CN112814640B - Multilayer pressured fracturing operation device for medium-low pressure well and application method - Google Patents

Abstract

The invention belongs to the technical field of coalbed methane reservoir reconstruction and fracturing operation, and particularly relates to a medium-low pressure well multilayer fracturing operation device under pressure and an application method thereof; in order to solve the problems of low efficiency of coal bed gas reservoir transformation, great damage to the reservoir caused by transformation and the like, the device comprises a wellhead device and an underground fracturing pipe string, wherein the underground fracturing pipe string comprises a guide head, a sieve tube, a uniflow valve, an ejector, a circulating sliding sleeve, a hydraulic release joint, a variant buckling joint, an adjusting oil pipe, a prefabricated working cylinder and an oil pipe which are sequentially connected from bottom to top, the oil pipe is connected to the wellhead device through an oil pipe hanger, the underground fracturing pipe string is suspended in a shaft, and the ejector is positioned at a fracturing point. The device is based on a conventional oil pipe, realizes the pressure state inside and outside the oil pipe through a wellhead pressure stabilizing device and a pressure maintaining device in the underground oil pipe, and finally realizes the pressure dragging fracturing operation by matching with the optimization of underground pipe column combination and lifting and lowering procedures; the device can be widely applied to fracturing reconstruction engineering of medium-low pressure coalbed methane reservoirs.

Description

Multilayer pressured fracturing operation device for medium-low pressure well and application method

Technical Field

The invention belongs to the technical field of coalbed methane reservoir reconstruction and fracturing operation, and particularly relates to a multi-layer fracturing operation device for a medium-low pressure well and an application method.

Background

Horizontal wells have become the primary well type for deep coal bed gas development. According to the coal bed gas drainage and recovery mechanism, after reservoir fracturing is reformed, pressure release can be performed slowly after pressure stabilization is performed for a period of time according to the closed pressure value of the coal bed, so that the pressure release can be performed after the fracturing operation of the horizontal section of the coal bed is completely completed; the coalbed methane horizontal well adopts a staged fracturing transformation process, and mainly comprises a pump injection bridge plug staged fracturing, a continuous oil pipe bottom seal dragging staged fracturing, a conventional oil pipe staged jet fracturing and a conventional oil pipe bottom seal dragging fracturing. The 4 fracturing processes described above may be preferred for different coal-based geological conditions. But each fracturing process has the advantages and the disadvantages that:

(1) Pumping bridge plug fracturing process: the bridge plug-perforation continuous operation is simple in fracturing procedure, the horizontal well is fractured for a period of time, the bridge plug is pumped in by high pressure, the cable transmits instructions to the bridge plug to seal, perforate and perform fracturing operation, and the circulation is performed. Large-displacement and large-scale fracturing can be realized, and each section is in a state with pressure before fracturing. However, this fracturing process itself has several drawbacks:

1) Because the bridge plug is pumped into the preset position underground from the ground through the high-pressure pump, the bridge plug can squeeze the liquid in the casing volume into the coal bed in the well entering process, and pollution is caused to the coal bed.

2) After the horizontal well is fractured for a period of time, a sand bed is formed in the fracturing channel by adding sand so as to support the fracture. When the bridge plug is pumped each time, the fluid squeezed into the formation will damage the sand bed, thereby affecting the fracturing effect.

Meanwhile, in order to improve the fracturing effect and prevent each section from being communicated in the fracturing process, casing cementing is also required to be produced. The well cementation cement directly seals most of gas production channels, so that the pollution to the coal reservoir is serious, and the pollution to the reservoir caused by the well cementation of the coal seam section cannot be completely removed even if holes are repaired.

(2) The continuous oil pipe bottom seal dragging fracturing process comprises the following steps: the connection of each link of the fracturing operation is compact, the bottom packer is set, the oil pipe is perforated by sand blasting, the annulus fracturing, the packer is unsealed, and the next circulation operation is carried out by pressing the lifting pipe column, so that the high-efficiency operation is easy to realize. However, the operation cost of the continuous oil pipe is higher, besides the fracturing cost (40 ten thousand yuan for each section of the horizontal well), each section of the horizontal well is fractured, the cost of the continuous oil pipe operation vehicle is 6-8 ten thousand, and 30 tons of cranes are needed to cooperate (the crane price is 5000 yuan/station class), and the number of the fracturing sections of one horizontal well is 8 on average at present, so that the additional cost is 80 ten thousand (the above prices are all local market prices).

And when the coal seam is buried deeply, the stratum fracture pressure is higher, the requirement on the compressive strength of the annular sleeve is higher, and the manufacturing cost of the selected steel-grade sleeve is higher.

(3) Conventional tubing string-free jet fracturing processes: the fracturing process is to throw fracturing balls with different sizes into oil pipe, shear pins in pressurized mode, slide sleeve to block the lower layer downwards and open the nozzle, and the pressure difference is produced by means of the throttling of the nozzle to convert the pressure energy of the perforating liquid into kinetic energy to shoot the casing and stratum. At present, the method is only suitable for two stages, the more the stages are, the smaller the fracturing ball is, the greater the safety risk is, and once sand is blocked or coal dust is returned, circulation is not easy to realize, so that the fracturing string is buried.

