WO2008127146A1 - Screw downhole motor for slant-hole directional and horizontal drilling - Google Patents

Abstract

The invention relates to drilling engineering and can be used for drilling slanted and horizontal wells on the curved sections and for stabilising the direction of a well bore. The inventive screw downhole motor comprises a gerotor type mechanism consisting of a stator and a rotor, a spindle provided with a bearing unit with radial and axial pivoting supports, the spindle shaft and the body, a drive shaft and adapters. The spindle body is coupled, in the lower part thereof, to a bit shank, and a viscoelastic lining encompassing the rotor is arranged in the top part of the spindle body on the inner surface thereof. The stator body, together with the viscoelastic lining of the spindle body, forms the pivoting radial support. In the bottom, the stator is connected to the spindle shaft which is provided with the bearing unit secured thereon, and, in the top, it is connected to the adapter for connecting to a drill string. The rotor and the bit shank are cinematically jointed by means of a drive shaft which is arranged inside the cavity of the spindle shaft.

Description

 Downhole helical motor for directional and horizontal drilling

The invention relates to the field of drilling equipment and, in particular, to downhole helical engines (VZD) for drilling directional and horizontal wells in areas of curvature and stabilization of the direction of the wellbore.

To carry out the drilling of such wells, various downhole motors and devices for them are known. For example, an additional drive to rotate the engine or drill stand.

The well-known downhole motor (Baldenko D.F., Baldenko F.D., Gnoev A.N. Screw downhole motors. M .: OJSC "Publishing House" Hedra ", 1999. C.357-359), consisting of two series-connected engines. To drive the drilling tool in this arrangement, a diverter motor with a curvature between its sections is used, and a second rotator motor connected to the housing of the diverter is periodically turned on when drilling in sections of stabilization of the well profile.

The rotary motor is periodically driven by the inclusion of a flow distributor that changes the flow direction of the flushing fluid, while the flushing fluid passes through both the working bodies of the rotary motor and the deflector motor. The working bodies of the motor-rotator are made in the right direction, and the deflector motor has working parts with the left direction of the helical teeth of the rotor and stator, which ensures rotation of the entire arrangement of two motors, as well as the output shaft of the motor of the deflector in one direction. In this case, the bottomhole the arrangement of two engines allows to increase the rotational speed of the drilling tool and the accuracy of the wiring of the wellbore in a given direction (stabilization mode). When the engine-deflector is running (without rotation by the motor-rotator), drilling is carried out in the set of curvature.

The disadvantage of this downhole assembly consisting of a diverter motor and a rotary engine is the significant length of the upper arm of the diverting assembly from the point of curvature between the sections of the diverter motor to the connection of the upper sub of the rotator motor with drill pipes. This circumstance does not allow drilling a wellbore with a set of curvature of more than 5 ° per 10 meters of penetration.

A drawback of the downhole assembly of two series-connected screw downhole motors is also the fact that when the curved bottomhole assembly of increased length is rotated in the wellbore, its external components experience complex maximum permissible deformations under the action of axial force, bending and torque. This leads to the fatigue failure of external rotating parts during operation of the well-known downhole screw motor, creating the likelihood of an emergency when drilling directional and horizontal wells.

In addition, the disadvantage of such a downhole arrangement is that in the spindle of the rotary motor, the used sealing system in movable joints operating in an abrasive medium at high pressures has low durability, as a result of which leaks of flushing fluid through the seals increase and the pressure decreases significantly. and the engine loses its load capacity. The need to install seals in the area of the radial bearings of the spindle due to the fact that when flushing fluid is supplied to rotate the entire bottomhole assembly during drilling, it is required to create a differential pressure differential of at least 4-5 MPa on the gerotor mechanism of the rotator motor.

The pressure that must be created for the effective operation of the bottomhole assembly at the inlet of the gerotor mechanism of the motor-rotator and in the seal area during drilling will be 8.5-10.5 MPa. The durability of the seals for the movable joints of screw downhole motors operating at large pressure drops of the flushing liquid under vibration conditions and large axial alternating loads will be insufficient.

The above drawbacks of the downhole assembly consisting of two series-connected helical downhole motors does not allow optimizing the parameters of the wellbore drilling process with a set rate of more than 5 ° per 10 meters of penetration, correcting the borehole according to a given profile and ensuring the operability of the downhole assembly with a high degree of reliability.

