CN115234207B - Methane in-situ combustion and explosion fracturing method considering shaft liquid discharge - Google Patents
Methane in-situ combustion and explosion fracturing method considering shaft liquid discharge Download PDFInfo
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- CN115234207B CN115234207B CN202211161471.1A CN202211161471A CN115234207B CN 115234207 B CN115234207 B CN 115234207B CN 202211161471 A CN202211161471 A CN 202211161471A CN 115234207 B CN115234207 B CN 115234207B
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- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 title claims abstract description 120
- 238000004880 explosion Methods 0.000 title claims abstract description 82
- 238000002485 combustion reaction Methods 0.000 title claims abstract description 78
- 239000007788 liquid Substances 0.000 title claims abstract description 56
- 238000000034 method Methods 0.000 title claims abstract description 28
- 238000011065 in-situ storage Methods 0.000 title claims abstract description 23
- 238000007789 sealing Methods 0.000 claims abstract description 41
- 238000011161 development Methods 0.000 claims abstract description 5
- 238000007599 discharging Methods 0.000 claims abstract description 4
- 239000007789 gas Substances 0.000 claims description 53
- 210000002445 nipple Anatomy 0.000 claims description 42
- 238000005422 blasting Methods 0.000 claims description 19
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 18
- 238000004200 deflagration Methods 0.000 claims description 11
- 230000000903 blocking effect Effects 0.000 claims description 9
- 229910052757 nitrogen Inorganic materials 0.000 claims description 9
- 239000011435 rock Substances 0.000 claims description 7
- 230000035939 shock Effects 0.000 claims description 6
- 238000005553 drilling Methods 0.000 claims description 5
- 238000010438 heat treatment Methods 0.000 claims description 4
- 239000007787 solid Substances 0.000 claims description 4
- 238000004519 manufacturing process Methods 0.000 claims description 3
- 239000007800 oxidant agent Substances 0.000 claims 4
- 230000015572 biosynthetic process Effects 0.000 abstract 1
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
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- 238000009434 installation Methods 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- 208000035126 Facies Diseases 0.000 description 2
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- 238000000605 extraction Methods 0.000 description 2
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- 230000004048 modification Effects 0.000 description 2
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- 238000012856 packing Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
- E21B43/24—Enhanced recovery methods for obtaining hydrocarbons using heat, e.g. steam injection
- E21B43/243—Combustion in situ
- E21B43/247—Combustion in situ in association with fracturing processes or crevice forming processes
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- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Earth Drilling (AREA)
Abstract
The invention discloses a method for methane in-situ combustion and explosion fracturing by considering shaft drainage, which comprises the steps of determining a target layer of combustion and explosion fracturing according to geological data and exploratory well development data, sequentially dividing a shaft in the target layer into a 1 st fracturing section to an Nth fracturing section from the bottom to the top, installing a bridge plug at one end part of the 1 st fracturing section, which is opposite to the 2 nd fracturing section, sealing, perforating at the 1 st fracturing section to establish a flow channel between the shaft and a reservoir, discharging liquid in the shaft, sealing and isolating a combustion and explosion space by using a packer after drainage is finished, accommodating an ignition device in the combustion and explosion space, producing and accumulating methane gas in the formation in a continuous oil pipe and the combustion and explosion space, injecting a combustion improver into the continuous oil pipe when the concentration of the methane gas in the combustion and explosion space reaches a preset combustion and explosion critical concentration, and placing a sealing piston into the continuous oil pipe.
Description
Technical Field
The invention belongs to the technical field of oil and gas field development, and particularly relates to a methane in-situ combustion-explosion fracturing method considering shaft drainage.
Background
The shale gas extraction technology is developed rapidly at present, for example, the shale gas is extracted by hydraulic fracturing, but the hydraulic fracturing technology can only form single-form cracks in the stratum, and in order to further improve the extraction efficiency of the shale gas, a complex crack network is required to be formed in the stratum to crush the reservoir. However, the continental facies shale gas accounts for over 50% of the current shale gas reserves, the clay content in the shale reservoir is high, the clay can expand when meeting water to block gaps where the shale gas flows, and the mining effect of the traditional hydraulic fracturing technology is poor.
The methane in-situ combustion-explosion fracturing is to inject a combustion improver into a reservoir stratum and utilize methane gas in a shale reservoir stratum to perform combustion explosion underground to fracture reservoir stratum rocks to form complex fractures. The fracturing mode can be combined with hydraulic fracturing to improve the complexity of fractures, and can also be independently applied to the fracturing of the continental facies shale. At present, methane in-situ combustion and explosion fracturing is in an early stage of research, most of related technologies only provide a simple implementation idea, the conditions of liquid in a stratum and a shaft are not considered, the shaft of an oil well is often filled with liquid such as slurry after drilling is completed, a large amount of water is generated in the methane generation process in certain strata, the generation of methane gas in the stratum is greatly limited under the condition of a large amount of water in the shaft, the success rate of combustion and explosion ignition is greatly influenced, and the methane in-situ combustion and explosion fracturing is an important factor influencing the combustion and explosion effect and the success rate.
