A deep shale in-situ self-powered low-vibration expansion fracturing system and method

Abstract

The application discloses a kind of deep shale in-situ self-powered low vibration expansion fracturing system and method, and the fuel explosion heat expansion reaction device is mixed with oxygen to form controllable fuel explosion gas by in-situ induced desorption shale gas, and the component of controllable fuel explosion gas is monitored and adjusted by safe fracturing control system, when reaching sub-fuel explosion slow combustion condition, controllable fuel explosion gas is ignited, expansion gas is generated in fuel explosion heat expansion reaction device to cause fracturing to shale reservoir, realize low vibration, directional and slow-release expansion fracturing, effectively reduce the vibration and disturbance caused by traditional blasting.In addition, each pressure relief hole can be opened in stages, so as to realize the effect of segmented delayed pressure relief, further improve the effect of directional expansion fracturing;Safe fracturing control system monitors the whole fracturing process to ensure the smooth implementation of fracturing;Finally, the fracturing effect is detected by microseismic monitoring system, if the required fracturing requirement is not reached, then repeat the implementation of fracturing, finally realize safe and efficient fracturing of deep shale reservoir.

Description

Technical Field

[0001] This invention belongs to the field of unconventional oil and gas extraction technology, specifically relating to a deep shale in-situ self-powered low-vibration expansion fracturing system and method, which is applicable to the safe, efficient and green extraction of deep shale. Background Technology

[0002] In the efficient development of shale gas reservoirs, fracture stimulation is the core step in releasing shale gas. In the development of deep shale gas resources, reservoirs are generally located in complex geological environments characterized by high temperatures (>80°C), high geostress (>40MPa), and low porosity and permeability, posing significant challenges to conventional fracturing technologies. Traditional hydraulic fracturing relies on high-pressure injection of liquid media to form fractures, but in deep environments, it suffers from the following serious problems: liquids have difficulty penetrating the pores of ultra-low permeability shale, limiting fracturing effectiveness; water-sensitive minerals expand upon contact with water at high temperatures, potentially inducing reservoir damage; high geostress makes fractures prone to closure, leading to rapid attenuation of fracturing conductivity; and it is highly dependent on water resources, making it unsuitable for widespread application in water-restricted areas.

[0003] To overcome the limitations of hydraulic fracturing, some studies have attempted to use explosive fracturing or chemical combustion to achieve dry fracturing. However, these methods have the following technical drawbacks: 1. The explosive energy release is extremely rapid (pressure rise rate > 1000 MPa / ms), causing strong vibrations and far-field disturbances, making them unsuitable for well areas with densely packed adjacent wells or complex structural zones; 2. Shock wave fracturing is uncontrollable and can easily damage casing, cement sheaths, or cause rock collapse; 3. The thermal structure of the wellbore is mismatched, and the stability of metallic materials decreases under thermal or gas explosion environments; 4. External gas injection or external energy sources are still required, making on-site operations complex, costly, and posing significant safety risks.

[0004] Meanwhile, shale reservoirs are rich in adsorbed methane, which can naturally desorb gas under temperature or pressure disturbances. If this in-situ shale gas resource can be effectively utilized and a combustion-explosion reaction environment can be constructed to induce a controlled combustion-explosion fracturing reaction in a confined space, it will become a new approach to replace explosive blasting and hydraulic fracturing.

[0005] However, to achieve this explosive-free, low-disturbance, and directionally controllable fracturing method in deep, high-stress, and high-temperature environments, the following key challenges still need to be addressed: How to induce sufficient shale gas desorption and in-situ enrichment? How to construct a stable combustible gas mixture at high temperatures? How to convert energy into slow-release expansion pressure rather than shock waves? How to achieve directional fracturing rather than full-area blasting through structural design?