(4) Conventional oil pipe bottom seal dragging fracturing technology: the fracturing procedure comprises packer setting, sand blasting perforation, oil pipe fracturing (annular fluid supplementing), pressure releasing, oil pipe lifting and recycling. The process has low construction cost, the production sleeve can not be well fixed, but the pipe string can be lifted only by releasing pressure after each stage of fracturing is completed, and the requirement on the wear resistance of the nozzle is extremely high. The process is influenced by the pressure diffusion speed of different coal-based stratum, each time of pressure control and open flow needs to last for 8-10 days, if the number of the fracturing intervals is large, the time occupied by the fracturing transformation stage is only several months, the development period of the coal-based gas well is greatly prolonged, and the transformation efficiency of the reservoir is low. The process is suitable for drilling tens of wells on a drilling platform to carry out pull saw type operation.

In view of the current situations that the reservoir damage of the pumping bridge plug fracturing process is large, the process is complicated, the cost of the continuous oil pipe fracturing process is huge, the safety risk of conventional oil pipe fixed-string jet fracturing is high, the conventional oil pipe bottom seal dragging fracturing efficiency is low, and the like, the adaptability of coal-based gas fracturing equipment and technology in coal-based gas development is poor, and the equipment and technology become a large technical bottleneck for restricting the development of coal-based gas industry.

Disclosure of Invention

Aiming at the technical problems of low coalbed methane transformation efficiency, high cost, great damage to reservoirs caused by transformation and the like, the invention develops a whole set of middle-low pressure well multilayer pressure fracturing operation device, the device is based on a conventional oil pipe, realizes the pressure state inside and outside the oil pipe through a wellhead pressure stabilizing device and a pressure maintaining device in the underground oil pipe, and finally realizes the pressure dragging fracturing operation by matching with the optimization of underground pipe column combination and lifting and lowering programs.

The invention adopts the following technical scheme: a multi-layer fracturing operation device for a medium-low pressure well; the underground fracturing string comprises a guide head, a screen pipe, a check valve, an ejector, a circulating sliding sleeve, a hydraulic release joint, a variant buckle joint, an adjusting oil pipe, a prefabricated working cylinder and an oil pipe which are sequentially connected from bottom to top, wherein the oil pipe is connected to the wellhead through an oil pipe hanger, the underground fracturing string is suspended in a shaft, and the ejector is located at a fracturing point.

Further, the wellhead device comprises a casing head, a wellhead four-way joint, a hydraulic single-ram blowout preventer, a hydraulic annular blowout preventer, a hanging upper flange and a wellhead ram valve bank which are sequentially arranged from the wellhead.

Further, the device also comprises an oil pipe internal pressure stabilizing device and a salvaging device, wherein the oil pipe internal pressure stabilizing device comprises a blanking plug which is connected with the prefabricated working cylinder in a matching way; the fishing device comprises an overshot, a weighting rod, a steel wire rope catcher, a pressure measuring blowout preventing joint, a blowout preventing pipe, a steel wire rope blowout preventing box and a crown block, wherein the steel wire rope catcher is connected with a wellhead gate valve group through a lower flange, the pressure measuring blowout preventing joint is connected with the steel wire rope catcher, the blowout preventing pipe is connected with the pressure measuring blowout preventing joint, the steel wire rope blowout preventing box is connected with the blowout preventing pipe, the crown block is fixed on a workover rig, and a coiled steel wire rope on the crown block stretches into a shaft to be connected with the weighting rod.

Further, the check valve comprises a check valve body, a fluid channel is arranged in the check valve body, a conical pipe section is arranged on the fluid channel, a steel ball a is arranged between a small-end pipe orifice and a big-end pipe orifice of the conical pipe section, a baffle is arranged on the side of the big-end pipe orifice in the check valve body, and a through hole with the width smaller than the diameter of the steel ball a is formed in the baffle.

Further, the outer surface of the sprayer is provided with a Ni60 alloy powder spraying layer; eight nozzles are distributed on the injector main body, the eight nozzles are distributed on the radial tetrad line of the injector main body in a row-by-row mode, adjacent nozzle groups are arranged in an up-down staggered mode, and the diameter of each nozzle is phi 6.3mm.

Further, the hydraulic pressure unhooking includes top connection, the lower clutch, the sliding sleeve, steel ball b, the one end of top connection is provided with the spigot, it has axial wire casing to open on the spigot, be provided with the slot on the lower clutch, the spigot inserts in the slot, the sliding sleeve inserts from the top connection, the end stretches into in the lower clutch, the external diameter of sliding sleeve waist is less than both ends, the outline of spigot is by link to free end tapering, the wall of slot with be spigot complex domatic, the lower tip of sliding sleeve, the spigot, slot interference fit, wear to have the shear pin on the pipe wall of top connection, the end of shear pin sinks into the heavy inslot of sliding sleeve upper end outer wall, have the shoulder of interception steel ball b in the sliding sleeve, the fluid passage of steel ball b shutoff sliding sleeve.

Further, the circulating sliding sleeve comprises a cylinder body and a steel ball c, wherein the two ends of the cylinder body are respectively connected with an upper connector and a lower connector, an inlet and an outlet are formed in the cylinder wall of the cylinder body, a sliding tube is sleeved in the cylinder body, the sliding tube seals the inlet and the outlet, a circumferential clamping ring is arranged on the outer pipe wall of the sliding tube in a protruding mode and is abutted to the inner wall of the cylinder body, the clamping ring is positioned above the inlet and the outlet, a concave section for accommodating the clamping ring is arranged on the inner wall of the cylinder body at the inlet and the outlet, a shoulder for intercepting the steel ball c is arranged in the sliding tube, and the steel ball c seals a fluid channel of the sliding tube.

