Downhole motor

Abstract

The invention relates to drilling equipment for use in the field of oil and gas and oil and gas production, and more particularly to a downhole motor for drilling directional, deep, vertical, horizontal and other wells. The technical result achieved through the use of the invention consists in a reduction in moment loads and an improvement in the ability of the downhole motor to follow a geometric path in the shaft of a well. The essence of the invention is that in a downhole motor consisting of an upper sub, a power section containing a stator and a rotor, and a bearing section containing a housing, a shaft and axial and radial bearings, an output shaft of the bearing section is arranged at an angle to the central longitudinal axis of the housing elements of the motor, and the housing of the bearing section has thereon at least one external supporting and centering element.

Description

[0001] Screw downhole motor

[0002] The invention relates to drilling equipment used in the oil and gas and oil and gas production fields, namely to a screw downhole motor designed for drilling directional, deep, vertical, horizontal and other wells.

[0003] A downhole motor (abbreviated as VZM) is a positive displacement rotary hydraulic mechanism - the main mechanism of drilling rigs, which converts the pressure of the liquid (drilling mud) pumped into the stator cavity into rotational movement of the output shaft.

[0004] By efficiently transmitting power to the drill string, downhole motors (DDMs) increase well penetration rates and reduce drilling time. These designs play a vital role in ensuring an efficient and cost-effective drilling process. However, drilling wells with a large deviation from vertical can lead to problems such as increased friction, equipment wear, and reduced engine efficiency.

[0005] A prior art discloses a downhole motor for horizontal drilling, comprising an upper sub, a drive section comprising a stator and rotor forming a gerotor mechanism, and a spindle section comprising a housing, a shaft, and axial and radial bearings. The rotor is connected to the shaft of the spindle section by a cardan shaft. A curvature unit (adjustable sub or rigid curved sub) is located between the stator and the housing of the spindle section. The longitudinal central axes of the housing and the shaft of the spindle section coincide (see Baldenko D.F., Baldenko F.D., Gnoevykh A.N. Screw Downhole Motors: Reference Guide. Moscow: OJSC "Izdatelstvo Nedra", 1999, hereinafter referred to as D1).

[0006] The main drawback of the known solution, under modern drilling conditions, is the high alternating cyclic bending loads that occur on the stator body threads or the upper sub. These loads arise due to the geometric impassability of the classic downhole motor design with a large curvature angle set in the wellbore. The motor position with the greatest deviation "A" from the borehole axis occurs during reaming with a rotating section of the slide (Fig. 2, view A).

[0007] Cyclic loads are caused by the fact that well drilling is carried out with the drill string rotating, including forward and reverse reaming of drilled sections of the well. Currently, the required drill string rotation speed reaches up to 80 rpm. However, this speed leads to a sharp reduction in the service life of downhole motor housing components due to the formation of fatigue cracks in the threaded connections.

[0008] The prior art also discloses a deflection device (see RU2323320, 27.04.2008, IPC E21B 7 / 08B - hereinafter D2), consisting of a central shaft 3 with seals and external threads. The central shaft has a curved section at an angle of α. A coupling is located outside the central shaft 3, on one of the ends of which end teeth are formed. A curved adapter with end teeth interacting with the end teeth of the coupling is screwed onto one end of the central shaft, and a straight adapter contacting the end of the coupling is screwed onto the other end of the central shaft. The deflection device 8 has four centering sections L, LI, L2, L3, formed with a radial clearance between the outer diameter of the central shaft 3 and the inner diameter of the straight 4 or curved 3 adapters located above it.

[0009] According to the description, the solution described in D2 improves wellbore drilling accuracy by preventing unplanned deviation of the hydraulic machine from the calculated drilling trajectory, and also increases the service life of the adjustable diverter by reducing wear on the outer surface of the coupling and the curved sub. The device features a thickening on the coupling in the form of a truncated cone segment with an inclination angle of α1, which increases the contact area with the borehole wall when operating in the curved configuration, which in turn reduces wear on the outer surface of the coupling. The increased service life of the device is ensured by the thickening of the coupling and its reinforcement with wear-resistant material. Also, to reduce wear on the outer surface of the curved sub, it is designed as a vane centralizer, increasing the contact area with the borehole wall when operating in the curved configuration, which in turn reduces wear on the outer surface of the curved sub.However, a disadvantage of the device is the retention of bending loads, which does not solve the problem of the formation of fatigue cracks on threaded connections and, as a consequence, the service life of the housing parts of the downhole motor.

[0010] The downhole motor selected as the closest in terms of its overall characteristics is the downhole motor known from RU2186188 (E21B 4 / 02, published July 27, 2002, hereinafter referred to as DZ). The downhole motor comprises a power section, comprising a housing with a stator and a rotor located within it, and a spindle section, comprising a housing with a shaft mounted within it via a bearing assembly. The rotor of the power section is connected to the shaft of the spindle section via a hinge joint.The invention is aimed at increasing the durability of the hinge assemblies of a downhole screw motor, which is ensured by the proposed design in the form of three successively arranged tubular elements, wherein the outer elements are connected respectively to the housings of the motor and spindle sections, and the middle one is connected to each outer element by means of a pair of axles and is installed with gaps that provide a skew of the axes of each pair of adjacent elements up to 2°30', and the hinge assembly connecting the rotor and the shaft of the motor and spindle sections, respectively, is made in the form of two splined shafts, one of which is connected by means of a torsion bar to the rotor of the motor section, and the other to the shaft of the spindle section, and a splined coupling installed in relation to the splined shafts with gaps that provide a skew of the axes of the motor and spindle sections up to 5°.The disadvantage of this solution is that at a drill pipe rotation speed of 80 rpm, the described problems of the prior art persist due to the described design of the screw motor.

