RU2238392C1 - Heater for oil well and heating cable for use in said heater - Google Patents

Abstract

FIELD: oil extractive industry.

SUBSTANCE: device has heating cable, adjuster and power source. Heating cable has three heating filaments protected by two thermo-isolation layers of blocks-polymer of propylene with ethylene and layer of winding of thermo-resistant fiber. Cable also has filling filaments made in form of isolated copper wires, placed along heating filaments. Diameters of filling filaments are selected to be such, that their outer surfaces are stopped against respective outer surfaces of heating filaments and inner surface of support for common cable armor. Above isolated heating and filling filaments a common winding is placed for armor and armor with forming of heating surfaces. Heating filaments in lower portion of cable are interconnected, and by other ends are connected to adjustable three-phase power source, control input of which is connected to output of adjuster. Filling filaments in lower portion of cable are also interconnected, and by upper ends are switched in shoulder of measurement bridge, measuring diagonal of which is connected to adjuster input.

EFFECT: higher durability, higher precision of temperature adjustment during operation.

2 cl, 4 dwg

Description

Technical field

The invention relates to equipment for oil wells and can be used to maintain optimal thermal conditions in wells in order to prevent and eliminate paraffin hydrate formations. In this case, the invention relating to the cable relates to electrothermal, namely, to designs of resistive electric heating cables of the surface type, which are intended for heating objects of various configurations, sizes and shapes, and can be used in the oil industry, in particular, for traveling electric heating of a highly viscous oil and gas mixture wells equipped with sucker-rod pumping units or submerged electric pumps.

State of the art

A heater for an oil well is known, comprising a first heating element located in a tubing in the form of a cable connected to a power source, while at the end of the cable there is an uninsulated section with conductive weights that provide electrical connection to one or more parallel cable conductors through which a current is passed, with a tubing, which is the second heating element; while the cable is connected to the positive terminal of the power source, and the tubing to the negative. The cable, in addition, is equipped with temperature sensors and connecting wires embedded in it for connecting them to the measuring device (Patent RU No. 2171363 C1, Application No.2000131536 / 03, filing date 2000.12.18, publication of the formula 2001.07.18).

Signs that are common to the known heater and claimed are the presence of a heating cable and a current source to which this cable is connected.

The reason for the failure in the known heater of the claimed technical result is the presence of conductive goods and the use of a tubing as a heating element.

A heating cable is known that contains a flexible heating element made of high-resistance material, for example, nichrome, closed externally with insulating and hermetic coatings, holders made in the form of tides of a sealed coating located at a given distance along the entire length of the cable, at least two holes are made in each holder, one of which is parallel to the longitudinal axis of the cable, and the second perpendicular to it (USSR Author's Certificate No. 830666, class N 05 B 3/56, 1981).

Signs that are common to the known cable and claimed are the presence of a flexible heating element (conductive heating core), closed from the outside with electrical insulating and hermetic coatings.

The reason for the failure in the known cable of the claimed technical result is the presence of one conductive heating core.

The closest analogue for the claimed heater is a heater for an oil well containing an adjustable current source, a regulator and a heating cable that contains a common armor with a cushion for this armor, three thermally insulated conductive heating conductors parallel to the inside of the armor, a local temperature sensor (primary converter), connecting wires that are located inside the armor parallel to the heating cores and through which the sensor is connected to the input of the controller, This heating conductors at one (lower) end of the cable are interconnected, and the other ends are connected to an adjustable current source, a control input coupled to an output regulator. (US Patent No. 5782301, CL E 21 B 36/04, publ. 21.07.1998).

Signs that are common to the known heater and claimed are the presence of an adjustable current source, regulator and electric heating cable, the cable contains a common armor with a pillow for this armor, three thermally insulated conductive heating conductors parallel to the inside of the armor, which are on one (lower) the end of the cable are interconnected, and the other ends are connected to an adjustable current source, the control input of which is connected to the output of the regulator.

The reason for the failure in the known heater of the claimed technical result is the use of a local temperature sensor, which due to its locality cannot provide objective information about the average temperature of the cable along its length.