[0006] Therefore, the research direction required by this invention is to provide a fracturing system and method that induces shale gas desorption in situ and mixes it with oxygen to form a controllable combustion and explosion gas. This gas is then ignited at low speed and slowly expanded in a closed cavity to achieve directional fracturing, thereby overcoming the shortcomings of traditional blasting methods, such as abrupt and uncontrollable energy loading and large disturbances. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention provides a deep shale in-situ self-powered low-vibration expansion fracturing system and method. By in-situ inducing shale gas desorption and mixing it with oxygen to form a controllable combustion and explosion gas, directional fracturing is completed in a closed cavity through low-speed ignition and slow-release expansion. This overcomes the shortcomings of traditional blasting methods, such as abrupt and uncontrollable energy loading and large disturbance, and achieves efficient fracturing of deep shale reservoirs.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is: a deep shale in-situ self-powered low-vibration expansion fracturing system, comprising a combustion-explosion thermal expansion reaction device, a safe fracturing control system, and a microseismic monitoring system; the combustion-explosion thermal expansion reaction device comprises a supporting frame, a flexible energy-absorbing layer, and a sealed combustion-explosion chamber, the sealed combustion-explosion chamber being installed within the supporting frame, the sealed combustion-explosion chamber being cylindrical, with a shale gas inlet and an oxygen inlet at one end for injecting shale gas and oxygen into the sealed combustion-explosion chamber, respectively; along its axis on the circumference of the sealed combustion-explosion chamber... The system has multiple pressure relief holes for the high-pressure gas generated by the combustion of shale gas and oxygen in a sealed combustion chamber to be ejected through these holes, achieving directional expansion and fracturing. A flexible energy-absorbing layer surrounds the circumferential surface of the sealed combustion chamber (excluding the pressure relief holes) to buffer and absorb energy in directions other than the orientation of the pressure relief holes during directional fracturing. The safe fracturing control system includes a data processor, thermometer, pressure sensor, igniter, gas analyzer, and oxygen flow controller. The thermometer, pressure sensor, and igniter are all installed inside the sealed combustion chamber. A thermometer and pressure sensor are used to monitor the temperature and pressure within the sealed combustion chamber, respectively. An igniter is used to ignite the mixed gas within the sealed combustion chamber. The gas analyzer's inlet is connected to the interior of the sealed combustion chamber to monitor the gas composition and concentration. An oxygen flow controller is installed on the pipeline between the oxygen inlet and the oxygen source to regulate the oxygen flow rate into the sealed combustion chamber. The shale gas inlet, oxygen inlet, and gas analyzer inlet are all equipped with shut-off valves to open or close each port. A data processor is connected to the thermometer, pressure sensor, igniter, gas analyzer, and oxygen flow controller. It receives gas data from the gas analyzer, analyzes it, and then controls the oxygen flow rate via the oxygen flow controller. Simultaneously, it controls the shut-off valves and igniter, and acquires monitoring data from the thermometer and pressure sensor to monitor the directional expansion fracturing process. The microseismic monitoring system includes multiple geophones, each receiving microseismic data from the fracturing area to determine the fracturing situation within the shale.

[0009] Furthermore, the supporting frame is made of rigid metal; the flexible energy-absorbing layer is made of foamed metal or porous ceramic.

[0010] Furthermore, some of the pressure relief holes are equipped with thermosensitive deformation structures, each with a different critical deformation temperature. Initially, each thermosensitive deformation structure blocks its respective pressure relief hole. When the temperature reaches the critical temperature of a particular thermosensitive deformation structure due to combustion and fracturing, the deformation opens the pressure relief hole, achieving segmented opening of the pressure relief holes for segmented delayed pressure relief. This structural approach allows the pressure release duration to be controlled within 3 to 10 milliseconds, effectively suppressing the formation of high-frequency stress waves and thus reducing far-field vibration effects.

[0011] Furthermore, the thermosensitive deformation structure is a shape memory alloy sheet or a ceramic spring. This material ensures the delayed opening function of each pressure relief hole, thereby achieving the effect of segmented delayed pressure relief and achieving the required directional expansion and cracking.

[0012] Furthermore, it also includes a touch screen display, which is connected to the data processor to display the data received by the data processor and to control the data processor to send commands to control the igniter and shut-off valve.

[0013] Furthermore, there are multiple sealed combustion and explosion chambers, which are connected in series through pipelines to achieve segmented fracturing at different locations.

