Method for conducting stratum heat storage transformation and heat removal through coiled tubing

Abstract

The invention discloses a method for carrying out stratum heat storage transformation and heat removal by using a coiled tubing, which belongs to the technical field of geothermal reservoir yield increase transformation, and is characterized by comprising the following steps of: a, mounting a tool string on the coiled tubing, putting the coiled tubing into a sleeve, putting the coiled tubing into a stratum, carrying out sand blasting perforation operation and fracturing operation, and injecting a heat conduction material; b, after the coiled tubing is tripped, the coiled tubing is taken out of the ground, perforation and fracturing components at the front end of the coiled tubing are detached, and a sealing device is installed to seal the front end of the coiled tubing; c, the well depth is measured, and liquid working medium injection and vacuumizing are conducted at the rear end of the continuous oil pipe provided with the liquid injection valve and the scavenging air valve according to the measured well depth; and d, the continuous oil pipe is arranged again, the continuous oil pipe is lowered to the set stratum position, and stratum heat removal is conducted. Directional perforation and continuous operation can be achieved, staged fracturing and fine fracturing can be achieved, large-scale transformation is achieved, the heat extraction efficiency is improved, and the good heat extraction effect is achieved.

Description

Technical Field

[0001] This invention relates to the field of geothermal reservoir enhancement and modification technology, and in particular to a method for geothermal reservoir modification and heat extraction using coiled tubing. Background Technology

[0002] Geothermal reservoirs, or simply reservoirs, are underground strata, rock masses, or structural zones with effective porosity and permeability, containing geothermal fluids that can be developed and utilized. Geothermal reservoirs store geothermal energy through the convection and enrichment of heat-carrying fluids. Therefore, a crucial characteristic of geothermal reservoirs is that cold water from outside the reservoir seeps into the aquifer, then passes through the heating zone at the bottom of the reservoir, where it is heated by a strong and continuous conductive heat flow. Geothermal reservoirs differ from oil, gas, and groundwater reservoirs in that the existing fluids can be replenished and heated by surrounding cold water. This replenishment process is vital in the movement of geothermal reservoirs.

[0003] Geothermal reservoirs are classified based on the amount of steam they contain. If they do not contain steam, they can be classified based on the location of the boiling zone at the Earth's surface. Within a hydrothermal system, the natural composition of a geothermal reservoir depends on its temperature, depth, gas content, and conductivity; therefore, multiple conductive layers or reservoirs may exist at different depths. In geothermal reservoir research, state parameters are crucial for analyzing reservoir characteristics and understanding dynamic trends. The most critical parameters in reservoir engineering are the rock layer's transmissivity and storage coefficient, which can be obtained through geological and geophysical measurements. Because these parameters are related to the distribution of pores and fractures, they are inherently anisotropic. Theoretical research on reservoir engineering is essential for understanding the distribution of geothermal resources, the migration state of thermal fluids, and the heat transfer processes of geothermal systems. It is also crucial for using physical and mathematical models to predict the changes in reservoir parameters, resource reserves, and maximum exploitation life during production and reinjection periods. Meanwhile, geothermal reservoir theory research can also provide important scientific basis for the amount of energy recovered, the optimal well spacing and pumping volume, the impact of cold peak surface of reinjection fluid, and the impact of land subsidence caused by excessive exploitation of geothermal resources.

[0004] When the rock mass is dense and has low natural porosity and permeability, geothermal energy can be better obtained by modifying the geothermal reservoir.

[0005] Chinese patent document CN115199251A, published on October 18, 2022, discloses a fracturing method for carbonate geothermal reservoirs, comprising: after completion of a radial well in a carbonate geothermal reservoir, running a CO2 fracturing string into the target section of the radial well using coiled tubing; wherein the CO2 fracturing string is equipped with a CO2 fracturing device filled with liquid CO2; inside the radial well, using a heater in the CO2 fracturing device to heat the liquid CO2 inside the CO2 fracturing device, performing CO2 pulse fracturing in the target section. The CO2 fracturing device opens up the reservoir fractures near the wellbore in the radial well. Inside the CO2 fracturing device, the liquid CO2 undergoes a phase transition to a supercritical state upon heating, causing volume expansion and increased pressure. Once the supercritical CO2 pressure reaches the opening pressure of the CO2 fracturing device, the energy release orifice opens. The supercritical CO2 inside the fracturing device immediately passes through the energy release orifice and impacts and enters the target layer. A pulsed stress wave instantaneously impacts the target layer, forming a crack. The supercritical CO2 then drives the crack to continuously propagate and fracture the target layer.