Disclosure of Invention
Therefore, the invention aims to solve the problem of providing a methane in-situ blasting fracturing method considering wellbore drainage.
In order to achieve the above object, the present invention provides a method for methane in-situ blasting fracturing in consideration of wellbore drainage, comprising:
s100, determining a target layer of the blasting fracturing according to geological data and exploratory well development data;
step S200, dividing a shaft in a target layer into a 1 st fracturing section to an Nth fracturing section from the bottom to the top in sequence;
step S300, mounting a bridge plug at the end part of one end, opposite to the No. 1 fracturing section and the No. 2 fracturing section, of the No. 1 fracturing section, sealing, and perforating at the No. 1 fracturing section to establish a flow channel between a shaft and a reservoir stratum;
step S400, discharging liquid in the shaft, sealing an explosion space by using a packer after liquid discharge is finished, and accommodating an ignition device in the explosion space;
step S500, methane gas in the stratum is produced and accumulated in the coiled tubing and the combustion and explosion space, and when the concentration of the methane gas in the combustion and explosion space reaches a preset combustion and explosion critical concentration, a combustion improver is injected into the coiled tubing;
s600, a sealing piston is placed into the continuous oil pipe, and then pressure retaining liquid is injected into the continuous oil pipe to push the sealing piston to move so as to compress methane gas and a combustion improver in the continuous oil pipe into the combustion and explosion space;
s700, controlling an ignition device to ignite and ignite methane gas in an explosion space, and after explosion is successful, suddenly raising the pressure in the explosion space, so that high-pressure gas and generated shock waves can crack rocks through perforation to generate complex cracks in a reservoir stratum;
and S800, unsealing the packer, repeating the steps from S300 to S700, and fracturing the No. 2 fracturing section to the No. N fracturing section.
Preferably, the step S300 includes:
connecting a perforating gun at the end part of the continuous oil pipe, connecting a bridge plug at the end part of the perforating gun, passing the continuous oil pipe through a shaft, placing the perforating gun and the bridge plug to the end part of one end of the 1 st fracturing section, which is opposite to the 2 nd fracturing section, and sealing;
perforating by using a perforating gun, and perforating bullets in a 1 st fracturing section to penetrate through a casing and penetrate through a part of a reservoir layer so as to establish a flow channel between a shaft and the reservoir layer;
and after the perforation is finished, taking the coiled tubing and the perforating gun out of the shaft.
Preferably, the step S400 includes:
connecting a hollow first reducing short section to the end part of the coiled tubing through threads;
installing an ignition device on the first reducing short section, and connecting the packer to the periphery of the coiled tubing;
extending the first reducing short section, the ignition device and the packer to the position of the 1 st fracturing section through a continuous oil pipe;
injecting liquid nitrogen from the surface into the wellbore through the coiled tubing to drain the wellbore from the liquid;
and setting the packer to seal the space between the continuous oil pipe and the well wall casing of the fracturing well after liquid drainage is finished so as to seal the explosion space.
Preferably, when the fracturing well is a vertical well, the step of extending the first reducing nipple, the ignition device and the packer into the position of the 1 st fracturing section through the coiled tubing comprises:
extending the first reducing short section, the ignition device and the packer to the position of the 1 st fracturing section through a continuous oil pipe, wherein the packer reaches the upper part of the 1 st fracturing section; or,
when the fracturing well is the horizontal well, stretch into the step of the position of 1 st fracturing section through coiled tubing with first reducing nipple joint, ignition, packer and include:
the first reducing nipple, the ignition device and the packer are stretched into the 1 st fracturing section through the continuous oil pipe, and the packer reaches the position, close to the vertical section of the horizontal well, of the 1 st fracturing section.
Preferably, the step S500 includes:
heating to accelerate liquid nitrogen flowback, so that the pressure of a combustion and explosion space is reduced, and methane gas in the stratum is promoted to be produced;
when the concentration reaches the critical concentration of combustion and explosion when the concentration reaches 10%, a combustion improver is injected into the combustion and explosion section through the coiled tubing.
Preferably, the step S600 includes:
placing a sealing piston into the continuous oil pipe, and then injecting a pressure retaining liquid into the continuous oil pipe to push the sealing piston to move so as to compress methane gas and a combustion improver in the continuous oil pipe into the combustion and explosion space;
and after the sealing piston reaches the first reducing nipple at the end part of the continuous oil pipe, the sealing piston stops moving under the limitation of the first reducing nipple, and the injection of the pressure retaining liquid is stopped.
