Deepwater hydrocarbon reservoir volume fracturing system and method based on high-strength electric detonation

Abstract

The invention discloses a deepwater oil and gas reservoir volume fracturing system and method based on high-strength electric detonation, and relates to the technical field of deepwater oil and gas reservoir fracturing and permeation enhancement, the system comprises a high-voltage power source, a boosting rectifier, an energy storage capacitor bank, a trigger control device and a high-voltage electrode, and the high-voltage power source is used for supplying power to the energy storage capacitor bank; the boost rectifier is used for converting power frequency alternating current into high-voltage direct current; the energy storage capacitor bank is used for storing high-voltage direct current; the trigger control device is used for controlling the on-off state of the whole circuit; the high-voltage transmission cable is used for transmitting the high-voltage direct current stored by the energy storage capacitor bank to the high-voltage electrode; the high-voltage electrode is used for instantaneously releasing the high-voltage direct current stored by the energy storage capacitor bank into the oil and gas reservoir, the reservoir top plate and the reservoir bottom plate, the working efficiency is high, the environment cannot be harmed, and green and efficient deepwater oil and gas reservoir volume fracturing permeation increasing is truly achieved.

Description

Technical Field

[0001] The present application relates to the technical field of deepwater oil and gas layer fracturing and permeability enhancement, and in particular to a deepwater oil and gas layer volume fracturing system and method based on high-intensity electric detonation. Background Art

[0002] Deepwater is a key area for the development and utilization of marine energy. Deepwater oil and gas have important strategic value. However, deepwater oil and gas exploitation often faces the problem of difficulty in long-term oil and gas flow caused by low permeability of oil and gas reservoirs and blockage of oil and gas migration paths. Currently, the commonly used deepwater oil and gas layer fracturing and permeability enhancement methods include hydraulic fracturing, high-pressure water jet method and high-energy gas fracturing method. The above methods have high requirements for the operating environment and geological conditions in actual operation, which will cause damage to the operating environment and geology, and cannot complete the deepwater oil and gas layer fracturing and permeability enhancement in a green and efficient manner.

[0003] Based on this, how to provide a green and efficient method for volume fracturing and permeability enhancement in deepwater oil and gas layers has become a technical problem that needs to be urgently solved in this field. Summary of the invention

[0004] The purpose of this application is to provide a deepwater oil and gas layer volume fracturing system and method based on high-intensity electric detonation, which not only has high working efficiency but also does not harm the environment, and truly realizes green and efficient deepwater oil and gas layer volume fracturing and permeability enhancement.

[0005] To achieve the above objectives, this application provides the following solutions:

[0006] In the first aspect, the present application provides a deep-water oil and gas layer volume fracturing system based on high-intensity electric detonation, wherein the deep-water oil and gas layer volume fracturing system based on high-intensity electric detonation is installed on an oil and gas production platform, wherein the oil and gas production platform is a platform installed on the water surface for producing oil and gas resources, and the oil and gas production platform is provided with a deep production well, wherein the deep production well passes through the seawater layer, the mudstone layer, the reservoir top plate and the oil and gas reservoir layer in sequence from shallow to deep water depth, and extends to the reservoir bottom plate; the deep-water oil and gas layer volume fracturing system based on high-intensity electric detonation includes a high-voltage power supply, a boost rectifier, a storage capacitor group, a trigger control device and a high-voltage electrode.

[0007] Among them, the high-voltage power supply, the boost rectifier, the energy storage capacitor group, and the trigger control device are connected in sequence, and the high-voltage electrode is connected to the trigger control device through a high-voltage transmission cable.

[0008] The high-voltage power supply is used to supply power to the energy storage capacitor group; the boost rectifier is used to convert the industrial frequency alternating current output by the high-voltage power supply into high-voltage direct current; and the energy storage capacitor group is used to store high-voltage direct current.

[0009] The trigger control device is used to control the on / off state of the entire circuit; the high-voltage transmission cable is used to transmit the high-voltage direct current stored in the energy storage capacitor group to the high-voltage electrode.

[0010] The high-voltage electrode is located inside the deep mining well, and the high-voltage electrode is at the same height as the oil and gas reservoir. The high-voltage electrode is used to instantly release the high-voltage direct current stored in the energy storage capacitor group into the oil and gas reservoir and the reservoir top plate and the reservoir bottom plate when the trigger control device controls the entire circuit to be in a connected state.

[0011] Optionally, the high-voltage electrode includes a connecting fixed end and an electrode end, the connecting fixed end is connected to the high-voltage transmission cable, two pointed hemispherical electrode heads are arranged inside the electrode end, a plasma channel is arranged between the two pointed hemispherical electrode heads, and the electrode end is also filled with water.