A device and method for rotating a drill string section in which the lower section is rotated by the upper section is known (US Pat. No. 6,446,737, E21B 4/00). The lower section includes a downhole motor and a drilling tool. The rotator of the upper section is located within the drill string in order to rotate the lower section. The upper and lower sections of the device can be connected by flexible or articulated tubing.

When the lower section of the drill string is rotated in the wellbore, the force required to advance the drill string decreases and the washing conditions of the horizontal wellbore from the cuttings are improved. The disadvantage of this device, the downhole motor and rotator in combination with flexible or articulated tubing (HKT), is the increased length of the entire arrangement, which, in turn, eliminates the possibility of using it for directional and horizontal drilling of wells along a given trajectory with the intensity of the set of curvature of more than 5 ° per 10 meters of penetration.

A well-known downhole motor for driving a tool when drilling wells associated with a drill string (US Patent 4.011.917 E21B 4/02), comprising a gerotor mechanism with helical gearing of the teeth of the stator and rotor, upper and lower radial bearings, an axial bearing, mounted on the spindle shaft and in the outer casing to allow the stator to rotate in this casing, the upper sub and the drive shaft that keeps the rotor from turning in the stator, but allowing the rotor to oscillate and I.

The gerotor mechanism of a downhole helical motor incorporates a rotor and a stator with the right direction of helical teeth.

In addition, the downhole screw motor has a lower shaft mounted in a lower radial bearing located in the outer casing. The lower shaft is connected to a rotating stator and a chisel sub.

The downhole motor has an upper and lower seal for sealing the cavity formed between the outer casing and the rotating stator with parts attached to it, in which there may be flushing fluid or viscous grease for lubricating the rubbing surfaces. With a tight upper seal, the flushing fluid under pressure enters the gerotor mechanism through the internal channel of the spindle shaft, providing rotation of the stator.

A disadvantage of the known invention is the low reliability of the upper seal, which is not able to maintain tightness for a long time at high pressure of the washing liquid in the cavity above the gerotor mechanism for its operation under conditions of intense vibration of the spindle shaft, coupled to a rotating stator.

With an increase in leaks of flushing fluid through the upper seal and at the same time with a decrease in pressure in the cavity above the gerotor mechanism, the engine speed and load capacity will decrease.

A disadvantage of the invention is the lack of a device that prevents the bit and stator from leaving the bottom of the well in case of destruction of the lower shaft or stator housing.

In addition, the disadvantage of the invention is that the rotating stator and the spindle shaft are placed in the lower and upper radial bearings without sufficient base, therefore, the lateral vibrations and radial loads arising from the operation of the gerotor mechanism due to cutting forces on the bit will lead to intensive wear of the working surfaces of the radial bearings with the formation of increased radial clearance. In the process of drilling a well under the action of radial loads, the rate of set of the curvature of the well using a layout consisting of a downhole screw motor and a curved sub, gradually decreases with increasing radial clearance in the lower radial bearing. This will lead to a change in the initial geometric parameters of the layout of the bottom of the drill string and, consequently, to deviations from the calculated trajectory of the wellbore during drilling. These disadvantages reduce the effectiveness of the application of the known invention using a curved sub over the engine when drilling directional and horizontal wells along a given profile of the wellbore and the possibility of an accident in the well in case of destruction of the lower shaft or stator housing is not ruled out. The technical problem to which the invention is directed is to increase the reliability, efficiency during drilling and the durability of a downhole screw motor, to optimize the drilling process with the aim of guiding the borehole in curved and horizontal sections in accordance with a given profile, and also to significantly improve the cleaning of the borehole rocks in the bottomhole zone and eliminating the likelihood of engine sticking in the well by creating a short downhole screw motor in which the rotor is directly It is connected via a drive shaft of bit sub mounted on the spindle housing, which allowed to carry out their simultaneous rotation in the wellbore relative to the drill string.

Optimization of the drilling process for the purpose of conducting the wellbore in curved and horizontal sections in accordance with a given profile is also ensured by placing support-centering or cutting elements on the bit sub and coupling of the coupled while rotating them with the drilling tool.

Reliability is also ensured by equipping the engine with a device to hold the spindle, stator or spindle shaft in the case in case of their destruction during emergency engine lift from the well.