Preferably, the step S700 includes:
and continuously injecting the pressure blocking liquid to enable the sealing piston to push the ignition device, so that an electric igniter in the ignition device is conducted to ignite methane gas in the explosion space, after the explosion is successful, the pressure in the explosion space can be suddenly increased, high-pressure gas and generated shock waves can crack rocks through perforation, and complex cracks are generated in the reservoir stratum.
Preferably, the bridge plug is a drillable bridge plug or a dissolvable bridge plug.
Preferably, the method further comprises:
and S900, drilling through a bridge plug in the shaft after the Nth fracturing section is fractured so as to ensure the production of shale gas.
Preferably, the combustion improver is one or more of a gas combustion improver, a liquid combustion improver or a solid combustion improver.
The invention has the following beneficial effects:
the invention provides a combustion and explosion fracturing pipe column structure capable of realizing shaft drainage, which provides sufficient space for the output of methane gas in a stratum through shaft drainage, adds a sealing piston and a pressure liquid blocking column into a coiled tubing, pushes the methane gas and a combustion improver retained in the coiled tubing into a combustion and explosion space, improves the utilization rate of the methane and the combustion improver, further reduces the cost, improves the safety of combustion and explosion fracturing through the pressure of the pressure liquid blocking column, and can judge whether combustion and explosion are successful and the effect of combustion and explosion through the pressure of the pressure liquid blocking column. Before the packer is set, the coiled tubing is lifted, the length of the coiled tubing in the explosion space is reduced as much as possible, and the problem that the coiled tubing cannot be lifted due to clamping after explosion and fracturing is solved;
further, because the blasting is performed in the whole wellbore, the blasting can act in the whole wellbore, and the blasting power cannot be concentrated to the level of the target. Or, a certain space is sealed in the shaft for blasting, but the method can only convey gas, liquid or solid combustion improver to the sealed space through an oil pipe. The oil pipe is directly communicated with the ground, and the force of blasting can be applied to the oil pipe with the length of thousands of meters. Neither of these approaches takes into account ground safety issues. Methane is exploded under the high-pressure environment of the stratum to generate hundreds of megapascals instantly, if the pressure cannot be balanced, the methane directly acts on a wellhead or an underground packer, so that the failure of a wellhead safety device and the packer is easily caused, and serious accidents are caused;
in the process of sealing off the combustion and explosion space, the invention discharges the accumulated liquid in the shaft, promotes the analysis of methane gas, considers the safer methane in-situ combustion and explosion fracturing method of shaft liquid discharge and stratum produced water, provides a shaft liquid discharge method, an explosion safety control method and an ignition method under the condition of considering the existence of liquid in the shaft, and has important significance for the landing application of methane in-situ combustion and explosion fracturing.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments or the technical solutions in the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a schematic representation of a tubular string provided by the present invention in the installation of a bridge plug and perforation;
FIG. 2 is a schematic view of a wellbore string during fluid drainage and blasting in accordance with the present invention;
FIG. 3 is an exploded schematic view of one embodiment of a downhole ignition device for methane in-situ deflagration fracturing provided in accordance with the present invention;
FIG. 4 is a cross-sectional view of the reducer nipple of FIG. 3;
fig. 5 is a cross-sectional view of the trigger module of fig. 3.
1-an electric ignition module, 11-a conductive shell, 12-a first conductor, 13-a first cylinder, 131-a first channel, 2-a reducing nipple, 21-a small diameter nipple, 22-a large diameter nipple, 23-a second channel, 24-a connecting step, 241-an electrode hole, 3-a trigger module, 31-an upper trigger part, 311-a second annular connecting plate, 312-a fourth cylinder, 3121-a fourth channel, 313-a fifth cylinder, 32-a lower trigger part, 321-a first annular connecting plate, 3211-an abdicating hole, 322-a second cylinder, 3221-a third channel, 323-a third cylinder, 33-an elastic reset piece, 34-a second conductor, 35-a third conductor, 36-an insulating washer and 37-a sealed cavity; 41-coiled tubing, 42-bridge plug, 51-1 st fracturing segment, 52-2 nd fracturing segment, 53-3 rd fracturing segment, 61-perforating gun, 62-perforating bullet, 63-perforating, 64-casing, 7-first reducing nipple, 8-ignition device, 91-packer, 92-wellhead safety device and 93-sealing piston.
The implementation, functional features and advantages of the present invention will be further described with reference to the accompanying drawings.
Detailed Description
In the embodiment of the present invention, the term "and/or" describes an association relationship of an associated object, and indicates that three relationships may exist, for example, a and/or B, and may indicate: a exists alone, A and B exist simultaneously, and B exists alone. The character "/" generally indicates that the former and latter associated objects are in an "or" relationship.
It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order.
The term "plurality" in the embodiments of the present invention means two or more, and other terms are similar thereto.
