabilizer segments with non-rotating sleeves. The load bearing surface between the sleeve and the drill pipe comprises a set of sliding or rolling element bearings. While such stabilizer segments reduce friction, they are relatively complex and costly. Because of the complexity, such stabilizer segments are more prone to failure than simpler devices. For example, ball bearing assemblies are particularly subject to degradation and failure in downhole environments. Not rotating the sleeves is also problematic when they are stuck in formation drilling because the bearings themselves prohibit the use of torsion to apply force to free the sleeves to move. Since it is the product of the unit cost of a stabilizer segment and the number of segments required, the total cost of using such a segment can be considerable. On a 30,000 foot drill string, 500 of these stabilizer segments would be required if they were used every 60 feet.

J.G.Boulet, J.A.Shepherd, J.Batham describe another approach to reduce drill string friction: Improved Hole Cleaning and Reduced Rotary Torque by New External Profile on Drilling Equipment, IADC/SPE Drilling Conference, New Orleans, Louisiana.No.59143, Feb 2000 ("Boulet"), which is hereby incorporated by reference. According to Boulet, the outer drill string segment profile includes hydrodynamic bearings. The bearing provides a pressurized fluid film between the drill string and the borehole. However, the shape of the hydrodynamic segments requires extremely complex and expensive machining, making such a solution uneconomical and impractical to achieve with current manufacturing techniques. Furthermore, the Boulet hydrodynamic segment design only reduces friction as the drill string rotates, and therefore, it does not assist in restarting rotation after adding a new joint of drill pipe at the surface.

Contents of the invention

According to one embodiment of the present invention, an apparatus for facilitating drilling operations includes: a drill string component adapted to be inserted into a well and comprising: a cavity capable of conveying pressurized fluid, the drill string component comprising: at least one hydrostatic bearing member , a pressurized fluid can be used to provide a fluid film between the hydrostatic bearing and a bearing surface such as a subterranean formation or sleeve.

According to another embodiment of the present invention, a steerable drilling apparatus for facilitating drilling a well includes a bottom hole assembly including a drill bit and a body having a cavity capable of delivering pressurized fluid, the bottom hole assembly including at least one Hydrostatic bearings can use a pressurized fluid to provide a fluid film between the hydrostatic bearing and the bearing surface.

According to another embodiment of the present invention, a method for facilitating drilling operations includes the step of: disabling a bearing surface between a load bearing surface and at least one hydrostatic bearing member of a drill string component by directing at least some pressurized fluid to the hydrostatic bearing member. To provide a fluid film between them, the drill string component includes a cavity capable of carrying fluid under pressure and is suitable for insertion into the well.

According to another embodiment of the present invention, a method for facilitating drilling operable drilling of a well comprises the steps of utilizing a bottom hole assembly comprising: a drill bit and a body having a cavity capable of carrying pressurized fluid, the bottom hole assembly comprising at least one Hydrostatic bearings use pressurized fluid to provide a fluid film between the hydrostatic bearing and the bearing surface. Specifically, one or more hydrostatic bearings can be operated at approximately the same pressure to drill a linear well; and in a time-varying fashion, a subset of the bearings can be operated at a relatively greater pressure than other bearings to Provides lateral force to drill non-linear wells.

The use of hydrostatic bearings for downhole applications offers advantages over prior art. For example, hydrostatic bearings and steering components in the stabilizer sections provide low wear, low friction, high load capacity and a simple, reliable design. Additionally, the pressure differential between the inside and outside of the drill pipe can be used as a source of power to drive the hydrostatic bearings. Additionally, multi-cavity bearings can be used to increase resistance to surface imperfections in formations.

Description of drawings

Figure 1 shows the elements of the drilling equipment.

Figures 2 and 3 show a single cavity hydrostatic bearing.

Figures 4 and 5 show multi-cavity hydrostatic bearings.

Figures 6 and 7 show a multi-chamber hydrostatic bearing where the restrictor diameter is equal to the chamber diameter.

Figures 8 and 9 show a multi-hole restrictor hydrostatic bearing.

Figure 10 shows the stabilizer sub-section of the drilling rig in more detail.

Figure 11 shows a cross-sectional view of the hydrostatic bearing in the stabilizer sub-section of Figure 10 along 10-10.

Figure 12 shows a hydrostatic bearing used in a steering recoil pad in the BHA of the drilling rig of Figure 1 along A-A.

Figures 13 and 14 show the hydrostatic bias manipulation system.

Figures 15 and 16 show a drill bit with a hydrostatic chamber operating as a bias control, wherein: Figure 16 is a cross-sectional view of the drill bit of Figure 15 along B-B.