The closest analogue for a heating cable is a heating cable containing three conductive heating cores, each of which is insulated with a single insulating dielectric sheath, a cushion for armor and general armor, while the heating cores are single-wire, the cushion for armor and armor are laid on the heating cores with the formation or flat parallel heat transfer surfaces, and the centers of the cross-sections of the heating cores are located on one straight line parallel to the flat heat transfer reaching surfaces, and are shifted towards one of the planes, or convex-concave heat transfer surfaces, and the centers of the cross-sections of the heating wires are located on the same arc with a constant radius and are shifted towards the concave surface or the cylindrical heat transfer surface with the centers of the sections of the heating wires located on the same circle (Utility Model Certificate No. 162020, class Н 01 В 7/18, Н 05 В 3/56, publ. 10.12.2000, Bull. No. 34).

Signs that are common to the known cable and the claimed one are three heating cores, each of which is insulated with a thermally insulating dielectric sheath, a cushion for armor and general armor, while the heating cores are single-wire, a cushion for armor and armor are laid on these cores with the formation of either flat parallel heat transfer surfaces, and the centers of the cross-sections of the veins are located on one straight line parallel to flat heat transfer surfaces, or convex-concave heat transfer surfaces, and the centers of the cross sections of the heating cores are located on the same arc with a constant radius, or a cylindrical heat transfer surface with the centers of the cross sections of the heating cores located on the same circle.

The reason for the failure to achieve the claimed technical result in the known cable is the presence of free (unfilled) spaces between the conductive conductors and the armor that reduce the mechanical characteristics of the cable, the performance of a heat-insulating dielectric sheath single-layer, in the absence of means to control the average temperature of the cable along its length.

SUMMARY OF THE INVENTION

The problem to which the invention is directed, is to increase the service life of the cable and increase the accuracy of regulating its temperature during operation.

The technical result that mediates the solution of this problem is: 1) to ensure longitudinal tightness of the conductive heating cores of the cable with a pressure drop of not more than 0.02 MPa per 1 m of length, 2) to increase the electrical strength of the insulation, 3) to combine the functions of the new cable elements increasing the stiffness and strength of the cable, as well as controlling its average temperature over the entire length.

A technical result is achieved in an oil well heater in that it contains an adjustable current source, a regulator and a heating cable that contains a common armor with a cushion for this armor, thermally insulated conductive heating conductors parallel to each other, connected at one end of the cable to each other, and other ends connected to an adjustable current source, as well as laid in parallel with thermally insulated conductive heating cores in the spaces between them and the common bro filling cores, the diameters of which are chosen so that their outer surfaces abut against the corresponding outer surfaces of thermally insulated conductive heating cores and the inner surface of the cushion under the overall armor of the cable, while at least two filling cores are made in the form of insulated copper wires connected at one end of the cable between themselves, and other ends included in the shoulder of the electrical bridge, the measurement diagonal of which is connected to the input of the regulator.

A technical result is achieved in the heating cable by the fact that it contains common armor with a pillow for this armor, thermally insulated conductive heating conductors parallel to the inside of the armor, as well as filling conductors laid parallel to the insulated conductive heating conductors in the spaces between them and the common armor, whose diameters are chosen such so that their outer surfaces abut against the corresponding outer surfaces of thermally insulated conductive heating cores and the inner the surface of the cushion under the overall armor of the cable, while at least two filling cores are made in the form of insulated copper wires, and the aforementioned cushion under the armor and armor are laid on these heating and filling cores with the formation of either flat parallel heat transfer surfaces or convex-concave heat transfer surfaces, or cylindrical heat transfer surface.

The technical result in the heating cable is also achieved by the fact that in it the cushion under the armor and the armor are laid either on three heating and four filling cores with the formation of flat parallel heat transfer surfaces, and the centers of the cross sections of the filling cores are arranged in pairs on two straight lines parallel to each other and indicated flat heat transfer surfaces, and the centers of the cross-sections of the heating cores are located on the third line parallel to the first two lines and located between them, or on three heating and more than filling cores with the formation of convex-concave heat transfer surfaces, and the centers of the cross sections of the filling cores are pairwise located on two arcs conjugate to the indicated convex-concave surfaces, and the centers of the cross-sections of the heating cores are located on the third arc, also conjugate to these convex-concave surfaces between the first two arcs, or into three heating and three filling cores with the formation of a cylindrical heat transfer surface with centers of sections of the heating cores, ra located on the first circle, and the centers of the cross-sections of the filling cores located on the second circle located between the first circle and the cylindrical heat transfer surface.