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, it will be appreciated by those of ordinary skill in the art that in various embodiments of the invention, numerous technical details are set forth in order to provide a better understanding of the present invention. However, the claimed invention may be practiced without these specific details or with various changes and modifications based on the following embodiments. The following embodiments are divided for convenience of description, and should not constitute any limitation to the specific implementation manner of the present invention, and the embodiments may be mutually incorporated and referred to without contradiction.
Example 1
The invention provides a methane in-situ combustion and explosion fracturing method considering shaft drainage, which comprises the following steps:
step S100, selecting a target layer. Determining a target layer of the blasting fracturing according to geological data and development data of the exploratory well;
specifically, a shale gas reservoir with the reservoir thickness of more than 6m, the brittleness index of more than 40% and the total organic carbon content of more than 1.2% is selected as a target layer of the combustion and explosion fracturing, a connecting channel between the ground and the target layer is established through drilling, and a casing 64 is selected for well completion. The well types include vertical wells and horizontal wells, among others.
And step S200, determining the positions and the number of stages of blasting. Dividing a shaft in a target layer into a 1 st fracturing section 51 to an Nth fracturing section from the bottom to the top in sequence;
for a vertical well, a shaft in a target layer is divided into N fracturing sections from bottom to top, and blasting construction is sequentially carried out from the 1 st fracturing section 51 at the bottom to the Nth fracturing section at the top. For the horizontal well, N fracturing sections are formed from the end part of the horizontal section to the joint of the vertical section and the horizontal section, and blasting construction is sequentially performed from the 1 st fracturing section 51 at the end part of the horizontal section.
In the present embodiment, taking a horizontal well as an example, the horizontal well is divided into 3 fracturing stages (1 st fracturing stage 51, 2 nd fracturing stage 52, 3 rd fracturing stage 53) from the end of the horizontal stage to the joint of the vertical stage and the horizontal stage, and blasting construction is performed in sequence from the 1 st fracturing stage 51 at the end of the horizontal stage.
In step S300, the bridge plug 42 is installed and the perforation 63 is operated. Installing and isolating a bridge plug 42 at the end of the 1 st fracturing segment 51 opposite to the 2 nd fracturing segment 52, and perforating 63 the 1 st fracturing segment 51 to establish a flow channel between the wellbore and the reservoir;
specifically, the step S300 includes:
step S310, connecting a perforating gun 61 to the end part of the continuous oil pipe 41, connecting a bridge plug 42 to the end part of the perforating gun 61, utilizing the continuous oil pipe 41 to pass through the shaft, and placing the perforating gun 61 and the bridge plug 42 to the end part of the 1 st fracturing segment 51 opposite to the 2 nd fracturing segment 52 for packing;
more specifically, while packing, for a vertical well, the bridge plug 42 is lowered into the lower portion of the 1 st fracture zone 51 and packed; for horizontal wells, the bridge plug 42 is lowered to a position near the end of the horizontal wellbore in the 1 st fracture zone 51 and sealed off.
In this embodiment, the bridge plug 42 is a drillable bridge plug 42 or a dissolvable bridge plug 42.
Step S320, perforating by using the perforating gun 61, wherein the perforating bullet 62 penetrates through the casing 64 and penetrates through a part of the reservoir layer in the 1 st fracturing section 51 so as to establish a flow channel between the shaft and the reservoir layer;
in step S330, the coiled tubing 41 and the perforating gun 61 are removed from the wellbore after the perforation 63 is completed.
It should be noted that, when the fractured well is a vertical well, the step of extending the first reducing nipple 7, the ignition device 8 and the packer 91 into the 1 st fractured segment 51 through the coiled tubing 41 includes:
extending the first reducing nipple 7, the ignition device 8 and the packer 91 to the position of the 1 st fracturing section 51 through the continuous oil pipe 41, wherein the packer 91 reaches the upper part of the 1 st fracturing section 51; or,
when the fracturing well is a horizontal well, the step of extending the first reducing nipple 7, the ignition device 8 and the packer 91 into the 1 st fracturing section 51 through the coiled tubing 41 comprises the following steps:
and (3) extending the first reducing nipple 7, the ignition device 8 and the packer 91 into the position of the 1 st fracturing section 51 through the continuous oil pipe 41, wherein the packer 91 reaches the position of the 1 st fracturing section 51 close to the vertical section of the horizontal well.
And S400, draining liquid from the shaft and sealing the explosion space. Discharging the liquid in the shaft, sealing and isolating an explosion space by using a packer 91 after liquid discharge is finished, and accommodating the ignition device 8 in the explosion space;
specifically, step S400 includes:
step S410, connecting a hollow first reducing nipple 7 to the end part of the coiled tubing 41 through threads;
step S420, installing an ignition device 8 on the first reducing nipple 7, and connecting a packer 91 to the periphery of the continuous oil pipe 41;
step S430, extending the first reducing nipple 7, the ignition device 8 and the packer 91 to the position of the 1 st fracturing section 51 through the coiled tubing 41;
step S440, injecting liquid nitrogen into the well bore from the ground through the coiled tubing 41 to discharge liquid in the well bore;
the liquid at the bottom of the well is displaced by the injected liquid nitrogen, allowing the liquid to pass up the annulus between the tubing and the borehole wall casing 64 back to the surface.