[0006] The fracturing method for carbonate geothermal reservoirs disclosed in this patent document combines the advantages of supercritical CO2 properties, high-pressure pulse fracturing, and radial well 3D stimulation. The highly fluid supercritical CO2 high-pressure pulse fracturing in radial wells helps to connect natural fractures in the reservoir. However, the fracturing process is complex and costly, making it unsuitable for large-scale stimulation. Summary of the Invention

[0007] In order to overcome the shortcomings of the prior art, this invention provides a method for formation thermal reservoir stimulation and heat extraction using coiled tubing. This invention can achieve both directional perforation and continuous operation, as well as segmented fracturing and fine fracturing, enabling large-scale stimulation, improving heat extraction efficiency, and achieving good heat extraction results.

[0008] This invention is achieved through the following technical solution: A method for formation thermal reservoir stimulation and heat extraction using coiled tubing, characterized by comprising the following steps: a. Install a tool string on the coiled tubing, insert it into the casing and lower it into the formation to perform sandblasting and fracturing operations, and inject heat-conducting material; b. After running the coiled tubing, remove the coiled tubing from the ground and remove the perforation and fracturing components at the front end of the coiled tubing. Install a sealing device to seal the front end of the coiled tubing. c. Measure the well depth, and inject the working fluid and evacuate the tubing at the rear end of the coiled tubing equipped with injection valve and venting valve according to the measured well depth. d. Next, run the coiled tubing down to the designated formation location to extract heat from the formation.

[0009] In step a, installing the tool string on the coiled tubing means connecting the fracturing valve tool to the coiled tubing, and then connecting the fracturing valve tool, hydraulic jet tool, packer, and guide stabilizer in sequence.

[0010] In step a, the sandblasting perforation operation specifically refers to injecting sand-carrying fluid into the continuous tubing. The sand-carrying fluid flows through the nozzle of the hydraulic jet tool to form a sand-carrying jet, which blasts open the casing and the formation.

[0011] In step a, fracturing operation refers to closing the casing gate after sandblasting and perforation, pumping liquid into the coiled tubing to induce fracturing in the formation, then dropping a ball to open the fluid outlet channel of the fracturing valve tool, and then pumping fracturing fluid into the coiled tubing.

[0012] In step b, the sealing device is an elastic rubber sealing sleeve.

[0013] The elastic rubber sealing sleeve includes a sealing sleeve body and an internal interlayer disposed on the sealing sleeve body. Multiple metal connecting rods are provided in the internal interlayer, and the multiple metal connecting rods are all arranged along the axial direction of the sealing sleeve body.

[0014] The metal connecting rod comprises multiple rods connected in series, with adjacent rods being movably connected by a rotating shaft that rotates radially along the sealing sleeve body.

[0015] In step c, liquid working fluid injection specifically refers to injecting water into the coiled tubing to maintain the fluid filling rate of the coiled tubing at 45%.

[0016] In step c, vacuuming specifically refers to drawing a vacuum into the coiled tubing to maintain a vacuum level of 10. -5 P.

[0017] In step d, arranging coiled tubing specifically refers to arranging multiple coiled tubings side by side.

[0018] The beneficial effects of this invention are mainly reflected in the following aspects: 1. This invention comprises: a) installing a tool string on a coiled tubing, inserting it into the casing and lowering it into the formation for sandblasting, perforation, and fracturing operations, and injecting heat-conducting material; b) after lowering the coiled tubing, removing it from the surface and disassembling the perforation and fracturing components at the front end of the coiled tubing, installing a sealing device to seal the front end of the coiled tubing; c) measuring the well depth, and injecting liquid working fluid and evacuating vacuum at the rear end of the coiled tubing equipped with an injection valve and a venting valve based on the measured well depth; d) then arranging the coiled tubing again and lowering it to the designated formation location for formation heat extraction. Compared with existing technologies, this invention enables both directional perforation and continuous operation, as well as segmented fracturing and fine fracturing, achieving large-scale transformation, improving heat extraction efficiency, and achieving excellent heat extraction results.

