CN112814640A - Multi-layer under-pressure fracturing operation device for medium-low pressure well and application method - Google Patents

Abstract

The invention belongs to the technical field of coal bed gas reservoir transformation and fracturing operation, and particularly relates to a multi-layer under-pressure fracturing operation device for a medium-low pressure well and an application method thereof; in order to solve the difficult problems of low transformation efficiency of the coal bed gas reservoir, large damage of the transformation to the reservoir 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 pipe, a check valve, an ejector, a circulating sliding sleeve, a hydraulic release, a fastening joint, an adjusting oil pipe, a prefabricated working barrel 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 pressurized state inside and outside the oil pipe through a wellhead pressure stabilizing device and an internal pressure maintaining device of the underground oil pipe, and finally realizes the pressurized 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 the fracturing modification engineering of medium and low pressure coal bed gas reservoirs.

Description

Multi-layer under-pressure fracturing operation device for medium-low pressure well and application method

Technical Field

The invention belongs to the technical field of coal bed gas reservoir transformation and fracturing operation, and particularly relates to a multi-layer under-pressure fracturing operation device for a medium-low pressure well and an application method thereof.

Background

At present, horizontal wells become the main well type for deep coal bed gas development. According to a coal bed gas extraction mechanism, after reservoir fracturing modification, pressure stabilization is carried out for a period of time according to a coal bed closed pressure value, and then pressure can be slowly released, so that pressure release can be carried out after fracturing operation of a horizontal section of a coal bed is completely finished; the coal bed gas horizontal well usually adopts a staged fracturing modification process, which mainly comprises pump injection bridge plug staged fracturing, continuous oil pipe bottom seal dragging staged fracturing, conventional oil pipe staged jet fracturing and conventional oil pipe bottom seal dragging fracturing. The 4 fracturing processes can be optimized for different coal series geological conditions. However, each fracturing process has its advantages and disadvantages:

(1) the pump injection bridge plug fracturing process comprises the following steps: and (3) bridge plug-perforation continuous operation, the fracturing procedure is simple, one-section fracturing of the horizontal well is completed, the bridge plug is pumped into the high-pressure pump, the cable transmits an instruction to set, perforate and perform fracturing operation, and the steps are repeated. The large-displacement and large-scale fracturing can be realized, and the pressure state is kept before each stage of fracturing. However, this fracturing process has several disadvantages in itself:

1) because the bridge plug is pumped into the preset position in the well from the ground through high pressure, the liquid in the volume of the casing can be squeezed into the coal bed by the bridge plug in the well entering process, and the pollution is caused to the coal bed.

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

Meanwhile, in order to improve the fracturing effect and prevent each section from communicating in the fracturing process, a casing pipe is required to be produced for well cementation. And the well cementation cement directly seals most gas production channels, so that the pollution to the coal reservoir is serious, and even if the holes are repaired, the pollution to the reservoir caused by the well cementation of the coal seam section cannot be completely eliminated.

(2) The continuous oil pipe bottom seal dragging fracturing process comprises the following steps: each link of fracturing operation links up compactly, and bottom packer setting, oil pipe sandblast perforation, annular space fracturing, packer deblocking, take the area to lift the tubular column and carry out next cycle operation, so, realize high efficiency operation easily. But the operation cost of the coiled tubing is high, besides the fracturing cost (the fracturing cost of each section of the horizontal well is 40 ten thousand yuan), each section of the horizontal well fractures, the cost of a coiled tubing operation vehicle is 6-8 thousand, 30 tons of cranes are required to be matched (the crane price is 5000 yuan/one shift), the number of fracturing sections of one horizontal well is 8 sections on average at present, and the extra cost is calculated to be 80 thousand (the prices are local market prices).

