Horizontal well reservoir liquid gun-explosive synergic fracturing method

Abstract

The application discloses a horizontal well oil layer liquid gun-explosive synergic fracturing method, which comprises the following steps: firstly, well washing is carried out to wash out the pollutants in the wellbore, and a liquid gun-liquid explosive ignition and explosion device and an ignition device are sequentially lowered to the designated position through the oil pipe; secondly, the prepared liquid gun, liquid explosive and multiple isolation liquids are sequentially injected into the wellbore target layer; thirdly, the prepared isolation liquid is injected into the well; the prepared liquid gun is injected into the well; finally, the isolation liquid is injected above the liquid gun again, the wellhead ignition device is arranged, and the kill fluid is injected above the isolation liquid. The ignition operation is completed, the liquid explosive of the liquid explosive explosion device is exploded first, a large amount of energy is generated by the liquid explosive, and a large number of micro cracks are fractured in the near wellbore zone; and the purpose of formation reconstruction is achieved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of anhydrous fracturing, and particularly relates to a horizontal well oil layer liquid gun-propellant and explosive synergistic fracturing method. BACKGROUND

[0002] Anhydrous fracturing has become an important research direction of oilfield formation fracturing. The reason is that water resources are scarce, and the pressure of formation geological environment pollution is expanding. In particular, old oilfields and old oil layers are in the middle and late stages, and the scale and quantity of hydraulic fracturing are increasing. The development of unconventional oil and gas resources such as shale gas and tight oil requires a large amount of water for hydraulic fracturing. For the above reasons, anhydrous and low-water fracturing has become a new important research direction of oil and gas layer fracturing.

[0003] High-energy gas fracturing is based on the principle of gunpowder and explosive action, and is specially developed for special oil and gas field stimulation technology suitable for oil layer fracturing. Its design principle is to produce cracks in the formation by burning gunpowder to produce high-pressure gas expansion or explosion to increase the permeability of the formation to achieve the purpose of increasing production. High-energy gas fracturing has achieved important technical results in solid gunpowder fracturing, composite perforation fracturing, and other aspects, and has achieved widespread results in field application. In recent years, in the face of complex oil layer fracturing, especially in low-permeability tight oil layers, due to the limited total energy and the need to protect the casing, it has been difficult to meet the development needs of such complex oil layers.

[0004] In recent years, the research on low-explosive velocity explosive liquid explosive technology has achieved a breakthrough in oil layer fracturing, and has good safety in field test application of horizontal well oil layer.

[0005] The existing hydraulic fracturing, as the main technology for oil and gas field development, has been widely promoted and applied. However, due to its slow pressure rise and constraint by ground stress, it can only produce a single wing crack with limited radial communication range. Moreover, in the face of an increasing number of old oilfields and old oil layers with decreasing efficiency, the rapid development of horizontal wells has reduced their effectiveness and increased fracturing costs. In addition, due to the use of a large amount of water during fracturing, it causes environmental pollution to the formation and damage to the oil layer, which promotes the development of anhydrous fracturing technology, i.e. high-energy gas fracturing technology. High-energy gas fracturing has been difficult to meet the development needs of such complex oil layers in recent years, especially in low-permeability tight oil layers, due to the limited total energy and the need to protect the casing.

[0006] In the face of complex oil reservoir, liquid gunpowder technology can produce long cracks and multiple short cracks in the formation, and has little damage to the formation, and has low cost and is not constrained by ground stress compared with hydraulic fracturing, but due to its limited total energy, especially in the face of oil reservoir with abnormally high ground stress, it is difficult to produce long cracks. The explosion fracturing technology of low-speed liquid explosive is based on the research of micro crack network generated in the deep formation, and has been used in horizontal well reservoir test. Because its detonation velocity is much faster than that of gunpowder, it can produce a large number of micro cracks in the formation at a moment, which is difficult to communicate with a large range of oil reservoir. SUMMARY

[0007] In order to overcome the defects existing in the prior art, the purpose of the present application is to provide a horizontal well reservoir liquid gunpowder-explosive synergistic fracturing method, which can produce a large number of micro cracks by explosion of liquid explosive, and then produce a large number of high-temperature and high-pressure gas by combustion of liquid gunpowder to provide energy for micro cracks, so as to make micro cracks expand and extend, produce more cracks, and achieve the purpose of reservoir reconstruction.

[0008] In order to achieve the above purpose, the technical scheme adopted by the present application is:

[0009] A horizontal well reservoir liquid gunpowder-explosive synergistic fracturing method, comprising the following steps:

[0010] Firstly, the well is washed to wash out the contaminants in the wellbore, and the liquid gunpowder-liquid explosive ignition explosive device and the detonator are sequentially lowered into the designated position through the tubing;

[0011] Secondly, the prepared liquid gunpowder, liquid explosive and various isolation liquids are respectively injected into the target formation in the wellbore;

[0012] Thirdly, the prepared isolation liquid is injected into the well, and the prepared liquid gunpowder is injected into the well;

[0013] Finally, the isolation liquid is injected above the liquid gunpowder, the wellhead detonator is set, and the kill fluid is injected above the isolation liquid.