Improving the efficiency and reliability is also ensured by placing in the upper part of the spindle housing an elastic-elastic cover covering the stator, with the formation of a radial support rotation of an increased length, perceiving a bending moment from the operation of the drilling tool when drilling directional wells, as well as transverse vibrations that occur when the rotor is run in the stator and is a limiter to the flow of flushing fluid through the bearing assembly. The radial support of rotation actually performs the function of a throttle with a given hydraulic resistance, creating the necessary pressure difference at the nozzles of the bit, and is a limiter to the flow of flushing fluid through the bearing assembly, including radial and axial bearings.

The technical result is achieved by the fact that in a downhole screw motor for directional and horizontal drilling of wells containing a gerotor mechanism including a stator and a rotor, a spindle comprising a bearing assembly with radial and axial bearings of rotation, a shaft and a spindle housing, a drive shaft and sub, according to the invention, the spindle housing in the lower part is interfaced with a chisel sub, and in the upper part of the spindle housing, on its inner surface, an elastic-elastic lining is made, covers the stator, and the stator housing together with the elastic-elastic cover of the spindle body make up the radial support of rotation, while the stator is connected to the spindle shaft with a bearing assembly fixed on it and to the top with an adapter to connect to the drill string, in addition, a rotor and a chisel the sub is kinematically connected by a drive shaft located in the inner cavity of the spindle shaft.

In addition, the length of the elastic-elastic plate on the inner surface of the spindle housing is comparable with the length of the elastic stator plate.

In addition, on the sub for connection with the drill string and on the coupling mounted in the upper part of the spindle housing and enclosing the sub for connecting with the drill string, annular collars are made, and the annular collar on the outer surface of the sub for connecting with the drill string is lower than the annular collar made on the inner surface of the coupling, in addition, when the contact ends of the annular collars of the coupling and the spindle housing with the parts mounted on it, they are fixed in the axial direction relative to the sub for connection with the drill string.

In addition, a replaceable centralizer is installed on the chisel sub, and the coupling is made with support-centering ribs.

Installation on the spindle body in the lower part of the bit sub and transmitting torque to the bit sub and allows them to simultaneously rotate in the wellbore, which ensures the wellbore is wired in accordance with a given path, that is, the accuracy of the wiring is increased.

In a downhole screw motor for directional and horizontal drilling of wells, unlike the prototype, in the upper part of the spindle body, on its inner surface, an elasto-elastic lining of increased length covering the stator is made, which allows to increase the reliability and life of radial engine mounts when perceiving bending moment arising from cutting forces on the bit, which provides increased efficiency during drilling.

The working bodies of a downhole screw motor for directional and horizontal drilling of wells are sufficient to perform with the left direction of the helical teeth on the rotor and stator, since the proposed design ensures the rotation of the bit in the left direction of cutting clockwise.

In addition, connecting the stator to the sub to connect to the drill string provides load transfer with the drill columns through axial support on the spindle body and the bit without the influence of this force on the spindle shaft section in its weak section. Thus, it is not necessary to check the spindle shaft for stability, as well as the use of seals to seal the pressure cavity above the gerotor mechanism due to the absence of movable mates between the parts in this zone.

Placing the drive shaft spindle kinematically connecting the rotor with the chisel sub in the inner shaft cavity allows reducing the length of the downhole screw motor and transmitting the torque from the rotor to the chisel sub.

When the flushing fluid from the pump enters the gerotor mechanism, the rotor under the influence of unbalanced hydraulic forces rotates inside the stator shell, making a planetary motion, which, with the help of the drive shaft, is converted into rotation of the bit sub and the spindle body connected to it on the radial bearings of rotation.

In addition, the use of a downhole screw motor with a rotating body, a chisel adapter and a drilling tool allows to optimize the drilling process when drilling directional and horizontal wells and to reduce the likelihood of sticking the drilling assembly due to improved cleaning of the borehole section in the bottomhole zone from cuttings.

The use of an elastic-elastic plate on the inner surface of the spindle body in a CDJ with a length commensurate with the length of the stator elastic plate allows the stator to be placed in the spindle body, creating a radial support of rotation of increased length compared to the prototype, capable of absorbing the bending moment from the operation of the drilling tool lateral vibrations that occur when the rotor is run in the stator. Length increase radial bearings of rotation leads to a decrease in specific loads on the elastic-elastic spacer body gasket.