[0019] 2. In step a of this invention, the sandblasting perforation operation specifically refers to injecting sand-carrying fluid into the continuous tubing. The sand-carrying fluid flows into the nozzle of the hydraulic jet tool to form a sand-carrying jet, which perforates the casing and the formation. Through the directional performance of the perforation, the perforation direction can be selected and the requirements of the modification scheme can be met.

[0020] 3. In step a of this invention, fracturing operation refers to closing the casing gate after sandblasting and perforation, pumping liquid into the coiled tubing to induce fracturing in the formation, then dropping a ball to open the liquid outlet channel of the fracturing valve tool, and then pumping fracturing fluid into the coiled tubing. Through the precise positioning of the coiled tubing, multiple thin interlayers in the vertical direction of the formation can be flexibly separated, thereby achieving the purpose of fine fracturing.

[0021] 4. In step b of this invention, the sealing device is an elastic rubber sealing sleeve. The elastic rubber sealing sleeve includes a sealing sleeve body and an inner interlayer disposed on the sealing sleeve body. The inner interlayer is provided with multiple metal connecting rods, which are all arranged along the axial direction of the sealing sleeve body. Each metal connecting rod includes multiple rods connected in series. Adjacent rods are movably connected by a rotating shaft, which rotates radially along the sealing sleeve body. Compared with the sealing structure of the prior art, this sealing device with a specific structure not only improves the reliability of the seal but also greatly enhances the sealing effect.

[0022] 5. In step c of this invention, the liquid working fluid injection specifically refers to injecting water into the continuous oil pipe to maintain the liquid filling rate in the continuous oil pipe at 45%, ensuring sufficient usable space for water circulation, which is beneficial to improving heat exchange efficiency.

[0023] 6. In step c of this invention, vacuuming specifically refers to drawing a vacuum into the continuous tubing to maintain a vacuum level of 10. -5 P can eliminate interfering factors that affect heat utilization, thus improving heat utilization efficiency.

[0024] 7. In step d of this invention, arranging continuous tubing specifically refers to arranging multiple continuous tubings in parallel, which can increase the heat extraction per unit time. Attached Figure Description

[0025] The present invention will now be further described in detail with reference to the accompanying drawings and specific embodiments: Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0026] Example 1 See Figure 1 A method for formation thermal reservoir stimulation and heat extraction using coiled tubing includes the following steps: a. Install a tool string on the coiled tubing, insert it into the casing and lower it into the formation to perform sandblasting and fracturing operations, and inject heat-conducting material; b. After running the coiled tubing, remove the coiled tubing from the ground and remove the perforation and fracturing components at the front end of the coiled tubing. Install a sealing device to seal the front end of the coiled tubing. c. Measure the well depth, and inject the working fluid and evacuate the tubing at the rear end of the coiled tubing equipped with injection valve and venting valve according to the measured well depth. d. Next, run the coiled tubing down to the designated formation location to extract heat from the formation.

[0027] This embodiment is the most basic implementation method. a) Install a tool string on the coiled tubing, insert it into the casing, and run it into the formation to perform sandblasting, perforation, and fracturing operations, and inject heat-conducting material; b) After running the coiled tubing, remove it from the surface and remove the perforation and fracturing components at the front end of the coiled tubing, install a sealing device, and seal the front end of the coiled tubing; c) Measure the well depth, and according to the measured well depth, inject liquid working fluid and evacuate at the rear end of the coiled tubing equipped with injection valve and venting valve; d) Arrange the coiled tubing again, run it to the designated formation location, and perform formation heat extraction. Compared with the existing technology, this method can achieve both directional perforation and continuous operation, as well as segmented fracturing and fine fracturing, enabling large-scale transformation, improving heat extraction efficiency, and achieving good heat extraction results.

[0028] Example 2 See Figure 1 A method for formation thermal reservoir stimulation and heat extraction using coiled tubing includes the following steps: a. Install a tool string on the coiled tubing, insert it into the casing and lower it into the formation to perform sandblasting and fracturing operations, and inject heat-conducting material; b. After running the coiled tubing, remove the coiled tubing from the ground and remove the perforation and fracturing components at the front end of the coiled tubing. Install a sealing device to seal the front end of the coiled tubing. c. Measure the well depth, and inject the working fluid and evacuate the tubing at the rear end of the coiled tubing equipped with injection valve and venting valve according to the measured well depth. d. Next, run the coiled tubing down to the designated formation location to extract heat from the formation.