[0012] The two pointed hemispherical electrode heads are used to instantly release the high-voltage direct current stored in the energy storage capacitor group into the plasma channel, so as to heat up the plasma channel, cause plasma expansion and generate shock waves.

[0013] Optionally, a wellbore casing is provided in the deep mining well, the outer wall of the wellbore casing is in contact with the inner wall of the deep mining well, and a number of wellbore perforations are provided in the parts of the wellbore casing located at the reservoir top plate, the oil and gas reservoir and the reservoir bottom plate, and the wellbore perforations are used to release the energy of the shock wave generated by the high-voltage electrode to the reservoir top plate, the oil and gas reservoir and the reservoir bottom plate respectively.

[0014] Optionally, the deepwater oil and gas layer volume fracturing system based on high-intensity electric detonation also includes an output control device, which is respectively connected to the high-voltage power supply, the energy storage capacitor group and the trigger control device, and the output control device is used to control the pulse discharge of the high-voltage power supply and the energy storage capacitor group respectively.

[0015] Optionally, the deepwater oil and gas layer volume fracturing system based on high-intensity electric detonation also includes a winch, which is connected to the trigger control device and the high-voltage transmission cable is wound around the winch. The winch is used to control the high-voltage electrode to rise or fall in the deep mining well by winding the high-voltage transmission cable.

[0016] Optionally, the deepwater oil and gas layer volume fracturing system based on high-intensity electric detonation further includes a remote controller, which is wirelessly connected to the trigger control device and is used to remotely control the working state of the trigger control device.

[0017] Optionally, the deepwater oil and gas layer volume fracturing system based on high-intensity electric detonation further includes an oscilloscope, which is connected to the high-voltage transmission cable and is used to monitor the working status of the entire circuit in real time.

[0018] Optionally, the deepwater oil and gas layer volume fracturing system based on high-intensity electric detonation also includes a plurality of oil rods, which are fixed to the high-voltage transmission cable by snaps, and the oil rods are used to support the high-voltage transmission cable so as to keep the high-voltage transmission cable in an unfolded and straightened state.

[0019] Optionally, the energy storage capacitor group includes 12 capacitors, and the maximum capacitance of each capacitor is 500 μF.

[0020] In a second aspect, the present application provides a method for volume fracturing of deepwater oil and gas layers based on high-intensity electric detonation, the method for volume fracturing of deepwater oil and gas layers based on high-intensity electric detonation comprising:

[0021] A high-voltage power supply is used to output industrial frequency alternating current, and a step-up rectifier is used to convert the industrial frequency alternating current output by the high-voltage power supply into high-voltage direct current, and then the high-voltage direct current is transmitted to the energy storage capacitor group.

[0022] The energy storage capacitor bank is used to store high voltage direct current.

[0023] The trigger control device is used to control the entire circuit to be in a connected state, and the high-voltage transmission cable is used to transmit the high-voltage direct current stored in the energy storage capacitor group to the high-voltage electrode.

[0024] The high-voltage electrodes are used to instantly release the high-voltage direct current stored in the energy storage capacitor group into the oil and gas reservoir and the reservoir top plate and reservoir bottom plate.

[0025] According to the specific embodiments provided in this application, this application discloses the following technical effects:

[0026] The present application provides a deepwater oil and gas layer volume fracturing system and method based on high-intensity electric explosion, which supplies power to the energy storage capacitor group through a high-voltage power supply, and continuously stores high-voltage direct current through the energy storage capacitor group. When the entire circuit is connected by a trigger control device, the high-voltage direct current stored in the energy storage capacitor group will be directly transmitted to the high-voltage electrode via a high-voltage transmission cable. Since the high-voltage electrode is located inside the deep well and is at the same height as the oil and gas reservoir, the high-voltage electrode will instantly release the transmitted high-voltage direct current into the oil and gas reservoir, the reservoir top plate and the reservoir bottom plate, thereby realizing the volume fracturing of the deepwater oil and gas reservoir. Since the blasting medium only involves electricity and water in the whole process, no product will be formed in the reaction process, and the shock wave generated by the instantaneous release of high-voltage direct current by the high-voltage electrode will fractur the oil and gas reservoir, which does not pollute the environment and has the technical advantages of being green, efficient, safe, range controllable and economically low cost. This method releases energy instantly through high-voltage electrodes and uses the liquid-electric effect to increase the permeability of deep-water oil and gas reservoirs and relieve pressure on the reservoir roof and reservoir floor. It can perform directional volume fracturing and seam creation on oil and gas reservoirs, reservoir roofs and reservoir floors, achieve permeability enhancement and efficient, green and sustainable development of oil and gas resources, and is beneficial to the development and utilization of marine resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 A structural diagram of a deepwater oil and gas layer volume fracturing system based on high-intensity electric detonation provided in one embodiment of the present application.

