RU82746U1 - BOTTOM ENGINE SPINDLE - Google Patents

Abstract

1. A downhole motor spindle comprising a housing, a shaft with a central bore, sealing axial and radial bearings mounted on the shaft by means of a coupling with windows for passing flushing fluid through the central bore of the shaft, characterized in that it is further provided with a reflector of the leakage of drilling fluid, which is installed in the lower part of the spindle shaft so as to provide a change in the direction of the flow of leakage of the drilling fluid. ! 2. The spindle according to claim 1, characterized in that under the lower end of the reflector on the spindle shaft an additional snap ring is installed.

Description

The invention relates to techniques for drilling oil and gas wells, in particular to designs of spindles of downhole motors.

Known mechanical shaft seal downhole motor [SU 1093778 A, EV 4/00, publ. 23.05.84], made in the form of a screw joint of at least one of the peripheral sealing rings with a housing or shaft and installed with the possibility of interaction with the leading element of friction.

Known gerotor hydraulic motor [RU 2162132 C2, E21B 4/02, E 21B 7/08 publ. January 20, 2001], comprising a spindle, the casing of which from the side of its end facing the bit has a circumferential side located between the rotation support and the circumferential rib. The circumferential board on the spindle shaft and the circumferential rib in the spindle housing are made as continuous, mating threads. The screwing direction of the shaft and spindle housing is opposite to the direction of rotation of the spindle shaft, and the smallest distance between the edges of the ribs on the shaft and in the spindle housing is equal to the pitch of the ribs. The drive shaft is made collapsible between the bent sub and the engine, the connection point of its sections is made in the form of surfaces of bodies of revolution relative to the common axis of the engine and spindle. The spindle housing on the connection side with a curved sub contains a flow restrictor made in the form of an elastic-elastic sliding support with screw channels directed against rotation of the spindle shaft.

Known downhole motor spindle [SU 1023053 A, E21B 4/00, 06/15/83], containing a mechanical seal, the contact surfaces of which are located in the area of the windows of the coupling. A spindle having an annular piston with a spring is placed on the coupling, and a fixed cage is fixed in the housing.

The reason that impedes the achievement of the claimed technical result in the known technical solutions is the low sealing performance of the spindle sealing elements, which affects the quality of cleaning the bottom of the well, ensuring the necessary pressure drop in the bit, as well as the preservation of the natural reservoir properties of the formation in the process of deepening the well.

Most of the engines manufactured in our country and abroad have an axial sealing support, mounted in a separate spindle assembly. It performs three main functions: transmitting torque from a screw pair to a rock cutting tool; the perception of hydraulic, bending, tensile, compressive loads (forces) - stresses in the process of drilling a well; ensuring tightness at the outlet of the engine in order to create the necessary pressure difference in the nozzles of the bit.

To perform the above functions, domestic engines use persistent - radial rolling bearings with conical, toroidal, combined raceways, as well as toroidal tracks and a rubber compensator. Spindle tightness can be carried out by the following types of seals:

an end gland installed in the upper part of the spindle, below the radial support;

multi-row thrust plain bearing, effectively acting as a seal;

labyrinth seal acting as a throttling device;

persistent radial bearings with rubber toroid rings, installed instead of one row of balls.

However, the issue of ensuring the required tightness of the spindle section remains open.

The task to which the invention is directed is to improve the quality of cleaning the bottom of the well during drilling, ensuring the safety of the natural reservoir properties of the wellbore.

When carrying out the invention, the task is solved by achieving a technical result, which consists in reducing the hydrodynamic pressure in the annular space of the well by changing the direction of the leakage velocity vector of the drilling fluid.

The specified technical result is achieved by the fact that the downhole motor spindle comprises a housing, a shaft with a central hole, sealing axial and radial bearings mounted on the shaft by means of a coupling with windows for passing the flushing fluid through the central hole of the shaft. In this case, the spindle is additionally equipped with a mud leakage reflector installed in the lower part of the spindle shaft so as to change the direction of the leakage flow. In addition, under the lower end of the reflector, a snap ring is additionally installed on the spindle shaft.

When drilling with helical downhole motors (VZD) often there are problems associated with the instability of its work - the sequence of modes, from optimal to braking, as well as engine shutdowns, due to the heterogeneity (hardness) of the drilled rocks. In the process of engine operation in extreme - braking mode, additional hydraulic losses occur, which add up to losses in the screw pair, as well as in the spindle section. This is due to both the wear of the elastic stator plate and the spindle sealing elements. In most cases, the wear of engine elements is caused by technological factors, namely: the use of a drilling fluid with a high content of sand (abrasive material).

The dependence of leakage through the seal on the differential pressure on the bit is the main indicator that characterizes both the hydromonitor effect (additional destruction of the rock) and the quality of the well flushing.

The implementation of high-quality washing, without taking into account leaks in the spindle of the engine, requires maintaining the necessary pressure spent on cleaning the face R _Pts . Fulfillment of the quality flushing condition

defined by the expression:

where: N _Pts - power needed to clean the face, W;

Q _min - the minimum required flow rate, m ³ / s.

