CN210370605U - Geothermal single well fracturing system - Google Patents
Geothermal single well fracturing system Download PDFInfo
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- CN210370605U CN210370605U CN201920846278.9U CN201920846278U CN210370605U CN 210370605 U CN210370605 U CN 210370605U CN 201920846278 U CN201920846278 U CN 201920846278U CN 210370605 U CN210370605 U CN 210370605U
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- 230000002035 prolonged effect Effects 0.000 abstract description 8
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Abstract
The utility model provides a geothermal single well fracturing system, this system includes: a main well drilled from the surface into the earth, the main well comprising: the vertical well section is communicated with the ground; the first end of the branch well is arranged at the straight well section of the main well and is communicated with the straight well section of the main well, a preset angle is formed between the branch well and the working section of the main well, and a plurality of cracks are arranged in a stratum between the working section of the main well and the branch well so as to enable the working section of the main well to be communicated with the branch well; and the conveying pipe is arranged in the straight well section or the branch well of the main well and is used for conveying fluid conveyed to the gap between the conveying pipe and the main well to the ground after heat exchange is carried out on the fluid through the working section of the main well and the branch well. The utility model discloses in, the fluid can flow between branch well and main well, has prolonged fluidic flow path, has increased fluidic heat exchange area, has prolonged the time of heat exchange, has improved the temperature behind the fluid heat transfer effectively, and then has improved heat exchange efficiency.
Description
Technical Field
The utility model relates to a heat energy development technical field particularly, relates to a geothermal single well fracturing system.
Background
The traditional single well heat exchange technology is generally that a casing is completed, the bottom of a well is sealed, then a heat-insulating central pipe column is put into the well, cold fluid is injected into an annular space between the central pipe column and the casing in the well, and the cold fluid is output by the central pipe column after being heated by a stratum. Although the cost of the method is low, the heat exchange is only completed in the casing, so the time for the fluid to contact the high-temperature deep part of the stratum is short, the heat exchange contact area is too small, and the defects of quick temperature drop and low heat exchange efficiency are easily caused.
To avoid the disadvantages of conventional single well heat exchange techniques, generally speaking, the formation is perforated at its upper and lower portions, and two sets of spacers are used to separate the annular space between the casing and the central string and at the sections corresponding to the upper and lower perforated sections, respectively, to block the space in the annular space corresponding to the upper and lower perforated sections. In this way, cold fluid is forced from the upper perforation zone into the formation for heating, then from the lower perforation zone into the wellbore, and out through the center string. However, under the influence of the seepage resistance of the formation porous medium, the fluid only flows in a range close to the casing outside the well casing, the whole heat exchange area is still small, and the heat exchange efficiency is still low.
SUMMERY OF THE UTILITY MODEL
In view of this, the utility model provides a geothermal single well fracturing system aims at solving the problem that the heat transfer area of current single well heat transfer technique leads to heat exchange efficiency low for a short time.
The utility model provides a geothermal single well fracturing system, this system includes: a main well drilled from the surface into the earth, the main well comprising: the vertical well section is communicated with the ground; the first end of the branch well is arranged at the straight well section of the main well and is communicated with the straight well section of the main well, a preset angle is formed between the branch well and the working section of the main well, and a plurality of cracks are arranged in a stratum between the working section of the main well and the branch well so as to enable the working section of the main well to be communicated with the branch well; and the conveying pipe is arranged in the straight well section or the branch well of the main well and is used for conveying fluid conveyed to the gap between the conveying pipe and the main well to the ground after heat exchange is carried out on the fluid through the working section of the main well and the branch well.
Further, in the geothermal single-well fracturing system, the working section of the main well is fractured to generate a plurality of fractures, and the branch well is arranged in each fracture in a penetrating mode to be communicated with the working section of the main well.
Further, in the geothermal single-well fracturing system, the working section of the main well is fractured to generate a plurality of fractures, and the fractures of the branch wells are fractured to generate a plurality of fractures corresponding to the fractures of the main well, and the fractures of the branch wells are communicated with the fractures of the main well so that the working section of the main well is communicated with the branch wells.
Further, above-mentioned geothermal single well fracturing system still includes: and the monitoring system is used for monitoring the condition that the working section of the main well generates cracks so as to determine the position of the branch well.
Further, in the geothermal single-well fracturing system, the preset angle and distance between the branch well and the working section of the main well and the distance between the branch well and the straight well section of the main well when the branch well is communicated with the working section of the main well are matched with the flow capacity of fluid in each fracture when the branch well is communicated with the working section of the main well.
