阅读说明：本技术 一种井下电加热器 (Underground electric heater ) 是由 王振东 杨甫 付德亮 段中会 马丽 田涛 于 2021-09-08 设计创作，主要内容包括：本发明提供一种井下电加热器,包括电缆仓、注气仓、加热仓、端头,本发明通过改变壳程流体的流动路径,提高了加热器的能量利用率。通过空心加热棒增大加热棒与流体的接触面积,以及加热器单体降低壳程流体的流通截面积,提高流体的流动速度,可有效降低辐射传热在壳体传热的占比,降低加热棒的壁面温度,提高井下电加热器的井下使用寿命。与现有的连续螺旋折流板式井下电加热器相比,该加热器的结构简单易于制造,成本低,便于大规模推广。(The invention provides an underground electric heater, which comprises a cable bin, an air injection bin, a heating bin and an end head. The contact area of the heating rod and the fluid is increased through the hollow heating rod, the flow cross section area of the shell pass fluid is reduced through the heater monomer, the flow speed of the fluid is improved, the heat transfer proportion of radiation heat transfer in the shell can be effectively reduced, the wall surface temperature of the heating rod is reduced, and the underground service life of the underground electric heater is prolonged. Compared with the prior continuous spiral baffle type underground electric heater, the heater has simple structure, easy manufacture, low cost and convenient large-scale popularization.)

1. A downhole electric heater, comprising: comprises a cable chamber, an air injection chamber, a heating chamber, an end head and an electric heating rod;

the cable bin is correspondingly arranged above the gas injection bin, the heating bin is correspondingly arranged at the lower part of the gas injection bin, the bottom of the heating bin is provided with an end head, the cable bin comprises a cable bin shell arranged on a cable bin support, and a cable sealing support is arranged on the cable bin shell;

the electric heating rod adopts the following two modes:

the first scheme is as follows: the middle of the cable bin support is provided with an air vent, a central air injection pipe passes through a central air injection hole of the support plate and a central air injection hole of the upper end cover, the heater shell consists of the upper end cover and the lower end cover which are respectively arranged at the upper end and the lower end of the heater outer shell and the heater inner shell, and the heater is arranged in the heating bin; the heater comprises a central column and a hollow heating rod, the cross section of a hollow heating rod shell is in a hollow annular shape, the hollow heating rod comprises a heating rod upper end cover positioned on a heating rod upper shell and a heating rod lower end cover positioned on a heating rod lower shell, insulating layers are arranged on two sides of the inner wall of the hollow heating rod shell, a heating wire is arranged in the middle of the insulating layers, a heating rod gas injection hole is formed in the heating rod upper shell, insulating glue is arranged on the top of the hollow heating rod shell, and a guide column penetrating through the insulating layers penetrates through the insulating glue;

scheme II: the cable bin support is connected with the central gas injection pipe and the electric heating rod;

the electric heating rod penetrates through the shell and the upper end cover of the gas injection bin, the upper part of the shell of the gas injection bin is connected with the cable bin support, and the lower part of the shell of the gas injection bin is connected with the upper end cover;

the heating bin comprises a heater inner shell, a heater outer shell and a supporting plate, the heater monomer comprises an electric heating rod, a continuous spiral baffle plate and a heater inner shell, the electric heating rod is arranged in the heater inner shell, and the continuous spiral baffle plate is arranged on the outer side of the electric heating rod; the central gas injection pipe and the electric heating rod penetrate through the supporting plate, and the inner shell of the heater penetrates through the supporting plate and the lower end cover.

2. A downhole electric heater according to claim 1, wherein: the center of the support plate and the center of the upper end cover of the heater are respectively provided with a central gas injection hole, at least one circle of gas injection hole ring is arranged around the central gas injection hole, and the gas injection holes are respectively and uniformly arranged on the gas injection hole ring.

3. A downhole electric heater according to claim 2, wherein: continuous spiral baffle plates are arranged between the inner wall of the hollow heating rod shell and the central column and between the outer wall of the hollow heating rod shell and the inner shell of the heater.