Cleaning power can be determined by the formula:

where: D _c - well diameter, m;

ρ _n is the density of the rock, kg / m ³ ;

V _m - mechanical drilling speed, m / s;

N - well depth, m;

g is the acceleration of gravity, m / s ² ;

The minimum required flow rate is determined in two ways:

For vertical sections according to the formula:

Q _min = (1.2 ÷ 1.3) × V _in × F _kn

For horizontal sections:

Q = (1.2 (1.2 ÷ 1.3) × V _in × F _kn × (1 + 0.21 × е ² )

where: V _in - the speed of the particles in the washing liquid, is determined by the formula:

where: d _h - the average particle diameter of the sludge, m

F _kn - the area of the annular space is determined as follows;

e - eccentricity is determined by the formula:

where: D _z , D _m - respectively, the diameter of the castle and the body of the pipe, m

For example, for a directional well with a depth of 2000, a well diameter of 0.139 m, a drilling speed of up to 20 m / h, a diameter of sludge from 0.006 to 0.008 m and a density of flushing fluids of 1100 and 1150 kg / m ³ , respectively, the velocity of particles (upward flow velocity) V _a ) was 0.52 m / s. The minimum required flow rate Q _min . flushing fluid and pressure drop P _Pts for data

conditions were respectively 0.0076 m ³ / s and 0.26 MPa.

Bench experimental studies have shown that spindle leaks depend both on the moments of resistance on the shaft, on the type (parameters) of the fluid, and on the operating time of the engine sealing elements. The results of the studies showed the following: - leakage rate V _y through the spindle seal (the moment of resistance varied from 300 to 2000 N · m) ranged from 0.06 to 0.18 m / s; - or 0.00085 to 0.0024 m ³ / s. These indicators confirm the need to take into account the required pressure in the formula for qualitative cleaning of the bottom face of the amount of leakage through the spindle seal. The expression for determining the necessary pressure spent on cleaning the face will take the form:

where q is the leak through the spindle seal, m3 / s [3].

Leaks through the seal are determined empirically. As the screw pair of the engine deteriorates to maintain its performance, as well as on the basis of the above conditions, it is accepted

increase the flow rate of flushing fluid. With an increase in flow rate, hydraulic losses also increase - drilling fluid leakage in the spindle, which leads to a constant change in the pressure drop in the annular space, and, as a rule, uncontrolled filtration of the solid phase into the formation.

The change in the pressure drop and the inability to control the filtration is primarily associated with an increase in the turbulence of the drilling fluid flow caused by the interaction of two oppositely directed flows: ascending - escaping fluid from under the bit (drilling mud is cut off from the cuttings) and fluid leaks through the seal of the spindle section engine.

The opposite direction of the leakage velocity vector V _y through the spindle seal, the upstream velocity vector V _в , leads to additional clogging of the reservoir pores in the bottom-hole part of the reservoir, as well as the formation of stagnant zones that impede the quality of bottom-hole cleaning (sludge removal) from the well.

Thus, improving the quality of cleaning the bottom of the well during drilling, ensuring the conservation of the natural reservoir properties of the wellbore without improving the sealing ability of the spindle sealing elements, is achieved by installing the leakage leakage flow reflector on the spindle shaft to change the direction of the leakage velocity vector V _y .

Created by changing the direction of the velocity vector V _otr leakage V _y of the mud flow through the seal of the spindle section of the engine, directed along the same trajectory with the upstream velocity vector V _в , helps to carry out the drilling fluid from the cleaved rock - sludge, thereby reducing the turbulence of the flow, which helps to reduce the hydrodynamic pressure in the annular space of the well, affecting the quality of opening of reservoirs.

In FIG. the downhole motor spindle is presented.

The downhole motor spindle comprises a hollow body 1, inside of which there is a shaft 2, sealing axial 3 and radial 4 bearings, mounted on the shaft 2 by means of a coupling 5 having flow channels 6. Shaft 2 contains a central hole 7. A reflector is installed in the lower part of the shaft 2 8 mud leak streams. To limit the axial movement of the reflector 8 relative to the housing 1, a retaining ring 9 is additionally installed under its lower end on the shaft 2.

The downhole motor spindle operates as follows.

The rotation from the working body of the downhole motor is transmitted to the coupling 5 and to the spindle shaft 2. The drilling fluid comes from the working body of the downhole motor flow channels 6 of the coupling 5, and then through the Central hole 7 of the shaft 2 is directed to the bit. Axial and radial loads are perceived by sealing seals - axial 3 and radial 4 bearings.

In the process of drilling a well, the supports 3 and 4 wear out, performing the function of sealing spindle shaft seals. As a result of wear of the seals between the housing 1 and the spindle shaft 2, drilling fluid leaks occur, the velocity vectors V _{y of} which are directed opposite to the upstream velocity vector V _c . The reflector 8 installed in the lower part of the shaft 2 changes the direction of the leakage velocity vector V _y to the opposite (reverse). The velocity vector of the reflected drilling fluid flux _Upr coincides in direction with the velocity vector of the upward flow V _c .

The installation of a reflector of the leakage flow of the drilling fluid on the spindle shaft will ensure the preservation of the natural reservoir properties of the formation, and improve the quality of face cleaning during well drilling.

Claims (2)

1. A downhole motor spindle comprising a housing, a shaft with a central bore, sealing axial and radial bearings mounted on the shaft by means of a coupling with windows for passing flushing fluid through the central bore of the shaft, characterized in that it is further provided with a reflector of the leakage of drilling fluid, which is installed in the lower part of the spindle shaft so as to provide a change in the direction of the flow of leakage of the drilling fluid. 2. The spindle according to claim 1, characterized in that under the lower end of the reflector on the spindle shaft an additional snap ring is installed.