[0014] The working method of the above-mentioned deep shale in-situ self-powered low-vibration expansion fracturing system includes the following steps:

[0015] Step 1: Construct shale gas wells into deep shale gas reservoirs and install the expansion fracturing system at the location of the shale gas reservoir, ensuring that each pressure relief hole is oriented close to the principal stress direction of the shale gas reservoir (i.e., within 10° of the maximum horizontal principal stress); then seal the shale gas wells to allow shale gas to desorb into the wells.

[0016] Step 2: Set the mixing ratio of shale gas and oxygen. Shale gas from the well enters the sealed combustion chamber through the shale gas inlet. Simultaneously, oxygen from the surface source is injected into the sealed combustion chamber through the oxygen inlet. The mixing ratio of shale gas and oxygen in the sealed combustion chamber is monitored by a gas analyzer and fed back to the data processor. The data processor issues an instruction to control the oxygen flow through the oxygen flow controller until the real-time monitored mixing ratio of shale gas and oxygen reaches the set value, indicating that the sub-detonation slow combustion conditions have been met. At this time, the data processor controls the closure of each shut-off valve and starts the igniter to ignite the shale gas and oxygen for sub-detonation slow combustion. This causes the expanding gas generated in the sealed combustion chamber to be ejected from each pressure relief hole, causing directional expansion and fracturing of the shale reservoir it faces. Furthermore, each pressure relief hole opens with a time delay, achieving segmented delayed fracturing.

[0017] Step 3: Directional expansion fracturing process. The thermometer and pressure sensor monitor the temperature and pressure inside the sealed combustion chamber in real time and feed them back to the data processor. The data processor determines whether there is any abnormality in the combustion and explosion based on the feedback temperature and pressure. If there is an abnormality, the combustion and explosion process is stopped and an early warning message is issued; otherwise, monitoring continues until the directional expansion fracturing process is completed.

[0018] Step 4: Use a microseismic monitoring system to conduct microseismic monitoring on the fractured area to determine its fracture status. If the fracture requirements are met, proceed with the directional expansion fracture process at the next location. If not, readjust the set shale gas to oxygen mixing ratio and repeat Step 3. After completion, conduct microseismic monitoring again until the requirements are met.

[0019] Furthermore, the mixing ratio of shale gas and oxygen is set to be less than the lower limit of the combustion-explosion ratio under the given pressure. Meeting this set ratio indicates that the closed combustion-explosion chamber has reached the conditions for sub-explosion and slow combustion. This allows for sub-explosion and slow combustion during subsequent ignition, achieving low-vibration, directional, and slow-release expansion-induced fracturing, effectively reducing the vibration and disturbance caused by traditional blasting.

[0020] Furthermore, the specific requirement for fracturing in step four is that the length of the fracturing fracture is 1 / 2 to 2 / 3 of the distance between two adjacent shale gas wells.

[0021] Compared with existing technologies, this invention combines a combustible thermal expansion reaction device, a safe fracturing control system, and a microseismic monitoring system. The combustible thermal expansion reaction device mixes in-situ induced desorbed shale gas with oxygen to form a controllable combustible gas. The safe fracturing control system monitors and adjusts the composition of this controllable combustible gas. When sub-combustion and slow combustion conditions are reached, the controllable combustible gas is ignited, causing sub-combustion and slow combustion. This induces the expansion gas generated within the combustible thermal expansion reaction device to be ejected from various pressure relief holes, causing directional expansion and fracturing of the shale reservoir it faces. In other directions, the expansion is absorbed by a flexible energy-absorbing layer, achieving low-vibration, directional, and slow-release expansion fracturing, effectively reducing the vibration and disturbance caused by traditional blasting. Furthermore, the pressure relief holes can be opened in stages with delayed opening, achieving a staged delayed pressure relief effect, further improving the directional expansion fracturing effect. The safe fracturing control system monitors the entire fracturing process to ensure smooth implementation. Finally, the microseismic monitoring system detects the fracturing effect; if the required fracturing requirements are not met, the fracturing process is repeated, ultimately achieving efficient fracturing of deep shale reservoirs. Attached Figure Description

[0022] Figure 1 This is an overall construction diagram of the present invention;

[0023] Figure 2 This is a schematic diagram of the expansion-induced fracturing system in this invention. Detailed Implementation

[0024] The present invention will be further described below.