[0029] Figure 2 A structural diagram of a high-voltage electrode provided in one embodiment of the present application.

[0030] Figure 3 A circuit diagram of the working principle of a high-voltage electrode forming a shock wave through a liquid-electric effect provided in one embodiment of the present application.

[0031] Figure 4 A schematic flow chart of a method for volume fracturing of deepwater oil and gas layers based on high-intensity electric detonation provided in one embodiment of the present application.

[0032] Reference numerals:

[0033] 1-remote control; 2-high voltage power supply; 3-output control device; 4-energy storage capacitor bank; 5-trigger control device; 6-high voltage transmission cable; 7-oscilloscope; 8-winch; 9-pumping unit; 10-oil rod; 11-clip; 12-well casing; 13-well perforation; 14-high voltage electrode; 15-water medium; 16-oil and gas production platform; 17-seawater; 18-mudstone layer; 19-oil and gas reservoir; 20-boost rectifier; 21-housing fixing screw; 22-tip hemispherical electrode head; 23-connection fixing end; 24-metal housing; 25-plasma channel; 26-reservoir top plate; 27-reservoir bottom plate; 28-volume fracturing network. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0035] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0036] Example 1

[0037] like Figure 1 As shown, this embodiment proposes a deep-water oil and gas layer volume fracturing system based on high-intensity electric detonation, and the deep-water oil and gas layer volume fracturing system based on high-intensity electric detonation is set up on an oil and gas production platform 16. The oil and gas production platform 16 is a platform set up on the water surface for the exploitation of oil and gas resources. The oil and gas production platform 16 is provided with a deep exploitation well. The deep exploitation well passes through the seawater 17 layer, the mudstone layer 18, the reservoir top plate 26 and the oil and gas reservoir 19 in order from shallow to deep water depth, and extends to the reservoir bottom plate 27.

[0038] In this embodiment, the deepwater oil and gas layer volume fracturing system based on high-intensity electric explosion includes a high-voltage power supply 2, a boost rectifier 20, an energy storage capacitor group 4, a trigger control device 5 and a high-voltage electrode 14. The high-voltage power supply 2, the boost rectifier 20, the energy storage capacitor group 4, and the trigger control device 5 are connected in sequence, and the high-voltage electrode 14 is connected to the trigger control device 5 through a high-voltage transmission cable 6.

[0039] In this embodiment, the high-voltage power supply 2 is used to supply power to the energy storage capacitor bank 4; the boost rectifier 20 is used to convert the conventional 220V or 380V industrial frequency AC power output by the high-voltage power supply 2 into high-voltage DC power. The energy storage capacitor bank 4 is used to store high-voltage DC power.

[0040] In this embodiment, the trigger control device 5 is used to control the on / off state of the entire circuit. The high-voltage transmission cable 6 is used to transmit the high-voltage direct current stored in the energy storage capacitor bank 4 to the high-voltage electrode 14. The high-voltage transmission cable 6 is kilometer-level and can adapt to the operating environment of deep-water oil and gas production.

[0041] In this embodiment, the high-voltage electrode 14 serves as the load of the circuit. The high-voltage electrode 14 is located inside the deep mining well. When working, the high-voltage electrode 14 is located in the oil and gas reservoir 19 between the reservoir top plate 26 and the reservoir bottom plate 27. Preferably, the high-voltage electrode 14 is at the same height as the oil and gas reservoir 19. The high-voltage electrode 14 is used to instantly release the high-voltage direct current stored in the energy storage capacitor group 4 to the oil and gas reservoir 19 and the reservoir top plate 26 and the reservoir bottom plate 27 when the trigger control device 5 controls the entire circuit to be connected. Specifically, the high-voltage electric energy in the energy storage capacitor group 4 is released into the oil and gas reservoir 19, the reservoir top plate 26 and the reservoir bottom plate 27 through the well wall perforations 13.

[0042] like Figure 2 As shown, in this embodiment, the high-voltage electrode 14 is cylindrical, with a diameter of 9 cm and a length of 80 cm, and the electrode type is a counter-pole pointed hemispherical electrode. Specifically, the high-voltage electrode 14 includes a connecting fixed end 23 and an electrode end, a metal shell 24 is arranged between the connecting fixed end 23 and the electrode end, and the metal shell 24 is fixed by a shell fixing screw 21, wherein the connecting fixed end 23 is connected to the high-voltage transmission cable 6, and two pointed hemispherical electrode heads 22 are arranged inside the electrode end, a plasma channel 25 is arranged between the two pointed hemispherical electrode heads 22, and the inside of the electrode end is also filled with a water medium 15. The two pointed hemispherical electrode heads 22 are used to instantly release the high-voltage direct current stored in the energy storage capacitor group 4 into the plasma channel 25, so that the plasma channel 25 is heated, plasma expansion occurs and shock waves are generated.

