RU2349732C1 - Vortex centrifugal separator well-packer - Google Patents

Abstract

FIELD: mechanics, mining.

SUBSTANCE: invention is designed to apply process compositions onto weal walls containing solid phase. The proposed device comprises a tubular casing with colmataging nozzles, a swirler with deflectors swirling the jet made from hard-alloy material and arranged in the casing, a branch pipe with slit-like holes fitted behind the swirler. The said swirler represents a replaceable tube with tangential openings. The walls of aforesaid colmataging nozzles fitted in sleeves pressed in the casing wall opposite to each other in between the casing wall and branch pipe, feature two tangential openings intended for repeated swirling of the drill fluid.

EFFECT: higher efficiency of well packing.

4 dwg

Description

The invention relates to drilling equipment and is intended for applying technological compositions to the well walls, for example, drilling fluids containing a solid phase.

A device is known for reducing the permeability of formations by hydromonitoring treatment of the walls of a well during drilling with a mud using a sub with a lateral hydromonitor nozzle mounted above the bit (AS USSR No. 819306, ЕВВ 33/138). Processing is carried out perpendicular to the wall of the well with a jet stream at a speed of 60-120 m / s.

The disadvantage of this device is that the impact on the walls of the borehole of a high-speed pressure jet with a small contact spot will have not so much a damaging effect on a low-strength rock as a destructive effect, which will inevitably lead to expansion of the wellbore and cavity formation. Therefore, this device can only be used for colmatation of high-strength rocks.

There is also known a device for mudding the walls of a well with a drilling fluid, including a hollow body, a swirl with radial blades and a nozzle located in the lower part of the body, inside of which a nozzle is installed (AS USSR No. 1439215, ЕВВ 37/02). The aim of this invention is to increase the efficiency of mudding by treating the walls of the well with a small fraction of the drilling fluid.

This device has the same disadvantages as the previous one. In addition, the swirling of the drilling fluid with a swirl with radial blades determines a weak separation of the fluid.

A device for colmatizing and cleaning the walls of a well is known, which is a suprasubbit sub in which a cylindrical nozzle is mounted perpendicular to its axis, in the middle part of which there are two tangential channels on either side of the axis of the device connecting the device’s internal cavity with the annular space. The device, according to the author, is a hydraulic generator of low-frequency oscillations, which allows you to effectively clog the walls of the well and flush clay cake during rotation of the drilling tool (AS USSR No. 1594264, ЕВВ 37/00, 33/138).

From the description of the design scheme and operation of this device, it follows that it is a vortex-type collimator, which provides an impact of the clogging jet on the borehole walls not perpendicularly, but at a certain angle, which minimizes its damaging effect.

The disadvantage of this device, as well as all the previous ones, is that effective mudding of rocks requires a drilling fluid with a sufficient solids content, which determines its increased density, especially if it is necessary to muddy rocks with high porosity and permeability, such as sands, weakly cemented sandstones, permafrost rocks with a low mineral content, etc. Since an increased density of the solution means increased pressure on the bottom, this leads to a decrease in mechanical speed and all other indicators of drilling, complications in the wellbore are possible.

Closest to the proposed one is a device for mudding the walls of the well with a drilling fluid, including a tubular body with radial drain nozzles, a swirler in the form of a replaceable sleeve with a swirling jet of reflectors along the inner generatrix, made of carbide material and placed in the body, a nozzle with slit-like openings located under swirl ring guide with through holes equipped with tangential throttle nozzles and a retaining ring for holding annular rail from moving (RF Patent №2219324 E 21 B 21/00, 33/138).

The disadvantage of this device is the high destructive effect of the liquid stream on the rock. The device is difficult in design and has a short service life, especially nodes subjected to intense exposure to high-speed abrasive blast. In addition, it has inherent disadvantages of creating increased pressure on the face.

The objective of the invention is to increase the efficiency of the mudding of permeable borehole walls, composed of low-strength and weakly cemented rocks, with a reduced solids content in the drilling fluid, for example, when drilling on clayey drilling fluids.

This problem is solved by the fact that in the device for mudding the walls of the well with a drilling fluid, including a tubular body with nozzles, a swirl with swirling reflectors made of carbide material and placed in the body, a nozzle with slit-like openings located under the swirl is made in the form of a replaceable tube with longitudinal windows, and in the walls of the clogging nozzles installed in the bushings pressed into the wall of the housing, are diametrically opposite to each other, in the region between the inner two tangential windows for secondary swirling of the mud flow are made by the body wall and the nozzle.

The implementation of the composite device affects its durability, as it provides the ability to replace any failed parts with a new one. The replaceable sleeve undergoes the most intensive wear, since it is exposed to a drilling fluid containing abrasive particles and flowing out of the windows of the swirl.

Due to the low solids content and, consequently, the density of the drilling fluid supplied to the bottom of the well, the drilling speed increases by at least 1.4-1.5 times and the penetration of the bit by at least 15%, and the vortex treatment of permeable formations in the process of opening allows you to effectively reduce the permeability of the rocks and increase their strength by colmatization hardening of rocks simultaneously with their opening.

