JPH0412800B2 - - Google Patents

Abstract

A downhole screw motor is intended for drilling oil and gas wells. The downhole screw motor comprises a stator (3) and a hollow rotor (4) in the axial channel (5) of which is mounted a flow regulator (6) with a nozzle (16). The surface of the nozzle (16), arround which the working liquid flows, is formed by two consecutively located chambers: a receiving one (A) and a discharging one (B), the surfaces (19, 20) of which are conjugated along a break line (21). The part (22) of the receiving chamber (A) which adjoins the break line (21) has a convex form in the direction of flow of the working liquid, whereas the cross-sectional area of the receiving chamber (A) at its outlet is smaller than at its inlet.

Description

Claim 1 Consists of a motor part 1 having a working member formed by a spindle part 2, a stator 3 and a hollow rotor 4 having an axial passage 5 leading to a high pressure zone of the working liquid, and having a nozzle 16. In a downhole screw motor in which a flow regulator 6 for the flow of the working liquid is installed in the axial passage, the nozzle 16 has two chambers arranged in series in the direction of flow of the working liquid, i.e. flushed and broken with the working liquid. Surfaces 19,2 joined by line 21
0, the annular portion 22 of the introduction chamber A adjacent to the break line 21 is convex with respect to the flow direction of the working liquid, and the cross-sectional area at the outlet of the introduction chamber A is A downhole screw motor characterized in that the cross-sectional area at the entrance of the same introduction chamber A is smaller than that at the entrance.

2 The nozzle 16 is connected to two members, namely the bush 2
3 and the rod 2 attached to the inside of the bush.
4, the introduction chamber A and the delivery chamber B are formed by the bush 23 and the rod 24, and the down is annular in shape. Hole screw motor.

3. Down according to claim 2, characterized in that the rod (24) is cylindrical and the bush (23) is provided with an annular projection (26) forming a convex portion (22) of the surface (19) of the introduction chamber (A). Hole screw motor.

4. The downhole screw motor according to claim 2, wherein the bush 23 is cylindrical and the rod 24 is provided with an annular projection 27 forming the convex portion 22 of the introduction chamber A.

5 Bush 23 and rod 24 are annular protrusions 2
8, 29, each of which is provided with an annular projection 26 therein forming a convex portion 22 of the surface 19 of the introduction chamber A. motor.

〔Technical field〕

The present invention relates to a positive displacement fluid machine, and more particularly to a downhole screw motor.

[Background of the invention]

Two fundamentally different methods are used today for drilling wells. The first method is a rotary drilling method in which the drive of the rock breaking tool, or bit, is located at ground level and the bit is rotated through a drill pipe string. The second method employs a downhole fluid machine located directly above the bit. In this case, the drill pipe string is kept stationary. The second method has various advantages. That is, there is no loss of energy to rotate the drill pipe string, the load on the drill pipe is reduced, and therefore the number of well shaft emergencies is reduced.

Of all the types of downhole motors employed in practical drilling today, downhole screw motors are the most widely used.
These motors are characterized by their ease of operation and maintenance, as well as their compactness and ability to work with drilling muds that vary widely in density and viscosity (see, 1981, M Nedra Publishers, Guzman M. Downhole Screw Motor for Well Drilling by T.Y., Vardenko D.F. et al.). Such screw machines generally consist of a casing, an output shaft with radial and thrust bearings, and a working member. The working member consists of two parts: a rubberized outer sleeve or stator with helical internal teeth, and a rotor and shaft with helical external teeth accommodated in the stator. The number of teeth on the sleeve is one greater than the number of teeth on the shaft so that the interior of the working member is divided into a high pressure chamber and a low pressure chamber by mutual engagement when liquid is pumped through the working member. It's summery. Under the action of the generated pressure difference, the rotor begins to move relative to the stator, and the axis of the rotor circles around the axis of the stator. This rotation is transmitted to the output shaft of the rotor. Typically, a flow of liquid is used as the energy source for motor operation;
However, fluid motors can also function using vented liquid or compressed air.

Downhole motors used today to drill wells pass all of the flow of liquid between the rotor and stator.

One of the major disadvantages of such motors is that the output parameters are dependent on the inlet flow of the working liquid. The productive demands of well drilling often do not take into account the energy capabilities of downhole motors.
Downhole motors are often operated under unreasonable conditions such as speeds and pressure differentials that are too high, resulting in premature damage to motor parts and assemblies.