Further, the inlet and the outlet are uniformly distributed around the axis of the cylinder, the inlet and the outlet are waist-round holes, the inlet and the outlet comprise a vertical section and an outward expansion section from the inner wall of the cylinder, and a hard alloy layer is welded in the outward expansion section in a spray manner.

Further, the guide head is sleeved on the pipe orifice of the screen pipe, and the end head of the guide head is a ball head.

The invention also provides an application method of the multi-layer pressurized fracturing operation device for the medium-low pressure well, which comprises the following steps:

s1: flushing and casing scraping, namely installing a wellhead four-way, a hydraulic single-ram blowout preventer and a hydraulic annular blowout preventer;

S2: the oil pipe is hung on the hydraulic annular blowout preventer; the ejector is positioned at the first fracturing point;

S3: installing a hanging upper flange and a wellhead gate valve bank, wherein the wellhead gate valve bank upper flange is connected with a ground fracturing pipeline and is used for pressure test;

s4: closing a hydraulic single ram blowout preventer, opening a hydraulic annular blowout preventer, performing sand blasting perforation in an oil pipe, and performing normal fracturing operation;

s5, stopping the pump to measure the pressure drop after the fracturing is finished;

s6: opening a pressure release valve of the wellhead four-way valve to perform annular empty pressure release between the oil pipe and the sleeve, and closing the pressure release valve when the pressure is reduced to below 15 MPa;

S7: opening a pressure release valve of a wellhead gate valve group to release pressure in an oil pipe, and closing the pressure release valve when the pressure is reduced to below 15 MPa;

s8: pumping the blanking plug into a preset working cylinder, opening a pressure release valve of a wellhead gate valve group to release pressure, and checking whether the blanking plug is well set;

s9: opening a hydraulic single ram blowout preventer, closing a hydraulic annular blowout preventer, and disassembling a wellhead ram valve group;

s10: oil pipe lifting operation, namely moving the injector to a second fracturing point;

S11: installing a wellhead gate valve group, a steel wire rope catcher, a pressure measuring blowout connector, a blowout prevention pipe, a steel wire rope blowout prevention box and a crown block;

s12: connecting the overshot and the weighting rod by using a steel wire, and putting the overshot and the weighting rod into a shaft to carry out the operation of fishing the blanking plug;

S13: closing an upper valve of the wellhead gate valve bank, opening a lower valve of the wellhead gate valve bank, closing the lower valve of the wellhead gate valve bank after the blanking plug and the overshot are moved between the upper valve and the lower valve, opening the upper valve of the wellhead gate valve bank, and fishing the blanking plug into the lubricator;

S14: the device comprises a steel wire rope catcher, a pressure measuring open-flow joint, a blowout prevention pipe, a steel wire rope blowout prevention box and a crown block;

s15: closing a hydraulic single ram blowout preventer, opening a hydraulic annular blowout preventer, connecting a wellhead ram valve bank with a ground fracturing pipeline, and opening a lower valve of the wellhead ram valve bank to perform normal fracturing operation;

s16: and repeating S5-S15 until the fracturing operation of the Nth fracturing point is completed.

Compared with the prior art, the invention has the advantages that:

The multi-layer fracturing operation device for the middle and low pressure wells provided by the invention is based on a conventional oil pipe, realizes the state of pressure inside and outside the oil pipe through a wellhead pressure stabilizing device and a pressure maintaining device in the underground oil pipe, and finally realizes the dragging fracturing operation under pressure by matching with the optimization of underground pipe column combination and lifting and lowering procedures; compared with the existing coiled tubing sand blasting perforation annular sand-sealing and belt-pressing dragging staged fracturing process which is commonly adopted, the process can save the table work cost of a high-capacity coiled tubing operation vehicle and a crane on the basis of realizing the operation under pressure, and simultaneously can better crack and expand cracks aiming at a thin reservoir, so that indirect aquifers of the roof and the bottom of the coal reservoir are avoided from being blocked, and the expected transformation effect is achieved. The device can be widely applied to fracturing reconstruction engineering of medium-low pressure coalbed methane reservoirs.

Drawings

FIG. 1 is a schematic diagram of a string of downhole fracturing tubes.

Fig. 2 is a schematic view of the structure of the screen pipe and the guide head.

Fig. 3 is a schematic structural view of the check valve.

Fig. 4 is a schematic structural view of the baffle.

Fig. 5 is a schematic structural view of the ejector.

Fig. 6 is a schematic structural view of the circulation sliding sleeve.

FIG. 7 is a schematic cross-sectional view of the cartridge.

Fig. 8 is a schematic view of a hydraulic release.

FIG. 9 is a schematic diagram of the connection of the pressure stabilizing device and the fishing device in the oil pipe.

Fig. 10 is a schematic view of the wellhead configuration.

FIG. 11 is a schematic view of the uphole portion of the fishing apparatus.