Further, in the above geothermal single well fracturing system, the number of the branch wells is at least two, the first end of each branch well is arranged above the vertical well section of the main well and arranged above the working section of the main well, the first end of each branch well is communicated with the vertical well section of the main well, each branch well is communicated with the working section of the main well, a preset angle is formed between the working section of the main well and each branch well, and a preset angle is formed between each branch well.
Further, in the geothermal single-well fracturing system, the main well is in the same direction with the minimum principal stress direction of the stratum or deviates from the minimum principal stress direction of the stratum by a preset angle.
Further, in the geothermal single-well fracturing system, the main well is a horizontal well or an inclined well; the branch well is a horizontal well or an inclined well; and/or the preset angle between the branch well and the working section of the main well is 30-45 degrees.
Further, above-mentioned geothermal single well fracturing system still includes: a separator; the first end of the conveying pipe is communicated with the ground, and the second end of the conveying pipe is arranged in the straight well section of the main well and below the first end of the branch well; the separator is arranged in a gap between the outer wall of the second end of the conveying pipe and the wall of the main well; the conveying pipe is used for enabling fluid in a gap between the conveying pipe and the main well to sequentially flow through the working sections of the branch well and the main well for heat exchange and then outputting the fluid; or the first end of the conveying pipe is communicated with the ground, and the second end of the conveying pipe is arranged in the branch well; the separator is arranged in a gap between the outer wall of the conveying pipe and the wall of the branched well; the conveying pipe is used for outputting the fluid in the gap between the conveying pipe and the main well after the fluid sequentially flows through the working section of the main well and the branch well for heat exchange.
Further, above-mentioned geothermal single well fracturing system still includes: a separator; the first end of the conveying pipe is communicated with the ground, and the second end of the conveying pipe is arranged in the straight well section of the main well and is arranged below the first end of the branch well closest to the working section of the main well; the separator is arranged in a gap between the outer wall of the second end of the conveying pipe and the wall of the main well; the conveying pipe is used for enabling fluid in the gap between the conveying pipe and the main well to sequentially flow through the working sections of the branch wells and the main well to be subjected to heat exchange and then output.
In the utility model, the branch well is communicated with the working section of the main well, so that the fluid can flow between the branch well and the main well, thereby greatly increasing the heat exchange area, moreover, the branch well and the working section of the main well are arranged at a preset angle, so that the flow path of the fluid between the main well and the branch well is prolonged, the heat exchange area of the fluid is increased, the heat exchange time is prolonged, the temperature of the fluid after heat exchange is effectively improved, thereby improving the heat exchange efficiency, solving the problem of low heat exchange efficiency caused by small heat exchange area of the prior single-well heat exchange technology, and only the main well is communicated with the ground, and the first end of the branch well is arranged at the straight well section of the main well, so that the main well and the branch well can be simultaneously and circularly heated by one well mouth, the heat exchange efficiency is improved, the drilling cost and the use area of a well site are greatly reduced, and the cost of geothermal energy utilization is reduced.
Drawings
Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:
fig. 1 is a schematic structural diagram of a geothermal single-well fracturing system provided by an embodiment of the present invention;
fig. 2 is a schematic top view of a geothermal single-well fracturing system provided by an embodiment of the present invention;
fig. 3 is a schematic structural diagram of a conveying pipe in a geothermal single-well fracturing system provided by an embodiment of the present invention;
fig. 4 is another schematic structural diagram of the conveying pipe in the geothermal single-well fracturing system provided by the embodiment of the present invention.
Detailed Description
Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. It should be noted that, in the present invention, the embodiments and features of the embodiments may be combined with each other without conflict. The present invention will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.
Referring to fig. 1 and 2, a preferred structure of a geothermal single well fracturing system provided by the embodiment of the invention is shown. As shown, a geothermal single well fracturing system comprises: a main well 1, a branch well 2 and a delivery pipe 4. Wherein, main well 1 is bored by ground to underground and is established, and main well 1 includes: the vertical shaft section 11 is communicated with the ground, that is, one end (the upper end shown in figure 1) of the vertical shaft section 11 is communicated with the ground, the other end (the lower end shown in figure 1) of the vertical shaft section 11 is communicated with the working section 12, and the working section 12 is drilled underground. The main well 1 can be a horizontal well or an inclined well. When the main well 1 is a horizontal well, the straight well section 11 is a vertical section of the horizontal well, and the working section 12 is a deflecting section and a horizontal section of the horizontal well. When the main shaft 1 is an inclined shaft, the straight shaft section 11 is a vertical section of the inclined shaft, and the working section 12 is an inclined section of the inclined shaft.
