WO2021135003A1

WO2021135003A1 - Method for constructing hot dry rock artificial geothermal reservoir by means of cooperation of hydraulic fracturing and millisecond blasting

Info

Publication number: WO2021135003A1
Application number: PCT/CN2020/087377
Authority: WO
Inventors: 冯帆; 陈绍杰; 常洪华; 沈宝堂; 张伟
Original assignee: 山东科技大学
Priority date: 2019-12-31
Filing date: 2020-04-28
Publication date: 2021-07-08
Also published as: CN111155979B; CN111155979A

Abstract

Disclosed is a method for constructing a hot dry rock artificial geothermal reservoir by means of the cooperation of hydraulic fracturing and millisecond blasting. The method comprises: firstly, determining the depth and range of a hot dry rock target layer; then, constructing a water injection well (1) and a production well (2) to the hot dry rock target layer (3); constructing multiple parallel horizontal boreholes (4) in the target layer so that the water injection well (1) communicates with the production well (2); producing cracks to a certain extent on the peripheries of hole walls of group holes by using a sectional hydraulic fracturing technology; next, mounting cartridges in the group holes, and blasting the boreholes by using a millisecond blasting technology; and finally, injecting a large amount of normal temperature water into the target layer from the water injection well (1), performing heat exchange adequately by means of an artificial geothermal reservoir to implement the conversion from solid heat to liquid heat, and exploiting high temperature water and superheated steam from the production well. According to the method, the organic combination of hydraulic fracturing and millisecond blasting technologies is implemented, the hot dry rock artificial geothermal reservoir can be constructed to the maximum, and the application prospects are broad.

Description

Method for constructing artificial heat storage of dry hot rock in cooperation with hydraulic fracturing and millisecond millisecond blasting

Technical field

The invention relates to the field of the construction of an enhanced geothermal system (EGS) dry hot rock artificial heat storage, and in particular to a method for constructing a dry hot rock artificial heat storage in conjunction with multi-hole hydraulic fracturing and millisecond millisecond blasting. The method is particularly suitable for low Deep dry hot rock with porosity and low permeability.

Background technique

Hot dry rock refers to a high-temperature rock mass with no fluid or only a small amount of fluid inside, and the temperature is between 150-650℃, and the general burial depth is 3000-10000m. The global geothermal energy resources are about 4900 trillion tons of standard coal, and China accounts for about 1/6 of the world's total. In China, hot dry rock geothermal resources are abundant, and the total amount of exploration is currently about 2×10 ²⁵ J, which is 300 times the total resources of oil and gas and coal in China. Based on the estimation of my country's "863" project "Key Technology Research on Hot Dry Rock Thermal Energy Development and Comprehensive Utilization", my country's hot dry rock geothermal energy resources are equivalent to 860 trillion tons of standard coal. Calculated on the basis of 2% of the exploitable resources, it is equivalent to 4000 times of my country's total energy consumption in 2015.

Enhanced Geothermal Systems (EGS) is a specific engineering method for developing hot dry rock resources. Injection wells and production wells are established through drilling and completion, and fracture channels are built through hydraulic fracturing, which eventually form artificial thermal storage and become "Man-made geothermal field". Circulate geothermal water in injection wells and production wells, extract geothermal energy in fractures through heat exchange, so as to achieve the goal of geothermal power generation and comprehensive heating utilization. The development of hot dry rock began in the 1970s. According to the development concept of enhanced geothermal system, field drilling and hydraulic fracturing tests have been carried out in many geothermal fields abroad, such as the United States, France, Switzerland, the United Kingdom, Germany, Japan and other countries. China's hot dry rock development is still in the experimental and exploratory stage. During the development of dry hot rocks, the focus of the formation of enhanced geothermal fields is to form long-term stable heat exchange areas, that is, artificial heat storage. Connecting thermal storage and injection wells and production wells through hydraulic fracturing technology is the core content of enhanced geothermal development. However, in the process of hydraulic fracturing of hot dry rock at home and abroad, the main difficult problems found are as follows: (1) The rock fracture pressure is extremely high. Because the rock matrix of the dry hot rock reservoir is very hard, resulting in extremely high fracture pressure, the pumping pressure required during hydraulic fracturing has to be greatly increased, which undoubtedly greatly increases the production cost; (2) Hydraulic fracture propagation prediction difficult. In hot dry rock reservoirs, high temperature and other complex environments cause missing measurement and monitoring data, which makes it difficult to predict the shape and extension of hydraulic fractures.