In the figure: 1-a guide head; 2-a screen pipe; 2.1-coupling; 3-uniflow valve; 3.1-a one-way valve body; 3.2-baffle; 3.3-steel ball a; 4-ejector; 4.1-injector body; 4.2-nozzles; 5-circulating sliding sleeve; 5.1-upper connector; 5.2-lower connector; 5.3-steel ball c; 5.4-slide tube; 5.5-a cylinder; 5.6-import and export; 5.7-a cemented carbide layer; 6-hydraulic hand-off; 6.1-upper joint; 6.2-sliding sleeve; 6.3-steel ball b; 6.4-lower joint; 6.5-shear pins; 7-a variant buckle joint; 8-adjusting an oil pipe; 9-presetting a working cylinder; 10-oil pipe; 11-casing head; 12-a wellhead four-way joint; 13-hydraulic single ram blowout preventer; 14-a hydraulic annular blowout preventer; 15-hanging an upper flange; 16-wellhead gate valve group; 17-blanking plug; 18-overshot; 19-a weighted rod; 20-a wire rope catcher; 21-pressure measuring open-flow joint; 22-blowout prevention pipe; 23-a steel wire rope blowout prevention box; 24-crown block; 25-steel wire rope cap.

Detailed Description

For a clearer understanding of technical features, objects, and effects of the present invention, a specific embodiment of the present invention will be described with reference to the accompanying drawings. The drawings are for illustrative purposes only and are not intended to represent actual proportions or actual shapes of the products, in which like reference numerals designate identical or functionally similar parts.

Herein, "parallel", "perpendicular", etc. are not strictly mathematical and/or geometric limitations, but may also include errors that would be understood by one skilled in the art and that would be permitted in making or using the product. In addition, "perpendicular" includes not only a mutually perpendicular where two objects are directly connected in space, but also a mutually perpendicular where two objects are not connected in space.

A multi-layer fracturing operation device with pressure for a medium-low pressure well comprises a wellhead device and a downhole fracturing pipe string, wherein the downhole fracturing pipe string is shown in figure 1; the underground fracturing string comprises a guide head 1, a screen pipe 2, a uniflow valve 3, an ejector 4, a circulating sliding sleeve 5, a hydraulic release 6, a variant buckle joint 7, an adjusting oil pipe 8, a prefabricated working cylinder 9 and an oil pipe 10 which are sequentially connected from bottom to top. The guide head 1 is connected with the screen pipe 2 in a threaded manner and plays a role in guiding a tool into a well; the guide head 1 is sleeved on the pipe orifice of the screen pipe 2, and the end head of the guide head 1 is a solid iron ball head. The sieve tube 2 is connected with the check valve 3 through the coupling 2.1 to play a role of a reverse circulation channel, namely, once sand is blocked in the fracturing operation process, annular injection liquid can enter the tool and the inside of the oil tube through the sieve tube 2. The check valve 3 is connected with the ejector 4 through an upper screw thread, and prevents the liquid from flowing back during the reverse circulation. The ejector 4 is connected with the circulating sliding sleeve 5 through an upper screw thread and is used for generating pressure difference by means of throttling of a small-caliber nozzle and converting pressure energy of perforating fluid into kinetic energy so as to eject the casing and the rock stratum. The circulating sliding sleeve 5 is connected with the hydraulic release handle 6 through an upper screw thread, and a lateral inlet and outlet of the circulating sliding sleeve are opened during fracturing, so that the internal displacement of an oil pipe is improved, and large-displacement fracturing is realized. The hydraulic release 6 is connected with the variable buckle joint 7 through an upper screw thread, and is blocked by sand or buried by sand after the construction of a fracturing string, and can not be released by the measures such as back flushing; the steel ball b6.3 is put into the oil pipe, the pressure is applied until the shear pin 6.5 is sheared, the sliding sleeve 6.2 descends, the upper connector and the lower connector are separated, at the moment, the oil pipe is lifted up, the part above the hydraulic release 6 is lifted up, and then the salvaging treatment of throwing out the pipe column is carried out. The variable buckle joint 7 is connected with the adjusting oil pipe 8 through an upper screw buckle, and plays a role in connecting different buckles. The adjusting oil pipe 8 is connected with the preset working cylinder 9 through an upper screw thread, and the position of the preset working cylinder 9 is adjusted by utilizing a plurality of oil pipes with different lengths according to fracturing points at different positions. The preset working cylinder 9 is connected with the oil pipe 10 through an upper screw thread, and the preset working cylinder 9 is the space position where the blanking plug 17 is seated. The lower end of the oil pipe 10 is connected with a preset working cylinder 9 through a screw thread, the upper end of the oil pipe is connected with a wellhead device through an oil pipe hanger, and then the underground fracturing pipe string is suspended in a shaft, and the injector 4 is positioned at a fracturing point.

Specifically, as shown in fig. 10; the wellhead device comprises a casing head 11, a wellhead four-way joint 12, a hydraulic single-ram blowout preventer 13, a hydraulic annular blowout preventer 14, a hanging upper flange 15 and a wellhead ram valve group 16 which are sequentially arranged from the wellhead. Casing head 11 is connected with wellhead four-way joint 12 through upper flange, and plays roles of hanging production casing and sealing annulus between production casing and technical casing. The wellhead four-way valve 12 is connected with a hydraulic single-ram blowout preventer 13 through an upper flange, a pressure gauge is arranged at a valve on the left side or the right side of the wellhead four-way valve, annular pressure between an oil pipe and a production casing is displayed, and annular pressure relief can be carried out through a valve on the other side after fracturing. The hydraulic single ram blowout preventer 13 is connected with the hydraulic annular blowout preventer 14 through an upper flange, and plays a role in sealing an oil sleeve annulus in fracturing operation. The hydraulic annular blowout preventer 14 is in flange connection up and down, the oil sleeve annulus can be closed in fracturing operation, and the pressure of the oil sleeve annulus can be maintained in the process of starting an oil outlet pipe after fracturing. The wellhead valve block 16 and the hydraulic annular blowout preventer 14 are connected by a hanging upper flange 15. In the fracturing process, the fracturing fluid can be injected into the oil pipe through the wellhead gate valve bank 16, a pressure gauge is arranged at one valve on the wellhead gate valve bank 16, the pressure in the oil pipe is displayed in real time, and the other valve is selected as a pressure release valve. Tubing 10 is suspended from a hydraulic annular blowout preventer 14 by tubing hangers.