The direction of the main well 1 is consistent with the direction of the minimum principal stress of the stratum, or the direction of the main well 1 deviates from the direction of the minimum principal stress of the stratum by a preset angle. In specific implementation, the preset angle may be determined according to actual conditions, and this embodiment does not limit this. Preferably, the main well 1 is oriented at an angle not exceeding plus or minus 30 ° from the direction of least principal stress of the formation.
In specific implementation, the main well 1 may be a complete well with all or part of open holes, or a complete well with all casing cement, which is not limited in this embodiment.
The first end (left end in fig. 1) of the branch well 2 is arranged at the straight well section 11 of the main well 1, and the first end of the branch well 2 is communicated with the straight well section 11 of the main well 1, and the second end of the branch well 2 is a free end. Specifically, the first end of the branch well 2 is disposed above the working section 12 of the main well 1, but the second end of the branch well 2 may be disposed underground at any place, that is, the second end of the branch well 2 may be disposed above the working section 12 of the main well 1, may be disposed below the working section 12 of the main well 1, and may extend to other directions of the formation.
The main well 1 is a horizontal well or a slant well, and the branch well 2 is a horizontal well or a slant well. That is, when the main well 1 is a horizontal well, the branch well 2 may be a horizontal well or a slant well. When the main well 1 is a slant well, the branch well 2 may be a horizontal well or a slant well. The present embodiment does not impose any limitation on the form of the main well 1 and the branch well 2.
In specific implementation, the well diameter of the branch well 2 is smaller than that of the main well 1.
During specific implementation, the main well 1 is drilled, then the branch well 2 is drilled, before the branch well 2 is drilled, a bridge plug is arranged on the straight well section 1 of the main well 1 and close to the working section 2 so as to plug the working section 12, so that the branch well 2 can be conveniently drilled, and the influence on the main well 1 when the branch well 2 is drilled is avoided.
The branch well 2 and the working section 12 of the main well 1 have a preset angle, specifically, the well body of the branch well 2 and the working section 12 of the main well 1 have a preset angle α in the vertical direction of the formation, referring to fig. 2, the well body track of the branch well 2 deviates from the working section 12 of the main well 1 by a preset angle α from the top view, and the branch well 2 is not arranged right above the working section 12 of the main well 1.
Preferably, the predetermined angle α between the well bore of the lateral 2 and the active portion 12 of the main well 1 is between 30 ° and 45 °.
Preferably, the main well 1 is a horizontal well or an inclined well, the branch well 2 is a horizontal well or an inclined well, and/or the preset angle α between the well body of the branch well 2 and the working section 12 of the main well 1 is 30-45 degrees.
A plurality of cracks 3 are arranged in the stratum between the working section 12 of the main well 1 and the branch well 2, so that the working section 12 of the main well 1 is communicated with the well body of the branch well 2, and hydraulic communication between the working section 12 of the main well 1 and the branch well 2 is realized, and thus, the straight well section 11 of the main well 1, the branch well 2 and the working section 12 of the main well 1 are communicated with each other.
The conveying pipe 4 is arranged in the straight well section 11 of the main well 1 or the branch well 2, and the conveying pipe 4 is used for conveying fluid conveyed to the gap between the conveying pipe 4 and the main well 1 to the ground after heat exchange is carried out on the fluid through the working section 12 of the main well 1 and the branch well 2. Specifically, the outer diameter of the conveying pipe 4 is smaller than the well diameter of the main well 1 and smaller than the well diameter of the branch well 2, so that the conveying pipe 4 can be conveniently placed in the straight well section 11 of the main well 1 or the branch well 2. And, the conveying pipe 4 is firstly inserted from the straight well section 11 of the main well 1, and a gap is formed between the outer wall of the conveying pipe 4 and the wall of the well at the straight well section 11 of the main well 1, and the gap is used for conveying cold fluid. The fluid is conveyed to the working section 12 of the main well 1 or the branch well 2 from the gap and flows through the working section 12 of the main well 1 and the branch well 2, the fluid exchanges heat with the stratum in the flowing process, the temperature of the fluid is increased, and the fluid after being heated is conveyed to the ground through the conveying pipe 4.
