KR101190326B1 - System and method of creating EGS having zonal injection wells - Google Patents

Abstract

The present invention relates to an AGS composition system and method for constructing injection wells for each section, and more particularly, when the entire section for producing geothermal water is completed with an open hole and subjected to hydraulic fracturing, In the deep rock layer where the crushing band is generated and is likely to expand to a short-circuit, the entire section is divided into an optimal number of sections based on the generation direction and shape of the crushing band and the geothermal production characteristics. The present invention relates to a system and method for constructing EGS (Enhanced Geothermal Systems) by constructing sectioned injection wells completed with open holes in the bay.

The present invention makes it possible to disperse and generate crushing zones over the entire section, and to control the injection pressure to prevent the formation of direct crushing zones, thereby providing an effect of significantly increasing the amount of geothermal energy that can be produced. Through the above-mentioned effects, by creating more high-performance EGS in Korea, by expanding geothermal power generation, it is possible to produce electricity with pure domestic energy, thereby increasing the energy self-sufficiency rate of Korea and the energy import and greenhouse. Provides the effect of reducing gas emissions.

Injection wells, hydraulic fracturing, deep drilling, production wells, GS, injection pressure, injection wells, geothermal power generation, geothermal water, direct shredding zones, shredding zones

Description

System and method of creating EGS having zonal injection wells

The present invention relates to an EGS composition system and method for constructing the injection wells for each section, and more particularly, when the entire section to produce geothermal water is completed in an open hole and subjected to hydraulic fracturing, the entire section Only a few of the fracture zones are generated, and in deep rock layers that are likely to extend to short-circuit, the entire section is divided into an optimal number of sections based on the generation direction and shape of the fracture zone and the geothermal production characteristics. By constructing EGS (Enhanced Geothermal Systems) by constructing injection wells in each section, which is completed with only open holes in each section, it is possible to disperse and generate crushing zones in the entire section, and also wellhead of each injection well. ), It is possible to prevent the formation of the direct crushing zone by adjusting the injection pressure for the section, which significantly increases the amount of geothermal energy that can be produced. GS relates to a composition system and method.

Binary Geothermal Power Generation, which uses Geothermal Fluid (EGS) to produce and produce Enhanced Geothermal Systems (EGS) as a heat source, is described in Literature 1. In addition, increasing pressures on greenhouse gases have emerged as a promising solution to the increasingly difficult energy situation.

Geothermal energy exists underground at any point in Korea's territory, and its size is almost infinite. However, the depth of geothermal energy at the same temperature is deeper than that of geothermal power generation projects around the world.

In many areas of Korea, it is possible to produce geothermal energy at a temperature that can achieve binary geothermal power generation if EGS is formed from 3km to 4km underground. Therefore, by securing and developing core technologies such as low-cost and high-efficiency deep drilling technology, it is possible to carry out geothermal power by drilling deeper and producing geothermal energy in parallel with rising energy prices.

Deep geothermal energy existing in our country has been left undeveloped because it was recognized as not worth developing with conventional geothermal power generation methods. Recently, however, beneficial geothermal energy production and binary geothermal power generation have been disclosed in Documents 1-5. Means and methods have been disclosed to achieve this.

Korea's energy self-sufficiency rate is as low as 3%, and it is a very fragile structure that requires 97% of the energy required to be imported, and oil and gas prices are rising, making matters worse, according to the UN Convention on Climate Change. Due to the increasing pressure on greenhouse gas reduction due to the emission country, the energy situation is being condemned in an increasingly difficult direction. Therefore, in addition to the systems and methods disclosed in Documents 1 to 5, EEG composition and geothermal energy The creation of means and methods to further improve the efficiency and economics of production and geothermal power generation is required.

Literature Information of the Prior Art

[Document 1] KR Patent Application No. 10-2008-0044966, "Method of binary geothermal power generation using deep seawater", filed: 2008.05.15.

[Document 2] KR Patent Application No. 10-2008-0105167, "System and method of binary geothermal power generation utilizing river zone", filed date: October 27, 2008.