As shown in fig. 9 and 11; the hydraulic oil pipe pressure stabilizing device comprises a blanking plug 17, and the blanking plug 17 is connected with the prefabricated working cylinder 9 in a matched mode. After the fracturing is finished, the blanking plug 17 is sent into the preset working cylinder 9 through well head input or pumping, and is fixed through a spring core, and the blanking plug 17 is matched with the inner wall of the preset working cylinder 9 by means of rubber setting, so that the pressure in the oil pipe below the blanking plug 17 is stable.

The fishing device comprises a fishing barrel 18, a weighting rod 19, a steel wire rope catcher 20, a pressure measuring blowout connector 21, a blowout prevention pipe 22, a steel wire rope blowout prevention box 23 and a crown block 24, wherein the steel wire rope catcher 20 is connected with a wellhead gate valve group 16 through a lower flange, the crown block 24 fails, and the steel wire rope can be locked when the steel wire rope loses force and slides down rapidly so as to prevent tools from falling into a well; the pressure measuring open-flow joint 21 is connected with the steel wire rope catcher 20 through a screw thread, the pressure measuring open-flow joint 21 can be subjected to pressure release before the whole fishing device is disassembled, and the opposite side can be connected with a pressure gauge for observing the pressure in the lubricator 22; the lubricator 22 is connected with the pressure measuring open-flow joint 21 through a screw thread and is used for temporarily storing the overshot 18 and the blanking plug 17; the steel wire rope blowout prevention box 23 is connected with the blowout prevention pipe 22 through a screw thread, and plays a role in sealing the periphery of the steel wire rope and preventing liquid from being ejected; the crown block 24 is fixed on the workover rig, and a coiled steel wire rope on the crown block 24 extends into the shaft and is connected with the weighting rod 19. The overshot 18 is connected with the weighting rod 19 by an upper screw thread for fishing the blanking plug 17 before the next fracturing. The upper end of the weighting rod 19 is connected with a steel wire rope through a steel wire rope cap 25 to play a weighting role for the overshot 18.

Specifically, as shown in fig. 3 and 4; the check valve 3 comprises a check valve body 3.1, a fluid channel is arranged in the check valve body 3.1, a conical pipe section is arranged on the fluid channel, a steel ball a3.3 is arranged between a small-end pipe orifice and a big-end pipe orifice of the conical pipe section, a baffle plate 3.2 is arranged on the side of the big-end pipe orifice in the check valve body 3.1, and a through hole with the width smaller than the diameter of the steel ball a3.3 is formed in the baffle plate 3.2; fluid flows in from a small-end pipe orifice and flows out from a large-end pipe orifice of the conical pipe section, when the fluid flows reversely, the steel ball a3.3 is pushed to block the conical pipe section, and the baffle plate 3.2 prevents the steel ball a3.3 from being flushed out of the ground when the fluid flows positively.

Specifically, the method comprises the following steps; eight nozzles 4.2 are distributed on the injector main body 4.1, the eight nozzles 4.2 are distributed on the radial tetrad line of the injector main body 4.1 in a row by row mode, adjacent nozzle groups are arranged in a staggered mode up and down, and the diameter of each nozzle 4.2 is phi 6.3mm. After the injector 4 is lowered to the designed position along with the pipe column, the pressure difference is generated by means of throttling of the nozzle 4.2, and the pressure energy of the perforating fluid is converted into kinetic energy to shoot out the casing and the rock stratum. During fracturing, after the quartz sand is sprayed out through the nozzle, part of the quartz sand can be bounced back by the external sleeve, and the bounced quartz sand can impact the sprayer 4 to cause damage, so that the outer surface of the sprayer 4 is provided with a Ni60 alloy powder spray welding layer 4.3.

Specifically, as shown in fig. 8; the hydraulic release handle 6 comprises an upper joint 6.1, a lower joint 6.4, a sliding sleeve 6.2 and a steel ball b6.3, wherein a spigot is arranged at one end of the upper joint 6.1, an axial wire slot is formed in the spigot, a slot is formed in the lower joint, the spigot is inserted into the slot, the sliding sleeve 6.2 is inserted from the upper joint 6.1, the end stretches into the lower joint 6.4, the outer diameter of the waist of the sliding sleeve 6.2 is smaller than that of the two ends, the outer contour of the spigot is gradually reduced from the connecting end to the free end, the wall surface of the slot is matched with a slope for the spigot, the lower end of the sliding sleeve 6.2, the spigot and the slot are in interference fit, a shear pin 6.5 penetrates through the pipe wall of the upper joint 6.1, the end of the shear pin 6.5 is sunk into a sinking slot on the outer wall surface of the upper end of the sliding sleeve 6.2, a shoulder for intercepting the steel ball b6.3 is arranged in the sliding sleeve 6.2, and a fluid channel for blocking the steel ball b6.3 is arranged in the sliding sleeve 6.2.