In specific implementation, before inserting the conveying pipe 4 into the straight well section 11 of the main well 1 or the branch well 2, the bridge plug in the straight well section 1 of the main well 1 should be removed, so that the conveying pipe 4 can be smoothly conveyed into the main well.
Preferably, the transfer pipe 4 is made of a heat insulating material so that the heat-exchanged fluid can maintain the temperature after heat exchange. In specific implementation, the material of the conveying pipe 4 may be determined according to actual conditions, and this embodiment does not limit this.
It can be seen that, in this embodiment, the branch well 2 is communicated with the working section 12 of the main well 1, so that the fluid can flow between the branch well 2 and the main well 1, thereby greatly increasing the heat exchange area, and the branch well 2 is arranged at a preset angle with the working section 12 of the main well 1, so that the path of the fluid flowing between the main well 1 and the branch well 2 is extended, thereby increasing the heat exchange area of the fluid, prolonging the heat exchange time, effectively increasing the temperature of the fluid after heat exchange, further improving the heat exchange efficiency, solving the problem of low heat exchange efficiency caused by the small heat exchange area of the existing single well heat exchange technology, and only the main well 1 is communicated with the ground, the first end of the branch well 2 is arranged at the straight well section 11 of the main well 1, thereby realizing the simultaneous cyclic heat collection of the main well 1 and the branch well 2 by one well mouth, improving the heat exchange efficiency, and greatly reducing the drilling cost and the use area of a well site, thereby reducing the cost of geothermal energy utilization.
Referring to fig. 1, in the above embodiment, one way of communicating the working section 12 of the main well 1 with the well bore of the branch well 2 is: the active section 12 of the main well 1 is fractured to create a plurality of fractures 3 in the formation. The branch well 2 is arranged through each crack 3 at the working section 12 of the main well 1, so that the branch well 2 is communicated with the working section 12 of the main well 1, and hydraulic communication between the branch well 2 and the main well 1 is further realized. Specifically, the working section 12 of the main well 1 is fractured using hydraulic fracturing to create fractures. When the branch well 2 is drilled, the well body of the branch well 2 penetrates through the crack 3 at the working section 12 of the main well 1, so that the well body of the branch well 2 is communicated with the working section 12 of the main well 1 through the crack 3, and hydraulic communication between the branch well 2 and the working section 12 of the main well 1 is realized.
The fracturing mode of the working section 12 of the main well 1 is as follows: when the main well 1 is completed in a full open hole mode or partially completed in an open hole mode, fracturing the working section 12 of the main well 1 in a general fracturing mode, so that a plurality of cracks 3 are generated in the stratum corresponding to the working section 12 of the main well 1. The general fracturing refers to that fracturing fluid is directly injected into the full main well 1 without any interlayer packing tool, when the pressure exceeds the fracture pressure of the stratum, the stratum can crack, and after the fracturing discharge capacity is increased to a certain degree, for example, 3-6 m3/min, multiple cracks can be generated in the stratum.
When the main well 1 is completely cased, the working section 12 of the main well 1 is fractured in sections by adopting a bridge plug perforation combined action mode, so that a plurality of cracks 3 are generated in the stratum corresponding to the working section 12 of the main well 1. The method is characterized in that a bridge plug perforation combined fracturing mode is a multi-section fracturing technology specially aiming at casing cementing and well completion, generally, a first section of fracturing is perforated from the bottom of a well, then a lower bridge plug is used for plugging a front section of fracture and simultaneously perforating a 2 nd section, then fracturing is carried out, and the like, so that a plurality of fractures are generated in a stratum.
It can be seen that, in this embodiment, the branch well 2 penetrates through the crack 3 at the working section 12 of the main well 1, and the communication between the main well 1 and the branch well 2 can be realized without other operations, so that the structure is simple and the implementation is convenient.
Another embodiment of the working section 12 of the main well 1 communicating with the well bore of the lateral well 2 is: the active section 12 of the main well 1 is fractured to create a plurality of fractures 3 in the formation. When the well body of the branch well 2 penetrates through each crack 3 at the working section 12 of the main well 1, the branch well 2 cannot be well communicated with the working section 12 of the main well 1 through the cracks at the working section 12 of the main well 1, at this time, a plurality of cracks are generated at the positions, corresponding to the cracks 3 of the main well 1, of the branch well 2 through fracturing, that is, a plurality of cracks are generated at the positions, corresponding to the cracks of the main well 1, of the well body of the branch well 2, so that the cracks at the well body of the branch well 2 are communicated with the cracks at the working section 12 of the main well 1, the working section 12 of the main well 1 is communicated with the well body of the branch well 2, and hydraulic communication between the working section 12 of the main well 1 and the well body of the branch well 2 is achieved. Simple structure and convenient operation.