Millisecond blasting, also known as millisecond blasting, is a delayed blasting with a delay time interval of several milliseconds to tens of milliseconds. Due to the extremely short blasting time interval between the front and rear blastholes, the energy fields generated by the blasting of the blastholes influence each other, which can not only improve the blasting effect, but also reduce the blasting seismic effect, shock wave and flying rock hazards. Millisecond blasting can effectively control the blasting shock wave, vibration, noise and flying rocks; the operation is simple, safe, and rapid; it can be blasted near the fire without causing damage; the degree of fragmentation is good, which can improve the blasting efficiency and technical and economic benefits. The principle of its action is as follows: (1) Due to the slight hour difference in each section of the millisecond series of detonators, it provides auxiliary free surfaces for the late explosives and creates favorable blasting conditions; (2) Because the first explosives excite compression waves in the rock mass After being reflected from the free surface into a tensile wave, and then detonating the explosive, it can not only eliminate the stress-free zone or the stress-reducing zone formed by the simultaneous explosion, but also increase the tensile stress in the zone and make the rock fall uniform; (3) ) Due to the extremely short interval between two adjacent explosives, the stress wave generated in the rock mass by the explosive that was detonated first has not disappeared, and the explosive that detonated later will explode, so that the blasted coal will be subjected to two-way stress, thereby improving the crushing effect. Reduce the amount of explosives; (4) When using millisecond blasting, if the time difference is selected reasonably, the vibration waves generated by the blasting will interfere with each other and weaken, thereby reducing the vibration effect on the rock formation and helping to reduce the possibility of man-made earthquake disasters.

At present, the millisecond millisecond blasting technology has been widely used in mining, highway and railway, water conservancy and hydropower, and foundation pit excavation projects. It is mainly used for the construction of a large number of mines and tunnels or for mining operations, but it is used for dry heat. There is no report on the construction of artificial thermal storage with rock-enhanced geothermal system combined with hydraulic fracturing technology.

Summary of the invention

technical problem

The solution to the problem

Technical solutions

The purpose of the present invention is to provide a method for constructing an artificial thermal storage of dry hot rock in collaboration with hydraulic fracturing and millisecond millisecond blasting, which creatively combines hydraulic fracturing technology and ultra-deep hole millisecond millisecond blasting technology and applies it In the field of dry hot rock artificial heat storage construction, on the one hand, it can overcome the shortcomings of a single hydraulic fracturing technology in the construction of artificial heat storage areas. On the other hand, it can reduce production costs, expand economic benefits, and meet commercial development needs.

In order to achieve the above objectives, the main technical problems to be overcome by the present invention are as follows: In the prior art, it is disclosed: "When a single hydraulic fracturing method is used to construct an artificial thermal storage of dry hot rock, extremely high pumping pressure (hydraulic pressure) is required. ) Can produce as many cracks as possible along the direction of the maximum principal stress (that is, a larger artificial heat storage range), and after the cracks are generated, as the stress recovers, the cracks will gradually close, resulting in a reduction in the artificial heat storage range. Based on this, how to build an artificial heat storage of dry hot rock to the maximum?