[Patent 3] KR Patent Application No. 10-2008-0131009, "System and method of producing geothermal energy utilizing off-peak power", application date: December 22, 2008.

[Patent 4] KR Patent Application No. 10-2009-0003582, "System and method of creating EGS utilizing off-peak power", filed: 2009.01.16.

[Patent 5] KR Patent Application No. 10-2009-0078070, "System and method of constructing drilling derrick utilizing tower crane mast", filed: 2009.08.24

Document 6 US Patent Application 20100000736, "Enhanced Geothermal Systems and Reservoir Optimization", Bour et al. January 7, 2010

Production wells or injection wells drilled to create EGS are casing throughout the entire drilled hole except for the rock layers in the subterranean core where geothermal water is produced or injected. Insert and comment. The section in which the casing is inserted is called a casing hole section, and the section in which the casing is not inserted is called an open hole section. A slotted liner is generally inserted into the open hole section.

Hydraulic fracturing is performed in the open hole section of the injection well or production well, and as a result of the hydraulic fracturing, if EGS is formed in an optimal form, a plurality of fine shredding zones are dispersed and generated throughout the open hole section. When the injection well and the production well are connected with a plurality of fine crushing zones, the injection water injected into the injection well slowly passes through the crushing zone to sufficiently absorb the geothermal heat of the deep rock layer and reach the production well while heating the geothermal well at the required temperature and flow rate. Water can be produced continuously in production wells.

However, the difficulty is that, when performing hydraulic fracturing in a relatively long open hole section, due to the stress distribution characteristics of the deep rock layer, in some cases, fine fracture zones are not dispersed throughout the open hole section. The crushing zone may be generated only in some sections. The worst case scenario is when the crushing band is concentrated and generated only in the very small section of the top of the open hole section of the injection well and is connected to the production well to form a short-circuit or channel.

When the direct crushing zone is formed as described above, most of the injected water reaches the production well too quickly through the direct crushing zone so that the geothermal water of the deep rock layer is not absorbed properly and the temperature of the produced geothermal water falls, as well. Not only geothermal energy existing in the rock layer of the unproduced portion, but also geothermal energy existing in the rock layer of the portion where the fine crushing zone is properly generated cannot be produced. If the direct failure zone is too extended, EGS will eventually become useless.

As noted in '4.11 Remaining Needs' of Document 1 of Document 1 (MIT Report), the creation of means and methods to prevent and overcome the formation of the direct breaking zone is necessary for the successful creation and operation of EGS. It is urgent.

The industry related to EGS (EGS) has made a lot of efforts to solve the problems associated with the direct shredding zone. One example is the technique disclosed in Document 6.

In the technique disclosed in Document 6, in the case where the crushing band is generated only in some sections as a result of the hydraulic fracturing in the open hole section, the resulting crushing stand is sealed with a temporary sealant, and then the secondary hydraulic fracturing is performed. In addition, if additional sections are generated in another section, and the second hydraulic fracturing resulted in a considerable number of sections in which the fracturing zone is still not generated, the third-generation hydraulic fracturing may be performed after the second fracturing fracturing unit is sealed with a temporary sealing agent. It is to distribute and generate a plurality of crushing zones over the entire open hole section using a method such as to generate additional crushing zone in another section.

However, even if a large amount of hydraulic fracturing is carried out using a special method as described above at a considerable cost to distribute a large number of shredding bands throughout the open hole section, how long can it prevent the formation of a direct fracturing band? It is hard to be optimistic about it. This is because, as a result of the hydraulic fracturing, the fracture zone is generated only in some sections of the open hole section because the fracture initiation pressure of the partial rock layer is lower than that of the other parts due to the stress distribution characteristics of the rock layer. Therefore, if the injection is continued, the expansion rate of the crushing zone generated in the rock layer of the portion of the low crushing zone starting pressure gradually becomes faster than the other portions, and can eventually expand to the direct crushing zone.

Even if there is a section with a rapid expansion speed, the section can be prevented from extending into a direct crushing block if it can be injected at a lower injection pressure than other sections. In the injection well structure, it is very difficult to control the injection pressure cost effectively for a particular section.