And S450, setting the packer 91 to seal the space between the continuous oil pipe 41 and the fracturing well wall casing 64 after the liquid drainage is finished so as to seal the explosion space.
Specifically, after no more fluid returns to the annulus, the packer 91 is set to seal off the annulus between the tubing and the borehole wall casing 64, and the detonation space is sealed off.
Step S500, methane gas in the stratum is produced and accumulated in the coiled tubing 41 and the combustion and explosion space, and when the concentration of the methane gas in the combustion and explosion space reaches a preset combustion and explosion critical concentration, a combustion improver is injected into the coiled tubing 41;
step S500 includes:
step S510, heating to accelerate liquid nitrogen flowback, so that the pressure of a combustion and explosion space is reduced, and methane gas in a stratum is promoted to be produced;
the injected liquid nitrogen is discharged back through the ground end of the coiled tubing 41, and the liquid nitrogen is accelerated to be discharged back through a heating mode, so that the pressure of the combustion and explosion space is reduced, the methane gas in the stratum is promoted to be produced, and the methane gas is accumulated in the coiled tubing 41 and the combustion and explosion space.
And step S520, when the concentration reaches the explosion critical concentration of 10%, injecting a combustion improver into the explosion section through the continuous oil pipe 41.
Monitoring the concentration of methane gas in the produced gas through the ground end of the oil pipe; when the concentration reaches the critical concentration of combustion and explosion, a combustion improver is injected into the combustion and explosion section through the continuous oil pipe 41.
Step S600, a sealing piston 93 is placed into the coiled tubing 41, and then a pressure blocking liquid is injected into the coiled tubing 41 to push the sealing piston 93 to move so as to compress methane gas and a combustion improver in the coiled tubing 41 into the combustion and explosion space;
the step S600 includes:
step S610, a sealing piston 93 is placed into the coiled tubing 41, and then a pressure retaining liquid is injected into the coiled tubing 41 to push the sealing piston 93 to move so as to compress methane gas and a combustion improver in the coiled tubing 41 into the combustion and explosion space;
in this embodiment, the combustion improver is one or more of a gas combustion improver, a liquid combustion improver, or a solid combustion improver.
Step S620, after the sealing piston 93 reaches the first reducing nipple 7 at the end of the coiled tubing 41, the sealing piston 93 stops moving under the limitation of the first reducing nipple 7, and stops injecting the pressure blocking liquid.
After the sealing piston 93 reaches the first reducing nipple 7 at the end of the coiled tubing 41, when the sealing piston 93 is limited by the first reducing nipple 7 to stop moving, the injection pressure at the ground end of the coiled tubing 41 can be obviously increased, which indicates that the injection of the hydraulic ram is finished.
The pressure-blocking liquid can be water or a mixture of water, other solutes and solid-phase particles.
Step S700, controlling an ignition device 8 to ignite and ignite methane gas in an explosion space, and after explosion is successful, suddenly increasing the pressure in the explosion space, and enabling high-pressure gas and generated shock waves to crack rocks through a perforation 63 to generate complex cracks in a reservoir stratum;
wherein the ignition device 8 can be a conventional ignition device 8, and the ignition device 8 of the embodiment 2 can also be adopted.
The step S700 includes:
and continuously injecting the pressure blocking liquid to enable the sealing piston 93 to push the ignition device 8, so that an electric igniter in the ignition device 8 is conducted to ignite methane gas in the blasting space, after the blasting is successful, the pressure in the blasting space can be suddenly increased, the high-pressure gas and the generated shock wave can crack the rock through the perforation 63, and complex cracks are generated in the reservoir.
Wherein, the high-pressure gas in the space that explodes also can be used on sealed piston 93, and pressure signal can transmit the ground end of oil pipe through the pressure in the oil pipe keeps off the liquid post, through the pressure in the monitoring oil pipe, can judge whether explode successfully with the power of exploding to further judge the effect of exploding.
And step S800, unsealing the packer 91, repeating the steps S300 to S700, and fracturing the No. 2 fracturing section 52 to the No. N fracturing section.
It should be noted that step S300 is to fracture the 1 st fracture section 51, and after repeating steps S300 to S700, step S300 is to fracture the 2 nd fracture section 52, \ 8230 \ 8230;, and the nth fracture section in sequence, wherein the fracturing method is the same as that of the 1 st fracture section 51.
And S900, drilling the bridge plug 42 in the shaft through after the Nth fracturing section is fractured so as to ensure the production of the shale gas.
In addition, at the ground end of the tubing, a wellhead safety device 92 is installed to prevent the flooding of the pressure barrier liquid during the blasting process and to monitor the wellhead pressure in real time.