[0029] In step a, installing the tool string on the coiled tubing means connecting the fracturing valve tool to the coiled tubing, and then connecting the fracturing valve tool, hydraulic jet tool, packer, and guide stabilizer in sequence.

[0030] In step a, the sandblasting perforation operation specifically refers to injecting sand-carrying fluid into the continuous tubing. The sand-carrying fluid flows through the nozzle of the hydraulic jet tool to form a sand-carrying jet, which blasts open the casing and the formation.

[0031] This embodiment is a preferred implementation. In step a, the sandblasting perforation operation specifically refers to injecting sand-carrying fluid into the continuous tubing. The sand-carrying fluid flows into the nozzle of the hydraulic jet tool to form a sand-carrying jet, which perforates the casing and formation. Through the directional performance of the perforation, the perforation direction can be selected and the requirements of the modification scheme can be met.

[0032] Example 3 See Figure 1 A method for formation thermal reservoir stimulation and heat extraction using coiled tubing includes the following steps: a. Install a tool string on the coiled tubing, insert it into the casing and lower it into the formation to perform sandblasting and fracturing operations, and inject heat-conducting material; b. After running the coiled tubing, remove the coiled tubing from the ground and remove the perforation and fracturing components at the front end of the coiled tubing. Install a sealing device to seal the front end of the coiled tubing. c. Measure the well depth, and inject the working fluid and evacuate the tubing at the rear end of the coiled tubing equipped with injection valve and venting valve according to the measured well depth. d. Next, run the coiled tubing down to the designated formation location to extract heat from the formation.

[0033] Preferably, in step a, installing the tool string on the coiled tubing means connecting the fracturing valve tool to the coiled tubing, and then sequentially connecting the fracturing valve tool, the hydraulic jet tool, the packer, and the guide stabilizer.

[0034] In step a, the sandblasting perforation operation specifically refers to injecting sand-carrying fluid into the continuous tubing. The sand-carrying fluid flows through the nozzle of the hydraulic jet tool to form a sand-carrying jet, which blasts open the casing and the formation.

[0035] In step a, fracturing operation refers to closing the casing gate after sandblasting and perforation, pumping liquid into the coiled tubing to induce fracturing in the formation, then dropping a ball to open the fluid outlet channel of the fracturing valve tool, and then pumping fracturing fluid into the coiled tubing.

[0036] This embodiment is another preferred implementation. In step a, fracturing operation refers to closing the casing gate after sandblasting and perforation, pumping liquid into the coiled tubing to induce fracturing in the formation, then dropping a ball to open the fluid outlet channel of the fracturing valve tool, and then pumping fracturing fluid into the coiled tubing. Through the precise positioning of the coiled tubing, multiple thin interlayers in the vertical direction of the formation can be flexibly separated, thereby achieving the purpose of fine fracturing.

[0037] Example 4 See Figure 1 A method for formation thermal reservoir stimulation and heat extraction using coiled tubing includes the following steps: a. Install a tool string on the coiled tubing, insert it into the casing and lower it into the formation to perform sandblasting and fracturing operations, and inject heat-conducting material; b. After running the coiled tubing, remove the coiled tubing from the ground and remove the perforation and fracturing components at the front end of the coiled tubing. Install a sealing device to seal the front end of the coiled tubing. c. Measure the well depth, and inject the working fluid and evacuate the tubing at the rear end of the coiled tubing equipped with injection valve and venting valve according to the measured well depth. d. Next, run the coiled tubing down to the designated formation location to extract heat from the formation.

[0038] In step a, installing the tool string on the coiled tubing means connecting the fracturing valve tool to the coiled tubing, and then connecting the fracturing valve tool, hydraulic jet tool, packer, and guide stabilizer in sequence.

[0039] In step a, the sandblasting perforation operation specifically refers to injecting sand-carrying fluid into the continuous tubing. The sand-carrying fluid flows through the nozzle of the hydraulic jet tool to form a sand-carrying jet, which blasts open the casing and the formation.

[0040] In step a, fracturing operation refers to closing the casing gate after sandblasting and perforation, pumping liquid into the coiled tubing to induce fracturing in the formation, then dropping a ball to open the fluid outlet channel of the fracturing valve tool, and then pumping fracturing fluid into the coiled tubing.

[0041] In step b, the sealing device is an elastic rubber sealing sleeve.

