CN115726735A - Downhole heating system - Google Patents
Downhole heating system Download PDFInfo
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- CN115726735A CN115726735A CN202110987724.XA CN202110987724A CN115726735A CN 115726735 A CN115726735 A CN 115726735A CN 202110987724 A CN202110987724 A CN 202110987724A CN 115726735 A CN115726735 A CN 115726735A
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Abstract
The invention relates to a downhole heating system comprising: a first tubular string configured for insertion into an outer casing; a second tubular string configured for insertion into a first tubular string and forming an annulus between the first and second tubular strings, the second tubular string having a lower end configured with an opening for communicating with the annulus; a first gas delivery tube configured to be connected to an upper end of the second tubular string; a second gas delivery tube configured to be connected to an annulus between the second tubular string and the first tubular string, the annulus in communication with the second tubular string through the opening; and a gas drive mechanism configured to cause heated gas to enter the wellbore through one of the first and second gas delivery tubes and exit the wellbore via the other of the first and second gas delivery tubes.
Description
Technical Field
The invention relates to the technical field of oil well exploitation, in particular to an underground heating system.
Background
In oil field development, particularly in the process of exploiting heavy oil, high-pour-point oil and high-wax oil wells, phenomena of wax precipitation, wax precipitation and the like of oil pipes often exist, and therefore the oil pipes are blocked, and the yield of the oil wells is influenced. When such a problem occurs, the blockage removal is generally achieved by means of wax scraping. However, this solution is time and labor consuming and can add significantly to the cost of crude oil recovery.
Currently, there are some methods for heating the wellbore to increase the mobility of the crude oil, thereby facilitating the flow of the crude oil in the wellbore. However, these methods generally require power generation from oil and gas resources at the surface, heating the environment in the wellbore by heating the cable inserted into the wellbore, or heating water by electric energy, and injecting hot water into the wellbore to heat the wellbore. These heating methods consume a large amount of valuable resources, and some of them also emit a large amount of sulfides and nitrides, causing certain environmental pollution. Large-scale power generation equipment and peripheral maintenance equipment also need to be established for power generation through oil and gas resources, so that the production cost is greatly increased. In addition, injecting hot water into the wellbore can inevitably affect the quality of the produced hydrocarbon resources.
Disclosure of Invention
In view of the above, the present invention proposes a downhole heating system that can be used to solve or at least mitigate at least one of the above problems.
According to a first aspect of the present invention, there is provided a downhole heating system comprising: a second tubular string configured for insertion into a first tubular string and forming an annulus between the first and second tubular strings, the second tubular string having a lower end configured with an opening for communicating with the annulus; a first gas delivery tube configured to be connected to an upper end of the second tubular string; a second gas delivery tube configured to be connected to an annulus between the second tubular string and the first tubular string, the annulus in communication with the second tubular string through the opening; and a gas drive mechanism configured to cause heated gas to enter the wellbore through one of the first and second gas delivery tubes and exit the wellbore via the other of the first and second gas delivery tubes.
Make heating gas circulate between second tubular column and first tubular column through the cooperation of first tubular column and second tubular column, can heat first tubular column and second tubular column effectively, avoid taking place to analyse wax, phenomenon such as wax deposition in the well to avoid the well to block up the influence production.
In a preferred embodiment, the gas drive mechanism is configured to move heated gas through the second gas delivery tube into the annulus, into the second tubular string via the opening and out of the wellbore from the first gas delivery tube; wherein the produced heavy oil leaves the wellbore through the second tubing string and the first gas delivery pipe together with the heated gas.
In a preferred embodiment, the ratio of the diameter of the second string to the diameter of the first string is between 0.5 and 0.7, preferably between 0.53 and 0.68.
In a preferred embodiment, the second string is inserted into the first string to a depth of between 1300m and 3000 m.
In a preferred embodiment, the downhole heating system further comprises a gas storage container for storing the heated gas, an inlet end of the gas storage container is connected to the first gas delivery pipe, and an outlet end of the gas storage container is connected to the second gas delivery pipe; wherein the heated gas is circulated between the gas storage container and the wellbore.
In a preferred embodiment, a heating mechanism is provided in the gas storage container, the heating mechanism being provided in the gas flow path between the inlet end and the outlet end.
In a preferred embodiment, the heating mechanism comprises a plurality of heating rods arranged spaced apart from each other in a plane perpendicular to the gas flow path such that the heating gas can flow between adjacent heating rods.
In a preferred embodiment, the heating means comprises a plurality of heating means arranged spaced apart along the gas flow path.
In a preferred embodiment, the downhole heating system comprises a plurality of the gas containers connected in series with each other, a temperature sensor for detecting the temperature of the heated gas leaving the gas container is mounted at the outlet end of each gas container, and the heating mechanism in the downstream gas container stops heating the heated gas when the temperature sensor detects that the temperature of the heated gas has reached a desired temperature.