The ignition device 8 in step 700 may also be a downhole ignition device, please refer to fig. 3 to 5, which includes an electric ignition module 1, a reducing nipple 2, and a triggering module 3.
Referring to fig. 3, the electric ignition module 1 includes a conductive housing 11, a first conductor 12, a storage battery, and an electric igniter, the storage battery and the electric igniter are accommodated in the conductive housing 11, the electric igniter, two ends of the storage battery, and one end of the first conductor 12 are electrically connected in sequence, the electric ignition module 1 further includes a first cylinder 13, a first channel 131 is defined in the first cylinder 13, the first cylinder 13 is disposed in the conductive housing 11 and defines a first accommodating cavity between the conductive housing 11, the storage battery and the electric igniter are disposed in the first accommodating cavity, and the other end of the first conductor 12 extends out of the first accommodating cavity and is electrically connected with the second conductor 34.
More specifically, the negative electrode of the battery is connected to the negative electrode of the electric igniter, the positive electrode of the electric igniter is connected to the conductive housing 11, one end of the first conductor 12 is connected to the positive electrode of the battery, a connection portion is connected between the first cylindrical portion 13 and the conductive housing 11, and the other end of the first conductor 12 is mounted on the connection portion and extends out of the electric ignition module 1. In this embodiment, the first conductor 12 is an electrode or other rigid rod-shaped conductor, so that the connection relationship is not affected when the control fluid pushes the downhole ignition device.
Electric ignition module 1 still includes major structure, and major structure is the cylindric setting of cavity, and major structure is including being located the inboard and being hollow first barrel 13, being located the electrically conductive casing 11 and the connecting portion in the outside, and the hollow structure of first barrel 13 is injectd and is formed first passageway 131, and electrically conductive casing 11 is the electrically conductive metal material. The first conductor 12 extends out of the connection portion and is insulated from the connection portion, and an insulator may be disposed outside the first conductor 12, or another manner may be adopted, which is not limited herein.
Referring to fig. 4, the reducing nipple 2 is installed on the conductive housing 11. Specifically, reducing nipple 2 includes minor diameter nipple 21 that extends along first direction and major diameter nipple 22 of being connected with minor diameter nipple 21, and minor diameter nipple 21 and major diameter nipple 22 are cavity setting and inject and form second passageway 23, in minor diameter nipple 21 installation first barrel 13, and second passageway 23 and first passageway 131 intercommunication.
The external diameter of minor diameter nipple joint 21 is the same with the internal diameter of first section of thick bamboo 13, and the external diameter of major diameter nipple joint 22 is greater than the external diameter of minor diameter nipple joint 21, so minor diameter nipple joint 21 install first section of thick bamboo 13 and with the inner wall tight fit of first section of thick bamboo 13, major diameter nipple joint 22 butt is at connecting portion. The connection step 24 is provided at the connection between the small diameter short section 21 and the large diameter short section 22, preferably, the inner diameter of the large diameter short section 22 may also be the same as the outer diameter of the conductive housing 11, so that after the small diameter short section 21 is installed in the first barrel portion 13, the conductive housing 11 abuts against the connection step 24. The connection step 24 is provided with an electrode hole 241, the other end of the first conductor 12 passes through the electrode hole 241 and is insulated from the inner wall of the electrode hole 241, and an insulator may be provided on the outer side of the first conductor 12 or in other manners, which is not limited herein. The small-diameter nipple 21 and the large-diameter nipple 22 are both hollow cylindrical structures to define a second passage 23. The inner wall of the large diameter nipple 22 is threaded so as to facilitate connection with the pipe string.
Referring to fig. 5, the triggering module 3 includes an upper triggering portion 31, a lower triggering portion 32, an elastic resetting member 33, and a second conductor 34, the lower triggering portion 32 is installed on a side of the reducer union 2 opposite to the electric ignition module 1, and defines a sealed cavity 37 together with the upper triggering portion 31, the lower triggering portion 32 and the upper triggering portion 31 are movably disposed relatively, the upper triggering portion 31 or the lower triggering portion 32 has an initial position and an abutting position along a moving stroke, the second conductor 34 is insulatively disposed on the lower triggering portion 32, the upper triggering portion 31 is electrically connected to the conductive housing 11 through the lower triggering portion 32 and the reducer union 2, the second conductor 34 is electrically connected to the other end of the first conductor 12, and the elastic resetting member 33 and the second conductor 34 are accommodated in the sealed cavity 37 and disposed between the upper triggering portion 31 and the lower triggering portion 32; when the upper trigger part 31/the lower trigger part 32 are at the initial position, the second conductor 34 is electrically disconnected from the upper trigger part 31, and the elastic restoring member 33 is in a natural state; when the lower trigger part 32/the upper trigger part 31 moves from the initial position to the abutting position when the lower trigger part 32/the upper trigger part 31 receives pressure towards the upper trigger part 31/the lower trigger part 32, the second conductor 34 is electrically connected with the upper trigger part 31; the electric ignition module 1, the reducing short section 2 and the trigger module 3 are sequentially provided with a fluid channel extending along a first direction. In the present embodiment, the elastic return element 33 is a return spring, and the required trigger pressure of the downhole ignition device is determined according to the pressure bearing of the spring return element.