Figure 1 shows a General view of the device; figure 2 is a section along the line aa of the swirler; figure 3 is a distribution diagram of a clogging jet; figure 4 - spot contact of the jet with the wall of the well.

The device includes a housing 1, a swirler 2, fixed coaxially to the housing using the upper annular plug 3 mounted on the end of the sleeve 4, pressed into the upper part of the channel of the housing and abutting against the shoulder in an annular groove. A plug 5 is attached to the lower end of the swirl, to which a coaxially located tube 6 is attached, extending to the lower annular plug 7 and connected to it. Two tangential windows 8 are made in the swirler for the drilling fluid to exit into the annular space formed by its outer wall and inner wall of the sleeve. A longitudinal slit-like window 9 is made in the tube 6 for passage of the drilling fluid from the annulus between its outer wall and the inner wall of the body to the bit. Two colmatating nozzles 10 are installed in the bushings 11 pressed into the wall of the housing 11 diametrically opposite to each other. In the walls of the nozzles in the region between the inner wall of the housing and the tube, two tangential windows 12 are made for secondary twisting of the solution before it enters the annulus.

All parts of the device subjected to intense exposure to the solution are made of superhard alloy type VK. All joints made on the thread are sealed with copper or rubber o-rings. A lock thread is cut at both ends of the body to connect the device to the shaft of the downhole motor and to the bit.

The device operates as follows. The flow of the drilling fluid, leaving through the tangential windows 8 of the swirler 3, receives intensive rotation, due to which it is centrifugally separated. The solution layer adjacent to the inner wall of the casing, enriched in the solid phase, passing through the tangential windows 12 of the clogging nozzle 10, is twisted a second time and leaves it in the form of a circular vortex (fan), covering a certain section of the borehole wall with mudding. Another part of the solution with a lower solids content adjacent to the tube 6 passes through the windows 9 and is supplied to the bit.

The cross-sectional area of the windows 8 is selected from the condition of achieving effective separation of the solution, and the ratio of the cross-sectional areas of the windows 9 and 12 is based on the assumption that vortex nozzles account for 1 / 4-1 / 3 of the total flow rate of the solution.

In the process, the vortex jet will apply a co-fluid to the borehole wall at acute angles to it, i.e. will have a sliding effect. Thus, the destruction of the borehole wall and the bounce of the mud from it are virtually eliminated. The colmatization layer gradually builds up by repeatedly “spreading” it over the surface.

Vortex divergence α is determined by the ratio of the tangential V _τ and axial V _α components of the flow velocity

The velocity components V _α and V _τ are related by the relation

where f _τ and f _α are the cross-sectional areas of the tangential and axial sections of the channels of the clogging nozzle.

An approximate hydrodynamic calculation of the swirler and the clogging nozzle can be easily carried out according to the hydrodynamic formulas, but the actual characteristic should be established experimentally. The velocity V _τ for a given ΔР will be determined by the ratio of f _τ and f _α . For a given f _{α, the} velocity V _τ will be almost entirely determined by the value of f _τ .

Calculations show that with the commonly used flushing parameters (Q = 30 l / s, ρ = 1100 kg / m ³ ) and structurally accepted device dimensions, V _α is of the order of 25 m / s, and V _τ - 75 m / s. Then by the formula (1) we get

.

.

The most important parameters of the vortex jet are:

1) the angle γ between the generatrix of the vortex cone and the borehole wall, which can be found by the formula

2) the angle β between the generatrix of the vortex cone and tangent to the wall of the well, which can be determined from the formula

3) the height h between the axis of the clogging nozzle and the highest point of the clogging spot

4) the distance l along an arc of a circle, covered in one revolution of the vortex,

In the above formulas, R _c and R _k are respectively the radius of the well and the outlet cut of the vortex nozzle.

Using the above formulas, we successively calculate

It is accepted here that the diameter of the collator is 3/4 of the diameter of the well. Then, in one revolution of the vortex, a distance equal to 2h = 0.165 m will be covered vertically.

From figure 3 we have:

.

.

Then

.

.

.

.

Thus, in one revolution of the vortex, the area will be covered by colmatation, which will be an ellipse with a larger vertical axis.

You can also determine the angular and circular frequency of the vortex.

The inner radius of the clogging nozzle is determined from the condition that 1 / m part of the total flow rate of the solution is directed through it:

The vortex frequency is approximately equal to:

1) angular

2) circular

Thus, during the period of one revolution of the bit (n _∂ = 8 rpm), the vortex will have time to make about 186 revolutions.

The use of a device for the mudding of the walls of the well does not require the use of special drilling modes, types and properties of drilling fluids, and additional technical and technological equipment. The separator-colmatator is simple in design, reliable in operation and can be used both with the rotary method and when drilling with downhole motors.

Claims (1)

A centrifugal centrifugal separator-collator, including a tubular casing with coaxing nozzles, a swirl with swirling reflectors made of carbide material and placed in the casing, a nozzle with slit-like openings located under the swirl, characterized in that the latter is made in the form of a replaceable tube with tangential windows and in the walls of the clogging nozzles installed in the bushings pressed into the wall of the housing, are diametrically opposite to each other, in the region between the wall of the housing and the sleeve are made of two tangential windows for the secondary spin mud flow.

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