Accordingly, in order to actively develop geothermal power generation by forming a large number of EGSs having excellent performance in the Korean land, creation of means and methods capable of solving the above-mentioned difficulties are required.

The present invention has been created in accordance with the above necessity, the object of the present invention, when the complete section to produce geothermal water to open holes (open hole) and the hydraulic fracturing, the crushing zone is generated only in a portion of the entire section Also, even in a deep rock layer having a high probability of expanding the crushing zone, the crushing zone can be dispersed and generated in the entire section, and the formation of the direct crushing zone can be prevented, thereby increasing the geothermal production period. It is to provide an EGS (EGS) composition system and method that can extend and significantly increase the amount of geothermal energy that can be produced in the core rock layer.

In order to achieve the above object, the present inventors have been conducting in-depth investigation and research on the characteristics, development conditions, and technologies of geothermal energy resources existing in various forms in our land for a long time. The injection section corresponding to is divided into an optimal number of sections based on the direction and shape of the fracture zone in the core rock layer, and the geothermal production characteristics. EGS) can be dispersed and generated throughout the injection section, and the injection pressure in the wellhead of the injection section for each section is adjusted to control the injection pressure (Short-circuit) for the section. ), It is possible to significantly increase the amount of geothermal energy that can be produced in the deep rock layer, to achieve the above object With conclusions that led to the present invention.

Accordingly, the present invention for achieving the above object, when the completion of the entire section to produce a geothermal fluid (Open Geothermal) (Open Hole) and the hydraulic fracturing (Hydraulic Fracturing), the whole EEG (EGS) that can generate significantly the amount of geothermal energy that can be produced by solving the above problems in the deep rock layer having a characteristic that is generated only in some sections of the section, and the fracture zone is likely to extend to the direct rupture zone Characterized in that.

In the present invention, a single EGS is composed of one production well and two or more injection wells, that is, interval 1 injection wells, interval 2 injection wells, and the like. The production well is characterized in that the entire section to produce geothermal water in the core rock layer is completed with an open hole section.

In addition, the injection wells for each section, the injection section corresponding to the open hole section of the production wells, from the bottom of the crusher created in the upper section, based on the generation direction and shape of the fracture zone in the core rock layer and geothermal production characteristics Section 1 injection wells are divided into the optimal number of sections, such as section 1, section 2, section 3, and the like by setting the required section from the required depth deeper than 50m deeper vertically into the next section. , By drilling and completing an optimal number of injection wells in each section, such as section 2 injection wells and section 3 injection wells, and performing hydraulic fracturing to connect the open hole section of the production well with the shredding zone, It is characterized in that the injection water injected into the absorbing geothermal heat of the deep rock layer while passing through the crushing zone to flow into the production well while heating.

Further, the open hole sections of the injection wells for each section are 200 m or more horizontally away from the position of the open hole section of the production well, and 50 m or more horizontally away from the positions of the open hole sections of all the other injection wells. And at locations.

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According to the above-described composition system and method, by constructing an optimal number of injection wells in intervals determined in accordance with all the conditions of the ground and ground of the EGS in order to form the EGS (EGS), It is possible to disperse and generate crushing zones in the sections, and to control the injection pressure for the sections in the wellhead of each injection section to prevent the formation of direct rupture zones. It is characterized by remarkably increasing the amount of geothermal energy.

In the EGS composition system and method of the present invention, when the entire section for producing geothermal water is completed by an open hole and subjected to hydraulic fracturing, the shredding stand is generated only in a portion of the whole section, and the shredding stand is a direct shredding stand. For deep rock formations that are likely to expand to short-circuit, the fracture zone can be dispersed and generated throughout the entire section, and also the injection pressure for that section in the wellhead of the sectioned injection wells. By controlling the injection pressure, it is possible to prevent the formation of a direct fracture zone, thereby extending the geothermal production period and providing a significant increase in the amount of geothermal energy that can be produced in the deep rock layers.

Accordingly, the present invention, through the above effect, to make geothermal power generation by developing more excellent EGS (EGS) in our country, by increasing the amount of power produced by pure domestic energy only, It increases the energy self-sufficiency rate and reduces the energy import and greenhouse gas emissions.