Detailed ways

Figure 1 shows the drilling equipment. The drilling apparatus includes: a surface assembly (100); a plurality of stabilizer subs, of which: stabilizer subs (or subs) (102) are exemplary; and a bottom hole assembly ("BHA") (104). Non-stationary subterranean components of drilling equipment such as drill pipe (112), stabilizer sections (102), and BHA (104) are typically referred to as "drill strings." The BHA includes a drill head (106) and at least one handling member (108), which may be located in the drill head or higher on the BHA. The drill bit is operable to abrade the formation (110) to form a borehole. In particular, the drill bit can form a larger diameter borehole than the drill rod (112), which accounts for most of the length of the drill string.

To operate effectively, cuttings produced by the drill bit are removed from the wellbore by forcing high-pressure water ("mud flow") through openings in the drill bit, thereby trapping the rock in an annular mud return flow outside the drill string but inside the wellbore. Crumbs are pushed to the surface. This return mud flow can then be filtered to separate cuttings and the resulting mud reused for circulation. To drive the mud flow and bring cuttings to the surface, the mud flow pressure inside the drill string is greater than the mud pressure outside the drill string.

Manipulation is achieved by generating a force between selected segments of the BHA and the formation. Typically, the BHA is rotated during drilling. In an embodiment in which multiple circumferential steering members (108) are included, only one member (108) is activated at any given time to steer while drilling. Where a single steering member (108) is included, the single member is periodically activated as the BHA rotates. In either case, the result is a relative imbalance of forces, also known as lateral forces, between the BHA and different parts of the formation. The application of lateral force during drilling results in deviated drilling. The BHA will also include orientation sensors to provide a geostationary reference and to steer the activation of components to achieve the desired outcome in the trajectory of the well, ie steer in the desired direction.

The stabilizer sub (102) reduces the possibility of damage to the drill string due to contact with the formation. A plurality of stabilizer sub components (114) define a diameter larger than the drill pipe or drill string. As a result, the stabilizer sub component prevents, or at least mitigates, the possibility of adjacent subs of the drill string contacting the formation. The drill string will typically include a plurality of stabilizer subs spaced equidistantly along the drill string.

One aspect of the present invention is the use of hydrostatic bearings to enhance the performance of various components of drilling equipment. Specifically, hydrostatic bearings can be used to reduce friction in stabilizers due to the compression film effect, to provide inherently wetted rotational support, or to provide steering forces for the BHA and drill bit. However, before describing those improved embodiments of drilling equipment, it is appropriate to describe a few embodiments of hydrostatic bearings that may be used in downhole applications.

Figures 2 and 3 show a single cavity hydrostatic bearing (200). The single chamber hydrostatic bearing comprises: a supply line (202) having a supply pressure ps; a restrictor (204) having a resistance _R ; a bearing pressure chamber (206) having a chamber pressure _p ; and a bearing seal surface ( 208 ), which forms a fine clearance (resistance R ₂ ) with the bearing surface ( 210 ), which in the example shown is the formation wall or casing. The bearing advantageously has a high load capacity. For example, a bearing with a cavity pressure of 500 psi and an area of 2" x 2" can potentially support loads in excess of 2000 lbs. This capability is potentially sufficient to support and suspend curved and horizontal sections of drill pipe along the directional walls. Furthermore, the mud flow pressure differential between the inside and outside of the drill string can be sufficient to enable hydrostatic bearing operation. Specific uses of the bearings will be described below.

Figures 4 and 5 show a multi-chamber hydrostatic bearing (400). Instead of a single pressure chamber, an array of smaller pressure chambers (402) is used. The individual pressure chambers of the array are at least partially independent. Specifically, each chamber has a separate restrictor (404). The restrictors terminate in a common gap (406). Because the individual pressure chambers are at least partially independent, the multi-chamber bearing is less sensitive to imperfections (408) in the load bearing surface (210). For example, when drilling into rock, the likelihood of fractures and scours in the wellbore wall is relatively high. Such imperfections tend to temporarily increase the clearance (406) portion, or otherwise compromise the pressure differential across the oil seal by reducing the flow resistance R2. In the case of a single chamber design, the pressurized fluid escapes more easily through the enlarged gap (304, Fig. 3), so when a sufficiently large surface rupture occurs, the pressure chamber relaxes and the bearing loses its overall load capacity. However, with multi-cavity bearings, the loss of load capacity is limited to the load-bearing portion directly over the defect (408), ie to a single cavity bearing the enlarged gap. Cavities that are not on the defect are relatively unaffected and are still able to carry the load.

