CN108167917B - Heating system of hot dry rock technology coupling heat pump - Google Patents

Abstract

The invention relates to the technical field of hot dry rock heat energy utilization, in particular to a high-efficiency hot dry rock technology coupled heat pump heating system, which solves the problems of low heating efficiency of a hot dry rock heating system and low long-term operation efficiency of a ground source heat pump. In the long term, the heat supply system can operate all the year round, the heat exchange efficiency of the whole system is higher than that of the traditional ground source heat pump, the cost performance is higher, and the operation is more stable and durable.

Description

A heating system with hot dry rock technology coupled with heat pump

technical field

The invention relates to the technical field of thermal energy utilization of dry-hot rock, in particular to a heating system with high-efficiency dry-hot rock technology coupled with a heat pump.

Background technique

With the development of the economy and the improvement of people's living standards, energy and environmental issues have increasingly become the subject of human concern. Among them, hot dry rock, as a kind of clean energy buried deep in the ground, is very rich in heat, but it has always been It has not been developed and utilized on a large scale.

At present, the domestic medium-deep geothermal energy mining technology is not mature, and no reports have been found on the use of artificial fracturing to extract the thermal energy of dry hot rock. Internationally, the single-cycle method is generally used to obtain geothermal energy, which has the defects of low acquisition rate and utilization rate of geothermal energy. At the same time, deep hot dry rock energy not only has large investment and high risk, but also has low power generation capacity, which greatly limits the exploitation of dry hot rock thermal energy.

In some high-latitude and cold regions in China (such as Shenyang, Beijing, etc.), heating in winter requires a lot of heat energy, the use of conventional fossil fuels is serious, and the cost performance of electricity is low, making ground source heat pumps widely used. However, the year-round thermal exploitation of ground source heat pump systems in these areas has caused serious problems such as the decline of formation temperature, formation pressure and heat extraction efficiency year by year.

With the continuous development and utilization of hot dry rock, patent CN201520986148.7 discloses a U-shaped tubular hot dry rock heat exchanger, patent CN107062352A discloses a dry hot rock heating system, and patent CN106885385A discloses a single well Hot dry rock thermal energy extraction systems have achieved the extraction and application of dry hot rock thermal energy to varying degrees.

However, none of the above patents really effectively solve the problem of low heating efficiency in the dry hot rock heating system, and the ground source heat pump also has the problem of decreasing efficiency year by year.

SUMMARY OF THE INVENTION

In order to solve the problems of low heating efficiency and ground source heat pump efficiency of the dry hot rock heating system, the invention effectively combines the dry hot rock mining technology and the heat pump technology to provide a high-efficiency dry hot rock technology coupled heat pump heating system .

The invention is realized by the following technical scheme: a heating system with high-efficiency dry hot rock technology coupled with heat pump, including a dry hot rock geothermal system set underground and a heat pump system set on the surface, the dry hot rock geothermal system is connected with a plate type The heat exchanger group, the plate heat exchanger group is connected with a heat pump system, and the heat pump system is connected with a terminal heating system.

The hot dry rock geothermal system includes a water injection well and a water pumping well. Both the water injection well and the water pumping well are horizontal wells. The water injection well is connected with a plate heat exchanger group. The water injection wells are spaced with a plurality of hydraulic fracturing parallel to each other and perpendicular to the water injection wells. For segmented fractures, the pumping wells are symmetrically arranged within the length of the hydraulic fracturing segmented fractures, the pumping wells are connected with a circulating pump, and the circulating pump is connected with a plate heat exchanger group.

The heat pump system includes an evaporator, a compressor, an expansion valve and a condenser. The cold water is heated by the plate heat exchanger and then flows through the evaporator and the compressor to be further heated, and then flows through the condenser to release the heat to the terminal heating system. The water flowing out of the boiler is cooled by the expansion valve and then circulated to the plate heat exchanger group.

The water injection well is set in the thermal reservoir with a vertical depth of 1500 to 2500 meters from the surface, and the length of the water injection well is 1800 to 2200 meters.

Hydraulic fracturing staged fractures are propped up by fracturing proppants. The fracturing proppant is a ceramic particle product with high fracturing strength. The ceramsite propping material is used to enter the formation together with the high-pressure solution to fill the fractures in the rock formation, so as to support the fractures from being closed due to stress release, so as to maintain the High diversion capacity, so that the hot air is smooth.

The working principle of the present invention is:

1) Inject 5°C cold water into the ground through the water injection well to the thermal reservoir in the range of 1500-2500 meters, and the temperature of the formation in this range is 45°C-75°C;

2) Cold water flows through the hydraulic fracturing staged fractures supported by proppant for heating, and then pumped out through the pumping well;

3) The extracted hot water is driven by the circulating pump to flow through the plate heat exchanger group;

4) Through the multi-stage heat exchange of the plate heat exchanger group, the cooled water (about 5°C) is injected into the dry hot rock thermal reservoir again through the water injection well for circulating heat;

5) The heat pump system feeds the internal cold water into the plate heat exchanger group for heating, and the outflowing hot water is further heated to a higher temperature through the evaporator and compressor;

6) The hot water in the heat pump system releases heat to the terminal heating system through the condenser. After the cooled water is further cooled by the expansion valve, it enters the plate heat exchanger group to circulate and obtain heat.

The system is mainly used in high-latitude and cold regions (such as North China, Northeast China, and Northwest China). The system is operated for heating during the heating period in winter every year, and the system is turned off during the rest of the year. In summer, it relies on air conditioning for cooling or natural cooling, which can solve the problem of ground source heat pump. The long-term extraction of geothermal heat causes the problem of formation temperature drop. In addition, the system can also be used in other areas, used for heating in winter, and cold water can be poured into the ground in summer to achieve the effect of heat pump cooling.