[0042] The elastic rubber sealing sleeve includes a sealing sleeve body and an internal interlayer disposed on the sealing sleeve body. Multiple metal connecting rods are provided in the internal interlayer, and the multiple metal connecting rods are all arranged along the axial direction of the sealing sleeve body.

[0043] The metal connecting rod comprises multiple rods connected in series, with adjacent rods being movably connected by a rotating shaft that rotates radially along the sealing sleeve body.

[0044] This embodiment is another preferred implementation. In step b, the sealing device is an elastic rubber sealing sleeve. The elastic rubber sealing sleeve includes a sealing sleeve body and an inner interlayer disposed on the sealing sleeve body. Multiple metal connecting rods are disposed in the inner interlayer. The multiple metal connecting rods are all arranged along the axial direction of the sealing sleeve body. The metal connecting rods include multiple rods connected in series. Adjacent rods are movably connected by a rotating shaft, and the rotating shaft rotates radially along the sealing sleeve body. Compared with the sealing structure of the prior art, the sealing device with this specific structure not only improves the reliability of the seal, but also greatly improves the sealing effect.

[0045] Example 5 See Figure 1A method for formation thermal reservoir stimulation and heat extraction using coiled tubing includes the following steps: a. Install a tool string on the coiled tubing, insert it into the casing and lower it into the formation to perform sandblasting and fracturing operations, and inject heat-conducting material; b. After running the coiled tubing, remove the coiled tubing from the ground and remove the perforation and fracturing components at the front end of the coiled tubing. Install a sealing device to seal the front end of the coiled tubing. c. Measure the well depth, and inject the working fluid and evacuate the tubing at the rear end of the coiled tubing equipped with injection valve and venting valve according to the measured well depth. d. Next, run the coiled tubing down to the designated formation location to extract heat from the formation.

[0046] In step a, installing the tool string on the coiled tubing means connecting the fracturing valve tool to the coiled tubing, and then connecting the fracturing valve tool, hydraulic jet tool, packer, and guide stabilizer in sequence.

[0047] In step a, the sandblasting perforation operation specifically refers to injecting sand-carrying fluid into the continuous tubing. The sand-carrying fluid flows through the nozzle of the hydraulic jet tool to form a sand-carrying jet, which blasts open the casing and the formation.

[0048] In step a, fracturing operation refers to closing the casing gate after sandblasting and perforation, pumping liquid into the coiled tubing to induce fracturing in the formation, then dropping a ball to open the fluid outlet channel of the fracturing valve tool, and then pumping fracturing fluid into the coiled tubing.

[0049] More preferably, in step b, the sealing device is an elastic rubber sealing sleeve.

[0050] The elastic rubber sealing sleeve includes a sealing sleeve body and an internal interlayer disposed on the sealing sleeve body. Multiple metal connecting rods are provided in the internal interlayer, and the multiple metal connecting rods are all arranged along the axial direction of the sealing sleeve body.

[0051] The metal connecting rod comprises multiple rods connected in series, with adjacent rods being movably connected by a rotating shaft that rotates radially along the sealing sleeve body.

[0052] In step c, liquid working fluid injection specifically refers to injecting water into the coiled tubing to maintain the fluid filling rate of the coiled tubing at 45%.

[0053] This embodiment is another preferred implementation. In step c, the liquid working fluid injection specifically refers to injecting water into the continuous oil pipe to maintain the liquid filling rate in the continuous oil pipe at 45%, ensuring sufficient usable space for water circulation, which is beneficial to improving heat exchange efficiency.

[0054] Example 6 See Figure 1A method for formation thermal reservoir stimulation and heat extraction using coiled tubing includes the following steps: a. Install a tool string on the coiled tubing, insert it into the casing and lower it into the formation to perform sandblasting and fracturing operations, and inject heat-conducting material; b. After running the coiled tubing, remove the coiled tubing from the ground and remove the perforation and fracturing components at the front end of the coiled tubing. Install a sealing device to seal the front end of the coiled tubing. c. Measure the well depth, and inject the working fluid and evacuate the tubing at the rear end of the coiled tubing equipped with injection valve and venting valve according to the measured well depth. d. Next, run the coiled tubing down to the designated formation location to extract heat from the formation.

[0055] In step a, installing the tool string on the coiled tubing means connecting the fracturing valve tool to the coiled tubing, and then connecting the fracturing valve tool, hydraulic jet tool, packer, and guide stabilizer in sequence.