In addition, with an increased length of the radial support of rotation, a slotted hydraulic resistance is formed for the flow of the washing liquid, which significantly reduces its leakage through the gap between the working surfaces of the elastic-elastic cover of the spindle housing and the stator housing. Thus, the flushing fluid, having passed the gerotor mechanism, can only enter the bit under high pressure and leak out through its nozzles, cleaning the bottom of the cuttings with high efficiency.

On the sub for connecting with the drill string and on the sleeve installed in the upper part of the spindle body and covering this sub, ring collars are made that provide reliable retention of the bit sub, the spindle housing with the parts mounted on it on the annular collar of the sub for connecting with the drill string in in case of destruction of the spindle shaft at the installation site of the axial support (bearing assembly) during drilling or with large tensile loads associated with the elimination of the grip of the bottom of the storm noy column in the well, which also provides a high-performance work to eliminate an emergency when drilling wells.

In addition, if during drilling a flap of the nut installed on the spindle shaft to fix the bearings of the bearing assembly or destruction of the stator housing occurs, then even in this case the bit retainer, the spindle housing with the parts mounted on it and the couplings on the ring collar of the sub for reliable connection with the drill string when lifting the downhole motor from the well. Thus, in case of destruction of the shaft, stator housing or flap nut, the proposed the design of the engine, in contrast to the prototype, avoids the fact that the engine will remain in the well when lifting.

The installation of a replaceable centralizer, calibrator or stabilizer on the chisel sub, as well as the implementation of a coupling with support-centering ribs while rotating them with the drilling tool, ensures the accuracy of the wellbore along a given path.

In addition, the downhole screw motor for directional and horizontal drilling of wells is used in an arrangement with a swivel sub or adjustable and curved sub, allowing angular misalignment between the axes of the downhole screw motor and the drill string, which also allows you to expand the scope of the engine and optimize the process of drilling sections changes in the direction of the wellbore.

According to the invention, in a downhole screw motor for carrying out its operation, the supply of washing liquid under pressure is carried out directly to the gerotor mechanism, without the use of sealing devices for the bearing assembly with a high degree of tightness, which simplifies the design of the spindle. In the prototype, the bearing assembly is located in the high pressure zone above the gerotor mechanism with the installation of an entire sealing system. Thus, in the proposed design, the bearing assembly is located in another zone, under the gerotor mechanism. This is due to the fact that the bearing assembly is located in the area through which the flow of flushing fluid is substantially limited, since a radial rotation bearing is installed above the bearing assembly, having a high hydraulic resistance and passing only such a quantity of flushing fluid that is necessary to lubricate the friction surfaces of the bearing assembly and radial rotation bearing. This, together with other features of the invention, leads to an increase in the efficiency of the drilling process due to the creation of a bit on the nozzles at the outflow of the flushing liquid under high pressure of a hydromonitor effect with the cleaning of the armament (diamond, plate, teeth) of the bit and face from the cuttings.

Figure l shows a longitudinal section of a downhole screw motor for directional and horizontal drilling of wells.

The downhole screw motor for directional and horizontal drilling of wells includes a spindle housing 1 with an elastic-elastic cover 2 made in its upper part, and a bit adapter 3 is connected to the spindle housing 1 in the lower part. In the elastic-elastic cover 2 of the spindle housing 1 there is a gerotor mechanism including a stator 4 and a rotor 5 installed inside the stator 4. A spindle shaft 6 is attached to the stator 4 at the bottom and a sub 7 at the top for connecting to the drill string 7. The rotor 5 is connected to the chisel adapter 3 dnym shaft 8, which is disposed in the internal cavity of the spindle shaft of the spindle 6. The body 1 with the elastically flexible plate of 2 and placed inside the stator plates 4 form a radial bearing rotation with the increased area of the contact surfaces at the optimum gap in this conjugation. The elastic-elastic cover 2 glued to the inner surface of the spindle body 1 is made comparable in length with the length of the elastic cover 9 of the stator 4, which are disposed without displacement relative to one another.

