RU1816849C - Method for asphalt-resin-paraffin hydrate bridge elimination - Google Patents

Abstract

Usage: oil and gas industry for cleaning wells from asphalt tar, paraffin hydrate deposits. SUMMARY OF THE INVENTION: a heating element on a cable is lowered into a well and filled with liquid containing hydrophobizing additives. A rim of non-Newtonian fluid is formed under the stuffing box. The initial shear stress of the non-Newtonian fluid is determined from the expression T0 P (R-r) / 2h, where T0 is the initial shear stress, Pa; P is the overpressure in the well at the time of gas breakthrough after tube breakage, Pa; R is the radius of the seal, m; g is the radius of the cable, m; h - gland height, m,

Description

The invention relates to the oil and gas industry, and in particular to methods for cleaning wells.

The aim of the invention is to increase the efficiency of the method by eliminating cable sticking while preventing hydrates from falling onto the walls of the well after breaking the plug and increasing safety.

The invention is as follows. In a method for eliminating ASPGO in a well, including lowering a heating device into a wellbore on a cable, sealing the wellhead with an oil seal, heating the plug with a heating device and moving it along the wellbore until the plug is completely destroyed, a fluid containing hydraulic fluid is used as a filling fluid rephobizing additives. Moreover, under

the gland additionally forms a rim of non-Newtonian fluid for sealing the wellhead, the temperature of the fluid with hydrophobic additives is maintained above the freezing temperature of water by selecting the cable resistivity, and the initial shear stress of the non-Newtonian fluid is determined from the expression

g p (g-r)

m ° - 2h where T0 is the initial shear conjugation, Pa;

P is the overpressure in the well at the time of gas breakthrough after tube breakage, Pa;

R, r are the radii of the gland and cable, respectively; h - gland height, m.

Filling the wellbore with liquid containing hydrophobizing additives ensures the formation of

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Cb 00

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the wall of the well has a thin film that prevents the formation of hydrate crystallization centers and, consequently, their further growth. As such fluids, you can use diesel fuel + surfactant, oil + surfactant, oil containing active components, alcohol containing 1-4 carbon atoms and water-soluble ethoxylated alkyl phenol and the like To prevent freezing of the cable in the permafrost zone, the temperature of the liquid is maintained above 0 ° C by heating the cable. For this, the cable resistivity is selected from the following considerations. The amount of heat generated by the cable should provide a positive temperature on the inner wall of the well.

We write the equation of heat flux through a cylindrical wall per unit length

Q 21 (tci - tea) m

Fan l, n da and;

d2lnҐT

where di, da inner and outer diameters of the casing, respectively, m;

tci, tc2 - temperature on the inner and outer surface of the wall, respectively, ° C; I - thermal conductivity of the wall material, W / m ° C.

The amount of heat generated per unit time when current flows through the cable is determined from the expression.

,

(3)

where p is the cable resistivity, Ohm / m;

 - current strength, A.

Equating (1) and (2) we get the expression for choosing the cable resistivity,

2A (tdi-tc2)

- d2, nЈ,

A hem formed under the gland serves to prevent gas breakthrough when the plug breaks into the gap between the gland and the cable. To do this, fluids having an initial shear stress (T0) are used. which can be determined on standard reoviekozimetry. As such fluids, greases, solutions of polyisobutylene in hydrocarbon solvents, solutions of synthetic polymers, and also lubricants with a filler (e.g. rubber crumb) can be used. The presence of these liquids ensures their movement only after application of certain

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fifteen

twenty

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thirty

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40

45

fifty

55

load. Otherwise, they do not move and can act as a shutter.

The selection of liquids is carried out as follows. Consider the equilibrium of the liquid in the gap between the gland and the cable.

The fluid load is determined from the expression

G P) .. (4)

Resistance Force for Non-Newtonian Fluid. F G02l- (R + r) h. (5)

In case of equality (i.e. in the absence of movement)

G F; P zr (RV) r0 2 w (R + r) h, (6) hence

. :: W

The choice of fluid with such r0 provides reliable sealing of the wellhead at the time of gas breakthrough after the tube breaks down .; .

The method is carried out as follows.

The well containing the plug is provided with wellhead equipment allowing for hoisting operations with the heating device under pressure and supplying energy to it. Then a heating device is lowered into the well and fluid containing hydrophobic additives (oil) is pumped. In this case, the upper liquid level must be between the central valve above the lateral branch of the tee and the stuffing box. Then, between the central valve above the lateral branch of the tee from the upper liquid level to the cable entry point. A rim of non-Newtonian fluid with an initial shear stress is formed into the stuffing box. A cementing unit for replenishing the well is connected to one of the flow lines of the wellhead reinforcement. The heating device is connected to the plug and voltage is applied to it. As the plug is destroyed by heat, the heating device descends along the wellbore. The fluid moves along with it. From the cemented aggregate, fluid is added. The rim remains in place.

At the moment the plug is destroyed, the bursting gas presses the rim against the gland, the gap 1 is sealed between the gland and the cable, and the well is sealed. After balancing the formation pressure, the heating device is removed from the well and put into normal operation.

An example of a specific implementation of the method:

a) selection of cable resistivity.

Initial data

Cement 0.9 W / mtrad, 1 tci 1 ° C; tc2 -1 ° C; di 0.175 m: d2 0.210 m; I 50 A,

Substituted these data in (3), we get 2-0.9-2

0.210 In

0.210

2500

 OTTB

 0.038 ohm / m.

Thus, standard geophysical cables can be used, in which the resistance (depending on the brand) varies from 0.011 to 0.045 Ohm / m

b) fluid selection

Initial data: R 6.5 mm; g 6.3 mm; P 0.2 108Pa; h 1500 mm.

Substituted these data in (7), we obtain

g -0.2

That - ---

108 0.2

 1.3 10J Pa.

2 1500

Measurements on a Volarovich instrument with coaxial cylinders showed that grease with solid rubber with crumb rubber of size 0.01-0.5 mm and a concentration of 8 10 had a value of 10 4 10 Pa and could be used to carry out the method.

Thus, the proposed method allows to increase the efficiency and safety when carrying out work to remove ASPGL from wells.

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Claims (1)

The claims A method for eliminating asphalt-resin-paraffin-hydrate plugs in a well, including descent into the well on the cable of the heating device to the surface of the plug, filling the well up to the mouth with liquid, sealing the mouth of the well with an stuffing box. heating the plug with a heating device and moving it along the well until the plug is completely destroyed, characterized in that, in order to increase its efficiency by eliminating cable sticking while eliminating hydrates falling on the walls of the well after breaking the plug and increasing safety, as a liquid for filling the well use fluid containing water-repellent additives, while under the gland an additional rim of non-Newtonian fluid is additionally formed to seal the wellhead, t mperaturu liquid water-repellent additive is maintained above the freezing point of water, by adjusting the resistivity of the cable, and the initial shear stress non-Newtonian fluid is determined from the expression TO - P (R-r) / 2h, where T0 is the initial shear stress, Pa; P is the overpressure in the well at the time of gas breakthrough after the destruction of the plug Pa; R is the radius of the seal, m: g is the radius of the cable, m; h - gland height, m.