[0056] In step a, the sandblasting perforation operation specifically refers to injecting sand-carrying fluid into the continuous tubing. The sand-carrying fluid flows through the nozzle of the hydraulic jet tool to form a sand-carrying jet, which blasts open the casing and the formation.

[0057] In step a, fracturing operation refers to closing the casing gate after sandblasting and perforation, pumping liquid into the coiled tubing to induce fracturing in the formation, then dropping a ball to open the fluid outlet channel of the fracturing valve tool, and then pumping fracturing fluid into the coiled tubing.

[0058] In step b, the sealing device is an elastic rubber sealing sleeve.

[0059] The elastic rubber sealing sleeve includes a sealing sleeve body and an internal interlayer disposed on the sealing sleeve body. Multiple metal connecting rods are provided in the internal interlayer, and the multiple metal connecting rods are all arranged along the axial direction of the sealing sleeve body.

[0060] The metal connecting rod comprises multiple rods connected in series, with adjacent rods being movably connected by a rotating shaft that rotates radially along the sealing sleeve body.

[0061] In step c, liquid working fluid injection specifically refers to injecting water into the coiled tubing to maintain the fluid filling rate of the coiled tubing at 45%.

[0062] In step c, vacuuming specifically refers to drawing a vacuum into the coiled tubing to maintain a vacuum level of 10. -5 P.

[0063] This embodiment is another preferred implementation. In step c, vacuuming specifically refers to drawing a vacuum into the continuous tubing to maintain a vacuum level of 10. -5P can eliminate interfering factors that affect heat utilization, thus improving heat utilization efficiency.

[0064] Example 7 See Figure 1 A method for formation thermal reservoir stimulation and heat extraction using coiled tubing includes the following steps: a. Install a tool string on the coiled tubing, insert it into the casing and lower it into the formation to perform sandblasting and fracturing operations, and inject heat-conducting material; b. After running the coiled tubing, remove the coiled tubing from the ground and remove the perforation and fracturing components at the front end of the coiled tubing. Install a sealing device to seal the front end of the coiled tubing. c. Measure the well depth, and inject the working fluid and evacuate the tubing at the rear end of the coiled tubing equipped with injection valve and venting valve according to the measured well depth. d. Next, run the coiled tubing down to the designated formation location to extract heat from the formation.

[0065] In step a, installing the tool string on the coiled tubing means connecting the fracturing valve tool to the coiled tubing, and then connecting the fracturing valve tool, hydraulic jet tool, packer, and guide stabilizer in sequence.

[0066] In step a, the sandblasting perforation operation specifically refers to injecting sand-carrying fluid into the continuous tubing. The sand-carrying fluid flows through the nozzle of the hydraulic jet tool to form a sand-carrying jet, which blasts open the casing and the formation.

[0067] In step a, fracturing operation refers to closing the casing gate after sandblasting and perforation, pumping liquid into the coiled tubing to induce fracturing in the formation, then dropping a ball to open the fluid outlet channel of the fracturing valve tool, and then pumping fracturing fluid into the coiled tubing.

[0068] In step b, the sealing device is an elastic rubber sealing sleeve.

[0069] The elastic rubber sealing sleeve includes a sealing sleeve body and an internal interlayer disposed on the sealing sleeve body. Multiple metal connecting rods are provided in the internal interlayer, and the multiple metal connecting rods are all arranged along the axial direction of the sealing sleeve body.

[0070] The metal connecting rod comprises multiple rods connected in series, with adjacent rods being movably connected by a rotating shaft that rotates radially along the sealing sleeve body.

[0071] More preferably, in step c, the liquid working fluid injection specifically refers to injecting water into the coiled tubing to maintain the fluid filling rate of the coiled tubing at 45%.

[0072] In step c, vacuuming specifically refers to drawing a vacuum into the coiled tubing to maintain a vacuum level of 10. -5 P.

[0073] In step d, arranging coiled tubing specifically refers to arranging multiple coiled tubings side by side.

[0074] This embodiment is the best implementation method. In step d, arranging the continuous tubing specifically refers to arranging multiple continuous tubings in parallel, which can increase the heat extraction per unit time.

[0075] The basic principle of this invention is as follows: By installing a tool string on the coiled tubing, placing the coiled tubing with the tool string installed into the casing, and then lowering the casing into the formation, sandblasting and fracturing operations can be carried out.