4. A downhole electric heater according to claim 2, wherein: the annular section of the lower end cover of the hollow heating rod is in an isosceles trapezoid shape and is used for limiting the axial displacement of the continuous spiral baffle plate.

5. A downhole electric heater according to claim 1, wherein: the number of the supporting plates is 3 at the lowest.

6. A downhole electric heater according to claim 5, wherein: the diameter of an outlet at the lower part of the inner shell of the heater is smaller than that of an inlet at the upper part of the inner shell of the heater.

7. A downhole electric heater according to claim 6, wherein: the heater inner shell and the lower end cover are not fixed, a space is reserved for axial expansion of the heater inner shell, and radial displacement of the heater inner shell is restrained through a limiting hole in the lower end cover.

8. A downhole electric heater according to claim 7, wherein: and a gas injection pipe connecting hole and a limiting hole are arranged between the cable bin support and the support plate.

Technical Field

The invention belongs to the technical field of oil and gas resource development, and particularly relates to an underground electric heater used in the field of in-situ exploitation of unconventional energy sources such as oil-rich coal, oil shale, heavy oil and thickened oil.

Background

The in-situ mining of unconventional energy sources such as oil-rich coal, oil shale, heavy oil and the like usually needs in-situ heating, but the unconventional energy source storage layer has low heat conductivity coefficient and is not suitable for underground heating in a heat conduction mode, and a high-temperature heat carrier in a convection heat conduction mode has large contact area with the storage layer, so that the heating efficiency is higher under the same condition.

The oil shale is a rock mass with low permeability and low thermal conductivity, and after the reservoir transformation is carried out on the oil shale, artificial cracks in the oil shale layer provide a flow channel for high-temperature fluid, so that the heat transfer area is increased, the time required for heating the oil shale to the cracking temperature in a heat convection mode is short, and the in-situ heating efficiency of the oil shale is improved. Although the permeability of the oil shale layer is improved after the reservoir is modified, the high-temperature fluid needs higher pressure (greater than the initiation pressure) to open a flow channel, the combustion under the high-pressure condition is not easy to control, and solid particles generated by insufficient combustion can block artificial cracks in the oil shale and are not beneficial to the injection of the high-temperature fluid. Meanwhile, the combustion reaction can not be stably and continuously carried out due to sudden water burst of the heat injection well, and the combustion type downhole heater is not easy to ignite again after the combustion reaction is stopped, so that the combustion type downhole heater is not suitable for in-situ exploitation of the oil shale.

The shell company develops an electric heating in-situ mining technology (E-ICP for short) test project in 2006, and the largest difference from the ICP is that a Y-type electric heater is used for heating an oil shale layer. The Y-shaped electric heater is composed of three electric heating rods (bare electrodes), and oil shale is heated in a heat conduction mode. Because the thermal conductivity coefficient of the oil shale is low, the heating efficiency of the mode is low, the heating time is long, high-temperature hot spots exist on the part of the bare electrode, and the electric heating rod is easy to generate local heat loss to fail.

The diameter of the underground electric heater is limited by the diameter of the heat injection well, and the electric heating rods need a certain space for connecting power lines, so that the quantity of the electric heating rods which can be installed in the underground electric heater is small. Based on this, patent CN201720974607.9 proposes an electrical heater for downhole fluid based on a continuous spiral baffle structure, which greatly reduces the wall temperature of an electrical heating rod and prolongs the service life of the electrical heater downhole, but the continuous spiral baffle of the heater needs drilling, which makes the processing and installation of the baffle difficult and the manufacturing cost higher, and when the heater is heated at high power and large flow, the wall temperature of the electrical heating rod is still higher, which is not favorable for prolonging the service life of the heater downhole.

Disclosure of Invention

In view of the above background, the present invention provides an underground electric heater, which can generate high-flow high-temperature fluid under the well, and has a lower wall temperature of the electric heating rod and a longer service life under the well.