The technical result in the heating cable is also achieved by the fact that each heating core is made of tinned copper wire and coated with a heat-insulating dielectric sheath made of a two-layer composition of propylene-ethylene block copolymer, and the thickness of the first layer of the heat-insulating dielectric sheath directly adjacent to the heating vein is less the radius of this core, and the thickness of the second layer of the specified shell is less than the outer radius of its first layer, in addition, over the second layer t thermo-insulating dielectric sheath of each heating core laid winding of heat-resistant fabric.

Signs of the claimed heater for an oil well, distinguishing from the closest analogue, are that the heating cable contains filling wires located inside the armor to ensure cable stiffness, at least two of which are made in the form of insulated copper wires, and the filling wires are laid in parallel with a thermally insulated heating veins in the spaces between them and common armor; and also in the fact that these filling cores, made in the form of copper wires, perform the function of a resistance thermometer, for which they are included in the shoulder of the electrical bridge, the measurement diagonal of which is connected to the input of the regulator.

The features of the claimed heating cable, distinguishing from the closest analogue, are that the heating cable contains parallel filler wires inside the armor designed to provide cable stiffness, at least two of which are made in the form of insulated copper wires, while the filler wires are laid in parallel thermally insulated heating cores in the spaces between them and the common armor.

The cable is also characterized in that each heating core is made of tinned copper wire and is coated with a heat-insulating dielectric sheath made of a two-layer material made from a block copolymer of propylene with ethylene, the thickness of the first layer of the heat-insulating dielectric sheath directly adjacent to the conductive core being smaller than the radius of this core and the thickness the second layer of the specified shell is smaller than the outer radius of its first layer, in addition, on top of the second layer of the insulating dielectric sheath chki each heating wires laid winding of heat-resistant fabric.

List of drawings

Figure 1 shows a functional diagram of a heater for an oil well;

figure 2 schematically shows the design of the heating cable (cross section), in which the pillow under the armor and the armor are laid on the heating and filling cores with the formation of flat parallel heat transfer surfaces;

figure 3 schematically shows the design of the heating cable (cross section), in which the pillow under the armor and the armor are laid on the heating and filling cores with the formation of convex-concave heat transfer surfaces;

figure 4 schematically shows the design of the heating cable (cross section), in which the pillow under the armor and armor are laid on the heating and filling cores with the formation of a cylindrical heat transfer surface.

The implementation of the invention

Figure 1 shows a well 1 having one or more casing 2 passing through the well. The riser 3 passes through the casing 2 to the surface. The wellhead 4 is located on the surface. The pressure pipe 5 extends from the wellhead 4 to transmit produced fluids. The heating cable 6 passes through the wellhead 4 and down the well along the lifting pipe 3 and directly adjoins this pipe with the orientation to the pipe by those filling cores that act as a resistance thermometer. The brackets 7 attach the heater cable 6 to the riser pipe 3 at regular intervals.

The heating cable 6 (Fig. 1) contains three thermally insulated conductive heating cores 8, through which current is passed during heating (Figs. 2, 3, 4). Veins 8 are made single-wire from tinned copper wire; two layers of a thermally insulating dielectric sheath are superimposed on each core - inner 9 and outer 10 from a composition of a block copolymer of propylene with ethylene; moreover, the thickness of the first layer 9 immediately adjacent to the conductive core 8 is less than the radius of this core, and the thickness of the second layer 10 is less than the outer radius of the first layer 9. A winding of heat-resistant (for example, non-woven) fabric 11 is laid on top of the outer layer 10; and on the heating cords so insulated, a common cushion was placed under the armor and a common armor 12 (cushion not shown).

The implementation of a two-layer thermal insulating dielectric sheath with the aforementioned ratio of the thickness of these layers and the thickness of the heating core provides: 1) simplification of the cable manufacturing technology, 2) the necessary longitudinal tightness of the heating cores with a pressure drop of not more than 0.02 MPa per 1 m of length, which increases the reliability of the cable in operation process, 3) increasing the electrical strength of the insulation.

The use of a block copolymer of propylene with ethylene as a material for the manufacture of a thermally insulating dielectric sheath increases the heating ability of the cable due to the high heat resistance of this material.