The easy composition system and method for constructing the injection well for each section of the present invention, when the entire section to produce geothermal fluid (Completion) to open holes (Completion) and the hydraulic fracturing (Hydraulic Fracturing) The amount of geothermal energy that can be produced by solving the problems in the deep rock layer having a characteristic that the crushing band is generated only in a part of the entire section and the crushing band is likely to be extended to a short-circuit or channel. It is used to create Enhanced Geothermal Systems (EGS), which significantly increases the yield.

In the present invention, one EGS is composed of one production well and two or more injection wells, which are constructed as follows, wherein the production well is geothermal in the deep rock layer. Completion the entire section to produce water into an open hole section, the injection wells for each section, the injection section corresponding to the open hole section of the production well, the direction and shape of the fracture zone in the rock layer Based on the geothermal production characteristics, as shown in the example of Figure 1, divided into the optimal number of sections, such as section 1, section 2, section 3, interval 1 injection wells, interval 2 injection wells to complete only each section with an open hole Injection and injection into the injection wells of each section by drilling and completing an optimal number of injection wells in each section, such as section 3 and injection wells. Number passing through the crusher As heat in absorbing the deep geothermal terrain and the composition to come to flow into the production process.

The open hole sections of the injection wells for each section are preferably arranged in such a way as to surround the production hole with the open hole section in the center.

The crushing zone generated by the hydraulic fracturing has a unique three-dimensional orientation and shape according to the stress distribution characteristics of the core rock layer. That is, it has a characteristic of being created and expanded in three directions in a specific direction and in a specific form. Therefore, based on the generation direction and the shape of the crushing bar, the open hole section of the production well, the injection hole and the corresponding injection section and the injection section so that the connection between the open hole intervals of the injection wells and the production hole open hole interval of each production zone Each interval divided by the optimal number is determined.

In order to divide the injection section corresponding to the open hole section of the production well into sections 1, 2, 3, etc., as shown in the example of FIG. From the depth, the next section is determined. The first reason for this is to produce geothermal water at the required temperature for over 20 years, based on geothermal production characteristics, especially the thermal conductivity of the rock, at least 50m between the crushing zones of the upper and lower sections. This is because a rock layer is needed. 50 m is a lower limit, and if conditions permit, it is more preferable to set it as 100 m-150 m. However, if it is larger than 150m, the profit is negligible.

The second reason for determining the next section from the required depth vertically 50 m or more deeper from the bottom of the shredding table generated in the upper section as described above is to prevent the shredding table generated by the hydraulic fracturing from extending to the adjacent upper section. Since 50m is also a lower limit for the said purpose, it is necessary to set it much larger especially in the rock layer with strong characteristic that a fracture zone expands up and down. The optimum distance can be calculated by drilling at least one injection well in the rock layer and performing hydraulic fracturing.

The open hole sections of the injection wells for each section are constructed at an optimal position at least 200 m horizontally from the position of the open hole sections of the production well. The reason for this is that the injection water absorbs geothermal heat while passing through the crushing zone at that distance. It is to reach the production wells when heated. Based on geothermal production characteristics, particularly geothermal heat absorption characteristics, since the 200m is the lower limit, a distance of 500m or more may be necessary depending on the temperature of the rock layer and the characteristics of the crushing zone. The optimum distance can be calculated by observing the performance of the injection wells and production wells of at least one section for a considerable period of time.

In addition, the open hole sections of the injection wells for each section are constructed at an optimal position 50 m or more horizontally from the positions of the open hole sections of all the other wells, and the reason for this is also about 20 geothermal waters of the required temperature. For annual production, at least 50 m of rock is required between open hole sections of sectioned injection wells, based on geothermal production characteristics, in particular the thermal conductivity of rock layers.

Even if the vertical distance between the upper open hole section and the lower open hole section is more than several hundred meters, when the injection well is operated for more than 10 years, the injection occurs to the section where casing or cementing was weakened and blocked. Can be. Considering such a situation, the open hole sections of all the injection wells are constructed at a position 50 m or more as described above.