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

(3) The conventional oil pipe immovable pipe column jet fracturing process comprises the following steps: the fracturing process comprises the steps of putting fracturing balls corresponding to different sizes from an oil pipe, pressurizing and shearing a pin, descending a sliding sleeve to plug a lower layer and open a nozzle, and converting the pressure energy of perforating fluid into kinetic energy to jet a casing and a rock stratum by means of differential pressure generated by throttling of the nozzle. At present, the fracturing string 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 blockage or pulverized coal return spitting is caused, circulation is not easy to realize, so that the fracturing string is buried.

(4) The conventional oil pipe bottom seal dragging fracturing process comprises the following steps: the fracturing procedure comprises packer setting, sand blasting and perforation, tubing fracturing (annular fluid infusion), pressure releasing, tubing lifting and recycling operation. The process has low construction cost, the casing can be produced without cementing, but the pipe string can be lifted only by releasing pressure after each stage of fracturing is finished, and the requirement on the wear resistance of the nozzle is extremely high. The process is influenced by the pressure diffusion speeds of different coal measure strata, each pressure control blowout lasts for 8-10 days, if the fracturing layer sections are multiple, the time occupied by only the fracturing modification stage is several months, the development cycle of the coal measure gas well is greatly prolonged, and the reservoir modification efficiency is low. The process is suitable for the drag-saw operation of tens of wells on a drilling platform.

In view of the current situations of large reservoir damage, complex process, huge cost of continuous oil pipe fracturing process, high safety risk of fixed tubular column jet fracturing of conventional oil pipes, low fracturing efficiency of bottom seal dragging of conventional oil pipes and the like in the pump-injection bridge plug fracturing process, the coal-series gas fracturing equipment and technology have poor adaptability in coal-series gas development and become a technical bottleneck restricting the development of the coal-series gas industry.

Disclosure of Invention

The invention aims at the technical problems of low coal bed gas transformation efficiency, high cost, large damage of transformation to a reservoir stratum and the like, and develops a whole set of middle-low pressure well multilayer under-pressure fracturing operation device.

The invention adopts the following technical scheme: a multi-layer pressurized fracturing operation device for a medium-low pressure well; including wellhead assembly, fracturing pipe cluster in the pit includes direction head, screen pipe, check valve, sprayer, circulation sliding sleeve, hydraulic pressure that connect gradually from bottom to top takes off the hand, becomes detain joint, adjustment oil pipe, prefabricated working barrel and oil pipe, and the oil pipe passes through the oil pipe hanger and connects on wellhead assembly, and then suspends fracturing pipe cluster in the pit shaft in the pit, and the sprayer is located the fracturing point department.

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

Further, the device comprises an oil pipe internal pressure stabilizing device and a fishing device, wherein the oil pipe internal pressure stabilizing device comprises a plug, and the plug is connected with the prefabricated working barrel in a matching manner; the fishing device comprises a fishing barrel, a weighting rod, a steel wire rope catcher, a pressure measuring blowout joint, a blowout prevention pipe, a steel wire rope blowout prevention 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 joint is connected with the steel wire rope catcher, the blowout prevention pipe is connected with the pressure measuring blowout joint, the steel wire rope blowout prevention box is connected with the blowout prevention pipe, the crown block is fixed on a workover rig, and a coiled steel wire rope on the crown block extends into a shaft to be connected with the weighting rod.

Furthermore, 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 opening and a large-end pipe opening of the conical pipe section, a baffle is arranged on the side of the large-end pipe opening in the check valve body, and a through opening with the width smaller than the diameter of the steel ball a is formed in the baffle.

Further, the outer surface of the ejector is provided with a Ni60 alloy powder spray welding layer; eight nozzles are distributed on the ejector main body, every two of the eight nozzles are distributed on a radial quartering line of the ejector main body in a row, adjacent nozzle groups are arranged in a staggered mode from top to bottom, and the drift diameter of the nozzles is phi 6.3 mm.