Referring to fig. 1, in the above embodiments, the geothermal single well fracturing system may further include: and (5) monitoring the system. The monitoring system is used for monitoring the condition of the cracks 3 generated in the working section 12 of the main well 1 when the working section 12 of the main well 1 is fractured, and then determining the position of the branch well 2 according to the fracture condition. Specifically, the geothermal single well fracturing system may further comprise: and the control device is connected with the monitoring system and is used for receiving the fracture condition of the working section 12 of the main well 1 monitored by the monitoring system and determining the well body track of the branch well 2 according to the fracture condition. The monitoring system may be a microseismic monitoring system.
It can be seen that, in this embodiment, the condition of the crack 3 generated by the working section 12 of the main well 1 is monitored by setting the monitoring system, so that the position of the branch well 2 and the well trajectory of the branch well 2 are conveniently determined, and further the well trajectory of the branch well 2 is better communicated with the working section 12 of the main well 1, so that the fluid smoothly flows, and the heat exchange area between the fluid and the formation is increased.
In the above embodiments, the preset angle between the branch well 2 and the working section 12 of the main well 1, the distance between the branch well 2 and the working section 12 of the main well 1, and the distance from the straight well section 11 of the main well 1 when the branch well 2 is communicated with the working section 12 of the main well 1 are all such that the fluid circulation capacity of each fracture 3 when the branch well 2 is communicated with the working section 12 of the main well 1 is matched. The distance and the angle are selected to ensure that the circulation capacity of the fluid in each crack 3 is basically consistent when the working section 12 of the main well 1 is communicated with the well body of the branch well 2, so that the phenomenon of short circuit caused by the flow of the fluid in a certain crack is avoided, the fluid can uniformly circulate in each crack, the flow path of the fluid is greatly prolonged, and the heat exchange area between the fluid and the stratum is increased. Wherein, the distance from the straight well section 11 of the main well 1 when the branch well 2 is communicated with the working section 12 of the main well 1 refers to: the distance between the position of the well body of the branch well 2 when communicating with the working section 12 of the main well 1 and the straight well section 11 of the main well 1 is more specifically: the distance between the location of the fracture 3 and the straight section 11 of the main well 1 is fractured by the active section 12 of the main well 1.
In the above embodiments, there may be at least two branch wells 2, the first end of each branch well 2 is disposed on the straight well section 11 of the main well 1, the first end of each branch well 2 is disposed above the working section 12 of the main well 1, the first end of each branch well 2 is communicated with the straight well section 11 of the main well 1, and the well bore of each branch well 2 is communicated with the working section 12 of the main well 1.
In specific implementation, the well bores of the branch wells 2 can be communicated with each other by fracturing to generate cracks.
In the vertical direction of the stratum, a preset angle is formed between the working section 12 of the main well 1 and each branch well 2, and a preset angle is formed between each branch well 2. Specifically, a preset angle is formed between the working section 12 of the main well 1 and a first drilled branch well, a preset angle is also formed between the first drilled branch well and a second drilled branch well, and so on, and each branch well and a branch well drilled before have a preset angle. The angle between the working section 12 of the main well 1 and the first branch well and the angle between the branch wells may be the same or different, and this embodiment is not limited in any way.
It can be seen that, in this embodiment, through setting up a plurality of branch wells 2, all can communicate between the well body of each branch well 2 and the working segment 12 of main well 1 to, also can communicate between the well body of each branch well 2, greatly increased the flow path of fluid, increased heat transfer area and heat transfer time, simultaneously, a well head can carry out the heat recovery circulation of main well 1 and a plurality of branch wells 2 simultaneously, has realized that single well stable cycle gets heat, greatly reduced the cost that geothermal energy utilized.
Referring to fig. 3, in the above embodiments, the geothermal single well fracturing system may further include: a separator 5. Wherein a first end (an upper end shown in fig. 3) of the conveying pipe 4 is communicated with the ground, a second end (a lower end shown in fig. 3) of the conveying pipe 4 is placed in the straight well section 11 of the main well 1, and the second end of the conveying pipe 4 is placed below the first end of the branch well 2. Specifically, if the position at which the first end of the branch well 2 corresponds to the straight well section 11 of the main well 1 is taken as the first position, the second end of the conveying pipe 4 is placed below the first position of the straight well section 11 of the main well 1.