In the arrangement as described above, the distance between the open hole intervals of the injection wells and the open hole intervals of the production wells is 200 m or more, and the open hole intervals of the production wells are centered on the plane as much as possible. Given the enclosed shape, there is no difficulty in arranging the distance between the open hole sections of the injection wells more than 50m apart. Since 50m is a lower limit, it is preferable to arrange | position further away as conditions permit.

In addition, in the present invention, since one EGS is composed of one production well and two or more injection wells in each section, the injection wells in each section have more than 0.75 times the diameter of the last casing of the production wells. It is desirable to install a small diameter final casing. The last casing is the casing corresponding to the production casing, which is installed last after the conductor pipe, surface casing, and intermediate casings in a conventional drilling process. In general, it is installed and cemented in a state connected from an upper end of an open hole section to a wellhead.

0.75 times is for the EEG composed of one production well and two interval injection wells, which is the simplest form of the present invention, and as the number of injection wells is increased, The diameter can be made smaller and smaller. For example, in the case of an EGS consisting of one production well and six division injection wells, the diameter of the last casing of the injection wells per section may be about 0.4 times the diameter of the last casing of the production wells. As a result, the drilling cost per injection well for each section is also reduced.

Using the above-described AGS composition system and method of the present invention, one AGS is formed in the core rock layer according to the following procedure.

(1) Drill and complete the first section 1 injection well. As shown in the example of FIG. 1, a predetermined section required from the depth corresponding to the top end of the entire section to produce geothermal water is defined as section 1 of the first section 1 injection well, and only section 1 is completed as an open hole section.

In the first section 1 injection well, insert the last casing with a diameter smaller than 0.75 times the diameter of the last casing of the production well, and perform the hydraulic fracturing in the first section 1 injection well. (Well Logging) to identify the direction and form of crushing zone and geothermal production characteristics.

In the complex where the basic data on the generation direction and shape of the crushing block is poor, the open hole section of the first section 1 injection well is completed into the whole section to produce the geothermal water to grasp the direction and form of the crushing table by the hydraulic fracturing. It is desirable to.

Analyze the data obtained from successive production wells and additional injection wells to better understand the direction and shape of the fracture zone and the geothermal production characteristics.

(2) Drill and complete production wells. The location and depth of the open hole section of the production well are determined based on the identified direction and shape of the fracture zone and the geothermal production characteristics.

Open hole section of the production well, as in the example of Figure 1, the depth corresponding to the upper end of the section 1 as the upper end of the entire section to produce geothermal water.

The open hole section of the production well is positioned at an optimal position at least 200m horizontally from the position of the open hole section of the first section 1 injection well.

Hydraulic fracturing is also carried out in the production wells, connecting the open hole section of the first section 1 injection well with the open hole section of the production well.

The reason for drilling and finalizing the production well after the first interval 1 injection well as described above is to grasp the direction and shape of the crushing stand in the injection well and to more accurately arrange the open hole section of the production well based on the injection well. . However, if necessary, the well can be drilled and completed first, and the direction and form of the crushing band can be identified.

(3) Drill and complete the second section 1 injection well. Based on the formation direction and shape of the fracture zone and the geothermal production characteristics, the position and depth of the open hole section of the second section 1 injection well are determined.

The required interval from the depth corresponding to the upper end of the open hole section of the production well is defined as section 1 of the second section 1 injection well, and only section 1 is completed as an open hole section.

The open hole section of the second section 1 injection well shall be positioned at an optimal position at least 200m horizontally from the position of the open hole section of the production well and at least 50m horizontally from the position of the open hole section of the first section 1 injection well.

In the second section 1 injection well, insert the last casing with a diameter smaller than 0.75 times the diameter of the last casing of the production well, and perform hydraulic fracturing to open the open hole section of the second section 1 injection well and the open hole section of the production well. Connect the liver to the crusher.

(4) Drill and complete the third 'Section 1 injection well'. Based on the identified direction and shape of the fracture zone and the geothermal production characteristics, the position and depth of the open hole section of the third section 1 injection well are determined.