Furthermore, the hydraulic release hand comprises an upper joint, a lower joint, a sliding sleeve and a steel ball b, wherein a plug nozzle is arranged at one end of the upper joint, an axial wire slot is formed in the plug nozzle, a slot is formed in the lower joint and is inserted into the slot, the sliding sleeve is inserted into the upper joint from the upper joint, the end of the sliding sleeve extends into the lower joint, the outer diameter of the waist of the sliding sleeve is smaller than the two end parts, the outer contour of the plug nozzle is gradually reduced from a connecting end to a free end, the wall surface of the slot is a slope surface matched with the plug nozzle, the lower end part of the sliding sleeve, the plug nozzle and the slot are in interference fit, a shear pin penetrates through the wall of the upper joint, the end of the shear pin sinks into a sinking groove in the outer wall surface of the upper end part.

Furthermore, the circulating sliding sleeve comprises a cylinder body and a steel ball c, 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 wall of the cylinder body, a sliding pipe is inserted in the cylinder body and seals the inlet and the outlet, a circumferential clamping ring protrudes from the outer pipe wall of the sliding pipe and is abutted against the inner wall of the cylinder body, the clamping ring is located above the inlet and the outlet, a concave section for containing 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 pipe, and the steel ball.

Furthermore, the inlet and the outlet are uniformly distributed around the axis of the cylinder body, the inlet and the outlet are oval holes, the inlet and the outlet comprise a vertical section and an outward-expanding section from the inner wall of the cylinder body, and a hard alloy layer is spray-welded in the outward-expanding section.

Furthermore, the guide head is sleeved on the pipe orifice of the sieve pipe, and the end head of the guide head is a ball head.

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

s1: washing a well and scraping a sleeve, and installing a wellhead four-way, a hydraulic single-ram blowout preventer and a hydraulic annular blowout preventer;

s2: the underground fracturing pipe string is put into the well, and the oil pipe is hung and seated on the hydraulic annular blowout preventer; the ejector is positioned at a first fracturing point;

s3: installing a suspension upper flange and a wellhead gate valve group, connecting the wellhead gate valve group upper flange with a ground fracturing pipeline, and carrying out pressure test;

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

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

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

s7: opening a pressure relief valve of a wellhead gate valve group to perform pressure relief in the oil pipe, and closing the pressure relief valve when the pressure is reduced to below 15 MPa;

s8: pumping the blanking plug to a preset working barrel, opening a pressure relief valve of a wellhead gate valve group for pressure relief, and checking whether the setting of the blanking plug is good or not;

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

s10: lifting the oil pipe, and moving the ejector to a second fracturing point;

s11: installing a wellhead gate valve group, 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;

s12: connecting the fishing barrel and the weighting rod by using a steel wire and putting the fishing barrel and the weighting rod into a shaft to perform fishing of the blanking plug;

s13: closing an upper valve of the wellhead gate valve group, opening a lower valve of the wellhead gate valve group, closing the lower valve of the wellhead gate valve group, opening the upper valve of the wellhead gate valve group and fishing the plug into the blowout prevention pipe after the plug and the fishing barrel move between the upper valve and the lower valve;

s14: the device comprises a steel wire rope catcher, a pressure measuring blowout joint, a blowout prevention pipe, a steel wire rope blowout prevention box and a crown block;

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

s16: and repeating the steps 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 invention provides a multi-layer under-pressure fracturing operation device for a medium-low pressure well, which is based on a conventional oil pipe, realizes the under-pressure state inside and outside the oil pipe through a wellhead pressure stabilizing device and an internal pressure maintaining device of the underground oil pipe, and finally realizes the under-pressure dragging fracturing operation by matching with the combination of an underground pipe column and the optimization of a lifting and lowering program; compared with the conventional coiled tubing sand blasting perforation annular sand adding bottom sealing belt pressure dragging staged fracturing process, the process can save the high machine-to-machine cost of a coiled tubing operation vehicle and a crane on the basis of realizing belt pressure operation, and can better crack and expand the crack aiming at a thin reservoir stratum, so that the phenomenon that the top and bottom plates of the coal reservoir stratum are pressed through to indirectly contain water in the water layer is avoided, and the expected transformation effect is achieved. The device can be widely applied to the fracturing modification engineering of medium and low pressure coal bed gas reservoirs.