In the upper part of the spindle housing 1, a clutch 10 is installed covering the sub for connecting with the drill string 7. At the same time, an annular collar 11 is made on the sub for connecting with the drill string 7, and an annular collar 12 is provided on the coupling 10. the sub 3 is connected by means of a threaded connection to a removable centralizer 13. The coupling 10 is made with ribs 14 designed to center the upper part of the spindle housing 1 in the well. The spindle shaft 6 is placed in the bearing assembly containing the axial support of rotation 15 and the radial support of rotation 16. The bearing assembly on the shaft of the spindle 6 is fixed with a nut 17, and in the spindle housing 1 with a chisel adapter 3.

Operation of a downhole screw motor for directional and horizontal well drilling.

On a drilling rig, a downhole screw motor assembly with an articulated or adjustable sub and a mounted chisel is attached to the lower drill pipe. The entire assembly on the drill pipe descends into the wellbore of the well being drilled to the bottom. When a drilling pump supplies flushing fluid through pipes to a downhole screw motor, the rotor of the gerotor mechanism runs around the teeth of the elastic stator lining under the influence of unbalanced hydraulic forces. The planetary motion of the rotor is converted by means of a drive shaft into the rotational movement of the chisel sub, the spindle housing and the coupling attached to it. The rotation of the bit sub, spindle housing and coupling clockwise is provided with the left direction of the helical teeth of the stator and rotor. When the flushing fluid is supplied to the gerotor mechanism, the axial force arising on the rotor is transmitted through the drive shaft to the bit sub, the spindle housing and is received by the bearing assembly mounted on the spindle shaft. The flushing fluid, having passed through the screw chambers of the gerotor mechanism, enters through the internal channel of the spindle shaft and flow channels in the bit sub to the bit. To create a bit on the nozzles, the necessary pressure drop in order to increase the flow rate the flushing fluid through the nozzles, the radial support of rotation of the helical downhole motor is made of increased length with a minimum clearance in the interface of cylindrical working surfaces. The slotted hydraulic resistance formed between the inner surface of the elastic-elastic cover of the spindle housing and the outer surface of the stator housing allows creating a pressure at the inlet of the bit nozzles up to 7-9 MPa, which is sufficient to create a hydro-monitor effect when the flushing fluid flows through the nozzles and effectively clean the bottom of drill cuttings.

The proposed design of a downhole screw motor for directional and horizontal well drilling, when the bit is rotated simultaneously with a chisel sub and a removable centralizer, the spindle body and the coupling relative to the drill string, will improve the accuracy of the wellbore wiring in curved and horizontal sections, and ensure improved wellbore cleaning wells in the bottom-hole zone, reduce the likelihood of a stuck downhole screw motor in the well and remove the entire layout together with the drill string from the well in case of spindle shaft failure on the annular collar of the sub for connection with the drill string.

Claims

Claim 1. A downhole screw motor for directional and horizontal drilling of wells, comprising a gerotor mechanism including a stator and a rotor, a spindle, comprising a bearing assembly with radial and axial bearings of rotation, a shaft and a spindle housing, a drive shaft and an adapter, characterized in that the spindle housing in the lower part is interfaced with a chisel sub, and in the upper part of the spindle housing, on its inner surface, an elastic-elastic lining covering the stator is made, moreover, the stator housing is combined but with an elastic-elastic cover of the spindle body make up a radial support of rotation, while at the bottom the stator is connected to the spindle shaft with a bearing assembly fixed to it, and at the top with an adapter for connecting to the drill string, in addition, the rotor and the bit adapter are kinematically connected by the drive shaft, located in the inner cavity of the spindle shaft; 2. A downhole screw motor for directional and horizontal drilling of wells according to claim 1, characterized in that the length of the elastic-elastic cover on the inner surface of the spindle housing is comparable with the length of the elastic stator cover. 3. A downhole screw motor for directional and horizontal drilling of wells according to claim 1, characterized in that annular collars are made on the sub for connecting to the drill string and on the coupling mounted in the upper part of the spindle body and covering the sub for connecting to the drill string moreover, the annular collar on the outer surface of the sub for connecting with the drill string is lower than the annular collar made on the inner surface of the coupling, in addition, when the contact end faces in the ring and clamps the clutch housing the spindle with the parts mounted on it are fixed in the axial direction relative to the sub for connection with the drill string. 4. A downhole screw motor for directional and horizontal drilling of wells according to claim 1, characterized in that a replaceable centralizer is installed on the bit sub, and the coupling is made with support-centering ribs.