[0014] Further, the liquid explosive is placed on the explosive device, the liquid gunpowder is placed on the detonator, the liquid explosive and the liquid gunpowder are separated by the isolation liquid, the liquid gunpowder and the kill fluid are separated by the isolation liquid, and the kill fluid covers the wellhead.

[0015] Further, the wellbore includes vertical direction and horizontal direction, the vertical direction is connected to the horizontal direction at the end of the vertical direction underground, the detonator and the explosive device are located in the horizontal direction, the detonator is located in the vertical direction, and the isolation liquid between the kill fluid and the liquid gunpowder is located at the connection between the horizontal direction and the vertical direction.

[0016] Further, after the injection process is completed, the wellhead is sealed, and the ignition operation is completed by selecting the impact rod ignition mode or the pressure initiation mode. The explosion device is exploded by the liquid explosive, and a large amount of energy generated by the liquid explosive fractures numerous micro cracks in the near wellbore zone;

[0017] Then, the liquid explosive is ignited by the liquid explosive ignition device, a large amount of high-temperature and high-pressure gas is generated by the combustion of the liquid explosive, and the energy is continuously provided along the micro cracks generated by the explosion of the liquid explosive, so that the micro cracks are further extended, a plurality of long cracks are generated, and the short cracks are extended, the probability of communication between the fracturing cracks and the natural cracks is increased, a complex fracture network structure is formed, the communication range of oil production is expanded, and the purpose of formation modification is achieved.

[0018] The beneficial effects of the present application are:

[0019] The present application adopts the technical method of horizontal well oil layer liquid explosive-explosive combined fracturing synergy, and the principle is liquid explosive-explosive combined action. The liquid explosive and liquid explosive fracturing technology are used for oil layer fracturing at the same time, and the synergy is exerted. A large number of micro cracks are generated by the explosion of the liquid explosive in the oil layer, the formation fracture pressure is effectively reduced, then a plurality of long cracks are generated by the liquid explosive fracturing, and the short cracks are extended, the permeation range is effectively expanded, and the comprehensive effect is improved. The method has the technical function of large-scale modification of oilfield formation, and can be used for single well fracturing, block fracturing, and overall fracturing effect. A new technical approach is provided for the development and modification of such complex oil layer formation.

[0020] The most important feature of the present application is that the liquid explosive generates a large number of short cracks first, reduces the formation fracture pressure, assists the liquid explosive to generate longer long cracks, simultaneously drives the short cracks to expand and extend, expands the effective range of the formation, increases the probability of communication between the fracturing cracks and the natural cracks, forms a complex fracture network structure, improves the comprehensive fracturing effect, and is beneficial to the protection of the formation environment. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of the present application. DETAILED DESCRIPTION

[0022] The present application will be further described in detail below in combination with the drawings and examples.

[0023] As shown in Figure 1 A horizontal well oil layer liquid explosive-explosive combined fracturing method comprises the following steps:

[0024] First, the well is washed, the contaminants in the wellbore are washed out, and the liquid explosive-liquid explosive ignition and explosion device and the detonation device are sequentially lowered to the designated position through the oil pipe;

[0025] Secondly, the prepared liquid firecracker, liquid explosive and various isolation liquids are sequentially injected into the target layer in the wellbore;

[0026] Thirdly, the prepared isolation liquid is injected into the well, and the prepared liquid firecracker is injected into the well;

[0027] Finally, the isolation liquid is injected above the liquid firecracker again, the wellhead igniter is set, and the kill fluid is injected above the isolation liquid.

[0028] Further, the liquid explosive is placed on the explosion device, the liquid firecracker is placed on the detonator, the liquid explosive and the liquid firecracker are separated by the isolation liquid, the liquid firecracker and the kill fluid are separated by the isolation liquid, and the kill fluid covers the wellhead.

[0029] Further, the wellbore includes a vertical direction and a horizontal direction, the vertical direction is connected to the horizontal direction at the end of the underground, the detonator and the explosion device are located in the horizontal direction, the igniter is located in the vertical direction, and the isolation liquid between the kill fluid and the liquid firecracker is located at the connection between the horizontal direction and the vertical direction.

[0030] Further, after the injection process is completed, the wellhead is sealed, the impact rod ignition mode or the pressure detonation mode is selected, the ignition operation is completed, the explosion device is exploded by the liquid explosive, a large amount of energy is generated by the liquid explosive to crack a large number of micro cracks in the near wellbore zone;

[0031] Then, the liquid firecracker is ignited by the liquid firecracker ignition device, a large amount of high-temperature and high-pressure gas is generated by the combustion of the liquid firecracker, the energy is continuously provided along the micro cracks generated by the explosion of the liquid explosive, the micro cracks are further extended, a plurality of long cracks are generated, the short cracks are extended, the communication probability of the fracturing cracks and the natural cracks is increased, the complex fracture network structure is formed, the communication range of the oil production is expanded, and the purpose of the formation modification is achieved.