Drawings

Fig. 1 is a schematic structural view of a downhole fracturing string.

Fig. 2 is a structural schematic diagram of a sieve tube and a guide head.

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

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

Fig. 5 is a schematic diagram of the structure of the ejector.

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

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

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

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

FIG. 10 is a schematic diagram of a wellhead configuration.

FIG. 11 is a schematic diagram of the uphole portion of the fishing device.

In the figure: 1-a guide head; 2-a sieve tube; 2.1-coupling; 3-a check valve; 3.1-one-way valve body; 3.2-baffle; 3.3-steel ball a; 4-an ejector; 4.1-injector body; 4.2-nozzle; 5-circulating the sliding sleeve; 5.1-upper connecting head; 5.2-lower connector; 5.3-steel ball c; 5.4-sliding tube; 5.5-cylinder; 5.6-import and export; 5.7-hard alloy layer; 6-hydraulic releasing the hand; 6.1-top connection; 6.2-sliding sleeve; 6.3-steel ball b; 6.4-lower joint; 6.5-shear pin; 7-a buckle-changing joint; 8-adjusting an oil pipe; 9-presetting a working barrel; 10-oil pipe; 11-casing head; 12-wellhead cross; 13-hydraulic single ram blowout preventer; 14-hydraulic annular blowout preventer; 15-hanging an upper flange; 16-a wellhead gate valve group; 17-a plug; 18-an overshot; 19-a weight bar; 20-a wire rope catcher; 21-pressure measuring open flow joint; 22-lubricator; 23-a wire rope blowout prevention box; 24-a crown block; 25-wire rope cap.

Detailed Description

In order to more clearly understand the technical features, objects, and effects of the present invention, embodiments of the present invention will now be described with reference to the accompanying drawings. The drawings are only for the purpose of illustrating the technology of the invention and are not to be construed as representing actual proportions or actual shapes of products, wherein like reference numerals indicate identical or functionally similar elements.

In this context, "parallel", "perpendicular", and the like are not strictly mathematical and/or geometric limitations, but may also include tolerances as would be understood by one skilled in the art and allowed for in the manufacture or use of the product. In addition, "perpendicular" includes not only mutually perpendicular in which two objects are directly connected in space but also mutually perpendicular in which two objects are not connected in space.

A multi-layer under-pressure fracturing operation device for a medium-low pressure well comprises a wellhead device and an underground fracturing pipe string, and is shown in figure 1; the underground fracturing pipe string comprises a guide head 1, a sieve pipe 2, a check valve 3, an ejector 4, a circulating sliding sleeve 5, a hydraulic release 6, a change-over joint 7, an adjusting oil pipe 8, a prefabricated working barrel 9 and an oil pipe 10 which are sequentially connected from bottom to top. The guide head 1 is connected with the sieve tube 2 in a screw thread mode and plays a role in guiding a tool to enter a well; the guide head 1 is sleeved on the pipe orifice of the sieve 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 a coupling 2.1 and plays a role of a reverse circulation channel, namely once sand is blocked in the fracturing operation process, liquid injected into the annular space can enter the tool and the interior of an oil pipe through the sieve tube 2. The check valve 3 is connected with the ejector 4 through an upper screw thread, and liquid is prevented from flowing backwards in the reverse circulation process. 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 the small-caliber nozzle and converting pressure energy of perforating fluid into kinetic energy, and therefore the casing and the rock stratum are ejected. The circulating sliding sleeve 5 is connected with the hydraulic release handle 6 through an upper screw thread, and the side body inlet and outlet of the circulating sliding sleeve are opened during fracturing, so that the discharge capacity in the oil pipe is improved, and large-discharge fracturing is realized. The hydraulic release handle 6 is connected with the variable buckle joint 7 through an upper screw thread, and if the hydraulic release handle is stuck or buried by sand after fracturing string construction, the hydraulic release handle cannot be released through measures such as backwashing and the like; and (3) putting the steel ball b6.3 from the oil pipe, pressurizing until the shear pin 6.5 is sheared, descending the sliding sleeve 6.2, separating the upper joint and the lower joint, lifting the oil pipe at the moment, lifting the part above the hydraulic release 6, and then carrying out salvage treatment for discarding the pipe column. The variable buckle joint 7 is connected with the adjusting oil pipe 8 through an upper screw thread to play a role in mutual connection of different buckle types. The adjusting oil pipe 8 is connected with the preset working barrel 9 through an upper screw thread, and the position of the preset working barrel 9 is adjusted by utilizing a plurality of oil pipes with different lengths according to fracturing points at different positions. The preset working barrel 9 is connected with the oil pipe 10 through an upper screw thread, and the preset working barrel 9 is a space position for setting the blanking plug 17. The lower end of an oil pipe 10 is connected with a preset working barrel 9 through a screw thread, the upper end of the oil pipe is connected to a wellhead device through an oil pipe hanger, then the underground fracturing pipe string is suspended in a shaft, and the ejector 4 is located at a fracturing point.