The hydraulic release 6 is connected to the fracturing string and is lowered to the designed depth along with the fracturing string. When the fracturing string is blocked by sand or buried by sand after construction, when the fracturing string cannot be blocked by measures such as back flushing, the steel ball b6.3 is put into the oil pipe, the pressure is 20-24MPa (except the formation pressure in the oil pipe) until the shear pin 6.5 is sheared off, the sliding sleeve 6.2 descends to the waist part at the joint of the spigot and the slot, the extrusion of the spigot is relieved, the upper joint and the lower joint are separated, at the moment, the oil pipe is lifted up, the part above the upper joint 6.1 is lifted up, and then the salvaging treatment of the lost string is carried out.

As shown in fig. 6 and 7; the circulating sliding sleeve 5 comprises a cylinder body 5.5 and steel balls c5.3, wherein two ends of the cylinder body 5.5 are respectively connected with an upper connector 5.1 and a lower connector 5.2, an inlet and outlet 5.6 is formed in the cylinder wall of the cylinder body 5.5, a sliding tube 5.4 is inserted in the cylinder body 5.5 in a sleeved mode, the sliding tube 5.4 seals the inlet and outlet 5.6, a circumferential clamping ring protrudes out of the outer pipe wall of the sliding tube 5.4 and is in butt joint with the inner wall of the cylinder body, the clamping ring is located above the inlet and outlet 5.6, a concave section for accommodating the clamping ring is formed in the inner wall of the cylinder body at the inlet and outlet 5.6, a shoulder for intercepting the steel balls c5.3 is formed in the sliding tube 5.4, and the steel balls c5.3 block a fluid channel of the sliding tube 5.4.

In the fracturing process, in order to improve the discharge capacity in the pipe, the circulating sliding sleeve 5 needs to be opened; when the oil pipe is used, the steel ball c5.3 is put into the oil pipe from the wellhead, the oil pipe is pressurized, the slide pipe 5.4 is pushed to move downwards, the clamping ring on the slide pipe 5.4 enters the concave section of the inner wall of the cylinder body, the slide pipe 5.4 naturally falls down, and the inlet and outlet 5.6 are opened. After the fracturing is completed, the steel ball c5.3 is washed out of the wellhead by backwashing, the ball is connected to a ground water outlet, and the steel ball c5.3 is ensured to go out of the well.

The inlet and outlet 5.6 are evenly distributed around the axis of the cylinder 5.5, the inlet and outlet 5.6 is a waist-round hole, the inlet and outlet 5.6 comprises a vertical section and an outer expansion section from the inner wall of the cylinder, and in order to slow down the abrasion of the inlet and outlet 5.6, a hard alloy layer 5.7 is welded in the outer expansion section in a spray mode.

As shown in connection with fig. 1, 9, 10, 11; an application method of a multilayer pressured fracturing operation device for a medium-low pressure well specifically comprises the following steps:

1. The diameter gauge and the scraper are utilized to carry out the operations of well dredging and casing scraping; installing a wellhead four-way joint 12, a hydraulic single-ram blowout preventer 13 and a hydraulic annular blowout preventer 14;

2. The guiding head 1, the screen pipe 2, the check valve 3, the injector 4, the circulating sliding sleeve 5, the hydraulic release 6, the variable buckle joint 7, the adjusting oil pipe 8, the preset working cylinder 9 and the oil pipe 10 are sequentially arranged, the oil pipe is connected with the oil pipe hanger by adopting screw threads, and the oil pipe hanger is arranged on the hydraulic annular blowout preventer 14; the ejector 4 is positioned at the first fracturing point;

3. The method comprises the steps of installing a hanging upper flange 15 and a wellhead gate valve bank 16, connecting the upper flange of the wellhead gate valve bank 16 with a ground fracturing pipeline, and performing pressure test;

4. Closing the hydraulic single ram blowout preventer 13, opening the hydraulic annular blowout preventer 14, and performing sand blasting perforation and normal fracturing operation in an oil pipe;

5. Stopping the pump to measure the pressure drop (measuring the pressure drop value) after the fracturing is finished;

6. opening a pressure release valve of the wellhead four-way valve 12 to perform annular empty pressure release between the oil pipe and the sleeve, and closing the pressure release valve when the pressure is reduced to below 15 MPa;

7. opening a pressure release valve of the wellhead gate valve group 16 to release pressure in the oil pipe, and closing the pressure release valve when the pressure is reduced to below 15 MPa;

8. pumping the blanking plug 17 to a preset working cylinder 9, if the pumping pressure rises, proving that the blanking plug is in place;

9. Slowly opening a pressure release valve of the wellhead gate valve group 16 to release pressure, and checking whether the blanking plug 17 is well set;

10. Opening the hydraulic single ram blowout preventer 13, closing the hydraulic annular blowout preventer 14, and disassembling the wellhead ram valve bank 16;

11. tubing operation, moving the injector 4 to a second fracturing point;

12. Installing a wellhead gate valve group 16, a wire rope catcher 20, a pressure measuring blowout connector 21, a blowout prevention pipe 22, a wire rope blowout prevention box 23 and a crown block 24;