In a preferred embodiment, the downhole heating system further comprises a solar photovoltaic charging panel, wherein the solar photovoltaic charging panel is electrically connected with the gas driving mechanism through a cable so as to supply power to the gas driving mechanism; the underground heating system also comprises a gas storage container for storing the heated gas, at least one heating mechanism is arranged in the gas storage container, and the solar photovoltaic charging panel is electrically connected with the heating mechanism through a cable so as to supply power to the gas driving mechanism.
In a preferred embodiment, a battery is provided on the cable.
In a preferred embodiment, the heating gas is air, nitrogen or carbon dioxide.
Drawings
The invention is described in more detail below with reference to the accompanying drawings. Wherein:
FIG. 1 shows a schematic view of a downhole heating system according to a first embodiment of the invention;
FIG. 2 shows a schematic view of a gas storage container in the downhole heating system of FIG. 1;
FIG. 3 shows a schematic view of the air container of FIG. 2 from another angle.
In the drawings, like parts are provided with like reference numerals. The figures are not drawn to scale.
Detailed Description
The invention will be further explained with reference to the drawings.
Fig. 1 schematically shows the structure of a downhole heating system 100 according to an embodiment of the invention. As shown in fig. 1, the downhole heating system 100 includes a solar charging panel 1. The solar photovoltaic charging panel 1 can be installed on the ground or any other platform through the bracket 2. The solar photovoltaic charging panel 1 can be hinged with the support 2, so that the orientation angle of the solar photovoltaic charging panel 1 can be adjusted according to the position of the sun.
The solar photovoltaic charging panel 1 is electrically connected to the storage battery 4 through the cable 3, so that the electric energy converted from the solar energy by the solar photovoltaic charging panel 1 can be stored in the storage battery 4 for use.
The downhole heating system further comprises a gas storage container 5. A heating mechanism may be provided in the gas storage container 5. On one hand, the solar charging panel 1 can be directly connected with the heating mechanism through the cable 3 to drive the heating mechanism to heat. On the other hand, the storage battery 4 may be connected to the heating mechanism through the cable 3 to drive the heating mechanism to heat by the electric energy stored in the storage battery 4.
As shown in fig. 2 and 3, the air container 5 is configured in a substantially cylindrical shape, and an inlet end 15 and an outlet end 19 are configured at both ends of the air container 5, respectively. A gas flow path is formed in the gas container 5 between the inlet end 15 and the outlet end 19. The heating mechanism is disposed in the air container 5. In the embodiment shown in fig. 2 and 3, the gas storage container 5 includes a plurality of heating rods 17 arranged to be spaced apart from each other. The plurality of heating rods 17 are spaced apart from each other in a plane perpendicular to the gas flow path so that the heated gas can flow through gaps between the heating rods 17 and be heated by the heating rods 17 while flowing. A plurality of spaced-apart heating rods 17 may be connected to each other by a frame and to the inner wall of the air container 5. The heating rod 17 here may be made of PTC ceramic. The voltage of the heating rod 17 may be between 12V and 380V. The desired temperature of the heated gas is between 200 ℃ and 300 ℃.
A plurality of heating mechanisms may be provided in the air container 5. Multiple heating mechanisms may be spaced along the gas flow path to facilitate adequate heating of the gas.
An insulating layer 20, such as a polyurethane insulating layer, may be provided on the inner wall of the air container 5. Therefore, the temperature in the gas storage container 5 can be maintained, and the heat of the heated gas is prevented from being dissipated at the temperature to reduce the working efficiency of the whole system. The thickness of the insulating layer 20 may be between 6cm and 15 cm. In addition, a corrosion-resistant layer (not shown) may be further provided on the inner wall of the air storage container 5, as necessary, and the corrosion-resistant layer may be provided inside the thermal insulation layer 20.
As shown in fig. 1, a plurality of air containers 5 may be provided in series with each other. In this case, the temperature sensor 18 may be provided only at the outlet end 19 of each air container 5. Thus, when the temperature sensor 18 associated with the upstream air container 5 detects that the temperature of the heated gas is below the expected temperature, it indicates that the heated gas leaving that air container 5 has not reached the expected temperature. In response to this detection result, the heating mechanism in the downstream air container 5 is turned on, and the heating of the heated gas introduced thereinto is continued. When the temperature sensor 18 at the outlet end 19 of a certain gas container 5 detects that the temperature reaches or exceeds the desired temperature, the heating mechanism in the gas container 5 downstream may be turned off to stop heating the heated gas, which is advantageous for saving energy. Alternatively, the heating mechanism in the downstream gas storage container 5 may continue to heat the heated gas at a lower power to ensure that the temperature of the heated gas is maintained at a sufficiently high level while saving energy.