The required interval from the depth corresponding to the top of the open hole section of the production well is defined as section 1 of the third section 1 injection well, and only section 1 is completed as an open hole section.

The open hole section of the third section 1 injection well is at least 200m horizontally from the position of the open hole section of the production well, and is also positioned at an optimal position 50m or more horizontally from the positions of the open hole section of all constructed section 1 injection wells. do.

In the third section 1 injection well, insert the last casing with a diameter smaller than 0.75 times the diameter of the last casing of the production well, and perform hydraulic fracturing to open the open hole section of the third section 1 injection well and the open hole section of the production well. Connect the liver to the crusher.

(5) According to the system and method described above, construct an optimal number of interval 1 injection wells, such as the fourth interval 1 injection well and the fifth interval 1 injection well.

(6) Drill and complete the first section 2 injection well. Based on the identified direction and shape of the fracture zone and the geothermal production characteristics, the location and depth of the open hole section of the first section 2 injection well are determined.

From the bottom of the crushing band created between the open hole intervals of the interval 1 injection wells and the open hole interval of the production wells, a predetermined interval from the required depth deeper than 50m or more is defined as the interval 2 of the first interval 2 injection wells, and the interval 2 Complete the bay into an open hole section.

The open-hole section of the first section 2 injection well is at least 200m horizontally from the position of the open-hole section of the production well, and is also positioned at an optimal position 50m or more horizontally from the positions of the open-hole section of all the constructed section 1 injection wells. do.

In the first section 2 injection well, insert the last casing with a diameter smaller than 0.75 times the diameter of the last casing of the production well, and perform hydraulic fracturing, breaking the gap between the open hole section of the first section 2 injection well and the open hole section of the production well. Connect with

(7) Drill and complete the second section 2 injection well. Based on the formation direction and shape of the fracture zone and the geothermal production characteristics, the position and depth of the open hole section of the second section 2 injection well are determined.

From the lower end of the crushing band generated between the open hole intervals of the interval 1 injection wells and the production hole open intervals of the production wells, a predetermined interval required from a depth required more than 50m deeper than the vertical interval is defined as interval 2 of the second interval 2 injection wells, and the interval 2 Complete the bay into an open hole section.

The open hole section of the second section 2 injection well is located at an optimum position spaced at least 200m horizontally from the position of the open hole section of the production well and at least 50m horizontally from the positions of the open hole section of all constructed injection wells.

In the second section 2 injection well, insert the last casing with a diameter smaller than 0.75 times the diameter of the last casing of the production well, and perform hydraulic fracturing, breaking the gap between the open hole section of the second section 2 injection well and the open hole section of the production well. Connect with

(8) Drill and complete the third 'Section 2 Injection Well'. Based on the formation direction and shape of the fracture zone and the geothermal production characteristics, the position and depth of the open hole section of the third section 2 injection well are determined.

From the bottom of the crushing band created between the open hole intervals of the interval 1 injection wells and the open hole intervals of the production wells, a predetermined interval required from a required depth of more than 50 m deeper is defined as the interval 2 of the third interval 2 injection wells, and the interval 2 Complete the bay into an open hole section.

The open hole section of the third section 2 injection well is located at an optimum position spaced at least 200m horizontally from the position of the open hole section of the production well and at least 50m horizontally from the positions of the open hole section of all the constructed wells.

In the third section 2 injection well, insert the last casing with a diameter smaller than 0.75 times the diameter of the last casing of the production well, and perform hydraulic fracturing to separate the open hole section of the third section 2 injection well and the open hole section of the production well. Connect with a crusher.

(9) According to the system and method described above, an optimal number of interval 2 injection wells, such as the fourth interval 2 injection well and the fifth interval 2 injection well, is constructed.

(10) Drill and complete the first section 3 injection well. Based on the formation direction and shape of the fracture zone and the geothermal production characteristics, the position and depth of the open hole section of the first section 3 injection well are determined.

From the bottom of the crushing band created between the open hole intervals of the interval 2 injection wells and the open hole intervals of the production wells, a predetermined interval required from a required depth of more than 50 m deeper is defined as the interval 3 of the first interval 3 injection wells, and the interval 3 Complete the bay into an open hole section.