[0043] In this embodiment, a wellbore casing 12 is provided in the deep mining well, and the outer wall of the wellbore casing 12 is in contact with the inner wall of the deep mining well. The wellbore casing 12 is provided with a plurality of wellbore perforations 13 at the parts located at the reservoir top plate 26, the oil and gas reservoir 19 and the reservoir bottom plate 27. The wellbore perforations 13 are used to release the energy of the shock wave generated by the high-voltage electrode 14 to the reservoir top plate 26, the oil and gas reservoir 19 and the reservoir bottom plate 27 respectively.

[0044] In this embodiment, the deepwater oil and gas layer volume fracturing system based on high-intensity electric detonation also includes an output control device 3, which is respectively connected to the high-voltage power supply 2, the energy storage capacitor group 4 and the trigger control device 5, and the output control device 3 is used to control the pulse discharge of the high-voltage power supply 2 and the energy storage capacitor group 4 respectively.

[0045] In this embodiment, the deepwater oil and gas layer volume fracturing system based on high-intensity electric explosion also includes a winch 8, the winch 8 is connected to the trigger control device 5, and the high-voltage transmission cable 6 is wound on the winch 8, and the winch 8 is used to control the high-voltage electrode 14 to rise or fall in the deep well by winding the high-voltage transmission cable 6, and adjust the position of the high-voltage electrode 14 in the deep well. Since the mass of the kilometer-level high-voltage transmission cable 6 is very large, it is difficult to lower the high-voltage transmission cable 6 only by manual labor, so the winch 8 is needed to assist in lowering the high-voltage transmission cable 6, thereby improving the lowering efficiency of the high-voltage transmission cable 6, and then improving the overall work efficiency.

[0046] In this embodiment, the deepwater oil and gas layer volume fracturing system based on high-intensity electric detonation also includes an oil pumping unit 9, which is installed at the wellhead of the deep well for pumping oil from the deep well.

[0047] In this embodiment, the deepwater oil and gas layer volume fracturing system based on high-intensity electric detonation also includes a remote controller 1, which is wirelessly connected to the trigger control device 5. The remote controller 1 is used to remotely control the working state of the trigger control device 5, and the control distance is not less than 20m.

[0048] In this embodiment, the deepwater oil and gas layer volume fracturing system based on high-intensity electric detonation also includes an oscilloscope 7, which is connected to the high-voltage transmission cable 6, and the oscilloscope 7 is used to monitor the working status of the entire circuit in real time.

[0049] In this embodiment, the deepwater oil and gas layer volume fracturing system based on high-intensity electric detonation also includes a plurality of oil rods 10, and the plurality of oil rods 10 are fixed to the high-voltage transmission cable 6 by buckles 11. The function of the oil rods 10 is to support the high-voltage transmission cable 6 so that the high-voltage transmission cable 6 remains in an unfolded and straightened state. The function of the buckle 11 is to fix the oil rods 10 and the high-voltage transmission cable 6. Through the fixing structure between the oil rods 10, the buckle 11 and the high-voltage transmission cable 6, the high-voltage transmission cable 6 can be effectively prevented from breaking due to its own weight, and the high-voltage transmission cable 6 can also be prevented from bending, tying, and other blockages in the wellbore in the oil and gas well.

[0050] Moreover, in the present embodiment, in the process of lowering the high-voltage transmission cable 6, the oil rod 10 and the high-voltage transmission cable 6 are fixed by using the buckle 11. In the present embodiment, the length of the oil rod 10 is 10 m. Every time the oil rod 10 is lowered by 10 m, the position information can be recorded once on the high-voltage transmission cable 6, and the second oil rod 10 is connected to the previous oil rod 10, and the step is repeated until the high-voltage transmission cable 6 and the high-voltage electrode 14 are in the oil and gas reservoir 19. The interval between adjacent buckles 11 can also be set, and the buckles 11 are evenly distributed on each oil rod 10. By recording the numbers of the buckles 11 in a manner of numbering the buckles 11, the lowering position of the high-voltage transmission cable 6 is indirectly recorded. While the oil rod 10 and the buckle 11 fix and support the high-voltage transmission cable 6, the phenomenon of the high-voltage transmission cable 6 blocking the wellbore due to the deadweight in the oil and gas well is avoided, and at the same time, a simpler and more accurate record of the lowering position of the high-voltage transmission cable 6 is achieved.

[0051] In this embodiment, the energy storage capacitor group 4 includes 12 capacitors, and the maximum capacitance of each capacitor is 500 μF.