The divider 5 is arranged in the gap between the outer wall of the second end of the conveying pipe 4 and the wall of the main well 1, and then the divider 5 blocks the space between the second end of the conveying pipe 4 and the main well 1. The conveying pipe 4 is used for outputting the fluid in the gap between the conveying pipe 4 and the main well 1 after the fluid sequentially flows through the branch well 2 and the working section 12 of the main well 1 for heat exchange.
During heat recovery, cold fluid is conveyed into the straight well section 11 of the main well 1 from a gap between the conveying pipe 4 and the main well 1, and because the space between the second end of the conveying pipe 4 and the main well 1 is blocked, the fluid cannot enter the working section 12 of the main well 1 and only can enter the branch well 2, then the fluid enters the working section 12 of the main well 1 through a crack between the well body of the branch well 2 and the working section 12 of the main well 1, the fluid exchanges heat with the stratum in the flowing process, the fluid after heat exchange and temperature rise flows to the straight well section 11 from the working section 12 of the main well 1, and because the space between the second end of the conveying pipe 4 and the main well 1 is blocked, the fluid after heat exchange and temperature rise can flow into the conveying pipe 4 and is conveyed to the ground through the conveying pipe 4, namely, a heat recovery cycle is completed. The operation is repeated, and a plurality of heat collecting cycles can be realized.
It can be seen that, in this embodiment, the separator 5 blocks the gap between the outer wall of the second end of the conveying pipe 4 and the wall of the main well 1, so that the fluid enters the branch well 2 and flows to the working section 12 of the main well 1 through the crack between the branch well 2 and the main well 1, the working path of the fluid is greatly prolonged, the heat exchange area is increased, and the heat exchange efficiency is improved.
Referring to fig. 4, in the above embodiments, the geothermal single well fracturing system may further include: a separator 5. Wherein a first end (upper end shown in fig. 4) of the conveying pipe 4 is communicated with the ground, and a second end (lower end shown in fig. 4) of the conveying pipe 4 is arranged in the branch well 2. The separator 5 is arranged in a gap between the outer wall of the second end of the conveying pipe 4 and the wall of the branch well 2 so as to seal off the space between the second end of the conveying pipe 4 and the branch well 2. The conveying pipe 4 is used for outputting the fluid in the gap between the conveying pipe 4 and the main well 1 after the fluid sequentially flows through the working section 12 of the main well 1 and the branch well 2 for heat exchange.
In one embodiment, the second end of the delivery tube 4 may be bent such that the second end of the delivery tube 4 extends into the branch well 2. Alternatively, the second end of the delivery pipe 4 may be provided with an insertable tail pipe, which is bent and extended into the branch well 2. The present embodiment does not limit the configuration of the second end of the conveying pipe 4, as long as the second end of the conveying pipe 4 can be ensured to be arranged in the branch well 2.
During heat recovery, cold fluid is conveyed into the straight well section 11 of the main well 1 from a gap between the conveying pipe 4 and the main well 1, the space between the second end of the conveying pipe 4 and the branch well 2 is blocked, so the fluid cannot enter the branch well 2 and only can enter the working section 12 of the main well 1, then the fluid enters the branch well 2 through a crack between the well body of the branch well 2 and the working section 12 of the main well 1, the fluid exchanges heat with the stratum in the flowing process, and the space between the second end of the conveying pipe 4 and the branch well 2 is blocked, so the fluid after heat exchange and temperature rise can flow into the conveying pipe 4 from the branch well 2 and is conveyed to the ground through the conveying pipe 4, and a heat recovery cycle is completed. The operation is repeated, and a plurality of heat collecting cycles can be realized.
It can be seen that, in this embodiment, the separator 5 blocks the gap between the outer wall of the second end of the conveying pipe 4 and the wall of the branch well 2, so that the fluid enters the working section 12 of the main well 1 and flows to the branch well 2 through the crack between the branch well 2 and the main well 1, the working path of the fluid is greatly prolonged, the heat exchange area is increased, and the heat exchange efficiency is improved.
In the above embodiments, the geothermal single-well fracturing system may further include: a separator. Wherein, when there are at least two branch wells 2, the first end of the conveying pipe 4 is communicated with the ground, the second end of the conveying pipe 4 is arranged in the straight well section 11 of the main well 1, and the second end of the conveying pipe 4 is arranged below the first end of the branch well 2 which is closest to the working section 12 of the main well 1. Specifically, if the position of the first end of the branch well 2 closest to the working section 12 of the main well 1 corresponding to the straight well section 11 of the main well 1 is taken as the second position, the second end of the conveying pipe 4 is placed below the second position of the straight well section 11 of the main well 1.