Specifically, as shown in fig. 10; the wellhead device comprises a casing head 11, a wellhead four-way 12, a hydraulic single ram blowout preventer 13, a hydraulic annular blowout preventer 14, a suspension upper flange 15 and a wellhead gate valve group 16 which are sequentially arranged from the wellhead upwards. The casing head 11 is connected with the wellhead four-way 12 through an upper flange, and plays a role in hanging the production casing and sealing the annulus between the production casing and the technical casing. The wellhead cross 12 is connected with the 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 cross, annular pressure between an oil pipe and a production casing is displayed, and annular pressure relief can be performed through the valve on the other side after fracturing is completed. 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 the annular space of an oil sleeve in fracturing operation. The hydraulic annular blowout preventer 14 is connected by flanges up and down, the annular space of the oil sleeve can be sealed in the fracturing operation, and the annular pressure of the oil sleeve can be maintained in the process of pulling out the oil pipe after fracturing. The wellhead gate valve block 16 and the hydraulic annular blowout preventer 14 are connected by a depending upper flange 15. In the fracturing process, fracturing fluid can be injected into the oil pipe through the wellhead gate valve group 16, a pressure gauge is installed at one valve on the wellhead gate valve group 16 to display the pressure in the oil pipe in real time, and the other valve is selected as a pressure relief valve. The tubing 10 is suspended from the annular hydraulic blowout preventer 14 by a tubing hanger.

As shown in fig. 9 and 11; the device further comprises an oil pipe internal pressure stabilizing device and a fishing device, wherein the oil pipe internal pressure stabilizing device comprises a plug 17, and the plug 17 is connected with the prefabricated working barrel 9 in a matched mode. After the fracturing is finished for one section, the plug 17 is delivered into the preset working barrel 9 through wellhead input or pumping, the fixing is carried out through the spring core, and the pressure in the oil pipe below the plug 17 is stable by means of the fit of the rubber setting and the inner wall of the preset working barrel 9.

The fishing device comprises a fishing barrel 18, a weighting rod 19, a steel wire rope catcher 20, a pressure measuring blowout joint 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 has a fault, and the steel wire rope can be locked when the steel wire rope rapidly slides downwards due to force loss so as to prevent tools from falling into a well; the pressure measuring blowout joint 21 is connected with the steel wire rope catcher 20 through a screw thread, the pressure measuring blowout joint 21 can be used for releasing pressure before the integral fishing device is disassembled, and a pressure gauge can be connected to the opposite side to observe the pressure in the blowout prevention pipe 22; the lubricator 22 is connected with the pressure-measuring blowout connector 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 sprayed out; the crown block 24 is fixed on the workover rig, and a wound 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 a weighting rod 19 through an upper screw thread and is used for fishing the blanking plug 17 before next fracturing. The upper end of the weighting rod 19 is connected with a steel wire rope through a steel wire rope cap 25, and plays a role in weighting the fishing barrel 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 large-end pipe orifice of the conical pipe section, a baffle 3.2 is arranged on the side of the large-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 3.2; the fluid flows in from the small-end pipe orifice and flows out from the 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 3.2 prevents the steel ball a3.3 from being flushed out of the ground when the fluid flows forwards.