In order to overcome the above technical difficulties, the present invention adopts the following technical solutions:

A method for constructing an artificial thermal storage of dry hot rock in collaboration with hydraulic fracturing and millisecond millisecond blasting, which sequentially includes the following steps:

The first step is to determine the depth and range of the target layer of dry hot rock;

Step 2. After determining the well group layout plan, construct the injection wells and production wells. At least one production well is arranged. When the construction of the injection wells and production wells reaches the target layer with the rock mass above 200°C, stop Drilling

The third step is to drill several rows of parallel horizontal boreholes in the target layer to form a group of holes, and the water injection wells and the production wells are connected through the group of holes;

The fourth step is to implement segmented hydraulic fracturing operations in the group of holes to produce a series of multiple fractures extending along the direction of the maximum principal stress in the target layer of dry hot rock, and the fractures formed in each horizontal borehole interpenetrate each other , Hydraulic fracturing is operated from the injection well side to the production well side, and stops when it reaches the production well;

The fifth step, according to the determined amount of explosives, send the charge from the water injection well to the hot dry rock target layer through the surface, carry out segmented charging operations on the group of holes, and install the detonation device and plugging, using millisecond difference Blasting technology maximizes the blasting of the group of holes that have formed multiple cracks to build a larger range of artificial heat storage of dry hot rock;

The sixth step is to inject a large amount of room temperature water into the water injection well to the target layer of dry hot rock. The room temperature water flows through the dry hot rock artificial heat storage for sufficient heat exchange to realize the transformation of solid heat to liquid heat, and produce high temperature water from the production well. Superheated steam is used for power generation or heating.

The beneficial technical effects directly brought about by the above technical solutions are:

The present invention revolves around the technical concept of combining "single hydraulic fracturing technology and millisecond millisecond blasting technology", and obtains the above technical solution. In the above technical solution, the single hydraulic fracturing technology can produce more Fracturing fractures, and then implement millisecond millisecond blasting technology in the same borehole. On the one hand, under the same pumping pressure, the further use of millisecond millisecond blasting technology will help to obtain a larger range of artificial heat storage for dry hot rock. On the other hand, the pre-formed fractures are millisecond millisecond blasting. The technology provides a lot of free space and greatly improves the blasting effect. Single hydraulic fracturing technology and millisecond millisecond blasting technology are complementary and indispensable. It can also be said that there is a synergy between the two.

As a preferred solution of the present invention, in the first step, the depth and range of the hot dry rock target layer are determined according to the geological data of the hot dry rock geothermal development zone in combination with geological exploration methods.

As another preferred solution of the present invention, in the third step, when several rows of parallel horizontal boreholes are drilled in the target layer, the distance between adjacent horizontal boreholes is less than or equal to two boreholes due to hydraulic pressure. The sum of the lengths of the cracks formed by the cracks.

Further, in the fourth step, when the segmented hydraulic fracturing operation is performed in the above-mentioned group of holes, it is ensured that the synchronous operation in each borehole is ensured.

Further, in the fifth step, before performing the segmented charging operation on the group of holes, the temperature of each drill hole is firstly cooled, and the scouring drill holes are cleaned at the same time to ensure the smooth progress of the charging.

Further preferably, in the fifth step, the device used in the millisecond millisecond blasting technique described above includes a charge coil and related lines, and the charge coil and related lines are used after being subjected to high temperature and high pressure resistance treatments.

Further preferably, in the fifth step, the millisecond millisecond blasting technology described above adopts radial uncoupling charge technology, and the charge steps of each segment are: plugging the bottom of the hole, installing the charge pack, connecting the lead wire, installing the detonating device, Fill the blasthole.

More preferably, the above-mentioned millisecond millisecond blasting technique is simultaneously detonated in the group of holes, and the detonation sequence is carried out sequentially from the water injection well side to the production well side.

The above-mentioned method for constructing an artificial thermal storage of dry hot rock by the combination of multi-hole hydraulic fracturing and millisecond millisecond blasting is applied in the field of constructing an artificial thermal storage of a hot dry rock enhanced geothermal system combined with hydraulic fracturing technology.

The above-mentioned hot dry rock is preferably a deep dry hot rock with low porosity and low permeability.

The beneficial effects of the invention

Beneficial effect

Compared with the prior art, the present invention brings the following beneficial technical effects:

(1) The present invention is easy to operate and has strong applicability. By organically combining hydraulic fracturing technology and millisecond millisecond blasting technology, it is possible to construct artificial heat storage of dry hot rock to the maximum, expand the range of heat exchange, and obtain more Geothermal resources greatly increase economic benefits.