As also shown in fig. 1, the downhole heating system 100 also includes a first tubular string 7 inserted into the outer casing in the wellbore, and a second tubular string 8 inserted into the first tubular string 7. The first string 7 may extend down to the bottom of the well for communication with the various reservoirs. The second pipe string 8 is inserted a distance into the first pipe string 7. Preferably, the second string 8 is inserted into the first string 7 to a depth of between 1300m and 3000 m. For example, the second string 8 may be inserted near the packer 9 on which the first string 7 is fitted, preferably near above this packer 9. An annulus is formed between the second tubing string 8 and the first tubing string 7. At the lower end of the second string 8 an opening 11 for communication with the annulus is formed.
The downhole heating system 100 further comprises a first gas delivery tube 13 connected between the upper end of the second tubing string 8 and the inlet end 15 of the gas storage vessel 5, and a second gas delivery tube 10 connected between the annulus and the outlet end 19 of the gas storage vessel 5. A blower 6 as a gas drive mechanism, for example, including a motor and a low-power pump and a rotational speed control module, is provided on the first gas delivery pipe 13. Thus, as shown in figure 1, heated gas can flow from the gas storage vessel 5 through the second gas delivery tube 10 into the annulus, down the wellbore to the opening 11. The heated gas can then enter the second tubular string 8 through the opening 11, thereby traveling up the wellhead 12 and returning to the gas storage vessel 5 via the first gas transfer pipe 13. The first and second columns 7, 8 can be heated by heating gas. This can provide a higher temperature environment for the thick oil recovered in the second string 8, especially near the wellhead, avoiding problems such as wax precipitation, etc.
The first gas delivery line 13 may also be provided with a treatment station 14. The treatment station 14 may be used to purify the heated gas passing therethrough to remove the mixed natural gas, such as methane produced from the formation, from entering the gas storage vessel 5, thereby preventing the heated natural gas from exploding. Through the arrangement, the heated gas can circulate between the gas storage container 5 and the borehole, so that on one hand, the first pipe column 7 and the second pipe column 8 can be continuously heated (especially at night and under the condition that the environmental temperature is lower than 50 ℃), on the other hand, the resources can be repeatedly utilized, the cost is reduced, and the environment-friendly effect is realized.
In addition, the heated gas introduced into the well bore can also play a role of gas lift, so that thick oil in the well is brought to the well mouth, and the production and exploitation efficiency is improved. In the section of outer casing 21 in which the second string 8 is inserted, the production of thick oil is mainly effected by the second string 8 and the first string 7 which is fitted between the second string 8 and the shaft 21. This avoids significant pressure drop in the annulus within the outer casing 21 which could cause the outer casing 21 to experience excessive differential pressures between the inside and outside and thus damage to the outer casing 21. This is a problem that tends to occur in conventional oil and gas wells.
In addition, the second string 8 will necessarily have a smaller size with respect to the first string 7, which allows a smaller amount of heated gas to be introduced into the wellbore, and the gas circulation rate can be faster, which contributes to a reduction in cost and an increase in heating efficiency.
In the case of production and exploitation by means of the second string 8, the processing station 14 can also be configured for oil-gas separation, the separated thick oil being sent to the corresponding storage tank, and the heated gas being recovered to the gas storage vessel 5.
Preferably, the ratio of the diameter of the second limb 8 to the diameter of the first limb 7 is between 0.5 and 0.7, preferably between 0.53 and 0.68. For example, the second string may employ 2/8 in tubing, the first string 7 may employ 4/2 in tubing and 3/2 in tubing in combination with a production packer, or 4/2 in tubing or 3/2 in tubing in combination with a production packer.
In addition, the inner wall of the first pipe column 7 can also be coated with an insulating layer, for example, polyurethane insulating layer. The thickness of the heat-insulating layer is between 4cm and 6 cm.
The heating gas in the downhole heating system 100 of the invention may be one or more of air, nitrogen and carbon dioxide. In one embodiment, air in the environment can be directly used as the heating gas, so as to reduce the cost and facilitate material selection. In another embodiment, exhaust gas produced near the wellbore, such as carbon dioxide, may be used as the heating gas. This is beneficial to recycling the exhaust gas, is environmentally friendly, and is beneficial to reducing the cost.