[0025] like Figure 2As shown, a deep shale in-situ self-powered low-vibration expansion fracturing system includes a combustion-explosive thermal expansion reaction device, a safe fracturing control system, and a microseismic monitoring system. The combustion-explosive thermal expansion reaction device includes a support frame, a flexible energy-absorbing layer, and a sealed combustion-explosive chamber. The support frame is made of rigid metal; the flexible energy-absorbing layer is made of foamed metal or porous ceramic; the sealed combustion-explosive chamber is installed inside the support frame and is cylindrical, with a shale gas inlet and an oxygen inlet at one end for injecting shale gas and oxygen into the sealed combustion-explosive chamber, respectively. Multiple pressure relief holes are formed along the axis of the circumference of the combustion chamber. These holes allow high-pressure gas generated by the combustion of shale gas and oxygen within the sealed combustion chamber to be ejected, achieving directional expansion and fracturing. A flexible energy-absorbing layer surrounds the outside of the sealed combustion chamber's circumference, excluding the pressure relief holes, to buffer and absorb energy in directions other than the orientation of the pressure relief holes during directional fracturing. The safe fracturing control system includes a data processor, thermometer, pressure sensor, igniter, gas analyzer, and oxygen flow controller. The thermometer, pressure sensor, and igniter are all mounted in a sealed enclosure. Inside the combustion chamber, thermometers and pressure sensors monitor the temperature and pressure within the sealed combustion chamber, respectively. An igniter ignites the mixed gas within the sealed combustion chamber. The inlet of a gas analyzer is connected to the interior of the sealed combustion chamber to monitor the gas composition and concentration. An oxygen flow controller is installed on the pipeline between the oxygen inlet and the oxygen source to regulate the oxygen flow rate into the sealed combustion chamber. The shale gas inlet, oxygen inlet, and gas analyzer inlet are all equipped with shut-off valves to open or close each port. A data processor is connected to the thermometer, pressure sensor, igniter, gas analyzer, and oxygen flow controller to receive gas data from the gas analyzer. After analysis, the processor controls the oxygen flow rate via the oxygen flow controller, simultaneously controlling the shut-off valves and igniter, and acquiring monitoring data from the thermometer and pressure sensor to monitor the directional expansion fracturing process. The microseismic monitoring system includes multiple geophones, each receiving microseismic data from the fracturing area to determine the fracturing situation within the shale. The sealed combustion chambers are multiple, and the multiple sealed combustion chambers are connected in series through pipelines to achieve segmented fracturing at different locations.

[0026] As an improvement of this invention, a portion of the pressure relief holes are equipped with thermosensitive deformation structures, each with a different critical temperature for thermal deformation. Initially, each thermosensitive deformation structure blocks its respective pressure relief hole. When the temperature reaches the critical temperature of a particular thermosensitive deformation structure due to combustion and fracturing, its deformation opens the pressure relief hole, achieving segmented opening of the pressure relief holes for segmented delayed pressure relief. This structural method controls the pressure release duration to within 3 to 10 milliseconds, effectively suppressing the formation of high-frequency stress waves and thus reducing far-field vibration effects. The thermosensitive deformation structure is a shape memory alloy sheet or a ceramic spring. This material ensures the delayed opening function of each pressure relief hole, thereby achieving the effect of segmented delayed pressure relief and achieving the desired directional expansion fracturing.

[0027] As another improvement of the present invention, a touch screen is also included. The touch screen is connected to the data processor and is used to display data received by the data processor. The touch screen can also control the data processor to send commands to control the igniter and the shut-off valve.

[0028] like Figure 1 As shown, the working method of the above-mentioned deep shale in-situ self-powered low-vibration expansion fracturing system includes the following steps:

[0029] Step 1: Construct shale gas wells into deep shale gas reservoirs and install the expansion fracturing system at the location of the shale gas reservoir, ensuring that each pressure relief hole is oriented close to the principal stress direction of the shale gas reservoir (i.e., within 10° of the maximum horizontal principal stress); then seal the shale gas wells to allow shale gas to desorb into the wells.