(2) The present invention overcomes the drawbacks of traditional single hydraulic fracturing to construct an artificial heat storage of dry hot rock. The fracturing fractures formed by the previous hydraulic fracturing (lower pumping pressure) provide more free surface and free space for the subsequent millisecond blasting, which greatly reduces the fracturing cost and blasting cost, and strengthens the deep dry hot rock. The development and utilization of geothermal energy provides a new way.

(3) When using millisecond millisecond blasting technology to construct artificial heat storage, the vibration waves generated by blasting will interfere with each other and weaken, thereby reducing the vibration effect on the rock formation, which can significantly weaken the seismic effect brought by enhanced geothermal mining, and maximize The reduction of the harm to the ecological environment and production and life has significant social value.

Brief description of the drawings

Description of the drawings

The present invention will be further explained below in conjunction with the accompanying drawings:

Figure 1 is a schematic diagram of the structure of the artificial heat storage structure of dry hot rock constructed by the combination of multi-hole hydraulic fracturing and millisecond millisecond blasting in the present invention;

2 is a schematic cross-sectional view of the arrangement of parallel horizontal group holes according to the present invention;

Figure 3 is a schematic diagram of the structure of the single-stage blasting charge of the present invention;

Fig. 4 is a flow chart of the method for constructing an artificial heat storage of dry hot rock in collaboration with group-hole hydraulic fracturing and millisecond millisecond blasting in the present invention;

In the picture: 1-water injection well; 2-production well; 3-dry hot rock target layer; 4-parallel horizontal drilling; 5-hydraulic fracturing; 6-artificial heat storage formed by hydraulic fracturing; 7 -Millisecond millisecond blasting fracture crack; 8-Hydraulic fracturing and millisecond millisecond blasting synergistically form artificial heat storage; 9- Leading blasting line; 10- Drilling and hydraulic fracturing construction platform; 11- Detonation device; 12- Chemical Volume; 13-radial uncoupled charge structure; 14-distance between adjacent boreholes; 15-cement plug; 16-river sand; 17-detonating line; 18-detonating bomb.

Invention embodiment

Embodiments of the present invention

The present invention proposes a method for constructing an artificial heat storage of dry hot rock in collaboration with hydraulic fracturing and millisecond millisecond blasting. In order to make the advantages and technical solutions of the present invention clearer and clearer, the present invention will be described in detail below with reference to specific embodiments. .

The main technical improvement of the present invention lies in the research of applying millisecond millisecond blasting technology to the hot dry rock enhanced geothermal system and combining the hydraulic fracturing technology to construct an artificial heat storage.

The "normal temperature water" mentioned in this article refers to water with a temperature of about 25°C.

Combining millisecond millisecond blasting technology and hydraulic fracturing technology to obtain the method of the present invention, the main steps are shown in combination with Figure 4, including:

A method for constructing an artificial thermal storage of dry hot rock in collaboration with hydraulic fracturing and millisecond millisecond blasting, which is characterized in that it includes the following steps in sequence:

The first step is to determine the depth and range of the hot dry rock target layer based on the geological data of the hot dry rock geothermal development area and combined with geological exploration methods;

The second step, after determining the well group layout plan, carry out construction of the water injection wells and production wells, and stop drilling when the water injection wells and production wells reach the target layer with a rock mass above 200°C;

The above-mentioned distance between the water injection well and the production well should not only consider the heat exchange efficiency of water in the dry hot rock artificial heat storage, but also consider the actual construction difficulty of ultra-deep hole millisecond millisecond blasting;

The third step is to drill several rows of parallel horizontal boreholes in the target layer to form a group of holes, and connect the injection wells and the production wells through the group of holes; when drilling several rows of parallel horizontal boreholes in the target layer, The distance between adjacent horizontal boreholes is less than or equal to the sum of the lengths of the fractures formed by the hydraulic fracturing of the two boreholes;

In order to reduce the production cost as much as possible, the pumping pressure can be appropriately reduced when the hydraulic fracturing technology is used in the early stage;