The open hole section of the first section 3 injection well is at least 200m horizontally from the position of the open hole section of the production well, and is also placed at an optimal position 50m or more horizontally from the positions of the open hole section of all constructed wells.

In the first section 3 injection well, insert the last casing with a diameter smaller than 0.75 times the diameter of the last casing of the production well and perform hydraulic fracturing to break the gap between the open hole section of the first section 3 injection well and the open hole section of the production well. Connect with

(11) Drill and complete the second section 3 injection well. Based on the formation direction and shape of the fracture zone and the geothermal production characteristics, the position and depth of the open hole section of the second section 3 injection well are determined.

From the bottom of the crushing band generated between the open hole intervals of the interval 2 injection wells and the open hole interval of the production wells, a predetermined interval required from the required depth of more than 50m deeper vertically is defined as the interval 3 of the injection interval 2, interval 3 Complete the bay into an open hole section.

The open hole section of the second section 3 injection well is located at an optimum position spaced at least 200m horizontally from the position of the open hole section of the production well and at least 50m horizontally from the positions of the open hole section of all constructed wells.

In the second section 3 injection well, insert the last casing with a diameter smaller than 0.75 times the diameter of the last casing of the production well, and perform hydraulic fracturing to break between the open hole section of the second section 3 injection well and the open hole section of the production well. Connect with

(12) Drill and complete the third section 3 injection well. Based on the identified direction and shape of the fracture zone and the geothermal production characteristics, the location and depth of the open hole section of the third section 3 injection well are determined.

From the bottom of the crushing band created between the open hole sections of the section 2 injection wells and the open hole section of the production wells, a predetermined section required from the required depth deeper than 50m deeper is defined as section 3 of the third section 3 injection section, and section 3 Complete the bay into an open hole section.

The open hole section of the third section 3 injection well is located at an optimal position spaced at least 200m horizontally from the position of the open hole section of the production well and at least 50m horizontally from the positions of the open hole section of all constructed injection wells.

In the third section 3 injection well, insert the last casing with a diameter smaller than 0.75 times the diameter of the last casing of the production well, and perform hydraulic fracturing, so that the gap between the open hole section of the third section 3 injection well and the open hole section of the production well is Connect with a crusher.

(13) According to the system and method described above, construct an optimal number of interval 3 injection wells, such as the fourth interval 3 injection well and the fifth interval 3 injection well.

(14) As described above, the interval 1 is determined, and the interval 1 injection wells are completed, and then the interval 2 is determined, the interval 2 injection wells are completed, the interval 3 is determined, and the interval 3 injection wells are completed. According to the method of drilling and completion, the section 4 is determined, the section 4 injection wells are drilled, and then the section 5 is determined and the section 5 injection wells are drilled and completed. Determine the optimal number of sections determined according to the conditions, complete by drilling the injection wells for each section, and perform hydraulic fracturing to connect the open hole sections of the injection wells and the open hole sections of the production wells , EGS is formed.

As described above, the open hole sections of the production wells and the injection wells for each section are determined in order based on the direction and shape of the fracture zone generation and the geothermal production characteristics in the corresponding deep rock layers. In other words, the vertical depths (sea level) of corresponding sections may be greatly changed. For example, the vertical depth of the upper end of the open hole section of the production wells may be 3,100 m based on sea level, and the vertical depth of the upper end of the open hole section of the interval 1 injection well corresponding to the upper end may be 3,200 m based on sea level.

For the same reason, even in the injection wells constructed in the same section, the vertical depths (sea level reference) of the open hole sections may vary depending on the position. For example, an upper end of the open hole section of the first section 2 injection well may be 3,350 m based on sea level, and an upper end of the open hole section of the second section 2 injection well may be 3400 m based on the sea level.

In the above-described composition system and method, EGS was formed in order to construct all interval 1 injection wells, then construct all interval 2 injection wells, and then construct all interval 3 injection wells. Construct one injection well for all the sections in the order of constructing one interval 1 injection well, then constructing one interval 2 injection well, and then constructing one interval 3 injection well. Next, the required number of additional injection wells in each of the sections may be constructed to form an EGS.