The use of copper wire for the manufacture of heating cores 8 allows the cable to be heated at a very low voltage and high current, since copper has a low resistance. The latter allows a large current to flow at low voltage, resulting in two advantages. Firstly, low voltage reduces the critical mechanical stress on the insulation, which increases the period of normal cable operation. Secondly, the cable can be manufactured in very long sections without supplying high voltage to the power source. Another advantage is that since heat is generated by current through conductors, the rate of heat generation can be predicted along the cable over its length. In addition, if it is desired to generate more heat in a particular part of the installation, the diameter of the heating cores can be reduced in this area to create more heat without adversely affecting heat dissipation over the rest of the cable. Moreover, each heating core is tinned, which protects the insulation of this core from the harmful effects of copper ions. This, in turn, simplifies the manufacture of insulation of the heating core, since it does not require the introduction of copper deactivator into its composition.

The presence of the winding 11 also increases the reliability of the cable, as this winding compensates for temperature deformation of the structural elements of the cable during its operation.

The cable also contains filling cores 13, laid parallel to the heating cores 8 in the spaces between them and the common armor 12. At least two filling cores are made in the form of insulated copper wires. Others may be made of non-conductive material. The diameter of each filling core 13 (together with insulation in the case of using copper wire) is chosen so that it abuts against the corresponding outer surfaces (windings 11) of the insulated heating cores 8 and the inner surface of the common cable cushion with its outer surface. For the cable variant shown in FIG. 2, this condition is satisfied when the diameter of the filling core 13 for its insulation is four times less than the diameter of the heating core 8 for its insulation (winding 11). In this case, the filling cores 13 provide their first function - increasing the rigidity and strength of the cable.

At the same time, the filling cores 13 (those made of copper wire) are a sensor of the temperature averaged over the length of the cable, namely, a resistance thermometer included in the measuring bridge (not shown). At least two filling cores 13 connected at the bottom of the cable can be used as a temperature sensor, and their upper ends are included in the arm of the measuring bridge. In this case, the other two filling cores, if they are copper, can be included in the other shoulder of the bridge, namely such that the measurement effect is enhanced. Other shoulders of the measuring bridge (third and fourth), which do not include filling cores, are made of material that is little dependent on temperature, and are located, for example, at the wellhead. In this case, the diagonal of the power supply of the measuring bridge is connected to a stabilized voltage source (not shown), and its measuring diagonal is connected to the input of the regulator 15, the output of which is connected to the control input of the regulated current source 16 (Fig. 1). The latter is a three-phase current source and, with its power leads, is connected on the surface to heating cores 8, the lower ends of which are directly connected together at the bottom in a common connection 17.

There are three possible versions of the heating cable (figure 2, 3, 4).

In the first embodiment of the heating cable (Fig. 2), the cushion under the armor and the armor 12 are laid on three heating 8 and four filling 13 strands with the formation of flat parallel heat transfer surfaces 12a and 12b, and the centers of the cross-sections of the filling strands are arranged in pairs on two straight lines 14a and 14b parallel to each other and heat transfer surfaces 12a and 12b, and the centers of the cross sections of the heating cores 8 are located on the third straight line 14, parallel to the first two (14a and 14b) and located between them with equal distance from the indicated planes 12a and 12b within the technological error of cable manufacture, not exceeding 5% of the distance between these planes.

In the second embodiment of the heating cable (Fig. 3), the cushion under the armor and the armor 12 are laid on three heating 8 and four filling 13 cores with the formation of convex-concave heat transfer surfaces 12a and 12b, and the centers of the cross-sections of the heating cores 8 are located on the first arc 14, paired with the indicated convex-concave surfaces, with an equal distance from these surfaces 12a and 12b within the technological error in the manufacture of the cable, not exceeding 5% of the distance between these planes, and the centers of the cross sections of the cores 13 are paired are located on the second 14a and third 14b arcs, also conjugate to these convex-concave surfaces. In this case, the arc 14 is located between the arcs 14a and 14b.

In the third embodiment of the heating cable (Fig. 4), the cushion under the armor and the armor 12 are laid on three heating 8 and three filling 13 cores with the formation of a cylindrical heat transfer surface 12 with centers of sections of the heating cores located on the first circle 14 with equal distance from this surface within the technological error of cable manufacture, not exceeding 5%, and the centers of the cross sections of the filling cores 13 located on the second circle 14a located between the first circle 14 and the cylindrical heat Reducing surface 12.

The equidistance of the heating cores 8 from the heating surfaces simplifies the cable manufacturing technology and ensures uniform heat transfer from these cores to the indicated heating surfaces.