[0011] The objective of the present invention is to eliminate these shortcomings, achieve reliability, and increase the service life of downhole motors used for drilling directional and horizontal oil and gas wells. This objective is achieved by reducing bending loads. An additional technical benefit is improved geometric performance of the downhole motor in the wellbore.

[0012] The technical result is achieved in that in a screw downhole motor consisting of an upper sub, a motor section containing a stator and a rotor, a spindle section containing a housing, a shaft, axial and radial supports, the output shaft of the spindle section is made at an angle a relative to the central longitudinal axis of the motor housing parts, and a support-centering element is made on the housing of the spindle section.

[0013] The invention is explained by the following description and the attached drawings, where Fig. 1 is a general view of a downhole motor (its longitudinal section); Fig. 2 shows the nominal position of a downhole motor with a deflected shaft of the spindle section during processing with rotation of a section of a slide, where A is the traditional arrangement of a downhole motor, B is the claimed solution).

[0014] The screw downhole motor consists of an upper sub 1, a motor section 2 containing a stator 3 and a rotor 4, a spindle section 5 containing a housing, a shaft, axial and radial supports, a support-centering element 6 made on the housing of the spindle section 5.

[0015] The motor section (power section) 2 is the section of the working elements, the working pair is the power component of the downhole motor, which determines its main energy characteristics (torque on the output shaft, rotation frequency of the spindle shaft, power and efficiency).

[0016] Motor section 2 (the working pair) is a positive displacement rotary hydraulic mechanism (a screw gerotor mechanism), the working elements of which are the stator 3 and rotor 4. Stator 3 has an elastic lining with an internal helical surface, forming the cavities of the high- and low-pressure chambers. Rotor 4 is a metal screw with a wear-resistant surface, through which torque is transmitted to the actuator (the shaft of the motor spindle section). When fluid, supplied by the pump, circulates into the working area of ​​the stator, under the influence of the pressure differential across the rotor, torque is generated.

[0017] The spindle section 5 is a support unit and serves to transmit rotation from the power section to the rock-cutting tool, and is also designed to withstand hydraulic loads, bottomhole reaction, and radial loads from the rock-cutting tool during drilling.

[0018] The rotation of the motor section rotor is transmitted to the spindle section shaft via transmission elements (cardan shaft or torsion bar). Axial and radial bearings support the spindle's axial and radial loads and are the section's primary wear parts.

[0019] A distinctive feature of the proposed design is that the central axes of the outer surfaces of the housing components lie on a common longitudinal axis. Because the central axes of the downhole motor's housing components lie on a single straight line, the theoretical deviation of the upper point of the downhole motor from the borehole axis is significantly reduced, significantly improving the motor's geometric maneuverability on curved sections of the borehole. Consequently, bending loads on the housing components and their threaded connections are reduced, and the number of cycles that can be withstood before fatigue cracks form increases, thereby extending the service life of the housing components. The motor position with the greatest deviation from the borehole axis (occurring during reaming with a rotating section of the slide) is illustrated in Fig. 2. The value of angle a is calculated such that the actual spatial intensity of the borehole curvature does not exceed the range of 2.5...3 g / 10 m.

[0020] By reducing the stresses generated during drilling and borehole reaming on the downhole motor's housing components and its threaded connections, the service life of the housing components is extended while maintaining the required borehole curvature parameters. Furthermore, reducing stress on the downhole motor's housing components allows for increased drill string rotation speed, which, in turn, potentially increases the drilling speed, thereby achieving the second technical result.

[0021] The possibility of implementing the invention with the realization of the specified purpose can be illustrated by the following example.

[0022] The maximum deviation from the borehole axis is 0.42 times the deviation of the top of the analog downhole motor from the borehole axis. The example shown is for 176-gauge downhole motors. In the proposed solution, the calculated stresses occurring on the housing threaded connections are reduced by more than half.

[0023] The device operates as follows.

[0024] The downhole motor is delivered to the drilling rig fully assembled with the safety plugs installed. Drilling operations are carried out in accordance with the site's established work procedures. The drilling pump provides a continuous forced supply of drilling fluid, which flows through the drill pipes into the screw pair and fills the cavities formed between the stator and rotor surfaces. The pressure difference in these cavities (chambers) generates a hydraulic force that acts on the rotor, causing it to perform a complex rotational motion within the stator.

[0025] Rotational motion of the rotor and torque are transmitted to the intermediate shaft of the spindle section via a cardan shaft. The intermediate shaft of the spindle section is connected to the output shaft of the spindle section via an additional hinge joint. During drilling, in the absence of additional rotation of the drill string attached to the upper sub of the downhole motor, the motor begins drilling along a radial trajectory due to the deflecting force from the support-centering element mounted on the spindle section body. When the drill string rotates, the drilling trajectory becomes straight. Alternating between these two modes—without and with drill string rotation—controls the wellbore trajectory.

Claims

Invention formula A screw downhole motor consisting of an upper sub, a motor section containing a stator and a rotor, a spindle section containing a housing, a shaft, axial and radial supports, characterized in that the output shaft of the spindle section is made at an angle relative to the central longitudinal axis of the housing parts of the motor, and at least one external support-centering element is made on the housing of the spindle section.

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