In order to achieve the purpose, the invention provides the following technical scheme:

an underground electric heater comprises a cable bin, an air injection bin, a heating bin, an end head and an electric heating rod;

the cable bin is correspondingly arranged above the gas injection bin, the heating bin is correspondingly arranged at the lower part of the gas injection bin, the bottom of the heating bin is provided with an end head, the cable bin comprises a cable bin shell arranged on a cable bin support, and a cable sealing support is arranged on the cable bin shell;

the electric heating rod adopts the following two modes:

the first scheme is as follows: the middle of the cable bin support is provided with an air vent, a central air injection pipe passes through a central air injection hole of the support plate and a central air injection hole of the upper end cover, the heater shell consists of the upper end cover and the lower end cover which are respectively arranged at the upper end and the lower end of the heater outer shell and the heater inner shell, and the heater is arranged in the heating bin; the heater comprises a central column and a hollow heating rod, the cross section of a hollow heating rod shell is in a hollow annular shape, the hollow heating rod comprises a heating rod upper end cover positioned on a heating rod upper shell and a heating rod lower end cover positioned on a heating rod lower shell, insulating layers are arranged on two sides of the inner wall of the hollow heating rod shell, a heating wire is arranged in the middle of the insulating layers, a heating rod gas injection hole is formed in the heating rod upper shell, insulating glue is arranged on the top of the hollow heating rod shell, and a guide column penetrating through the insulating layers penetrates through the insulating glue; the annular section of the lower end cover of the hollow heating rod is in an isosceles trapezoid shape and is used for limiting the axial displacement of the continuous spiral baffle plate.

Scheme II: the cable bin support is connected with the central gas injection pipe and the electric heating rod;

the electric heating rod penetrates through the shell and the upper end cover of the gas injection bin, the upper part of the shell of the gas injection bin is connected with the cable bin support, and the lower part of the shell of the gas injection bin is connected with the upper end cover;

the heating bin comprises a heater inner shell, a heater outer shell and a supporting plate, the heater monomer comprises an electric heating rod, a continuous spiral baffle plate and a heater inner shell, the electric heating rod is arranged in the heater inner shell, and the continuous spiral baffle plate is arranged on the outer side of the electric heating rod; the central gas injection pipe and the electric heating rod penetrate through the supporting plate, and the inner shell of the heater penetrates through the supporting plate and the lower end cover.

In the technical scheme, the center of the supporting plate and the center of the upper end cover of the heater are respectively provided with a central gas injection hole, at least one circle of gas injection hole ring is arranged around the central gas injection hole, and the gas injection holes are respectively and uniformly arranged on the gas injection hole ring.

In the technical scheme, continuous spiral baffle plates are arranged between the inner wall of the hollow heating rod shell and the central column and between the outer wall of the hollow heating rod shell and the inner shell of the heater.

In the above technical solution, the number of the support plates is 3 at least.

In the technical scheme, the diameter of the outlet at the lower part of the inner shell of the heater is smaller than the diameter of the inlet at the upper part of the inner shell of the heater.

In the technical scheme, the inner shell of the heater and the lower end cover are not fixed, a space is reserved for axial expansion of the inner shell of the heater, and the radial displacement of the inner shell of the heater is restrained through the limiting hole in the lower end cover.

In the technical scheme, a gas injection pipe connecting hole and a limiting hole are formed in the middle of the cable bin support and the supporting plate, and a gas injection pipe connecting hole is formed in the middle of the supporting plate.

The invention improves the energy utilization rate of the heater by changing the flow path of the shell-side fluid. The contact area of the heating rod and the fluid is increased, the flow cross section area of the shell pass fluid is reduced by the heater monomer, the flow speed of the fluid is improved, the heat transfer proportion of radiation heat transfer in the shell can be effectively reduced, the wall surface temperature of the heating rod is reduced, the underground service life of the underground electric heater is prolonged, and compared with the existing continuous spiral baffle type underground electric heater, the heater is simple in structure, easy to manufacture, low in cost and convenient to popularize on a large scale.

Drawings

In order to more clearly illustrate the embodiments of the patent of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, it is obvious that the drawings in the following description are only some embodiments of the patent of the present invention, and other drawings can be obtained by those skilled in the art without inventive exercise.

FIG. 1 is a schematic structural view of example 1 of the present invention;

FIG. 2 is a schematic structural view of a heating rod according to example 1 of the present invention;

FIG. 3 is a schematic structural view of a heating rod A-A according to example 1 of the present invention;

fig. 4 is a schematic structural diagram of embodiment 2 of the present invention.