The operation of the heater for the oil well and the heating cable used in this heater are as follows.

Cable 6 is placed on a lifting pipe 3 and a three-phase electric current is passed through its heating cores 8 from an adjustable source 16. The current heats these cores, from which heat is transferred through the insulating dielectric sheath to the heating surfaces 12a and 12b, and from them to the pipe 3. In this case, the temperature change causes a proportional change in the electrical resistance of the filling cores 13, as a result of which the measuring bridge is unbalanced, in the shoulder of which the indicated filling cores are included. The imbalance signal of the measuring bridge from its measurement diagonal is fed to the input of controller 15. As the latter, for example, a microprocessor equipped with a corresponding analog-to-digital converter (not shown) can be used. The controller 15 in accordance with the analog signal received from the output of the measuring bridge about the actual value of the average temperature of the cable 6 along its length and converted into a digital signal using an analog-to-digital converter, generates a control signal to the source 16 of an alternating three-phase current. In accordance with the selected type of influence on the source 16 from the side of the regulator 15, the desired regulation aimed at maintaining the specified temperature of the cable 6 can be carried out either by changing the angle of the thyristor switch (not shown), or by changing the frequency of passage through the heating cores 8 of the cable 6 for half periods alternating (sinusoidal) current from source 16. The second method is preferable, since the power circuit is switched using a thyristor switch at the moments of current passage through zero, which eliminates the occurrence of high-frequency radiation and does not degrade cos φ of the power circuit.

Claims (4)

1. A heater for an oil well, comprising an adjustable current source, a regulator and a heating cable that contains a common armor with a cushion for this armor, thermally insulated conductive heating conductors parallel to each other, connected at one end of the cable to each other, and connected to the adjustable end at the other ends a current source, as well as filling cores laid in parallel with thermally insulated conductive heating cores in the spaces between them and with common armor, the diameters of which are selected so that their outer surfaces abut against the corresponding outer surfaces of thermally insulated conductive heating cores and the inner surface of the cushion under the overall armor of the cable, while at least two filling cores are made in the form of insulated copper wires connected to each other at the end of the cable and the other ends included in the shoulder of the electrical bridge, the measurement diagonal of which is connected to the input of the regulator. 2. A heating cable that contains common armor with a cushion for this armor, thermally insulated conductive heating conductors parallel to the inside of the armor, as well as filling conductors laid parallel to the thermally insulated conductive heating conductors in the spaces between them, the diameters of which are selected so that their outer surfaces abut against the corresponding outer surfaces of thermally insulated conductive heating cores and the inner surface of the cushion under general armor cable, while at least two filling cores are made in the form of insulated copper wires, and the aforementioned cushion under the armor and armor are laid on these heating and filling cores with the formation of either flat parallel heat transfer surfaces, or convex-concave heat transfer surfaces, or a cylindrical heat transfer surface. 3. The heating cable according to claim 2, in which the cushion under the armor and the armor are laid either on three heating and four filling cores with the formation of flat parallel heat transfer surfaces, and the centers of the cross sections of the filling cores are arranged in pairs on two straight lines parallel to each other and to the indicated flat heat transfer surfaces, and the centers of the cross-sections of the heating cores are located on the third straight line parallel to the first two straight lines and located between them, or on three heating and four filling cores with the formation of convex-concave heat transfer surfaces, and the centers of the cross-sections of the filling cores are arranged in pairs on two arcs conjugate to the indicated convex-concave surfaces, and the centers of the cross-sections of the heating cores are located on the third arc, also conjugate to these convex-concave surfaces and located between the first two arcs, or three heating and three filling cores with the formation of a cylindrical heat transfer surface with centers of sections of heating cores located on the first circle, and prices trams of cross-sections of filling cores located on the second circle located between the first circle and the cylindrical heat transfer surface. 4. The heating cable according to one of claims 2 and 3, in which each heating core is made of tinned copper wire and is coated with a thermo-insulating dielectric sheath made of a two-layer polypropylene block copolymer composition with ethylene, the thickness of the first layer of the thermo-insulating dielectric sheath directly adjacent to the heating core, less than the radius of this core, and the thickness of the second layer of the specified shell is less than the outer radius of its first layer, in addition, on top of the second layer of thermal insulation The electrical heating of each envelope is stacked winding cores of the heat-resistant cloth.

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