The downhole heating system 100 of the present invention is particularly suitable for remote non-electric fields such as desert, partition, sea, etc. because the solar photovoltaic charging panel 1 is used to convert solar energy into electric energy. The underground heating system 100 can fully utilize gas heated by the solar technology to heat the oil pipe, so that the flowability of crude oil is improved; the properties of high closed-cell rate and low heat conductivity coefficient of the rigid polyurethane material are utilized to insulate the gas storage container and the first tubular column, so that the heat dissipation of the gas storage container and the first tubular column is prevented; the storage battery is used for absorbing the solar energy excessively converted in the daytime, and the gas is heated by discharging when the temperature is low at night, so that the effect of heating and insulating the first pipe column and the second pipe column in all weather is achieved.
The downhole heating system 100 of the present invention is particularly suited for use in a flowing well, a gas lift well, or a shallow well.
While the invention has been described with reference to a preferred embodiment, various modifications may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In particular, the technical features mentioned in the embodiments can be combined in any way as long as there is no structural conflict. It is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
Claims (12)
1. A downhole heating system, comprising:
a first tubular string configured for insertion into an outer casing;
a second tubular string configured for insertion into a first tubular string and forming an annulus between the first and second tubular strings, the second tubular string having a lower end configured with an opening for communicating the annulus;
a first gas delivery tube configured to be connected to an upper end of the second tubular string;
a second gas delivery tube configured to be connected to an annulus between the second tubular string and the first tubular string, the annulus in communication with the second tubular string through the opening; and
a gas drive mechanism configured to cause heated gas to enter the wellbore through one of the first and second gas delivery tubes and exit the wellbore via the other of the first and second gas delivery tubes.
2. The downhole heating system of claim 1, wherein the gas drive mechanism is configured to pass heated gas through the second gas delivery tube into the annulus, into the second tubular string via the opening, and out of the wellbore from the first gas delivery tube;
wherein the produced heavy oil exits the wellbore through the second string and the first gas delivery pipe together with the heated gas.
3. A downhole heating system according to claim 1 or 2, wherein the ratio of the diameter of the second string to the diameter of the first string is between 0.5 and 0.7.
4. A downhole heating system according to claim 1 or 2, wherein the second string is inserted into the first string to a depth of between 1300m and 3000 m.
5. A downhole heating system according to claim 1 or 2, further comprising a gas storage container for storing the heated gas, an inlet end of the gas storage container being connected to the first gas delivery pipe and an outlet end of the gas storage container being connected to the second gas delivery pipe; wherein the heated gas is circulated between the gas storage container and the wellbore.
6. The downhole heating system according to claim 5, wherein a heating mechanism is provided within the gas storage container, the heating mechanism being disposed in a gas flow path between the inlet end and the outlet end.
7. A downhole heating system according to claim 5, wherein the heating mechanism comprises a plurality of heating rods arranged spaced apart from each other in a plane perpendicular to the gas flow path such that the heating gas can flow between adjacent heating rods.
8. A downhole heating system according to claim 5, wherein the heating mechanism comprises a plurality of heating mechanisms arranged at intervals along the gas flow path.
9. The downhole heating system according to claim 5, wherein the downhole heating system comprises a plurality of the gas storage containers connected in series with each other, a temperature sensor for detecting the temperature of the heated gas leaving the gas storage container is installed at an outlet end of each gas storage container, and the heating mechanism in a downstream gas storage container stops heating the heated gas when the temperature sensor detects that the temperature of the heated gas has reached a desired temperature.
10. The downhole heating system of claim 1 or 2, further comprising a solar photovoltaic charging panel electrically connected to the gas-powered mechanism by a cable to supply power to the gas-powered mechanism;
the underground heating system also comprises a gas storage container for storing the heated gas, at least one heating mechanism is arranged in the gas storage container, and the solar photovoltaic charging panel is electrically connected with the heating mechanism through a cable so as to supply power to the gas driving mechanism.
11. A downhole heating system according to claim 10, wherein a battery is arranged on the cable.
12. A downhole heating system according to claim 1 or 2, wherein the heating gas is air, nitrogen or carbon dioxide.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110987724.XA CN115726735A (en) | 2021-08-26 | 2021-08-26 | Downhole heating system |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110987724.XA CN115726735A (en) | 2021-08-26 | 2021-08-26 | Downhole heating system |
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| CN115726735A true CN115726735A (en) | 2023-03-03 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN202110987724.XA Pending CN115726735A (en) | 2021-08-26 | 2021-08-26 | Downhole heating system |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117266792A (en) * | 2023-11-06 | 2023-12-22 | 沧州润涛石油设备有限公司 | Multifunctional multi-coupling oil well heating system |
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2021
- 2021-08-26 CN CN202110987724.XA patent/CN115726735A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117266792A (en) * | 2023-11-06 | 2023-12-22 | 沧州润涛石油设备有限公司 | Multifunctional multi-coupling oil well heating system |
| CN117266792B (en) * | 2023-11-06 | 2024-04-30 | 沧州润涛石油设备有限公司 | Multifunctional multi-coupling oil well heating system |
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