Specifically; eight nozzles 4.2 are distributed on the ejector main body 4.1, the eight nozzles 4.2 are distributed on the radial quartering line of the ejector main body 4.1 in two-by-one rows, adjacent nozzle groups are arranged in a staggered mode from top to bottom, and the drift diameter of the nozzles 4.2 is phi 6.3 mm. After the ejector 4 is lowered to a 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 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 rebounded by the external sleeve, the rebounded quartz sand can impact the ejector 4 to cause damage, and therefore the Ni60 alloy powder spray welding layer 4.3 is arranged on the outer surface of the ejector 4.

Specifically, as shown in fig. 8; the hydraulic release 6 comprises an upper joint 6.1, a lower joint 6.4, a sliding sleeve 6.2 and a steel ball b6.3, wherein one end of the upper joint 6.1 is provided with a plug nozzle, an axial line slot is formed in the plug nozzle, a slot is formed in the lower joint, the plug nozzle is inserted into the slot, the sliding sleeve 6.2 is inserted from the upper joint 6.1, the end head of the sliding sleeve 6.4 extends into the lower joint 6.4, the outer diameter of the waist of the sliding sleeve 6.2 is smaller than the two end parts, the outer contour of the plug nozzle is gradually reduced from the connecting end to the free end, the wall surface of the slot is a slope surface matched with the plug nozzle, the lower end part of the sliding sleeve 6.2, the plug nozzle 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 head of the shear pin 6.5 sinks into a sinking groove in the outer wall surface of the upper end part of the sliding sleeve 6.2, a shoulder.

The hydraulic release handle 6 is connected on the fracturing string and is lowered to the designed depth along with the fracturing string. When the fracturing string is stuck by sand or buried by sand after construction and cannot be released by measures such as backwashing, and the like, the steel ball b6.3 is put into the fracturing string from the oil pipe, the pressure is increased by 20-24MPa (except for the formation pressure in the oil pipe) until the shear pin 6.5 is sheared, the sliding sleeve 6.2 descends to the waist part and is positioned at the matching part of the plug nozzle and the slot, the extrusion on the plug nozzle is relieved, the upper joint and the lower joint are separated, the oil pipe is lifted up at the moment, the part above the upper joint 6.1 is lifted out, and then the fishing treatment for discarding the string is carried out.

As shown in fig. 6 and 7; the circulating sliding sleeve 5 comprises a cylinder body 5.5 and a steel ball c5.3, 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, the wall of the cylinder body 5.5 is provided with an inlet and an outlet 5.6, a sliding pipe 5.4 is inserted in the cylinder body 5.5 in a sleeved mode, the inlet and the outlet 5.6 are sealed by the sliding pipe 5.4, a circumferential clamping ring is protruded on the outer pipe wall of the sliding pipe 5.4 and is abutted against the inner wall of the cylinder body, the clamping ring is positioned above the inlet and the outlet 5.6, the inner wall of the cylinder body at the inlet and the outlet 5.6 is provided with a sunken section for accommodating the clamping ring, a shoulder for intercepting the steel ball c5.3 is arranged in the sliding.

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 device is used, the steel ball c5.3 is required to be thrown from a wellhead, pressure is applied to the oil pipe to push the sliding pipe 5.4 to move downwards, the snap ring on the sliding pipe 5.4 enters the sunken section of the inner wall of the cylinder body, the sliding pipe 5.4 naturally falls, and the inlet and the outlet 5.6 are opened. And after fracturing is finished, backwashing to wash out the steel ball c5.3 from the well mouth, and collecting balls at a water outlet on the ground to ensure that the steel ball c5.3 is discharged from the well.