The lower trigger part 32 includes a first annular connecting plate 321, a second cylinder 322 and a third cylinder 323 extending from the first annular connecting plate 321 toward the upper trigger part 31, the second cylinder 322 is located in the third cylinder 323, the second cylinder 322, the third cylinder 323 and the upper trigger part 31 together enclose to form a sealed cavity 37, the third cylinder 323 is movably disposed in the upper trigger part 31 along the first direction, a third channel 3221 is defined in the second cylinder 322, and in addition, the first annular connecting plate 321 is provided with an offset hole 3211 through which the first conductor 12 passes.
The upper trigger part 31 includes a second annular connecting plate 311, a fourth cylinder 312 and a fifth cylinder 313, the fourth cylinder 312 extends from the second annular connecting plate 311 toward the upper trigger part 31, the fourth cylinder 312 is located in the fifth cylinder 313, and the fourth cylinder 312, the fifth cylinder 313, the second cylinder 322 and the third cylinder 323 jointly enclose to form a sealed cavity 37, wherein the sealed cavity 37 may be a vacuum or may be filled with air, which is not limited herein. The third cylinder 323 can be movably arranged on the inner wall of the fifth cylinder 313 along the first direction, a fourth channel 3121 is defined in the fourth cylinder 312, the third channel 3221 is communicated with the fourth channel 3121, and the second annular connecting plate 311 is electrically connected with the fifth cylinder 313.
The use method of the downhole ignition device comprises the following steps:
step S210, determining and installing an underground ignition device with trigger pressure P1+ P0 according to liquid column pressure P1 generated at the bottom of a fracturing well, wherein P0 is more than 0;
specifically, step S210 includes calculating a fluid column pressure P1= ρ gH generated at the bottom of the fractured well according to the fractured well depth H and the density ρ of the fracturing fluid injected into the coiled tubing 41; g is 9.8N/kg; and selecting a downhole ignition device with trigger pressure P1+ P0 according to the liquid column pressure generated at the bottom of the fractured well.
During installation, the downhole ignition device is installed at the end part of the coiled tubing 41, the downhole ignition device is placed to a target layer position through the coiled tubing 41, and the volume inside the coiled tubing 41 is calculated through the inner diameter d and the lowering length L of the coiled tubing 41
And injecting the combustion improver into the well bottom through the continuous oil pipe 41 so that the combustion improver is mixed with methane gas at the well bottom.
Step S220 of feeding a sealing piston 93 having the same inner diameter as the coiled tubing 41 into the coiled tubing 41;
and step S230, injecting well killing fluid into the coiled tubing 41, pushing the sealing piston 93 to move towards the underground ignition device until the piston pushes the electric ignition module 1 of the underground ignition device, and triggering and igniting methane gas in the fractured well by the electric igniter.
Specifically, step S230 includes injecting a control fluid into the coiled tubing 41 to push the sealing piston 93 to move toward the downhole ignition device, and when the wellhead pressure of the fractured well rises and is equivalent to the amount V of the injected control fluid, the sealing piston 93 reaches the downhole ignition device; and (3) continuing to inject the well killing fluid into the continuous oil pipe 41, so that the wellhead pressure of the fracturing well reaches above P0, the pressure applied to the underground ignition device is P1+ P0 at the moment, and the underground ignition device is triggered.
It is to be understood that the above-described embodiments are only a few, but not all, embodiments of the present invention. Based on the embodiments of the present invention, those skilled in the art may make other changes or modifications without creative efforts, and all of them should fall into the protection scope of the present invention.
Claims (10)
1. A method of methane in situ deflagration fracturing that takes into account wellbore drainage, comprising:
s100, determining a target layer of the blasting fracturing according to geological data and exploratory well development data;
step S200, dividing a shaft in a target layer into a 1 st fracturing section to an Nth fracturing section from the bottom to the top in sequence;
step S300, mounting a bridge plug at the end part of one end, opposite to the No. 1 fracturing section and the No. 2 fracturing section, of the No. 1 fracturing section, sealing, and perforating at the No. 1 fracturing section to establish a flow channel between a shaft and a reservoir stratum;
step S400, discharging liquid in the shaft, sealing an explosion space by using a packer after liquid discharge is finished, and accommodating an ignition device in the explosion space;
step S500, methane gas in the stratum is produced and accumulated in the coiled tubing and the combustion and explosion space, and when the concentration of the methane gas in the combustion and explosion space reaches a preset combustion and explosion critical concentration, a combustion improver is injected into the coiled tubing;
s600, a sealing piston is placed into the continuous oil pipe, and then pressure retaining liquid is injected into the continuous oil pipe to push the sealing piston to move so as to compress methane gas and a combustion improver in the continuous oil pipe into the combustion and explosion space;
s700, controlling an ignition device to ignite and ignite methane gas in an explosion space, and after explosion is successful, suddenly raising the pressure in the explosion space, so that high-pressure gas and generated shock waves can crack rocks through perforation to generate complex cracks in a reservoir stratum;
and step S800, unsealing the packer, repeating the steps S300 to S700, and fracturing the No. 2 fracturing section to the No. N fracturing section.