[0052] In this embodiment, the size of the capacitors in the energy storage capacitor group 4 is directly related to the releasable energy. The theoretical value of the energy released by a single electric pulse can be calculated by formula (1).

[0053]

[0054] Among them, E is the energy released by the electric pulse, the unit is kJ; C is the energy storage capacitor, the unit is μF; U is the working voltage, the unit is kV.

[0055] In this embodiment, during the lowering of the oil rod 10, a water level detection device such as a simple water level discrimination device or a water level detector can be used to detect the water level in the well. The simple water level discrimination device is assembled from a power bank, a data transmission line and an indicator light. The use process is as follows: connect the positive and negative poles of the data transmission line to the positive and negative poles of the high-voltage cable. When the indicator light flashes, it indicates that the high-voltage electrode 14 that is discharged is already in the water; when the indicator light does not flash, it indicates that the high-voltage electrode 14 that is discharged is not in the water. Therefore, when the indicator light starts to flash, it indicates that the high-voltage electrode 14 that is discharged begins to contact the well water, so that the positional relationship between the high-voltage electrode 14 and the well water level can be identified according to the flashing state of the indicator light, and the well water level can be judged to ensure that the high-voltage electrode 14 is always in a water environment. Usually, the well wall of the exploitation section of the deepwater oil and gas reservoir 19 contains water, so it is generally not necessary to inject additional water into the well wall.

[0056] In this embodiment, the working principle of the high voltage electrode 14 forming a shock wave through the liquid-electric effect is as follows: Figure 3 As shown, the operation process can be described as follows:

[0057] The experimental platform of the deepwater oil and gas layer volume fracturing system based on high-intensity electric explosion converts the conventional 220V industrial frequency power supply into 520V, 5000Hz high-frequency AC power through a control cabinet, and then rectifies it into a high-voltage DC power supply of tens of kV through a high-voltage rectifier silicon stack; then the DC high-voltage power supply 2 charges the energy storage capacitor group 4 through a choke until the set voltage value is reached; when the energy storage capacitor reaches the working voltage threshold, the energy control switch is turned on, and the energy stored in the energy storage capacitor group 4 will be transmitted to both ends of the high-voltage electrode 14, generating a liquid-electric effect, shearing and creating fractures in the surrounding rock mass.

[0058] The deepwater oil and gas layer volume fracturing system and method based on high-intensity electric detonation provided in this embodiment mainly adopts the liquid phase discharge principle of high-intensity electric detonation, utilizes the energy of the expansion of the plasma channel 25 to generate shock waves to act on the oil and gas reservoir 19, the reservoir top plate 26 and the reservoir bottom plate 27, so as to form a volume fracturing network 28 with a wider range and higher fracture degree, and at the same time relieves the pressure on the oil and gas reservoir 19, the reservoir top plate 26 and the reservoir bottom plate 27, thereby realizing the volume fracturing and permeability enhancement of the deepwater oil and gas reservoir 19, which involves the energy conversion process of electrical energy-mechanical energy-shock wave.

[0059] When the present embodiment is actually applied, the output control device 3, the high-voltage power supply 2, the boost rectifier 20, the energy storage capacitor group 4, the trigger control device 5, the high-voltage transmission cable 6, the high-voltage electrode 14, and the oscilloscope 7 are first integrated into a deep-water oil and gas layer volume fracturing system based on high-intensity electric explosion, which is convenient for being carried to the oil and gas production platform 16. The high-voltage transmission cable 6 is arranged on the winch 8, and the winch 8 is slowly rotated to realize the lifting of the high-voltage transmission cable 6. The high-voltage electrode 14 is lowered to the reservoir top plate 26 through the high-voltage transmission cable 6. In the oil and gas reservoir 19 between the oil and gas production platform 16 and the reservoir bottom plate 27, there is a vertically closed well casing 12 in the whole stage before the target oil and gas reservoir 19. During the lowering process, the high-voltage transmission cable 6 and the oil rod 10 are fixed by the buckle 11, and then the trigger control device 5 is closed by the remote control 1 to close the entire discharge circuit. The energy storage capacitor group 4 transmits energy to the high-voltage electrode 14, and the gap between the high-voltage electrode 14 forms a plasma channel 25. The electric energy stored in the energy storage capacitor group 4 will be released into the plasma channel 25. The plasma channel 25 is heated to (10-20)×10 by the Joule effect. 3The temperature of K leads to extremely fast channel pressure accumulation and plasma expansion. In an extremely short time (microsecond level), the plasma generates very high power in the discharge channel, usually reaching hundreds of megawatts. The liquid around the discharge channel is subjected to the high temperature and high pressure to generate a strong shock wave of detonation (the maximum pressure can reach hundreds of MPa). The shock wave is transmitted to the oil and gas reservoir 19 through the well wall perforations 13. Through cavitation, shear fracture formation and thermal action, the fractured rock mass in the oil and gas reservoir 19, the reservoir top plate 26 and the reservoir bottom plate 27 is further developed, forming a volume fracture network 28 with a wider range and higher fracture degree. At the same time, the shock wave can clear the blocked oil and gas migration path, release the ground stress of the reservoir top plate 26, the reservoir bottom plate 27 and the oil and gas reservoir 19, and increase the permeability of the oil and gas reservoir 19, thereby realizing the volume fracturing and permeability enhancement of the deepwater oil and gas reservoir 19 and increasing the average daily oil and gas production.