To eliminate this disadvantage, a conical nozzle was installed in the axial passage of the rotor (see USSR Inventor's Certificate No. 436595, c1, E21B4/
00, 1972), the working liquid flow is throttled in the nozzle.

The characteristics of such a motor deteriorate, ie the speed of the output shaft decreases faster with increasing load torque than a fluid motor without such a nozzle. Therefore, as the load increases, the speed of the output motor shaft is strongly reduced until it stops at a low load torque, resulting in a decrease in output torque and a decrease in excavation efficiency.

[Disclosure of the invention]

The present invention provides a motor configured such that a working liquid flow regulator increases the output torque and speed of the output shaft of the motor such that the speed of the output shaft remains practically unchanged at no load. It is based on the problem it provides.

This problem consists of a motor part with a spindle part and a working member formed by a stator and a hollow rotor with an axial passage leading to a high pressure zone of the working liquid, and a motor part with a nozzle for directing the flow of the working liquid. In downhole screw motors in which a flow regulator is installed in the axial passage, the invention provides that the nozzle is flushed with the working liquid and connected to the break line in two chambers arranged in series in the flow direction of the working liquid. an inlet chamber and an outlet chamber having surfaces that are joined together, the annular part of the inlet chamber adjacent to the break line being convex with respect to the flow direction of the working liquid, and the cross-sectional area at the outlet of the inlet chamber being the same; The problem is solved by a downhole screw motor, which is characterized by a cross-sectional area smaller than that at the entrance of the chamber.

The present invention makes it possible to improve the torque and speed of the output motor shaft, thus improving the efficiency of well drilling. When the working liquid enters the nozzle, the jet stalls at the break line, forming a strong vortex in the introduction chamber, and the energy of this vortex increases as the pressure difference increases, leading to an increase in the fluid resistance of the nozzle. and will increase the flow of liquid between the rotor and stator.

The regulator according to the invention is very compact and can be attached to any motor,
Additionally, the fluid motor can be replaced without disassembling it.

In one embodiment of the invention, the nozzle is made of two members, a bush and a rod mounted inside the bush, an inlet chamber and an outlet chamber being formed by the bush and the rod; The shape is circular.

In another embodiment, the rod is cylindrical and the bush is provided with an annular projection forming a convex portion of the surface of the introduction chamber.

In yet another embodiment, the bush is cylindrical and the rod is provided with an annular projection forming a convex portion of the introduction chamber.

In yet another embodiment, the bush and the rod have annular projections, each projection having an annular projection therein forming a convex portion of the surface of the introduction chamber.

All embodiments of the invention make it possible to improve the stability of the motor characteristics, ie to reduce the dependence of the speed on the output shaft load. This is achieved because the liquid flowing along the curved surface of the introduction chamber stalls at the jet break line, creating a space with strong swirling currents. The higher the pressure difference across the working members (rotor and stator) and thus the nozzle, the more intense the mixing of the liquid jets, the higher the resistance of the nozzle, and the greater the amount of liquid passing through the regulator. This configuration allows more liquid to reach the helical surfaces of the rotor and stator than if conical nozzles were used.

This result, i.e. an increase in the flow of liquid through the helical surfaces of the rotor and stator upon increasing loading of the output shaft, can also be obtained using other construction measures, but the basic principle of the invention is The concept remains unchanged.

In order to reduce the specific load on the nozzles, it is preferred to provide a plurality of nozzles in the axial passage of the rotor. The operation of the overall device in such cases is the same.

[Brief explanation of drawings]

Other objects and advantages of the invention will become more apparent from the following description of embodiments illustrated in the accompanying drawings. In the drawings, FIG. 1 is a longitudinal sectional view of a downhole screw motor with a nozzle of an embodiment of the regulator installed in the axial passage of the rotor, and FIG. 2 is an enlarged longitudinal sectional view of a flow regulator with a nozzle. , FIG. 3 is a diagram showing the flow of liquid through the nozzle, FIGS. 4 to 6 are diagrams showing embodiments of various structures of the nozzle, and FIGS. 7 and 8 are diagrams showing the prior art and the present invention. FIG. 2 is a diagram showing the energy characteristics experimentally obtained.