The separator is arranged in a gap between the outer wall at the second end of the conveying pipe 4 and the wall of the main well 1 so as to seal the space between the second end of the conveying pipe 4 and the main well 1. The conveying pipe 4 is used for outputting the fluid in the gap between the conveying pipe 4 and the main well 1 after sequentially flowing through the branch wells 2 and the working section 12 of the main well 1 for heat exchange.
During heat recovery, cold fluid is conveyed into the straight well section 11 of the main well 1 from a gap between the conveying pipe 4 and the main well 1, the space between the second end of the conveying pipe 4 and the main well 1 is sealed, so the fluid cannot enter the working section 12 of the main well 1 and only can enter each branch well 2, then the fluid enters the working section 12 of the main well 1 through a crack between the well body of each branch well 2 and the working section 12 of the main well 1, or the fluid finally enters the working section 12 of the main well 1 through a crack between each branch well 2 and a crack at the working section 12 of the main well 1, the fluid exchanges heat with the stratum in the flowing process, the fluid after heat exchange and temperature rise flows to the straight well section 11 from the working section 12 of the main well 1, the space between the second end of the conveying pipe 4 and the main well 1 is sealed, so the fluid after temperature rise flows to the conveying pipe 4, the heat is conveyed to the ground through the conveying pipe 4, and a heat collecting cycle is completed. The operation is repeated, and a plurality of heat collecting cycles can be realized.
It can be seen that, in this embodiment, the separator 5 seals the gap between the outer wall of the second end of the conveying pipe 4 and the wall of the main well 1, so that the fluid can enter each branch well 2, and then flow to the working section 12 of the main well 1 through the crack between the branch well 2 and the working section 12 of the main well 1, and since the fluid can flow to the cracks at the plurality of branch wells 2, the working path of the fluid can be extended to the maximum extent, the heat exchange area is increased, and the heat exchange efficiency is improved.
In summary, in this embodiment, the fluid may flow between the branch well 2 and the main well 1, so that the heat exchange area is greatly increased, and the branch well 2 and the working section 12 of the main well 1 are arranged at a preset angle, so that the path of the fluid flowing between the main well 1 and the branch well 2 is extended, the heat exchange area of the fluid is increased, the heat exchange time is prolonged, the temperature of the fluid after heat exchange is effectively increased, and further the heat exchange efficiency is improved, and only the main well 1 is communicated with the ground, and the first end of the branch well 2 is arranged at the straight well section 11 of the main well 1, so that a wellhead can simultaneously and circularly heat the main well 1 and the branch well 2, the heat exchange efficiency is improved, the drilling cost and the use area of a well site are greatly reduced, and the cost of geothermal energy utilization is reduced.
It will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (10)
1. A geothermal single well fracturing system, comprising:
a main well (1) drilled from the surface into the ground, the main well (1) comprising: the vertical well section (11) is communicated with the working section (12), and the vertical well section (11) is communicated with the ground;
the branch well (2) is provided with a first end arranged on the straight well section (11) of the main well (1) and communicated with the straight well section (11) of the main well (1), a preset angle is formed between the branch well (2) and the working section (12) of the main well (1), and a plurality of cracks (3) are arranged in a stratum between the working section (12) of the main well (1) and the branch well (2) so as to enable the working section (12) of the main well (1) to be communicated with the branch well (2);
the conveying pipe (4) is arranged in the straight well section (11) of the main well (1) or the branch well (2) and used for conveying fluid conveyed to a gap between the conveying pipe (4) and the main well (1) to the ground after heat exchange is carried out on the fluid through the working section (12) of the main well (1) and the branch well (2).
2. A geothermal single well fracturing system according to claim 1, wherein the working section (12) of the main well (1) is fractured to create a plurality of fractures (3), and the branch well (2) is arranged through each of the fractures (3) to communicate with the working section (12) of the main well (1).
3. A geothermal single well fracturing system according to claim 1, wherein the working section (12) of the main well (1) is fractured to create a plurality of fractures (3) and the branch wells (2) are fractured to create a plurality of fractures corresponding to the fractures of the main well (1), the fractures of the branch wells (2) being in communication with the fractures of the main well (1) to place the working section (12) of the main well (1) in communication with the branch wells (2).