[0060] Example 2

[0061] like Figure 4 As shown, this embodiment proposes a deep-water oil and gas layer volume fracturing method based on high-intensity electric detonation, which is applied to the deep-water oil and gas layer volume fracturing system based on high-intensity electric detonation in Example 1. The deep-water oil and gas layer volume fracturing method based on high-intensity electric detonation mainly includes the following steps:

[0062] Step S1, using the high-voltage power supply 2 to output industrial frequency alternating current, and using the boost rectifier 20 to convert the industrial frequency alternating current output by the high-voltage power supply 2 into high-voltage direct current, and then transmitting the high-voltage direct current to the energy storage capacitor group 4.

[0063] Step S2: using the energy storage capacitor bank 4 to store high voltage direct current.

[0064] Step S3: Use the trigger control device 5 to control the entire circuit to be in a connected state, and use the high-voltage transmission cable 6 to transmit the high-voltage direct current stored in the energy storage capacitor group 4 to the high-voltage electrode 14.

[0065] Step S4: using the high-voltage electrode 14 to instantly release the high-voltage direct current stored in the energy storage capacitor group 4 into the oil and gas reservoir 19 and the reservoir top plate 26 and the reservoir bottom plate 27.

[0066] The following is an example of a deepwater oil field in the South China Sea, where the average water depth is 1500m and the average gas layer burial depth is 210m, to illustrate the specific operation process of the deepwater oil and gas layer volume fracturing method based on high-intensity electric detonation, which specifically includes the following practical operation steps:

[0067] (1) Determine the operation mode of electric detonation volume fracturing to increase the permeability of the oil and gas layer, and design a high-intensity electric detonation fracturing scheme by adopting the fracturing method from the bottom of the well oil and gas reservoir 19 to the upward direction. The electric detonation fracturing position points of the oil and gas reservoir 19 are set at intervals of 0.5 m, and each position point is operated 20 times. After each position point is completed, the high-voltage electrode 14 is moved upward by the winch 8 to complete the next operation until a volume fracturing network 28 is formed in the oil and gas reservoir 19, the reservoir top plate 26 and the reservoir bottom plate 27.

[0068] (2) Arrange the deepwater oil and gas layer volume fracturing system based on high-intensity electric detonation in Example 1, wherein the deepwater oil and gas layer volume fracturing system based on high-intensity electric detonation is placed on an offshore oil and gas production platform 16, a 2000m high-voltage transmission cable 6 is assembled on a winch 8, and the high-voltage electrode 14 is lowered to the target oil and gas reservoir 19 by using the winch 8 and the kilometer-level high-voltage transmission cable 6. There is a vertical closed wellbore casing 12 in the entire stage from the oil and gas production platform 16 to the oil and gas reservoir 19. During the lowering process, the oil rod 10 and the high-voltage transmission cable 6 are fixed by a buckle 11. The length of the oil rod 10 is 10m. The position information is recorded every time the high-voltage transmission cable 6 is lowered by 10m. The second oil rod 10 is connected to the previous oil rod 10, and the above steps are repeated until the high-voltage transmission cable 6 and the high-voltage electrode 14 are in the oil and gas reservoir 19, and the position of the high-voltage electrode 14 is clear.

[0069] (3) Implementing electric detonation volume fracturing to increase the permeability of the oil and gas reservoir 19, using a high-voltage power supply 2 to provide a stable voltage of 220V / 380V to power the system. After charging to a set voltage value, the energy of the energy storage capacitor group 4 is instantly released through the high-voltage electrode 14, and a plasma channel 25 is formed in the gap between the high-voltage electrodes 14. The energy of the plasma channel 25 expansion is released from the well wall perforations 13 to the oil and gas reservoir 19, the reservoir top plate 26 and the reservoir bottom plate 27 through the water medium 15, so as to achieve the purpose of fracturing the oil and gas reservoir 19 to increase the permeability. At this point, a single high-intensity electric detonation fracturing of the oil and gas reservoir 19 is completed.