Figures 6 and 7 show a multi-chamber hydrostatic bearing (600) where the restrictor diameter is equal to the chamber diameter (602). Although the present embodiment appears to be cavityless since the cavity and the restrictor are not significantly different, the bearing could be molded as a multi-cavity bearing where the restrictor diameter is equal to the cavity diameter. As for the previously described embodiments, an array of small pressure chambers (602) is used, and each pressure chamber of the array is at least partially independent. Because the individual pressure chambers are at least partially independent, multi-chamber bearings are less sensitive to imperfections in the bearing surface (210).

Figures 8 and 9 show a multi-hole restrictor hydrostatic bearing (800). In this embodiment, a porous material (802) is used in place of the restrictor and cavity. Because the material is porous, a number of paths that act as chokes provide for fluid movement from the supply source to the gap between the bearing and the formation. Therefore, this embodiment can still be considered an extreme case of a multi-cavity bearing.

Referring to Figures 2 to 9, the mechanical properties of single-chamber and multi-chamber bearings are determined by the flow resistance of the restrictor (202), the size of the bearing chamber and the clearance (304) between the bearing seal surface and the surface. For drilling applications, there are certain constraints on the mechanical design of such equipment. If drilling mud is used as the bearing fluid, the system must be robust enough to handle the given particle size. Preferably, particle size restrictions can be accommodated by an optional mud filtration system. For reliable smooth operation, the restrictor and bearing seal face clearance should be larger than the particle size to reduce the possibility of clogging. Furthermore, to reduce the possibility of friction of the bearing pads against the surfaces, the bearing clearance or fly height should be greater than the surface roughness of the well wall. The design of hydrostatic bearing support equipment must also consider mud circulation in order to: Give the mud flow some annular area for conveying rock cuttings from the drill bit. Multi-cavity hydrostatic bearings may be less sensitive to damage by wear/wear because if some of the bearing pad material wears away due to friction with the well wall, the only effect will be a slight reduction in the length of the choke bore. Since this will only have a linear effect on the flow resistance of the restrictor, it is likely to be tolerated and will not reduce the functionality of the bearing.

Referring now to Figures 1, 10 and 11, single and multi-chamber hydrostatic bearings can be used as part of the outer surface of the drill string and as part of the stabilizer sub (102). In the illustrated example showing a single chamber bearing for simplicity, the 4 bearing chambers (1100) are fed by drilling mud ("central mud flow") flowing through the center (1102) of the stabilizer. Specifically, the fluid is fed into the bearing cavity via a restrictor (1104) integrated in the stabilizer rib. Either the formation (110) itself or the internal surface of the intermediate casing (1106) provides a support surface against which the bearings can operate. Friction against the casing is reduced because the stabilizer components will slide on the film of pressurized mud formed by the bearing cavity (1100) and bearing seal face (1108), rather than a bare metal surface. As a result, friction and wear on the bushing and stabilizer chopping will be reduced. This bearing is especially useful at the stage where the production area is drilled, as the drill string is at its longest and thinnest and requires the greatest amount of support and friction reduction.

Referring now to Figures 1 and 12, single and multi-chamber hydrostatic bearings can also be used to reduce friction in rotationally steerable systems. In this embodiment, the maneuvering member (108) includes a hydraulically actuated kickpad (1200), a "push bit" system operable to push the front of the BHA (104) into a prescribed direction. Each recoil pad (1200) rotates about a hinge (1202) and has an angular range of motion determined by an arc in a plane perpendicular to the axis defined by the BHA. The recoil pads rotate with the drill string and are actuated in a coordinated manner to generate relatively greater force into a selected direction, generally perpendicular to the drilling direction, to maneuver the BHA. Friction between the formation and the recoil pad is reduced because the bearing land (1204) and bearing cavity (1206) maintain a pressurized fluid film between the recoil pad and the formation, particularly when a steering force is applied. As already mentioned, the pressurized fluid used to operate the hydrostatic bearing may be the same fluid used to actuate the recoil pads, eg a central mud flow.

Figures 13 and 14 show the hydrostatic bias manipulation system. The hydrostatic bias steering system (1300) uses variable hydrostatic pressure to steer the BHA instead of movable recoil pads. The manipulation member (1302) does not move relative to the BHA. More precisely, the manipulating member is in the example shown a hydrostatic bearing (in the example shown a multi-chamber bearing, but a single-chamber bearing could be used), by changing the hydrostatic pressure in the pressure chamber of the hydrostatic bearing, suitable Relatively different forces are applied to the formation (110).