It is preferable to cool down the borehole before charging, and at the same time to clean and flush the borehole to make charging proceed smoothly;

Furthermore, the length of the charge in the millisecond millisecond blasting mentioned above should be extended as much as possible to reduce the number of sections in a single horizontal borehole, and reduce the difficulty of the charge process and the complexity of the initiation network;

Furthermore, the millisecond millisecond blasting technology described above adopts radial uncoupling charge technology, and the charge process of each segment includes: plugging the bottom of the hole, installing the charge pack, connecting the lead wire, installing the detonating device, and filling the blast hole;

Further, the millisecond millisecond blasting technique described above should be detonated simultaneously in the parallel horizontal group of holes, and the detonation sequence is carried out sequentially from the side of the water injection well to the side of the production well.

A further description will be given below in conjunction with specific embodiments:

Example 1:

Figure 1 is a schematic diagram of the structure of the artificial thermal storage of dry hot rock constructed by the combination of multi-hole hydraulic fracturing and millisecond millisecond blasting in the present invention. The figure includes a water injection well 1, a production well 2, a hot dry rock target layer 3, and a parallel type. Horizontal drilling 4, hydraulic fracturing cracks 5, artificial thermal storage formed by hydraulic fracturing 6, millisecond millisecond blasting cracks 7, hydraulic fracturing and millisecond millisecond blasting synergistically form artificial thermal storage 8, leading blasting line 9. Drilling and hydraulic fracturing construction platform 10. Detonation device 11.

The above-mentioned target layer is located within the rock formation 3000m from the surface, and the spacing L between the production well and the water injection well is initially taken as 200m, that is, the length of the group of holes formed by parallel horizontal drilling is 200m, and the production well and the water injection well are connected through the group of holes.

In this embodiment, 9 parallel horizontal boreholes are designed, as shown in Figure 2, which shows the parallel horizontal borehole 4, the charge roll 12, the radial uncoupled charge structure 13, and the distance between adjacent boreholes ( d) 14. Estimate the distance d between adjacent boreholes based on the length of hydraulic fracturing cracks, and it is planned to be 50m, that is, the maximum length of cracks produced by hydraulic fracturing in each horizontal borehole is 25m. The borehole diameter is planned to be 139mm, the length of each section of hydraulic fracturing operation is 20m, and 10 fracturing operations are required.

As shown in Figure 3, Figure 3 is a schematic diagram of the single-stage blasting charge structure, which shows the charge roll 12, the cement plug 15, the river sand 16, the branch detonating line 17, and the detonating bomb 18, of which the charge roll 12 Adopt PYX type (2,6-bis(bitter amino)-3,5-dinitropyridine) heat-resistant explosive, adopt uncoupled charging method, diameter 100mm, length of each charge 500mm, each section can be installed 3 The total length of each segment is 5m for short-distance blasting with two adjacent charge coils. Using detonating bomb-branch detonating line 17-dominant detonating line 9 detonating network to detonate the explosive, the millisecond interval needs to be calculated by the delay time calculation formula.

The invention has simple operation and strong adaptability, overcomes the shortcomings of low efficiency and high cost of using a single hydraulic fracturing technology to construct artificial heat storage, realizes the organic combination of hydraulic fracturing and millisecond blasting technology, and can maximize The construction of dry hot rock artificial heat storage, while millisecond blasting can reduce the mutual interference between shock waves, can significantly reduce the seismic effect brought by geothermal mining, and has a wide range of application prospects.

The parts not mentioned in the present invention can be realized by referring to the prior art.

It should be noted that all equivalent replacements made by those skilled in the art under the enlightenment of the present invention should fall within the protection scope of the present invention.