[0032] The construction steps of the present application include:

[0033] I) Preparation part:

[0034] 1. The tank truck, square tank, pump truck and boiler truck liquid preparation equipment are prepared on site, the liquid firecracker, liquid explosive and isolation liquid are prepared on site, and the respective design amount is reached;

[0035] 2. The detonation string includes a detonator, a liquid firecracker ignition device, a liquid explosive explosion device, and a delay control ignition system.

[0036] II) Wellbore washing:

[0037] 1. Verify the wellhead pressure, when the pressure is greater than 0MPa, drain and depressurize, and use the tank truck to transport to the designated place;

[0038] 2. After the pressure drops to 0 MPa, the wellhead is disassembled, the original well pipe column is pulled out, and the 350 type Christmas tree is installed;

[0039] 3. The replacement and washing pipe column is lowered, and the water density difference of the inlet and outlet is less than 0.01 g / cm 3 to stop replacement and washing;

[0040] 4. The well is closed for 24 hours, clean water is poured into the tubing, and the water in the casing is stopped. The filtration loss of the formation is calculated.

[0041] III) Liquid explosive pump and detonation:

[0042] 1. First, lower the pump replacement fluid pipe column to the replacement fluid design position; liquid explosive pump pipe column, according to the liquid explosive pump design program and dosage, respectively, in turn; the basic pump sequence is as follows: isolation fluid A + liquid explosive + isolation fluid B + liquid explosive + isolation fluid C + displacement fluid, according to the design displacement fluid, ensure that the liquid explosive + liquid explosive is squeezed to the horizontal well section design position, stay for 1-2 hours, and pull out the pump replacement fluid pipe column.

[0043] 2. Lower the detonation pipe column, and connect the detonation pipe column + detonator + liquid explosive ignition device + liquid explosive detonation device delay control ignition system in turn, lower the detonation pipe column through the tail pipe hanger seat, the build-up section, and the horizontal well section, control the tubing lowering speed (less than 20 roots / hour), and pass slowly; until the detonator is located at the design position, and the wellhead device is installed;

[0044] 3. Install the wellhead device and close the casing gate. Install high-pressure pressure taking device on one side of the casing valve, quickly close the valve after the rod is launched and detonated, and prepare for microseismic crack orientation and form monitoring before the rod is launched and detonated.

[0045] 4. Use rod launching and detonation or pressure detonation. After successful detonation, close the well for 5 hours, observe the casing pressure change, if the wellhead pressure is greater than 10 MPa, close the well to reduce pressure, the wellhead pressure is 0-10 MPa, connect the discharge pipeline to the oil tank truck from the tubing, and open the production valve slightly to discharge and produce. When the wellhead pressure drops to 0 MPa, pull out the detonation pipe column and carry out salvage production;

[0046] 5. The oil production team detects and collects production data, and comprehensively evaluates the fracturing effect.

Claims

1. A method for synergistic fracturing of horizontal well oil reservoirs using liquid explosives and detonators, characterized in that, Includes the following steps; First, the well is cleaned and flushed to remove contaminants from the wellbore. Then, the explosive device, detonator, and initiator are sequentially lowered to the designated location via the tubing. Secondly, liquid explosives, isolation fluid, liquid gunpowder, and isolation fluid are pumped in sequence. Finally, inject kill fluid over the isolation fluid; The liquid explosive is placed on the detonation device, the liquid gunpowder is placed on the detonation device, the liquid explosive and the liquid gunpowder are separated by an isolation fluid, the liquid gunpowder and the well kill fluid are separated by an isolation fluid, and the well kill fluid covers the wellhead; The wellbore includes a vertical direction and a horizontal direction, with the vertical end connected to the horizontal direction underground. The detonating device and the explosive device are located in the horizontal direction, the detonator is located in the vertical direction, and the isolation fluid between the kill fluid and the liquid explosive is located at the connection between the horizontal and vertical directions.

2. The method for synergistic fracturing of horizontal well oil reservoirs using liquid explosives and detonators according to claim 1, characterized in that, After the injection process is completed, the wellhead is sealed. The ignition operation is completed by selecting either the impact rod ignition method or the pressure detonation method. First, the liquid explosive is detonated by the explosive device. The liquid explosive generates a large amount of energy to create numerous tiny cracks in the near-wellbore area. The liquid gunpowder is then ignited using a liquid gunpowder detonation device. The combustion of the liquid gunpowder produces a large amount of high-temperature and high-pressure gas, which continuously provides energy along the tiny cracks created by the liquid explosive explosion. This causes the tiny cracks to extend further, producing multiple long cracks and extending short cracks. This increases the probability of communication between the fracturing cracks and natural cracks, forming a complex fracture network structure. This expands the oil production communication range, thereby achieving the purpose of formation modification.

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