Compared with the traditional ground source heat pump or the solar energy combined ground source heat pump heating system, the advantages of the present invention are:

The heating system of the present invention occupies a small area and has no restrictions on the site, and can realize central heating in a large range. In addition, since the temperature of the formation and the temperature of the underground water are reduced more slowly than the traditional ground source heat pump, in the long run, the present invention The heating system can be operated all year round and the overall system heat exchange efficiency is higher than that of traditional ground source heat pumps. Compared with the dry hot rock heating system, the advantages of the present invention are: the underground part of the present invention draws on the technology of mining dry hot rock, and the thermal reservoir reached by drilling can be sedimentary rock, magmatic rock or metamorphic rock, and only the temperature of the reservoir is required. It is enough to reach above 50 °C, so it does not require high geological conditions. Compared with traditional hot dry rock heating, it has a wider range of regional applications and reduces drilling costs.

Description of drawings

FIG. 1 is a schematic structural diagram of the heating system of the dry hot rock thermal energy coupled heat pump in the present invention.

In the picture: 1- hydraulic fracturing staged fracture, 2- pumping well, 3- water injection well, 4- circulating pump, 5- plate heat exchanger group, 6- evaporator, 7- compressor, 8- expansion valve, 9-Condenser, 10-Terminal heating system, 11-Heat pump system, 12-Dry hot rock geothermal system.

Detailed ways

The present invention will be further elaborated with reference to FIG. 1 , a heating system with high-efficiency hot dry rock technology coupled with a heat pump includes a hot dry rock geothermal system 12 set underground and a heat pump system 11 set on the surface, and the hot dry rock geothermal system 12 is connected to There is a plate heat exchanger group 5, the plate heat exchanger group 5 is connected with a heat pump system 11, and the heat pump system 11 is connected with a terminal heating system 10.

Among them, the underground hot dry rock geothermal system needs to be transformed before it can be formed and used. The formation process is as follows: first, a horizontal well is drilled as the water injection well 3, and the vertical depth of the water injection well 3 relative to the surface is about 2000 meters, and the water injection well 3 The length is about 2000 meters; further, multi-fracture staged hydraulic fracturing is performed in the water injection well 3, and a proppant-type fracturing method is used to obtain a plurality of hydraulic fracturing staged fractures 1 arranged at intervals and perpendicular to the water injection well 3; Further, according to the microseismic monitoring results, two more horizontal wells were drilled at both ends of the hydraulic fracturing staged fracture 1 as pumping wells 2. The pumping wells 2 should pass through the hydraulic fracturing staged cracks 1 in turn to form hot dry rock geothermal heat. system 12.

The overall operation process of the system is:

1) Inject 5°C cold water into the target thermal reservoir through water injection well 3;

2) The injected cold water flows through the hydraulic fracturing staged fracture 1 supported by the proppant for heating, and then is pumped out through the pumping well 2;

3) The extracted hot water is driven by the circulating pump 4 and flows through the plate heat exchanger group 5;

4) Through the multi-stage heat exchange of the plate heat exchanger group 5, part of the water is cooled, and the cooled water (about 5°C) is injected into the hot dry rock thermal reservoir through the water injection well 3 again for circulating heat;

5) The heat pump system 11 pumps the internal cold water into the plate heat exchanger group 5 for heating, and the outflowing hot water is further heated to a higher temperature through the evaporator 6 and the compressor 7;

6) The hot water in the heat pump system 11 releases heat to the terminal heating system 10 through the condenser 9, and the cooled water is further cooled down by the expansion valve 8, and then enters the plate heat exchanger group 5 for circulating heat.

The arrows shown in the figure are the direction of water flow, of which the single arrow is the cold flow, and the double arrow is the heat flow.

Claims (1)

1. A heating system of hot dry rock technology coupling heat pump which characterized in that: the system comprises a hot dry rock geothermal system (12) arranged underground and a heat pump system (11) arranged on the earth surface, wherein the hot dry rock geothermal system (12) is connected with a plate heat exchanger group (5), the plate heat exchanger group (5) is connected with the heat pump system (11), the heat pump system (11) is connected with a terminal heating system (10), the hot dry rock geothermal system (12) comprises a water injection well (3) and a water pumping well (2), the water injection well (3) and the water pumping well (2) are both horizontal wells, the water injection well (3) is connected with the plate heat exchanger group (5), a plurality of hydraulic fracturing segmented cracks (1) which are parallel to each other and vertical to the water injection well (3) are arranged in the water injection well (3) at intervals, the water pumping wells (2) are symmetrically arranged in the length range of the hydraulic fracturing segmented cracks (1), the water pumping wells (2) are connected with circulating pumps (4), and the circulating pumps, the heat pump system (11) comprises an evaporator (6), a compressor (7), an expansion valve (8) and a condenser (9), cold water is heated by a plate-type heat exchanger group (5) and then flows through the evaporator (6) and the compressor (7) to be further heated, then flows through the condenser (9) to release heat to a terminal heating system (10), water flowing out of the condenser (9) is cooled by the expansion valve (8) and then circulates to the plate-type heat exchanger group (5), a water injection well (3) is arranged in a heat storage layer with the vertical depth of 1500-2500 m from the ground surface, the length of the water injection well (3) is 1800-2200 m, and a hydraulic fracturing segmented fracture (1) is supported by a fracturing propping agent.

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