Claims

A method for constructing an artificial heat storage of dry hot rock in collaboration with multi-hole hydraulic fracturing and millisecond millisecond blasting, which is characterized in that it includes the following steps in sequence:

The first step is to determine the depth and range of the target layer of dry hot rock;

Step 2. After determining the well group layout plan, construct the injection wells and production wells. At least one production well is arranged. When the construction of the injection wells and production wells reaches the target layer with the rock mass above 200°C, stop Drilling

The third step is to drill several rows of parallel horizontal boreholes in the target layer to form a group of holes, and the water injection wells and the production wells are connected through the group of holes;

The fourth step is to implement segmented hydraulic fracturing operations in the group of holes to produce a series of multiple fractures extending along the direction of the maximum principal stress in the target layer of dry hot rock, and the fractures formed in each horizontal borehole interpenetrate each other , Hydraulic fracturing is operated from the injection well side to the production well side, and stops when it reaches the production well;

The fifth step, according to the determined amount of explosives, send the charge from the water injection well to the hot dry rock target layer through the surface, carry out segmented charging operations on the group of holes, and install the detonation device and plugging, using millisecond difference Blasting technology maximizes the blasting of the group of holes that have formed multiple cracks to build a larger range of artificial heat storage of dry hot rock;

The sixth step is to inject normal temperature water into the water injection well to the target layer of dry hot rock. The normal temperature water flows through the dry hot rock artificial heat storage for sufficient heat exchange to realize the conversion of solid heat to liquid heat, and produce high temperature water and waste water from the production well. Hot water vapor is also used for power generation or heating.
The method for constructing an artificial thermal storage of dry hot rock in combination with multi-hole hydraulic fracturing and millisecond millisecond blasting according to claim 1, characterized in that: in the first step, according to the geological data of the hot dry rock geothermal development zone, combined Geological exploration means to determine the depth and scope of the target layer of dry hot rock.
The method for constructing an artificial thermal storage of dry hot rock in collaboration with multi-hole hydraulic fracturing and millisecond millisecond blasting according to claim 1, characterized in that: in the third step, a plurality of parallel horizontal rows are drilled in the target layer When drilling, the distance between adjacent horizontal boreholes is less than or equal to the sum of the lengths of the fractures formed by the two boreholes due to hydraulic fracturing.
The method for constructing an artificial thermal storage of dry hot rock in collaboration with group-hole hydraulic fracturing and millisecond millisecond blasting according to claim 1, characterized in that: in the fourth step, a segmented method is implemented in the group-holes. During hydraulic fracturing operations, ensure synchronized operations in each borehole.
The method for constructing an artificial thermal storage of dry hot rock in collaboration with group-hole hydraulic fracturing and millisecond millisecond blasting according to claim 1, characterized in that: in the fifth step, the group-holes are subjected to segmented charging operation before , First of all, cool down the holes, and clean the scouring holes at the same time to ensure the smooth progress of the charge.
The method for constructing an artificial heat storage of dry hot rock in collaboration with multi-hole hydraulic fracturing and millisecond millisecond blasting according to claim 1, wherein: in the fifth step, the device used in the millisecond millisecond blasting technology It includes medicine rolls and related lines, and the medicine rolls and related lines are used after being treated with high temperature resistance and high pressure resistance.
The method for constructing an artificial thermal storage of dry hot rock in collaboration with multi-hole hydraulic fracturing and millisecond millisecond blasting according to claim 1, wherein: in the fifth step, the millisecond millisecond blasting technology adopts radial Without coupling charge technology, the charge process of each segment is: plugging the bottom of the hole, installing the charge package, connecting the lead, installing the detonating device, and filling the blast hole.
The method for constructing a dry hot rock artificial heat storage in conjunction with group-hole hydraulic fracturing and millisecond millisecond blasting according to claim 1, characterized in that the millisecond millisecond blasting technology detonates simultaneously in the group of holes, and The initiation sequence is carried out in sequence from the side of the water injection well to the side of the production well.
According to any one of claims 1-8, a method for constructing an artificial heat storage of dry hot rock in combination with multi-hole hydraulic fracturing and millisecond millisecond blasting Application in the field of heat storage construction.
The method for constructing an artificial thermal storage of dry hot rock in collaboration with multi-hole hydraulic fracturing and millisecond millisecond blasting according to claims 1-8, characterized in that: the dry hot rock has low porosity and low permeability Deep dry hot rock.