[Best mode for carrying out the invention]

The downhole screw motor (FIG. 1) consists of a motor section 1 and a spindle section 2. The motor section 1 includes a stator 3 and a hollow rotor 4 mounted therein as working members. The rotor 4 has an axial passage 5 leading to the high pressure zone of the liquid, in which a flow regulator 6 is arranged. The lower part of the rotor 4 is connected to a cardan shaft 7, which in turn is connected to an output shaft 8 of the spindle part 2. Output shaft 8
The radial bearing 9 and thrust bearing 10 held in the casing 1 of the spindle part 2
1 between the nipple 12 and the stub sub 13. The upper part of the motor is provided with a sub 14 for connection to the drill pipe string. A rock breaking tool (not shown) is connected to the lower part of the output shaft 8.

The flow regulator 6 (FIG. 2) comprises a removable casing 15, on which is fitted a nozzle 16 made of ceramic material, for example. For example, rubber seal ring 1
7 and 18 are provided between the casing 15 and the rotor 4 and between the nozzle 16 and the casing 15.

The nozzle 16 has two chambers arranged in series in the flow direction of the working liquid, namely an introduction chamber A and a delivery chamber B. The surfaces 19, 20 of the inlet chamber A and the outlet chamber B are each connected by a break line 21. The annular portion 22 adjacent to the break line 21 of the introduction chamber A is convex with respect to the flow direction of the working liquid. The diameter D of the inlet of the introduction chamber A is larger than the diameter d of the outlet of the same introduction chamber A. In other words, the cross-sectional area of the introduction chamber A at the inlet is larger than the cross-sectional area of the same introduction chamber A at the outlet.

The surface 20 of the delivery chamber B can be of any suitable shape. Preferably, however, the shape of the delivery chamber B is such that it provides the maximum possible resistance to the flow of working liquid through the nozzle 16. The surface 20 of the delivery chamber B, like the surface 19 of the introduction chamber A, is formed by rotating a convex curve about the axis O--O with respect to the flow direction of the working liquid.

The curves forming the inlet chamber A and the outlet chamber B intersect each other at a point corresponding to a break point in the longitudinal region of the nozzle 16 . Such points spatially form an intersection 21, which is equivalent to a break line.

The downhole screw motor works as follows. When the drill pump located at ground level is switched on, drilling mud is supplied through the drill pipe string to the working member of the motor section 1 (FIG. 1). This flow is split just above the working member. The main part of the flow passes between the stator 3 and the rotor 4 giving motion to the rotor 4, and the remaining small part of the flow passes between the stator 3 and the rotor 4.
through an axial passage 5 to a flow regulator 6 disposed in this axial passage 5.
After passing through these working members, these two streams again become a single stream and flow through the internal bore of the output shaft 8 of the spindle part 2 to the underside.

The torque obtained by the motor section 1 is transmitted from the rotor 4 via the cardan shaft 7 to the output shaft 8, and further transmitted to the rock breaking tool (bit).

The amount of resistive torque to be overcome by the motor depends on the relationship between the bit and the rock being broken. During operation of the motor, the motor torque and the load or resistance torque change.

It is known that the torque of such types of motors is proportional to the pressure difference in the working member (at the working of the motor characteristic) when the working liquid is flowing at a constant rate. In prior art motors, when the motor is loaded by an external resistive torque during rotation of the bit, the amount of fluid passing between the rotor and stator is proportional to the route P, where P is the pressure difference across the motor. and decrease. The characteristics of the motor are therefore reduced and the speed of the output shaft 8 is considerably reduced.

In the motor according to the invention, the liquid flow reaching the introduction chamber A (FIG. 3) moves in two flow types. The main flow along the axis O-O of the nozzle 16 moves from the introduction chamber A through an outlet section of diameter d formed by its break line 21, and the remaining peripheral part of the flow passes through the surface 19 of the introduction chamber A. wash. At the break line 21, this peripheral flow stalls and mixes heavily with the main central flow. The flow in this peripheral area is hereinafter referred to as resistance flow.

Therefore, intense mixing of the central flow and the resistive flow results in a reduction in the energy of the flow reaching the delivery chamber B. The greater the pressure difference between the working members, i.e., the stator 3 and the rotor 4, as well as at the nozzle 16, the stronger the mixing of the liquid flows, and the smaller the amount of liquid flowing from the introduction chamber A to the delivery chamber B, the smaller the amount of liquid introduced into the working member. The amount of liquid applied increases.

