RU2003781C1 - Method for elimination of hydrate and paraffin plugs in wells and device for its realization - Google Patents

Abstract

Usage: when operating oil wells to eliminate hydrate and paraffin plugs in them Summary of the invention, the electric heater is lowered into the well on a multicore cable. Part of the multicore cable cores is shorted and independently connected to a lithium source. The cork material is maintained in the molten state by additional heating by a shorted multicore cable. The electric heater and multicore cable work with the possibility of separation or joint connection to a power supply of 1 sludge.

Description

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The invention relates to the operation of oil wells and can be used to eliminate hydrate or paraffin plugs in them.

There is a method of eliminating hydrated and paraffin plugs, providing for their melting down by electric cable into the well with an electric heater 1.2.

The main disadvantage of this method is that it does not provide the ability to eliminate long plugs. Calculations show that in standard production wells, without fear of cable entrapment, plugs with a length of not more than 90 m can be melted, while in the fields of Western Siberia (Variogansk, Tallinn, etc.) there are wells in which plugs are formed up to several hundred meters long, and cable hooks have already occurred on the electric heater. Significant material and labor costs are required to eliminate such emergency tacking.

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There is a method for preventing the formation of paraffin and hydrate deposits in wells, which involves connecting a cable with shorted cores to a power source installed in the well 3 Nafewate provides heating throughout the formation zone of paraffin-hydrate deposits, which eliminates its sticking in the well, but this heater ( as well as the method implemented with its use) cannot be used to eliminate cork-type deposits, since when blocking the wellbore with a cork, it cannot be lowered into the well Zhin.

Electric heating devices are known for eliminating hydrate-paraffin plugs in wells 1,2 and 4, comprising an electric heater, a power source and an electric cable on which the electric heater is lowered into the well and by which it is connected to the power source.

An object of the invention is to prevent accidental cable tacking during the elimination of long plugs.

The goal is achieved. that during the elimination of hydrate and paraffin plugs in wells by melting them with an electric heater, lowered into the well on a cable, part of its shorted cores is connected to a power source, and the additional heat generated by it is removed to the molten substance above the plug, maintaining its temperature is higher than the crystallization temperature.

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The proposed method meets the criterion of significant differences, since the known materials of scientific and technical information lack information on technical solutions containing features similar to the distinguishing features of the claimed method and exhibiting similar properties.

The known device 4, after appropriate modernization, can be used to implement the proposed method. For this, in an electric heating device containing a power source and an electric heater connected to it by a multi-core cable, part of the cable cores is shorted and connected to the power source.

The drawing shows a diagram of an electric heating device for implementing the method.

The electric heating device comprises a surface mounted power supply 1; a multiplier cable connected to it through switch 2 in an armored metal sheath 3, and an electric heater 4. The wires 5 and 6 of the cable are shorted, and the central electrode 8 of the electrode heater 4, the case of which (second electrode) is connected to the shell (armor) is connected to a free core 7 cable) 3.

The proposed method is implemented as follows.

An electric heater 4 on the cable, part of cores 5 and 6 of which is shorted, is lowered into the well to the upper boundary of the hydrate-paraffin plug and is switched on by supplying power to it through the core 7 and the sheath 3, which acts as a zero core. As the plug melts, heater 4 is lowered into the well for another 80-90 m and shorted cores 5 and b are connected to the power source, the heat additionally generated by the cable is removed to the molten substance above the plug, maintaining its temperature above the crystallization temperature .

The depth at which it is advisable to connect shorted cores is easily determined experimentally for any field. To do this, when eliminating the first few plugs, the electric heater is lowered until the cable is gripped, then it is turned off, but shorted cores are connected and the substance is melted over the plug again, after which the electric heater is turned on and the plug is melted completely. Temporary cable tacking is not dangerous, as it is eliminated without additional funds and, therefore, does not create an emergency.

