1. Project introduction

Fracturing assisted conventional geothermal energy development systems, as shown in Figure 1, heat extraction consists of a pumping well and a recharge well. This method consumes almost no geothermal water. Geothermal water exchanges heat through heat exchangers and outputs heat to the outside without entering the heating or power generation system pipes. Artificial fracturing is carried out between hot water pumping and filling wells to form cracks and enhance the recharge of geothermal water, thereby reducing waste of geothermal resources and damage to the environment. Select a reasonable spacing between pumping and charging wells, and reasonably control the recharge temperature, so that the temperature of geothermal water will not drop.

The closed cycle heat extraction technology based on horizontal branch wells, as shown in Figure 2, uses the multi-branch horizontal well technology to drill multiple horizontal branch boreholes in the main borehole. The heat exchange fluid enters from the main borehole and then expands to each branch horizontal borehole. When the fluid flows in the horizontal branch borehole, it absorbs heat, then returns to the surface from the insulated inner pipe, and then enters the heat exchanger to heat the surface circulating fluid through convective heat exchange. Finally, the heat-carrying fluid that releases heat enters the main wellbore under the action of the circulation pump, forming a closed circulation system.

2. Technological innovation and leadership

For fracking assisted conventional geothermal energy development systems, artificial fracturing is carried out between conventional injection wells and production wells to create fractures and form a closed circulation loop of geothermal water. This system only extracts heat and does not consume geothermal water, so it will not cause problems such as thermal pollution and ground subsidence to the surrounding environment. On the other hand, it can also ensure the service life of the heat storage.

The multi-branch horizontal heat exchange well enhanced geothermal system belongs to a downhole closed circulation system. When exchanging heat with the heat reservoir, it only extracts the heat from the heat reservoir and does not exchange material with the heat reservoir. It belongs to an environmentally friendly system. The use of multi-branch horizontal wells to build a heat exchange system greatly increases the heat exchange area between fluid and heat storage, improves heat exchange power, and reduces drilling costs. Clean water is used as the heat-carrying fluid in the closed cycle system, which ensures stable operation of the system and prolongs the life of ground equipment.

3. Economics and market prospects

Whether heating or power generation, compared with conventional coal-fired and oil-fired boilers, the initial investment of the geothermal utilization system is equivalent or relatively higher. However, when it is built and put into operation, the geothermal system does not consume coal, oil and other fuels, and the operating cost is only conventional heating or The power generation system is 1/4 to 1/3 of the system, so the geothermal utilization system has good economy.

In recent years, with the increasing requirements for environmental protection and a low-carbon economy, geothermal energy as a clean and renewable energy source has received more and more attention. my country is rich in geothermal resources, and there are broad prospects for the development and utilization of geothermal resources. The development goal of geothermal energy during the 12th Five-Year Plan is that by 2015, the total development and utilization of various types of geothermal energy will reach 15 million tons of standard coal. In the next few years, there will be broad prospects for geothermal energy utilization.

4. main application fields

The enhanced geothermal energy development technology is mainly used for geothermal heating and is an environmentally friendly geothermal energy mining technology.