The cable cabin comprises a cable cabin shell 101, a cable cabin support 102, a cable sealing support 103, an air injection cabin shell 201, an upper end cover 202, a heater shell 3, a hollow heating rod 301, a heating rod air injection hole 302, a heating rod upper end cover 303, a center column 304, a heater inner shell 305, a heating rod lower end cover 306, an outer shell pass 4, a heater outer shell 401, a support plate 402, a center air injection pipe 403, a lower end cover 406, an end head 5, a continuous spiral baffle 6, a wire guide column 701, a heating wire 702, insulating glue 703 and an insulating layer 704.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given in the present patent application without inventive step, shall fall within the scope of protection of the present patent application.

Referring to fig. 1-3, a downhole electric heater as shown in embodiment 1 comprises a cable chamber, an air injection chamber, a heating chamber, and a head.

The cable bin is correspondingly arranged above the gas injection bin, the heating bin is correspondingly arranged at the lower part of the gas injection bin, and the bottom of the heating bin is welded with an end head.

The gas injection bin is formed by arranging a gas injection bin shell between the cable bin and the heating bin, and the gas injection bin shell is welded with the cable bin support and the upper end cover.

The cable bin comprises a cable bin shell arranged on a cable bin support, and a cable sealing support is welded on the cable bin shell. The middle of the cable bin support is provided with an air vent, a central gas injection pipe penetrates through a central gas injection hole of the support plate and a central gas injection hole of the upper end cover of the heater, and the central gas injection pipe is welded with the cable bin support, the upper end cover and the support plate; when the cable is installed, the power cable penetrates through the cable sealing support and is connected with the electric heating rod; and then, penetrating the cable bin shell through the cable bin support, welding the cable bin shell and the cable bin support together, and finally sealing the cable sealing support.

The upper end and the lower end of the heating bin are respectively provided with an upper end cover and a lower end cover, and a heater is arranged in the heating bin.

The heater shell is composed of an upper end cover and a lower end cover which are respectively arranged at the upper end and the lower end of the heater outer shell and the heater inner shell. The heater shell and the connection mode of the upper end cover and the lower end cover are welded. The connection mode of the inner shell of the heater and the upper end cover is welding, the inner shell of the heater is tightly matched with the lower end cover, the lower end cover is made of a thermosensitive material, the connection part of the inner shell of the heater and the lower end cover is sealed through thermal expansion, and the connection mode of the upper shell of the hollow heating rod and the cable bin support is welding.

A heater is arranged in the heating bin; the inner shell journey of heater includes center post and hollow heating rod, the cross section of hollow heating rod casing is hollow annular, hollow heating rod is including the heating rod upper end cover that is located the heating rod upper housing and the heating rod lower end cover that is located the heating rod lower housing, the connected mode of casing is the welding on hollow heating rod upper end cover and the lower casing of hollow heating rod and the hollow heating rod, the connected mode of casing and heating rod lower end cover is the welding under the hollow heating rod, the inner wall both sides of hollow heating rod casing set up the insulating layer, the heater sets up in the middle of the insulating layer, the casing sets up heating rod gas injection hole on the heating rod, hollow heating rod casing top sets up insulating glue, the guide post of connecting the heater passes insulating glue.

The center of the supporting plate and the center of the upper end cover of the heating rod are respectively provided with a central gas injection hole, at least one circle of gas injection hole ring is arranged around the central gas injection hole, and the gas injection holes are respectively and uniformly arranged on the gas injection hole ring.

Continuous spiral baffle plates are arranged between the inner wall of the hollow heating rod shell and the central column and in the space between the outer wall of the hollow heating rod shell and the inner shell of the heater.

When the heating power of the heater is 5kW and the air flow rates are 0.0289kg/s, 0.0253kg/s, 0.0218kg/s, 0.0188kg/s and 0.0158kg/s respectively, the average shell heat loss of the single-shell heater at the 5 flow rates is 642.3W, while the average shell heat loss of the double-shell heater is 42.5W, the shell heat loss is reduced by 93.4% compared with the single-shell heater, and experiments show that: the product of the invention not only has higher energy utilization rate, but also has longer service life under the well.