[0076] Sandblasting and perforation operation: Sand-carrying fluid is injected into the coiled tubing. The sand-carrying fluid flows through the nozzle of the hydraulic jet tool to form a sand-carrying jet, which blasts open the casing and formation.

[0077] Fracturing operation: Close the casing gate valve, pump fluid into the coiled tubing to initiate fracturing in the formation, then drop a ball to open the fluid outlet channel of the fracturing valve tool, and then pump fracturing fluid into the coiled tubing.

[0078] Next, the coiled tubing is taken out of the ground and the perforation and fracturing components at the front end of the coiled tubing are removed. A sealing sleeve is installed to seal the front end of the coiled tubing. By measuring the well depth, liquid working fluid is injected and vacuum is drawn at the rear end of the coiled tubing, which is equipped with an injection valve and a venting valve, according to the measured well depth. Finally, the coiled tubing is laid out and lowered to the designated formation location for formation heat extraction.

[0079] Directional perforation is achieved through sandblasting perforation, and segmented fracturing and fine fracturing are carried out through hydraulic fracturing operations, thereby completing large-scale transformation of the formation thermal reservoir and improving heat extraction.

Claims

1. A method for formation thermal reservoir stimulation and heat extraction using coiled tubing, characterized in that, Includes the following steps: a. Install a tool string on the coiled tubing, insert it into the casing and lower it into the formation to perform sandblasting and fracturing operations, and inject heat-conducting material; b. After running the coiled tubing, remove the coiled tubing from the ground and remove the perforation and fracturing components at the front end of the coiled tubing. Install a sealing device to seal the front end of the coiled tubing. c. Measure the well depth, and inject the working fluid and evacuate the tubing at the rear end of the coiled tubing equipped with injection valve and venting valve according to the measured well depth. d. Next, run the coiled tubing down to the designated formation location to extract heat from the formation.

2. The method for formation thermal reservoir stimulation and heat extraction using coiled tubing according to claim 1, characterized in that: In step a, installing the tool string on the coiled tubing means connecting the fracturing valve tool to the coiled tubing, and then connecting the fracturing valve tool, hydraulic jet tool, packer, and guide stabilizer in sequence.

3. A method for formation thermal reservoir stimulation and heat extraction using coiled tubing according to claim 2, characterized in that: In step a, the sandblasting perforation operation specifically refers to injecting sand-carrying fluid into the continuous tubing. The sand-carrying fluid flows through the nozzle of the hydraulic jet tool to form a sand-carrying jet, which blasts open the casing and the formation.

4. A method for formation thermal reservoir stimulation and heat extraction using coiled tubing according to claim 2, characterized in that: In step a, fracturing operation refers to closing the casing gate after sandblasting and perforation, pumping liquid into the coiled tubing to induce fracturing in the formation, then dropping a ball to open the fluid outlet channel of the fracturing valve tool, and then pumping fracturing fluid into the coiled tubing.

5. A method for formation thermal reservoir stimulation and heat extraction using coiled tubing according to claim 1, characterized in that: In step b, the sealing device is an elastic rubber sealing sleeve.

6. A method for formation thermal reservoir stimulation and heat extraction using coiled tubing according to claim 5, characterized in that: The elastic rubber sealing sleeve includes a sealing sleeve body and an internal interlayer disposed on the sealing sleeve body. Multiple metal connecting rods are disposed in the internal interlayer, and the multiple metal connecting rods are all arranged along the axial direction of the sealing sleeve body.

7. A method for formation thermal reservoir stimulation and heat extraction using coiled tubing according to claim 6, characterized in that: The metal connecting rod comprises multiple rods connected in series, with adjacent rods being movably connected by a rotating shaft that rotates radially along the sealing sleeve body.

8. A method for formation thermal reservoir stimulation and heat extraction using coiled tubing according to claim 1, characterized in that: In step c, liquid working fluid injection specifically refers to injecting water into the coiled tubing to maintain the fluid filling rate of the coiled tubing at 45%.

9. A method for formation thermal reservoir stimulation and heat extraction using coiled tubing according to claim 1, characterized in that: In step c, vacuuming specifically refers to drawing a vacuum into the coiled tubing to maintain a vacuum level of 10. -5 P.

10. A method for formation thermal reservoir stimulation and heat extraction using coiled tubing according to claim 1, characterized in that: In step d, arranging coiled tubing specifically refers to arranging multiple coiled tubings side by side.

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