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Since the designs of conventional production wells and the physicochemical properties of plugs in different wells do not differ significantly, the additional connection to the power supply of shorted cores at around 80 m (the length of the plug section melted only by the electric heater) almost always ensures plug elimination, which is confirmed by calculations.

The time during which the temperature in the well decreases from the value of ti (melt heating temperature by the heater) to the onset temperature of the paraffin hardening tmi is described by the equation

MS +. ti-t0

t g; s- In-,

IN1PL 10

where M is the mass of a unit length of the pipe, kg;

C is the specific heat of the pipe, kJ / kgK;

Cn is the specific heat of paraffin;

p is the density of paraffin;

R is the radius of the well, m;

t0 is the temperature of the surrounding rocks, K;

K is the linear coefficient of heat transfer from the walls of the borehole to the surrounding rocks, W / m K.

The calculation shows that at the initial temperature of molten paraffin (after passage of the electric heater) ti is 150 ° C and K 1 W / m, K cooling time to a solidification temperature of 60 ° C is 2.5 hours.

The time during which the entire paraffin melt becomes solid can be determined by the equation

GT

jrR2 DNG

K (tnn-to)

where DNpl is the heat of fusion of paraffin, kJ / kg.

Calculation using this equation shows that complete curing of paraffin takes 2 hours.

Thus, the time during which the cable is completely seized by the re-formed plug is 4.5 hours.

If we assume that the penetration rate of the paraffin plug-in heater is 20 m / h, the melting depth without cable grip is not more than 90 m.

To implement the proposed method can be used cables KGZ-70-

180 or KG7-70-180 and electrode heater according to ed. St. USSR No. 1539310.

Cable K GZ-70-180 has three cores. Two cores of the cable are shorted, and an electric heater is connected to the third and armor according to the scheme shown in the drawing, e.

When only an electric heater is operating, part of the power is released as heat on the cable

Cf2

where W is the power on the supply core of the cable;

1k - current flowing through the heater and cable;

RK - cable core resistance;

UV - phase supply voltage,

With the additional connection of two shorted cores, the total power on the cable increases the amount of power released on these cores

Wk

5

W

3 K.

c.k.

2RK Ј

3

2 RK

where is Wa.K. - power on shorted cable conductors;

B.k. - current flowing through a shorted core.

The total power is

5

0

5

0

5

W WK + W3. -t

7

4 ; Rk

When shorted cores are turned on, the power, and therefore the amount of heat released on it, increases by 7 times, which completely ensures that the temperature of the molten substance above the cork is maintained above its recrystallization temperature.

The method provides smelting plugs of any length and, in addition, eliminates emergency sticking of electric heat when stopping its descent into the well, for example, when a power outage occurs.

(56) 1. USSR Copyright Certificate No. 1114782, cl. E 21 B 43/24, 1984.

2. The author's certificate of the USSR Ig 122113, cl. E 21 B 43/24, 1959.

3. Techniques for preventing hydrate formation in oil well tubing by electric heating. RD 39-0148070-043 VNII-86. Tyumen; Rotaprint SibNIINP. 1986, ".4.

4. The author's certificate of the USSR No. 1539310, cl. E 2.) B 43/24, 1990

Formulas of the invention

1. A method of eliminating hydrated and paraffin plugs in wells, including descent into the well to the upper boundary of the plug of an electric heater on a multicore cable connected to a power source, transferring the plug material to the molten state by turning on the electric heater and moving it as the plug material melts, characterized in that that, in order to avoid accidents during the elimination of plugs, the plug material in the molten state in the area of the multicore cable is additionally heated uniformly along the entire length of multicore cable

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to prevent hardening of the cork material.

2. A device for eliminating hydrated and paraffin plugs, comprising a power source and a multicore cable connected to it with an electric heater, characterized in that, in order to prevent accidents during the elimination of plugs, the multicore cable is occupied by the electric heater with one part of the cores, the other part of the cores of the multicore cable is shorted and independently connected to a power source with the possibility of separately or simultaneously switching on the electric heater and the shorted New stranded cable.