2. The method for methane in situ deflagration fracturing in view of wellbore drainage of claim 1, wherein step S300 comprises:
connecting a perforating gun at the end part of the continuous oil pipe, connecting a bridge plug at the end part of the perforating gun, passing the continuous oil pipe through a shaft, placing the perforating gun and the bridge plug to the end part of one end of the 1 st fracturing section, which is opposite to the 2 nd fracturing section, and sealing;
perforating by using a perforating gun, and perforating bullets in a 1 st fracturing section to penetrate through a casing and penetrate through a part of a reservoir layer so as to establish a flow channel between a shaft and the reservoir layer;
and after the perforation is finished, taking the coiled tubing and the perforating gun out of the shaft.
3. The method for methane in situ deflagration fracturing considering wellbore drainage as claimed in claim 1, wherein said step S400 comprises:
connecting a hollow first reducing short section to the end part of the coiled tubing through threads;
installing an ignition device on the first reducing short section, and connecting the packer to the periphery of the coiled tubing;
extending the first reducing short section, the ignition device and the packer to the position of the 1 st fracturing section through a continuous oil pipe;
injecting liquid nitrogen from the surface into the wellbore through the coiled tubing to drain the wellbore from the liquid;
and after the liquid drainage is finished, setting the packer to seal the space between the continuous oil pipe and the well wall casing of the fracturing well so as to seal the explosion space.
4. The method of in situ methane deflagration fracturing in view of wellbore drainage of claim 3, wherein when the fracturing well is a vertical well, the step of extending the first variable diameter sub, the ignition device and the packer through the coiled tubing to the location of the 1 st fracturing section comprises:
extending the first variable-diameter short section, the ignition device and the packer to the position of the 1 st fracturing section through a continuous oil pipe, wherein the packer reaches the upper part of the 1 st fracturing section; or,
when the fracturing well is the horizontal well, stretch into the step of the position of 1 st fracturing section through coiled tubing with first reducing nipple joint, ignition, packer and include:
and (3) extending the first reducing nipple, the ignition device and the packer into the position of the 1 st fracturing section through the coiled tubing, and enabling the packer to reach the position of the 1 st fracturing section close to the vertical section of the horizontal well.
5. The method for methane in situ deflagration fracturing in view of wellbore drainage of claim 3, wherein the step S500 comprises:
heating to accelerate liquid nitrogen flowback, so that the pressure of a combustion and explosion space is reduced, and methane gas in the stratum is promoted to be produced;
when the concentration reaches the critical concentration of combustion and explosion when the concentration reaches 10%, a combustion improver is injected into the combustion and explosion space through the coiled tubing.
6. The method for methane in situ deflagration fracturing in view of wellbore drainage of claim 3, wherein the step S600 comprises:
placing a sealing piston into the continuous oil pipe, and then injecting a pressure retaining liquid into the continuous oil pipe to push the sealing piston to move so as to compress methane gas and a combustion improver in the continuous oil pipe into the combustion and explosion space;
and after the sealing piston reaches the first reducing nipple at the end part of the continuous oil pipe, the sealing piston stops moving under the limitation of the first reducing nipple and stops injecting the pressure blocking liquid.
7. The method for methane in situ deflagration fracturing in view of wellbore drainage of claim 1, wherein the step S700 comprises:
and continuously injecting the pressure blocking liquid to enable the sealing piston to push the ignition device, so that an electric igniter in the ignition device is conducted to ignite methane gas in the explosion space, after the explosion is successful, the pressure in the explosion space can be suddenly increased, high-pressure gas and generated shock waves can crack rocks through perforation, and complex cracks are generated in the reservoir stratum.
8. The method for methane in situ deflagration fracturing considering wellbore drainage as claimed in claim 1, wherein the bridge plug is a drillable bridge plug or a soluble bridge plug.
9. The method for methane in situ deflagration fracturing in view of wellbore drainage of claim 1, further comprising:
and S900, drilling through the bridge plug in the shaft after the Nth fracturing section is fractured so as to ensure the production of shale gas.
10. The method for methane in situ deflagration fracturing considering wellbore drainage as claimed in claim 1, wherein the oxidizer is one or more of a gaseous oxidizer, a liquid oxidizer or a solid oxidizer.
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