As shown in FIG. 4, nozzle 16 is made of two members, a bush 23 and a cylindrical rod 24 connected by a bridge 25. As shown in FIG. Similar to the structure described above, the nozzle 16 has two annular chambers arranged axially in series, an inlet chamber A and an outlet chamber B with surfaces 19, 20 which are washed with working liquid. Introduction chamber A and delivery chamber B
is formed by the surface of the bush 23 and the cylindrical rod 24. The surface of the bush 23 is formed by rotating a curve convex to the generatrix of a cylinder with radius R around the axis O-O, where R is the distance from the axis O-O of the nozzle 16 to the introduction chamber A. surface 19 of
is the minimum distance to a line equal to the break line 21 formed by the intersection of the surface 20 of the delivery chamber B and the surface 20 of the delivery chamber B. In this case, similarly to the embodiment of the present invention described above, the surface 20 of the delivery chamber B has an arbitrary curve along the axis O.
- formed by rotating around O.

An annular projection is provided on the inner surface of the bush 23 to form a convex portion 22 of the introduction chamber A.

During operation of the regulator embodiment, the same results as in the device shown in FIG. It becomes a part that mixes with the main flow (secondary mixing).

FIG. 5 also shows a nozzle 16 having a bush 23, a rod 24 and two chambers, an inlet chamber A and an outlet chamber B. FIG. In this embodiment of nozzle 16:
The bush 23 is cylindrical and the rod 24 is provided with an annular projection 27 forming a convex portion 22 of the surface 19 of the introduction chamber A. The surface of the bush 23 that is washed with the working liquid is cylindrical, and the surface of the bush 24 is cylindrical.
The surface of the delivery chamber B with radius R is formed by rotating a curve convex with respect to the generatrix of the cylinder around the axis O-O, where R is the radius R from the axis O-O of the nozzle 16. A line 21 equal to the break line formed by the intersection of the surface area of 24 (of the inlet chamber A) and the surface area of the rod 31 (of the delivery chamber B).
is the minimum possible distance to

Unlike the motor shown in FIG. 3, here the resistive flow moving along the curved surface from the center of the nozzle to its periphery is reflected from the cylindrical surface of the bushing 23 to the center and again and with low energy Mix with the flow.

The nozzle 16 shown in FIG. 6 has two members as in the previous two embodiments, namely the bridge 2
Bush 23 and rod 24 connected by 5
and has. The nozzle likewise has two chambers arranged axially in series, an inlet chamber A and an outlet chamber B with surfaces 19, 20 which are washed with working liquid. The bush 23 has an annular projection 28, and the rod 24 has an annular projection 29. Protrusion 28,2
9 each form a convex portion 22 on the surface 19 of the introduction chamber A. The surfaces of the bush 23 and the rod 24 arranged in the introduction chamber A are each formed by rotating a curve convex to the generatrix of a cylinder of radius R around the axis O-O, where: R is nozzle 1
It is the minimum distance from the axis O-O of No. 6 to the line that is equal to the break line 21, respectively.

The operation of this flow regulator is distinguished in that two resistive flows are created. That is, one is
One moves along the curved surface of the bush 23 from the periphery of the nozzle 16 to the center, and the other moves along the curve of the rod 24 from the center of the nozzle 16 to the periphery. These streams cross each other in the ring formed by radii R, R' and contribute to further mixing of the liquid streams.

Therefore, in the embodiment of the motor according to the invention described above, by providing two parallel flows, one of which has its own auxiliary resistance flow, the energy of this auxiliary resistance flow is increases with increasing pressure difference, ie the dependence of the amount of liquid passing through the working member and nozzle 16 on the motor load conditions becomes a complex character.
However, the use of a flow regulator in a nozzle constructed as described herein stabilizes the energy characteristics of the motor to a large extent, thus allowing very natural increases in load capacity and motor output shaft speed. It refines a very small drop.

7 and 8 show the energy characteristics of the screw motors according to the prior art and the present invention, that is, the relationship between the relative pressure difference value ΔP, the rotation speed n of the output shaft 8, and the relative torque value M. It shows.

Considering the characteristics shown in the figures, the stable operating zone S of the motor of FIG. 8 is 18 percent greater in terms of torque than the stable operating zone Z of the motor of FIG. The reduction in speed for the prior art motor is 57 percent at the same point, while for the motor according to the invention
50%. The difference becomes even larger when the speed reduction is considered for both motors in an application with the same external torque. This means that every time a motor with a flow regulator increases the pressure in the working member (compared to the prior art)
This is due to the fact that an increased amount of liquid is supplied, so that the stability of the properties is indeed improved and the average values of working torque and speed are also increased.

[Industrial applicability]

The present invention can be most efficiently used in positive displacement downhole motors used as drives for rock breaking tools for drilling oil and gas wells.

The invention can also be used in turbo drills.