By constructing the EGS as described above, when the entire section to produce geothermal fluid is completed with an open hole and subjected to hydraulic fracturing, a fracture zone is generated only in a partial section of the entire section. Even in deep rock layers having a high probability of expanding the crushing zone into a short-circuit, the crushing zone can be dispersed and generated in the entire section, and the corresponding section in the wellhead of the sectioned injection wells. The injection pressure can be adjusted with respect to the zone, and the injection pressure is adjusted in the section where the fracture initiation pressure is lower than the other sections, thereby preventing the formation of the direct fracture zone. It is possible to increase the amount of geothermal energy that can be produced in the deep rock layers.

In the AGS composition system and method of the present invention, the number of injection wells that can be constructed is determined in accordance with various conditions of underground and ground of the EGS, in particular according to drilling cost.

Even if you drill both production wells and section injection wells by skidding drilling rigs at one drilling site, it is difficult to do the above costs using conventional drilling rigs. This is expected.

However, if the drilling tower using the tower crane mast disclosed in Document 5 is used, not only the drilling wells can be drilled without skid drilling tower but also the drilling auxiliary workshop is added to the drilling workshop. It can be installed, and also the maximum hook load generated during the casing lowering operation can be solved by hypothesizing the reinforcement column tower only during the inserting operation. It can be installed in narrow spaces connected by lanes that cannot be transported or installed, and has many functions that conventional drilling equipment does not have, so that the required number of wells can be drilled at a much lower cost.

1 is an explanatory view schematically showing a preferred example in which open hole sections of injection wells of each section and open hole sections of production wells are connected to a crushing zone.

Description of the Related Art

10: Open hole section of production well

11: Open hole section of section 1 injection well

12: Open hole section of section 2 injection well

13: Open hole section of section 3 injection well

14: Crushing stand connecting section 1 injection hole and production hole open hole section

15: Crushing stand connecting section 2 injection hole and production hole open hole

16: crushing stand connecting section 3 injection hole and production hole open hole section

20: Cased Hole Section

Claims (1)

When the entire section to produce geothermal fluid is completed with an open hole and the hydraulic fracturing is performed, a fracture zone is generated in only a part of the entire zone, and the fracture zone is a short-circuit. In a method of forming enhanced geothermal systems (EGS) in a deep rock layer having a high potential to expand, It is composed of one production well and two or more injection wells (section 1 injection wells, interval 2 injection wells, etc.), and the production well (opening section) is a whole hole for producing geothermal water as an open hole section. The horizontal distance between the open hole section of the production well and the open hole sections of the injection wells for each section is 200 m or more, and the horizontal distance between the open hole sections of the injection wells for each section is 50 m or more. EEG (EGS) is formed by dispersing and arranging the open hole sections of the injection wells for each section and performing hydraulic fracturing to connect the open hole sections of the injection wells for each section with the open hole sections of the production well. ; A predetermined number of interval 1 injection tablets for setting a predetermined interval as the interval 1 from the upper end of the injection interval corresponding to the open hole interval of the production well of the EGS and completing only the interval 1 as an open hole interval; From the lower end of the crushing table created between the open hole intervals of the interval 1 injection wells and the open hole interval of the production wells, a predetermined interval is required as the interval 2 from the required depth deeper than 50m vertically, and only the interval 2 is an open hole interval. The required number of interval 2 injection wells to complete; From the bottom of the crushing table created between the open hole intervals of the interval 2 injection wells and the open hole interval of the production wells, a predetermined interval is required as the interval 3 from the required depth more than 50 m deeper vertically, and only the interval 3 is an open hole interval. The required number of interval 3 injection tablets to complete; And As described above, the interval 1 is determined and the interval 1 injection wells are completed, and the interval 2 is determined, the interval 2 injection wells are completed, and the interval 3 is determined, and the interval 3 injection wells are completed. Determine 4, complete interval 4 injection wells, determine interval 5, complete interval 5 injection wells, and define the required number of intervals, and complete the injection wells for each interval to form the EGS. The method of forming ASG to build injection wells for each section.

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