[0030] Step 2: Set the mixing ratio of shale gas and oxygen to be less than the lower limit of the combustion ratio under the given pressure. Meeting this set ratio indicates that the closed combustion chamber has reached the conditions for sub-combustion and slow combustion. This allows for sub-combustion and slow combustion during subsequent ignition, achieving low-vibration, directional, and slow-release expansion fracturing, effectively reducing the vibration and disturbance caused by traditional blasting. Shale gas from the well enters the sealed combustion chamber through the shale gas inlet. Simultaneously, an oxygen source on the surface injects oxygen into the sealed combustion chamber through the oxygen inlet. A gas analyzer monitors the mixing ratio of shale gas and oxygen in the sealed combustion chamber and feeds it back to the data processor. The data processor issues an instruction to control the oxygen flow through the oxygen flow controller until the real-time monitored shale gas-oxygen mixing ratio reaches the set value, indicating that the sub-detonation slow combustion conditions have been met. At this point, the data processor controls the closure of each shut-off valve and activates the igniter to ignite the shale gas and oxygen for sub-detonation slow combustion. This causes the expanding gas generated in the sealed combustion chamber to be ejected from each pressure relief hole, causing directional expansion and fracturing of the shale reservoir it faces. Furthermore, each pressure relief hole opens with a time delay, achieving segmented delayed fracturing.

[0031] Step 3: Directional expansion fracturing process. The thermometer and pressure sensor monitor the temperature and pressure inside the sealed combustion chamber in real time and feed them back to the data processor. The data processor determines whether there is any abnormality in the combustion and explosion based on the feedback temperature and pressure. If there is an abnormality, the combustion and explosion process is stopped and an early warning message is issued; otherwise, monitoring continues until the directional expansion fracturing process is completed.

[0032] Step 4: Use a microseismic monitoring system to perform microseismic monitoring on the fractured area to determine its fracture status. If the fracture requirements are met, proceed with the directional expansion fracture process at the next location. If not, readjust the set shale gas to oxygen mixing ratio and repeat Step 3. After completion, perform microseismic monitoring again until the requirements are met. The specific fracture requirements in Step 4 are: the fracture length is 1 / 2 to 2 / 3 of the distance between two adjacent shale gas wells.

[0033] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A deep shale in-situ self-powered low-vibration expansion fracturing system, characterized in that, This includes a combustion and explosion thermal expansion reaction device, a safety cracking control system, and a microseismic monitoring system; The combustion and explosion thermal expansion reaction device includes a supporting frame, a flexible energy-absorbing layer, and a sealed combustion and explosion chamber. The sealed combustion and explosion chamber is housed within the supporting frame and is cylindrical. One end of the chamber has a shale gas inlet and an oxygen inlet for injecting shale gas and oxygen into the chamber, respectively. Multiple pressure relief holes are formed along the axis of the sealed combustion and explosion chamber's circumference, allowing the high-pressure gas generated by the combustion and explosion of shale gas and oxygen within the chamber to be ejected through these holes, achieving directional expansion and fracturing. The flexible energy-absorbing layer surrounds the pressure relief holes. The outer surface of the sealed combustion chamber is used to buffer and absorb energy in directions other than the orientation of the pressure relief hole during directional fracturing; a portion of the pressure relief holes are equipped with thermal deformation structures, and each thermal deformation structure has a different critical temperature for thermal deformation. Initially, each thermal deformation structure blocks its respective pressure relief hole. When the combustion and fracturing cause the temperature to reach the critical temperature of a certain thermal deformation structure, its deformation opens the pressure relief hole, realizing segmented opening of the pressure relief hole for segmented delayed pressure relief. The safety fracturing control system includes a data processor, a thermometer, a pressure sensor, an igniter, a gas analyzer, and an oxygen flow controller. The thermometer, pressure sensor, and igniter are all installed inside a sealed combustion chamber. The thermometer and pressure sensor monitor the temperature and pressure within the sealed combustion chamber, respectively, while the igniter ignites the mixed gas within the chamber. The gas analyzer's inlet is connected to the interior of the sealed combustion chamber to monitor the gas composition and concentration. The oxygen flow controller is installed on the pipeline between the oxygen inlet and the oxygen source to regulate the oxygen flow rate into the sealed combustion chamber. The shale gas inlet, oxygen inlet, and gas analyzer inlet are all equipped with shut-off valves to open or close each port. The data processor is connected to the thermometer, pressure sensor, igniter, gas analyzer, and oxygen flow controller. It receives gas data from the gas analyzer, analyzes it, and then controls the oxygen flow rate via the oxygen flow controller. Simultaneously, it controls the shut-off valves and igniter, and acquires monitoring data from the thermometer and pressure sensor to monitor the directional expansion fracturing process. The microseismic monitoring system includes multiple geophones, each of which receives microseismic data from the fractured area to determine the fractured state inside the shale.