[0070] (4) Repeating steps (2) to (3) can complete multiple electric detonation fracturing operations to increase the permeability of the oil and gas reservoir 19 until the electric detonation volume fracturing permeability increase scheme for the oil and gas reservoir 19 designed in (1) is completed.

[0071] The deepwater oil and gas layer volume fracturing system based on high-intensity electric detonation in this embodiment has the following advantages:

[0072] 1) The system of this embodiment has the characteristics of being green, environmentally friendly, and controllable in range. The blasting medium is electricity and water, and no products are formed during the reaction. Only the shock wave generated destroys the oil and gas reservoir 19, and does not pollute the environment.

[0073] 2) The discharge power of the system in this embodiment is adjustable, and the maximum discharge energy can reach 600kJ, breaking through the technical bottleneck of the existing electric pulse discharge energy being small. In addition, it is graded and adjustable, has a larger range of action, better transient performance, and faster overpressure boost.

[0074] 3) The system of this embodiment can realize remote control and has higher security.

[0075] 4) The electric detonation technology equipment of the system in this embodiment has a long life cycle and low subsequent repair and maintenance costs, and has the characteristics of strong adaptability and high economy.

[0076] 5) The system of this embodiment can store energy through the energy storage capacitor group 4, or can also store energy through the generator (220V / 380V). The energy storage time using 380V voltage is about 1 minute, which is short and improves work efficiency.

[0077] 6) The system of this embodiment can form a three-dimensional fracture network with a wider range and higher fracture degree in the oil and gas reservoir 19, the reservoir top plate 26 and the reservoir bottom plate 27, thereby achieving the release of ground stress and increased reservoir permeability in the oil and gas reservoir 19, the reservoir top plate 26 and the reservoir bottom plate 27.

[0078] This embodiment comprehensively considers the discharge energy of deep-water oil and gas layer volume fracturing based on high-intensity electric explosion according to the water depth, rock thickness, geological conditions and other factors of the oil and gas reservoir 19, the reservoir top plate 26 and the reservoir bottom plate 27, so as to ensure that the shock wave realizes directional volume fracturing on the oil and gas reservoir 19, the reservoir top plate 26 and the reservoir bottom plate 27, and realizes controllable energy and range of electric explosion operation. The boost rectifier 20 is used to convert low-voltage alternating current into high-voltage direct current, and the electric energy is stored in the energy storage capacitor group 4. Through the kilometer-level high-voltage transmission cable 6 and the high-voltage electrode 14, the high-voltage electric energy in the energy storage capacitor group 4 is instantly released into the water medium 15 in the well wall. The shock wave generated by the liquid-electric effect is released to the oil and gas reservoir 19, the reservoir top plate 26 and the reservoir bottom plate 27 through the well wall perforations 13, so as to realize the shock wave directional volume fracturing based on the high-intensity electric explosion technology. This embodiment can effectively create a large-scale three-dimensional fracture network in the oil and gas reservoir 19, the reservoir top plate 26 and the reservoir bottom plate 27 under deep water conditions, clear the blockage of the migration path in the oil and gas reservoir 19, release the ground stress of the oil and gas reservoir 19, the reservoir top plate 26 and the reservoir bottom plate 27, increase the permeability of the oil and gas reservoir 19, solve the problem of long-term oil and gas flow difficulties faced by deep-water energy exploitation, and realize technical innovation of volume fracturing and permeability enhancement in deep-water oil and gas reservoirs 19.

[0079] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0080] This article uses specific examples to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core ideas of this application. At the same time, for those skilled in the art, according to the ideas of this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. A deepwater oil and gas layer volume fracturing system based on high-intensity electric detonation, wherein the deepwater oil and gas layer volume fracturing system based on high-intensity electric detonation is installed on an oil and gas production platform, wherein the oil and gas production platform is a platform installed on the water surface for producing oil and gas resources, wherein the oil and gas production platform is provided with a production deep well, wherein the production deep well sequentially passes through a seawater layer, a mudstone layer, a reservoir top plate and an oil and gas reservoir layer according to the water depth from shallow to deep, and extends to the reservoir bottom plate; wherein: The deepwater oil and gas layer volume fracturing system based on high-intensity electric explosion includes a high-voltage power supply, a boost rectifier, an energy storage capacitor bank, a trigger control device and a high-voltage electrode; Wherein, the high-voltage power supply, the boost rectifier, the energy storage capacitor group, and the trigger control device are connected in sequence, and the high-voltage electrode is connected to the trigger control device through a high-voltage transmission cable; The high-voltage power supply is used to supply power to the energy storage capacitor bank; the boost rectifier is used to convert the industrial frequency alternating current output by the high-voltage power supply into high-voltage direct current; the energy storage capacitor bank is used to store high-voltage direct current; The trigger control device is used to control the on / off state of the entire circuit; the high-voltage transmission cable is used to transmit the high-voltage direct current stored in the energy storage capacitor bank to the high-voltage electrode; The high-voltage electrode is located inside the deep mining well, and the high-voltage electrode is at the same height as the oil and gas reservoir. The high-voltage electrode is used to instantly release the high-voltage direct current stored in the energy storage capacitor group into the oil and gas reservoir and the reservoir top plate and the reservoir bottom plate when the trigger control device controls the entire circuit to be in a connected state.