13. the overshot 18 and the weighting rod 19 are connected by steel wires and are put into a shaft to carry out the operation of the fishing plug 17;

14. Closing the upper valve of the wellhead gate valve bank 16, and opening the lower valve of the wellhead gate valve bank 16;

15. After the blanking plug 17 and the overshot 18 move between the upper valve and the lower valve of the wellhead gate valve group 16, closing the lower valve of the wellhead gate valve group 16, opening the upper valve of the wellhead gate valve group 16, and fishing the blanking plug 17 into the lubricator 22;

16. Disassembling the steel wire rope catcher 20, the pressure measuring blowout connector 21, the blowout prevention pipe 22, the steel wire rope blowout prevention box 23 and the crown block 24;

17. closing the hydraulic single ram blowout preventer 13 and opening the hydraulic annular blowout preventer 14;

18. Connecting the wellhead gate valve group 16 with a ground fracturing pipeline, opening a lower valve of the wellhead gate valve group 16, and performing normal fracturing operation;

19. Repeating 5-18 until the Nth fracturing point is completed.

It should be understood that although the present disclosure has been described in terms of various embodiments, not every embodiment is provided with a separate technical solution, and this description is for clarity only, and those skilled in the art should consider the disclosure as a whole, and the technical solutions in the various embodiments may be combined appropriately to form other embodiments that will be understood by those skilled in the art.

The above list of detailed descriptions is only specific to practical embodiments of the present invention, and they are not intended to limit the scope of the present invention, and all equivalent embodiments or modifications that do not depart from the spirit of the present invention should be included in the scope of the present invention.

Claims (8)

1. The utility model provides a well multilayer area pressure fracturing operation device at medium and low pressure, its characterized in that includes: the underground fracturing string comprises a guide head (1), a screen pipe (2), a check valve (3), an ejector (4), a circulating sliding sleeve (5), a hydraulic release joint (6), a buckle joint (7), an adjusting oil pipe (8), a prefabricated working cylinder (9) and an oil pipe (10), wherein the guide head, the screen pipe (2), the check valve, the ejector (4), the circulating sliding sleeve (5), the hydraulic release joint (6), the buckle joint (7), the adjusting oil pipe (8), the prefabricated working cylinder (9) and the oil pipe (10) are sequentially connected from bottom to top, the oil pipe (10) is connected to the wellhead through an oil pipe hanger, the underground fracturing string is suspended in a shaft, and the ejector (4) is positioned at a fracturing point;

The hydraulic release device is characterized in that the hydraulic release device comprises an upper connector (6.1), a lower connector (6.4), a sliding sleeve (6.2) and a steel ball b (6.3), wherein an inserting nozzle is arranged at one end of the upper connector (6.1), an axial slot is formed in the inserting nozzle, a slot is formed in the lower connector, the inserting nozzle is inserted into the slot, the sliding sleeve (6.2) is inserted into the lower connector (6.4) from the upper connector (6.1) and extends into the lower connector (6.4) from the end, the outer diameter of the waist of the sliding sleeve (6.2) is smaller than that of the two ends, the outer contour of the inserting nozzle is gradually reduced from the connecting end to the free end, the wall surface of the slot is a slope matched with the inserting nozzle, the lower end of the sliding sleeve (6.2), the inserting nozzle and the inserting slot are in interference fit, the end of the shearing pin (6.5) is sunk into the slot on the outer wall surface of the upper end of the sliding sleeve (6.2), the shoulder of the steel ball b (6.3) is sunk into the slot on the outer wall surface of the upper end of the sliding sleeve (6.2), and the fluid channel of the steel ball b (6.3) is blocked;

The circulating sliding sleeve (5) comprises a cylinder body (5.5) and a steel ball c (5.3), wherein the two ends of the cylinder body (5.5) are respectively connected with an upper connector (5.1) and a lower connector (5.2), an inlet and outlet (5.6) are formed in the cylinder wall of the cylinder body (5.5), a sliding tube (5.4) is sleeved in the cylinder body (5.5), the sliding tube (5.4) seals the inlet and outlet (5.6), a circumferential clamping ring is protruded on the outer pipe wall of the sliding tube (5.4) and is abutted to the inner wall of the cylinder body, the clamping ring is positioned above the inlet and outlet (5.6), a concave section for accommodating the clamping ring is formed in the inner wall of the cylinder body at the inlet and outlet (5.6), a shoulder for intercepting the steel ball c (5.3) is formed in the sliding tube (5.4), and the steel ball c (5.3) seals a fluid channel of the sliding tube (5.4).

2. The multi-layer pressurized fracturing operation device of the medium-low pressure well according to claim 1, wherein: the wellhead device comprises a casing head (11), a wellhead four-way valve (12), a hydraulic single-ram blowout preventer (13), a hydraulic annular blowout preventer (14), a hanging upper flange (15) and a wellhead ram valve group (16) which are sequentially arranged from the wellhead.