By providing the bearing with bearing fluid through a variable restrictor unit (1304), varying hydrostatic pressure can be achieved. In this example, the variable restrictor unit includes a restrictor rod (1306), which can be placed centrifugally inside an outer cylinder (1308), with three radial valves each fluidly connected to its corresponding bearing pad. drilling. The radial boreholes are equidistant relative to each other. The throttle rod is oriented along an axis parallel to the axis determined by the outer cylinder so that: the volume of fluid flow space between the rod and any given portion of the outer cylinder depends on and varies with the Rotational change of the diverter rod. The difference in volume of the fluid flow space results in a difference in flow resistance. In operation, the cylindrical portion of the variable throttle unit remains eccentric and geostationary while the throttle rod member rotates with the biasing unit. Thanks to this geometry, during each revolution, the flow resistance applied to each bearing changes smoothly and continuously, providing smoother maneuvering. By modifying the circular shape of the cylindrical part, ie making the radius of the cylinder a suitable function of the circumference angle, the non-linearity of the drag or the adjustment of the handling characteristics (dynamics) can be reduced or eliminated. In an alternative embodiment, independently operated valves are used instead of variable restrictor units.

It should be appreciated that the hydrostatic bias steering system (1300) may be multi-modal, ie capable of directional and linear steering. Multi-mode operation is achieved by axially shifting the position of the throttle rod (1306) relative to the outer cylinder (1308). When the restrictor is in the center of the outer cylinder, ie when the restrictor stem and the outer cylinder are oriented along opposite axes, the flow resistance and thus the bearing pad pressure is the same on all bearings. As a result, the same pressure is applied to each bearing surface and the BHA will tend to drill along a linear path. When the axis of the cylinder is displaced relative to the shaft of the throttle as shown, the flow resistance of the throttle (1402) is higher than that of the throttles (1401) and (1403). As a result, the line pressure supplied by restrictor (1402) to the bearing pads is lower than the pressure associated with restrictors (1401) and (1403). This results in an imbalance of forces on the load-bearing surface for nonlinear manipulation in a similar manner to that already described above. To maintain balance, the biasing unit will be displaced inside the wellbore in the direction of the lowest pressure bearing pad, in this case the bearing pad associated with the restrictor (1402). Systems like this one are capable of generating strong biasing forces while exhibiting extremely low friction and wear.

In the example shown, the hydrostatic bias unit is shown with three bearing pads and a 3-way restrictor unit. However, the biasing unit may have any number of bearing pads, including but not limited to a single bearing pad and more than three bearing pads, for smoother circumferential transfer. Continuous systems can be used without special pads.

Figures 15 and 16 show a drill bit (1500) with a hydrostatic chamber (1502) operating as a bias control. This member operates in substantially the same manner as the hydrostatic deflection system of FIGS. 13 and 14 . However, in this embodiment, the hydrostatic chamber is located on the bit itself rather than higher up on the BHA. The hydrostatic chamber uses mud pressure to generate lift on selected sides of the bit to push the bit in the desired direction. The pressurized mud fluid film between the pressure chamber and the formation is capable of supporting large forces with little or no wear. In the illustrated embodiment, the drill bit includes three pressure chambers (1502), however only one pressure chamber may be used. Each pressure chamber is equipped with a feed pipe (1504) for introducing mud into the chamber. A simple and robust steering system can be achieved by locating a single, geostationary mud supply line (1506) near the drill bit so that the supply line sequentially supplies each feed pipe with pressurized mud as the drill bit rotates. Since the mud supply line is geostationary, the drill bit will operate away from the flow direction of the mud supply line. Linear drilling is enabled by synchronizing the rotation of the mud supply line with the rotation of the drill bit. The mud operated hydrostatic bearing can additionally provide a wetting effect due to, for example, pressure film wetting, resulting in a smoother drilling operation. The cut away part (1508) provides a passage for the mud flow with debris.

While the present invention has been described in terms of the foregoing exemplary embodiments, those of ordinary skill in the art will appreciate that modifications and changes to the illustrated embodiments can be made without departing from the inventive concepts disclosed herein. Furthermore, although the preferred embodiment has been described in connection with a variety of display configurations, those skilled in the art will recognize that the system can be implemented using a variety of specific results. Accordingly, the invention is not to be limited except by the scope and spirit of the appended claims.

Claims (26)

1. for being conducive to the device of drilling operation, wherein:

Described device comprises the drill string parts that are applicable to inserting drilling well, and described drilling well is limited with load-bearing surface;

Described drill string parts comprise the cavity that can transport pressure fluid, and at least one hydrostatic bearing, and this hydrostatic bearing can be used the gap of pressure fluid between hydrostatic bearing and described load-bearing surface that fluid film is provided.