Referring to fig. 4, a downhole electric heater as shown in embodiment 2 includes a cable chamber, an air injection chamber, a heating chamber, a heater unit, a shell side, a central air injection pipe, and an end socket, where the cable chamber is disposed above the air injection chamber, the heating chamber is disposed below the air injection chamber, and the end socket is disposed at the bottom of the heating chamber. The cable bin comprises a cable bin shell 101, a cable bin support 102 and a cable sealing support 103, wherein the cable bin shell is arranged on the cable bin support, the cable sealing support is arranged on the cable bin shell, and during installation, the cable bin support 102 is firstly welded with the central gas injection pipe 403; then, the cable bin support 102 is in threaded connection with the electric heating rod 301, the joint is sealed, an electric heating rod bundle is formed, and on the premise that the outer shell of the heater can smoothly enter the heat injection well, the larger the diameter of the cross section of the cable bin support 102 is, the more the number of the electric heating rods in the electric heating rod bundle is, the larger the heating area is, and the longer the underground service life of the heater is under the same condition.

The gas injection bin shell 201 penetrates through the electric heating rod bundle, and the upper part of the gas injection bin shell 201 is welded with the cable bin support 102. The upper end cover 202 penetrates through the electric heating rod bundle and is welded with the lower part of the gas injection bin shell 201. The continuous helical baffle 6 is passed through the electrical heating rod 3011 and the heater inner housing 305 is passed through the continuous helical baffle; support plate 402 passes through central gas injection tube 403 and heater inner housing 305 and support plate 402 is welded to central gas injection tube 403.

The heating chamber comprises a heater inner shell, a heater outer shell and a support plate, wherein the heater outer shell 401 penetrates through the support plate 402, and the upper end cover 202 and the upper part of the heater outer shell 401 are welded together. The number of the support plates 402 is a minimum of 3, and the specific number may be increased as appropriate according to the length of the electric heater.

The lower cap 406 is passed through the heater inner case 305, and the lower cap 406 and the lower portion of the heater outer case 401 are welded together. A certain gap is left between the lower end cover 406 and the central gas injection pipe 403 for circulating heated fluid, the lower end cover 406 and the heater inner shell 303 only restrict the radial displacement of the heater inner shell 305 through the limiting hole, a space is reserved for the axial expansion of the heater inner shell 305, and the end head 5 and the lower end cover 406 are welded together.

In use, a power cable is passed through the cable sealing mount 103 and connected to the electrical heating rod 301. Then, the cable storage housing 101 is passed through the cable storage support 102, and the cable storage housing 101 and the cable storage support 102 are welded together, and finally the cable sealing support 103 is sealed.

The working principle of the heater is as follows: the electric heating wire converts the electric energy into heat energy to provide a heat source for the heater. The shell-side fluid of the heater firstly flows through the shell side, then flows into the inner shell side of the heater through the gas injection bin (namely the internal flow channel of the heater monomer, the inner space and the outer space of the hollow heating rod in the figure 1, and the outer space of the solid heating rod in the figure 4), and finally is discharged out of the heater. The double-shell structure of the heater not only reduces the heat radiation energy and the natural convection heat exchange quantity generated by the shell of the single-shell electric heater by changing the flow path of the shell pass fluid, but also can recover the heat dissipated by the shell of the single-shell electric heater, is used for preheating the shell pass fluid, and improves the energy utilization rate of the heater. The hollow heating rod structure of the heater can heat fluid on the inner side and the outer side of the heating rod, the contact area between the heating rod and the fluid is increased, the flow cross section area of shell pass fluid is reduced by the single heater, the flowing speed of the fluid is improved, the occupation ratio of radiation heat transfer in shell pass heat transfer can be effectively reduced, the wall surface temperature of the heating rod is reduced, and the underground service life of the underground electric heater is prolonged.

The above description is only for the specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto, and any person skilled in the art can easily think of the changes or substitutions within the technical scope of the present invention, and shall be covered by the protection scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the protection scope of the claims.