SU1469092A1 - Method of flushing a borehole - Google Patents

Abstract

The invention relates to the mining industry and M.6. - used to clean the cavities from sludge during the washing of wells. The goal is to increase the efficiency of removing sludge from cavities by using the effect of breaking the continuity of the cavitir of a lean stream with vacuum generation. Down into the well a string of pipe with an element of larger diameter on its outer surface. The element is made in the form of a cone and is set at the mouth of the cavity with its top towards the flow. The latter is created from the annular space in the cavity of the column. The flow rate under the cone exceeds the flow rate above the cone. 1 1 lam, removed from the cavity by a stream of fluid, is removed from the well by a stream of fluid. This method involves creating a vacuum in the cavity of the cavity before washing out the sludge from it. 2 Il. S O)

Description

The invention relates to the mining industry, in particular to the technique of drilling wells, and can be used to clean the cavities from sludge when washing wells.

The purpose of the invention is to increase the efficiency of removing the sludge from the cavity by using the effect of breaking the continuity of the cavitating flow with vacuum formation.

Figures 1 and 2 show the method for implementing the method before and after creating a fluid flow.

The diagram shows a well 1, a cavity 2 in the wall of the well, sludge 3 in a cavity, a casing or drill string 4, a cone 5, an annulus space 6 of the well, a cavity 7 inside the string.

The method is carried out as follows.

In the drilled well 1, cavernometric work is performed and the location and shape of the cavity 2 filled with drill cuttings 3 is determined. A tubular column 4 is lowered into the well with a larger diameter element made in the form of a cone 5 on its outer surface located in the cavity 2, more precisely in its mouth. When this element 5 of a larger diameter (cone) set the top towards the stream with the formation of a gap between the outer surface of the element 5 and the borehole wall in the cavity 2.

If flushing is performed before the well is fixed, then as

four

05 Г About with

o

tubing columns use a casing string, and when washing a cavity in an open hole drilling well, a drill string is used as a tubing string. Cone 5 is made of polymers (rubber, polyethylene, etc.) with elastic properties for good conductivity when going down the well.

After descending into the borehole, the tubular column 4 with a cone 5 creates a fluid flow, including in the slot formed by a larger diameter element and the borehole wall in the cavity, from the annulus 6 into the cavity 7 of the tubular column with a higher flow rate under the cone fluid flow over the cone. Fluid flow is created due to the density difference in the fluid, for example, by pumping the flushing fluid into the annulus under the cone, followed by a bypass.

20 pores are created due to the density difference in the fluid: between the cavity of the well and the cavity due to the density of the liquid above the cone (in the cavity - vacuum), and between the annular fluid from the annulus 25 space and cavity of the column - for the well into the cavity of the pipe column, the density difference smoothed or swabbed tubular cavity

packs of fluid (; e) and well fluid (Then finally the condition for exceeding the flow rate under the cone over the flow rate over the cone takes the form

columns, or aeration of the liquid in the cavity of the pipe column. Then, the sludge removed from the cavity is removed from the well by direct or backwashing.

The cavern wash parameters are determined using the following relationships.

The velocity V of a jet in a gap between the cone and the borehole wall is related to the pressure created by the hydrostatic column from the liquid H above the cone, the dependence

V If V2gH,: Cl) where If 0.6 t 1.0 is a constant coefficient, is the consumption coefficient; g is the acceleration of the force of gravity,

 liquids are determined by the formula

.Q V-w, (2)

where CJ is the flow area.

When creating a fluid flow due to a density difference, the choice of the density of an upgraded fluid stack and its height in the annulus. Under the cone, you can

 the area of the annular section of the well below the cavity (between the casing and the wall of the well), jet ejection pressure P, corresponding to this pressure, minimum erosion area F, fluid flow

Realize using relation (2), written for the gap between jj in Q, the blasting jet and the area by the cone and wall of squalvesin and dl. jet flow (the gap area between the annular space between the casing and the borehole wall (below the cone) in the form of inequality, the conde and the borehole wall in the plane of the base of the cone)

satisfying the condition of excess fluid flow Qj under the cone over the flow} "joy Q, above the cone: Q 2 Q, or V ,,), from where

V2 (-, V, or taking into account ratio (1)

 iVfTi, f - "

W ,,

tf, s, -1

Since the coefficient of fluid flow, y, in the gap is less than the coefficient of flow, gi, in a wider annular

the space between the casing and the borehole wall, and the limits of variation of this flow rate are 0.6-0.8, then we take q, 0.6, 8;

In addition, it is necessary to take into account that the heads are created due to the density difference in the fluid: between the cavity of the well and the cavity due to the density of the liquid above the cone (in the cavity there is a negative pressure), and between the annular space and the cavity of the column

space and cavity of the column - for the difference in densities of

packs of fluid (; e) and well fluid (Then finally the condition for exceeding the flow rate under the cone over the flow rate over the cone takes the form

4TfHi (Pa-Pi) CON

-----.-- 7 --VJ /

3 / ii7.

or

16 Hi (fa-p; :) 9 H, p,

where H, is the height of the column of the purging liquid of density p, above the cone; C - height of the desired bundle

liquids density. under a cone;

UJ, is the area of the gap between the base of the cone and the wall of the well;

 the area of the annular section of the well below the cavity (between the casing and the wall of the well), jet ejection pressure P, corresponding to this pressure, minimum erosion area F, fluid flow

in Q, the blasting jet and the jet outflow area (the gap area between

in Q, the blasting jet and the jet outflow area (the gap area between

cone and borehole wall in the plane of the base of the cone) w, are related by

F - (J2

L -, r

U, P

(four

The required jet erosion pressure in formula (4) should have a value not lower than 150 kPa (15 N / cm) under conditions of comprehensive overpressure when the sludge particles are tightly pressed to each other in the medium of drilling mud. However, the proposed method involves creating a vacuum in the cavity of the cavity before washing out the sludge from it, as a result of which the impregnating sludge (particles of cuttings) washing fluid boils, so that the sludge particles become separated vapor bubbles and liquid interlayers. Therefore, the maximum bond voltage between the sludge particles is reduced to the shear stress of the washing liquid, which for a very viscous state of thickened washing liquids, such as mud, reaches a value of the order of 1 N / cm. Thus, under conditions of sludge erosion, the proposed method. Calculation according to the formula (4) should be carried out

using ipichina daplepi erosion And / cm,

Claims (1)

Invention Formula The method of drilling a borehole, including the descent into the borehole of a tubular string with a larger diameter element on its outer surface located in the cavity zone to create a gap between the outer surface of the element and the borehole wall in the cavity, creating a flow of fluid in the slot, characterized in that To increase the efficiency of removal of sludge from the cavity by using the effect of breaking the continuity of the cavitating flow with vacuum formation, the element of larger diameter is made in the form of a cone and installed in the mouth of the chamber rny apex facing upstream, flow is effected from the annulus into the cavity of the column, the flow rate under flow cone prevsh1aet zhidkoe- minute over a cone is withdrawn from the hole remote from cavity slurry liquid stream.