2. device according to claim 1, wherein: drill string parts comprise drilling rod and stabilizer pipe nipple, stabilizer pipe nipple has at least one parts, when rotation, described at least one parts are determined the diameter that is greater than drill pipe diameter, and wherein: hydrostatic bearing is arranged on stabilizer pipe nipple parts.

3. device according to claim 1, wherein: hydrostatic bearing comprises single pressure chamber.

4. device according to claim 1, wherein: hydrostatic bearing comprises a plurality of pressure chambers.

5. device according to claim 1, wherein: pressure fluid is provided by central slurry flows.

6. for being conducive to the equipment of the probing handled of drilling well, described drilling well is limited with load-bearing surface, and described equipment comprises:

Bottom drill tool assembly, described bottom drill tool assembly comprises: drill bit and the main body with the cavity that can transport pressure fluid, described bottom drill tool assembly comprises: at least one hydrostatic bearing, this hydrostatic bearing part can be used the gap of pressure fluid between hydrostatic bearing and load-bearing surface that fluid film is provided.

7. equipment according to claim 6, also comprises: with respect to mobilizable at least one kick-pad of bottom drill tool module body, hydrostatic bearing is arranged in kick-pad.

8. equipment according to claim 6, also comprises: at least one control member, comprising: described hydrostatic bearing; With for changing selectively the device of pressure in the chamber of bearing.

9. equipment according to claim 8, wherein: pressure change device comprises variable throttler, described variable throttler has the externally restriction choke parts of cylinder interior displacement prejudicially, and described outer cylinder has the radial bore that is fluidly connected to bearing.

10. equipment according to claim 9, comprising: a plurality of bearings, and wherein: restriction choke parts are applicable to by directed along the common axis with outer cylinder selectively, so that identical with respect to the flow resistance of each bearing.

11. equipment according to claim 6, wherein: hydrostatic bearing comprises single pressure chamber.

12. equipment according to claim 6, wherein: hydrostatic bearing comprises a plurality of pressure chambers.

13. equipment according to claim 6, wherein: pressure fluid is provided by central slurry flows.

14. 1 kinds of methods that are conducive to drilling operation, comprise the following steps:

The drill string parts that are applicable to inserting drilling well are provided, and described drill string parts comprise the cavity that can transport pressure fluid, and described drilling well is limited with load-bearing surface;

By at least some in pressure fluid are directed to hydrostatic bearing, the gap between load-bearing surface and at least one hydrostatic bearing of drill string parts provides fluid film.

15. methods according to claim 14, wherein: drill string parts comprise drilling rod and stabilizer pipe nipple, and stabilizer pipe nipple has a plurality of parts, when rotation, described parts are determined the diameter of the diameter that is greater than drilling rod, and wherein hydrostatic bearing is arranged on stabilizer pipe nipple parts.

16. methods according to claim 14, further comprising the steps of: to utilize hydrostatic bearing to form single pressure chamber.

17. methods according to claim 14, further comprising the steps of: to utilize hydrostatic bearing to form a plurality of pressure chambers.

18. methods according to claim 14, further comprising the steps of: by central slurry flows, to provide compression fluid.

19. 1 kinds of methods that are conducive to the probing handled of drilling well, described drilling well is limited with load-bearing surface, said method comprising the steps of:

Bottom drill tool assembly is provided, and described bottom drill tool assembly comprises drill bit and the main body with the cavity that can transport pressure fluid, and bottom drill tool assembly comprises at least one hydrostatic bearing;

Use pressure fluid to provide fluid film with the gap between described hydrostatic bearing and described load-bearing surface.

20. methods according to claim 19, further comprising the steps of: with respect to bottom drill tool module body, movably at least one kick-pad is to handle drill bit in use, and hydrostatic bearing is arranged in kick-pad.

21. methods according to claim 19, also comprise: comprise at least one control member of hydrostatic bearing, and comprise step: change selectively the pressure in the chamber of bearing.

22. methods according to claim 21, also comprise: variable throttler, has restriction choke parts and have the outer cylinder that fluid is connected to the radial bore of bearing, and comprise step: make the externally displacement prejudicially in cylinder of restriction choke parts.

23. methods according to claim 22, comprise a plurality of bearings, and comprise the following steps: along with the common axis of outer cylinder directed restriction choke parts selectively so that identical with respect to the flow resistance of each bearing.

24. methods according to claim 19, further comprising the steps of: to utilize hydrostatic bearing to form single pressure chamber.

25. methods according to claim 19, further comprising the steps of: to utilize hydrostatic bearing to form a plurality of pressure chambers.

26. methods according to claim 19, further comprising the steps of: by central slurry flows, to provide pressure fluid.

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