2. The deep shale in-situ self-powered low-vibration expansion fracturing system according to claim 1, characterized in that, The supporting frame is made of rigid metal; the flexible energy-absorbing layer is made of foamed metal or porous ceramic.

3. The deep shale in-situ self-powered low-vibration expansion fracturing system according to claim 1, characterized in that, The thermosensitive deformation structure is a shape memory alloy sheet or a ceramic spring sheet.

4. The deep shale in-situ self-powered low-vibration expansion fracturing system according to claim 1, characterized in that, It also includes a touch screen display, which is connected to the data processor to display the data received by the data processor and to control the data processor to send commands to control the igniter and shut-off valve.

5. The deep shale in-situ self-powered low-vibration expansion fracturing system according to claim 1, characterized in that, The sealed combustion chambers are multiple, and the multiple sealed combustion chambers are connected in series through pipelines to achieve segmented fracturing at different locations.

6. A method for operating a deep shale in-situ self-powered low-vibration expansion fracturing system according to any one of claims 1 to 5, characterized in that, Includes the following steps: Step 1: Construct shale gas wells into deep shale gas reservoirs and install the expansion fracturing system at the location of the shale gas reservoir, ensuring that each pressure relief hole faces the direction of the principal stress of the shale gas reservoir; then seal the shale gas wells to allow shale gas to be desorbed into the wells. Step 2: Set the mixing ratio of shale gas and oxygen. Shale gas from the well enters the sealed combustion chamber through the shale gas inlet. Simultaneously, oxygen from the surface source is injected into the sealed combustion chamber through the oxygen inlet. The mixing ratio of shale gas and oxygen in the sealed combustion chamber is monitored by a gas analyzer and fed back to the data processor. The data processor issues an instruction to control the oxygen flow through the oxygen flow controller until the real-time monitored mixing ratio of shale gas and oxygen reaches the set value, indicating that the sub-detonation slow combustion conditions have been met. At this time, the data processor controls the closure of each shut-off valve and starts the igniter to ignite the shale gas and oxygen for sub-detonation slow combustion. This causes the expanding gas generated in the sealed combustion chamber to be ejected from each pressure relief hole, causing directional expansion and fracturing of the shale reservoir it faces. Furthermore, each pressure relief hole opens with a time delay, achieving segmented delayed fracturing of each pressure relief hole. Step 3: Directional expansion fracturing process. The thermometer and pressure sensor monitor the temperature and pressure inside the sealed combustion chamber in real time and feed them back to the data processor. The data processor determines whether there is any abnormality in the combustion and explosion based on the feedback temperature and pressure. If there is an abnormality, the combustion and explosion process is stopped and an early warning message is issued; otherwise, monitoring continues until the directional expansion fracturing process is completed. Step 4: Use a microseismic monitoring system to conduct microseismic monitoring on the cracked area to determine its cracking status. If the cracking requirements are met, proceed with the directional expansion cracking process at the next location. If the requirements are not met, readjust the set shale gas to oxygen mixing ratio and repeat step three. After completion, perform microseismic monitoring again until the requirements are met.

7. The working method according to claim 6, characterized in that, In step two, the mixing ratio of shale gas and oxygen is set to be less than the lower limit of the combustion and explosion ratio under the pressure.

8. The working method according to claim 6, characterized in that, The specific requirement for fracturing in step four is that the length of the fracturing fracture is 1 / 2 to 2 / 3 of the distance between two adjacent shale gas wells.

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