3. The multi-layer pressurized fracturing operation device of the medium-low pressure well according to claim 2, wherein: the hydraulic oil pipe hydraulic oil recovery device also comprises an oil pipe internal pressure stabilizing device and a salvaging device, wherein the oil pipe internal pressure stabilizing device comprises a blanking plug (17), and the blanking plug (17) is connected with the prefabricated working cylinder (9) in a matched manner; the fishing device comprises an overshot (18), a weighting rod (19), a steel wire rope catcher (20), a pressure measuring blowout preventing joint (21), a blowout preventing pipe (22), a steel wire rope blowout preventing box (23) and a crown block (24), wherein the steel wire rope catcher (20) is connected with a wellhead gate valve group (16) through a lower flange, the pressure measuring blowout preventing joint (21) is connected with the steel wire rope catcher (20), the blowout preventing pipe (22) is connected with the pressure measuring blowout preventing joint (21), the steel wire rope blowout preventing box (23) is connected with the blowout preventing pipe (22), the crown block (24) is fixed on a workover rig, and a coiled steel wire rope on the crown block (24) stretches into a shaft to be connected with the weighting rod (19).

4. The multi-layer pressurized fracturing operation device of the medium-low pressure well according to claim 1, wherein: the check valve (3) comprises a check valve body (3.1), a fluid channel is arranged in the check valve body (3.1), a conical pipe section is arranged on the fluid channel, a steel ball a (3.3) is arranged between a small-end pipe orifice and a big-end pipe orifice of the conical pipe section, a baffle plate (3.2) is arranged on the side of the big-end pipe orifice in the check valve body (3.1), and a through hole with the width smaller than the diameter of the steel ball a (3.3) is formed in the baffle plate (3.2).

5. The multi-layer pressurized fracturing operation device for a medium-low pressure well according to claim 4, wherein: the outer surface of the ejector (4) is provided with a Ni60 alloy powder spray welding layer (4.3); eight nozzles (4.2) are distributed on the injector main body (4.1), the eight nozzles (4.2) are distributed on the radial tetrad line of the injector main body (4.1) in a row by row mode, adjacent nozzle groups are arranged in an up-down staggered mode, and the diameter of each nozzle (4.2) is phi 6.3mm.

6. The multi-layer pressurized fracturing operation device of the medium-low pressure well according to claim 1, wherein: the inlet and outlet (5.6) are uniformly distributed around the axis of the cylinder (5.5), the inlet and outlet (5.6) is a kidney-shaped hole, the inlet and outlet (5.6) comprises a vertical section and an outward expansion section from the inner wall of the cylinder, and a hard alloy layer (5.7) is welded in the outward expansion section in a spray manner.

7. The multi-layer pressurized fracturing operation device for a medium-low pressure well according to claim 6, wherein: the guide head (1) is sleeved on the pipe orifice of the screen pipe (2), and the end head of the guide head (1) is a ball head.

8. A method of using the multi-layer pressurized fracturing operation apparatus of a low and medium pressure well as claimed in any one of claims 1 to 7, comprising the steps of:

S1: flushing and casing scraping operations, and installing a wellhead four-way joint (12), a hydraulic single-ram blowout preventer (13) and a hydraulic annular blowout preventer (14);

S2: the oil pipe (10) is hung on the hydraulic annular blowout preventer (14); the ejector (4) is positioned at the first fracturing point position;

S3: installing a hanging upper flange (15) and a wellhead gate valve group (16), wherein the wellhead gate valve group upper flange is connected with a ground fracturing pipeline and is used for pressure test;

S4: closing a hydraulic single ram blowout preventer (13), opening a hydraulic annular blowout preventer (14), and performing sand blasting perforation and normal fracturing operation in an oil pipe (10);

s5, stopping the pump to measure the pressure drop after the fracturing is finished;

s6: opening a pressure release valve of a wellhead four-way valve (12) to perform annular empty pressure release between an oil pipe and a sleeve, and closing the pressure release valve when the pressure is reduced to below 15 MPa;

s7: opening a pressure release valve of a wellhead gate valve group (16) to release pressure in an oil pipe, and closing the pressure release valve when the pressure is reduced to below 15 MPa;

s8: pumping the blanking plug (17) to a preset working cylinder (9), opening a pressure release valve of a wellhead gate valve group (16) to release pressure, and checking whether the blanking plug (17) is well set;

S9: opening a hydraulic single ram blowout preventer (13), closing a hydraulic annular blowout preventer (14), and disassembling a wellhead ram valve group (16);

s10: an oil lifting pipe (10) is used for working, and the ejector (4) is moved to a second fracturing point;

S11: installing a wellhead gate valve group (16), a steel wire rope catcher (20), a pressure measuring blowout connector (21), a blowout prevention pipe (22), a steel wire rope blowout prevention box (23) and a crown block (24);

S12: the overshot (18) and the weighting rod (19) are connected by steel wires and put into a shaft to carry out the operation of a salvaging plug (17);

S13: closing an upper valve of the wellhead gate valve bank, opening a lower valve of the wellhead gate valve bank, closing the lower valve of the wellhead gate valve bank after the blanking plug (17) and the overshot (18) are moved between the upper valve and the lower valve, opening the upper valve of the wellhead gate valve bank, and fishing the blanking plug (17) into the lubricator (22);

S14: installing a steel wire rope catcher (20), a pressure measuring blowout connector (21), a blowout prevention pipe (22), a steel wire rope blowout prevention box (23) and a crown block (24);

s15: closing a hydraulic single ram blowout preventer (13), opening a hydraulic annular blowout preventer (14), connecting a wellhead ram valve bank (16) with a ground fracturing pipeline, and opening a lower valve of the wellhead ram valve bank to perform normal fracturing operation;

s16: and repeating S5-S15 until the fracturing operation of the Nth fracturing point is completed.