4. A geothermal single-well fracturing system according to claim 2 or 3, further comprising:
a monitoring system for monitoring the occurrence of fractures in the working section (12) of the main well (1) to determine the location of the branch well (2).
5. A geothermal single well fracturing system according to claim 1, characterized in that the preset angles and distances between the branch well (2) and the working section (12) of the main well (1) and the distance from the straight well section (11) of the main well (1) when the branch well (2) is in communication with the working section (12) of the main well (1) are such that the flow capacity of the fluids in the fractures (3) when the branch well (2) is in communication with the working section (12) of the main well (1) is matched.
6. A geothermal single well fracturing system according to claim 1, wherein the number of the branch wells (2) is at least two, the first end of each branch well (2) is arranged at the straight well section (11) of the main well (1) and is arranged above the working section (12) of the main well (1), the first end of each branch well (2) is communicated with the straight well section (11) of the main well (1), each branch well (2) is communicated with the working section (12) of the main well (1), the working section (12) of the main well (1) is at a preset angle with the branch wells (2), and the branch wells are at a preset angle.
7. A geothermal single well fracturing system according to claim 1, wherein the main well (1) is oriented in line with or at a predetermined angle away from the direction of least principal stress of the formation.
8. The geothermal single-well fracturing system of claim 1,
the main well (1) is a horizontal well or an inclined well;
the branch well (2) is a horizontal well or an inclined well; and/or the presence of a gas in the gas,
the preset angle between the branch well (2) and the working section (12) of the main well (1) is 30-45 degrees.
9. The geothermal single-well fracturing system of claim 1, further comprising: a separator (5); wherein,
the first end of the conveying pipe (4) is communicated with the ground, and the second end of the conveying pipe (4) is arranged in the straight well section (11) of the main well (1) and below the first end of the branch well (2); the separator (5) is arranged in a gap between the outer wall of the second end of the conveying pipe (4) and the wall of the main well (1); the conveying pipe (4) is used for enabling fluid in a gap between the conveying pipe (4) and the main well (1) to sequentially flow through the branch well (2) and the working section (12) of the main well (1) for heat exchange and then output; or,
the first end of the conveying pipe (4) is communicated with the ground, and the second end of the conveying pipe (4) is arranged in the branch well (2); the separator (5) is arranged in a gap between the outer wall of the conveying pipe (4) and the wall of the branched well (2); the conveying pipe (4) is used for enabling fluid in a gap between the conveying pipe (4) and the main well (1) to sequentially flow through the working section (12) of the main well (1) and the branch well (2) to be subjected to heat exchange and then to be output.
10. The geothermal single-well fracturing system of claim 6, further comprising: a separator; wherein,
the first end of the conveying pipe (4) is communicated with the ground, and the second end of the conveying pipe (4) is arranged in the straight well section (11) of the main well (1) and is arranged below the first end of the branch well (2) closest to the working section (12) of the main well (1);
the separator is arranged in a gap between the outer wall of the second end of the conveying pipe (4) and the wall of the main well (1);
the conveying pipe (4) is used for enabling fluid in a gap between the conveying pipe (4) and the main well (1) to sequentially flow through the branch wells (2) and the working section (12) of the main well (1) for heat exchange and then output.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112127862A (en) * | 2019-06-05 | 2020-12-25 | 新奥科技发展有限公司 | Geothermal single well fracturing method |
| WO2022045950A1 (en) * | 2020-08-28 | 2022-03-03 | Hydroc Energy Storage Ab | Thermal energy storage and method for constructing such a thermal energy storage |
| US11976236B2 (en) | 2022-01-26 | 2024-05-07 | Halliburton Energy Services, Inc. | Methods and compositions for enhancing integrity and thermal conductivity of wellbores in geothermal operations |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112127862A (en) * | 2019-06-05 | 2020-12-25 | 新奥科技发展有限公司 | Geothermal single well fracturing method |
| WO2022045950A1 (en) * | 2020-08-28 | 2022-03-03 | Hydroc Energy Storage Ab | Thermal energy storage and method for constructing such a thermal energy storage |
| US11988455B2 (en) | 2020-08-28 | 2024-05-21 | Hydroc Energy Storage Ab | Thermal energy storage and method for constructing such a thermal energy storage |
| US11976236B2 (en) | 2022-01-26 | 2024-05-07 | Halliburton Energy Services, Inc. | Methods and compositions for enhancing integrity and thermal conductivity of wellbores in geothermal operations |
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