2. The deepwater oil and gas layer volume fracturing system based on high-intensity electric detonation according to claim 1 is characterized in that: The high-voltage electrode comprises a connection fixing end and an electrode end, the connection fixing end is connected to the high-voltage transmission cable, two sharp hemispherical electrode heads are arranged inside the electrode end, a plasma channel is arranged between the two sharp hemispherical electrode heads, and the electrode end is also filled with water; The two pointed hemispherical electrode heads are used to instantly release the high-voltage direct current stored in the energy storage capacitor group into the plasma channel, so as to heat up the plasma channel, cause plasma expansion and generate shock waves.

3. The deepwater oil and gas layer volume fracturing system based on high-intensity electric detonation according to claim 2 is characterized in that: The deep mining well is provided with a well casing, the outer wall of which is in contact with the inner wall of the deep mining well, and the well casing is provided with a plurality of well perforations at the reservoir top plate, the oil and gas reservoir and the reservoir bottom plate. The well perforations are used to release the energy of the shock wave generated by the high-voltage electrode to the reservoir top plate, the oil and gas reservoir and the reservoir bottom plate respectively.

4. The deepwater oil and gas layer volume fracturing system based on high-intensity electric detonation according to claim 1 is characterized in that: The deepwater oil and gas layer volume fracturing system based on high-intensity electric detonation also includes an output control device, which is respectively connected to the high-voltage power supply, the energy storage capacitor group and the trigger control device, and the output control device is used to control the pulse discharge of the high-voltage power supply and the energy storage capacitor group respectively.

5. The deepwater oil and gas layer volume fracturing system based on high-intensity electric detonation according to claim 1 is characterized in that: The deepwater oil and gas layer volume fracturing system based on high-intensity electric detonation also includes a winch, which is connected to the trigger control device and the high-voltage transmission cable is wound around the winch. The winch is used to control the high-voltage electrode to rise or fall in the deep mining well by winding the high-voltage transmission cable.

6. The deepwater oil and gas layer volume fracturing system based on high-intensity electric detonation according to claim 1 is characterized in that: The deepwater oil and gas layer volume fracturing system based on high-intensity electric detonation also includes a remote controller, which is wirelessly connected to the trigger control device and is used to remotely control the working state of the trigger control device.

7. The deepwater oil and gas layer volume fracturing system based on high-intensity electric detonation according to claim 1 is characterized in that: The deepwater oil and gas layer volume fracturing system based on high-intensity electric detonation also includes an oscilloscope, which is connected to the high-voltage transmission cable and is used to monitor the working status of the entire circuit in real time.

8. The deepwater oil and gas layer volume fracturing system based on high-intensity electric detonation according to claim 1 is characterized in that: The deepwater oil and gas layer volume fracturing system based on high-intensity electric detonation also includes a plurality of oil rods, which are fixed to the high-voltage transmission cable by buckles. The oil rods are used to support the high-voltage transmission cable so that the high-voltage transmission cable remains in an unfolded and straightened state.

9. The deepwater oil and gas layer volume fracturing system based on high-intensity electric detonation according to claim 1 is characterized in that: The energy storage capacitor group includes 12 capacitors, and the maximum capacitance of each capacitor is 500 μF.

10. A method for volume fracturing of deepwater oil and gas layers based on high-intensity electric detonation, characterized in that: The deepwater oil and gas layer volume fracturing method based on high-intensity electric detonation comprises: Outputting industrial frequency alternating current using a high-voltage power supply, converting the industrial frequency alternating current output by the high-voltage power supply into high-voltage direct current using a step-up rectifier, and then transmitting the high-voltage direct current to an energy storage capacitor bank; Using the energy storage capacitor bank to store high voltage direct current; The entire circuit is controlled to be in a connected state by using a trigger control device, and the high-voltage direct current stored in the energy storage capacitor bank is transmitted to the high-voltage electrode by using a high-voltage transmission cable; The high-voltage electrodes are used to instantly release the high-voltage direct current stored in the energy storage capacitor group into the oil and gas reservoir and the reservoir top plate and reservoir bottom plate.

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