Three inlets and outlets 5.6 are uniformly distributed around the axis of the cylinder body 5.5, the inlets and outlets 5.6 are waist-shaped circular holes, the inlets and outlets 5.6 comprise a vertical section and an outward-expanding section from the inner wall of the cylinder body, and hard alloy layers 5.7 are spray-welded in the outward-expanding section in order to reduce the abrasion of the inlets and outlets 5.6.

Shown in combination with fig. 1, 9, 10, 11; an application method of a multi-layer under-pressure fracturing operation device for a medium-low pressure well specifically comprises the following steps:

1. carrying out well cleaning and casing scraping operation by using a drift diameter gauge and a scraper; installing a wellhead four-way 12, a hydraulic single ram blowout preventer 13 and a hydraulic annular blowout preventer 14;

2. sequentially putting a guide head 1, a sieve tube 2, a check valve 3, an injector 4, a circulating sliding sleeve 5, a hydraulic release 6, a variable buckle joint 7, an adjusting oil pipe 8, a preset working barrel 9 and an oil pipe 10, wherein the oil pipe is connected with an oil pipe hanger by adopting a screw thread, and the oil pipe hanger is seated on a hydraulic annular blowout preventer 14; the ejector 4 is positioned at the first fracturing point;

3. installing a suspension upper flange 15 and a wellhead gate valve group 16, connecting the upper flange of the wellhead gate valve group 16 with a ground fracturing pipeline, and performing pressure test to be qualified;

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

5. stopping the pump after fracturing to measure the pressure drop (measuring the pressure drop value);

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

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

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

9. slowly opening a pressure relief valve of the wellhead gate valve group 16 for pressure relief, and checking whether the setting of the blanking plug 17 is good or not;

10. opening the hydraulic single ram blowout preventer 13, closing the hydraulic annular blowout preventer 14 and disassembling the wellhead ram block 16;

11. lifting the oil pipe, and moving the ejector 4 to a second fracturing point;

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

13. connecting the fishing barrel 18 and the weighting rod 19 by steel wires and putting the fishing barrel and the weighting rod into a shaft to salvage the blanking plug 17;

14. closing the upper valve of the wellhead gate valve group 16, and opening the lower valve of the wellhead gate valve group 16;

15. after the blanking plug 17 and the fishing barrel 18 are moved 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 a steel wire rope catcher 20, a pressure measuring blowout joint 21, a blowout prevention pipe 22, a steel wire rope blowout prevention box 23 and a 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. repeat 5-18 until the Nth fracturing point is completed.

It should be understood that although the present description has been described in terms of various embodiments, not every embodiment includes only a single embodiment, and such description is for clarity purposes only, and those skilled in the art will recognize that the embodiments described herein may be combined as suitable to form other embodiments, as will be appreciated by those skilled in the art.

The above-listed detailed description is only a specific description of a possible embodiment of the present invention, and they are not intended to limit the scope of the present invention, and equivalent embodiments or modifications made without departing from the technical spirit of the present invention should be included in the scope of the present invention.

Claims (10)

1. The utility model provides a fracturing operation device is pressed to well low pressure multilayer area which characterized in that includes: well head device, fracturing pipe cluster in pit includes direction head (1), screen pipe (2), check valve (3), sprayer (4), circulation sliding sleeve (5), hydraulic pressure release hand (6), change buckle joint (7), adjustment oil pipe (8), prefabricated working barrel (9) and oil pipe (10) that connect gradually from bottom to top, oil pipe (10) are connected on the well head device through the oil pipe hanger, and then suspend fracturing pipe cluster in the pit shaft in midair, sprayer (4) are located the fracturing point department.

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

3. The multi-layer pressurized fracturing operation device for the medium and low pressure well as defined by claim 2, wherein: the device also comprises an oil pipe internal pressure stabilizing device and a fishing device, wherein the oil pipe internal pressure stabilizing device comprises a plug (17), and the plug (17) is connected with the prefabricated working barrel (9) in a matching way; the fishing device comprises a fishing barrel (18), a weighting rod (19), a steel wire rope catcher (20), a pressure measuring blowout joint (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 pressure measuring blowout joint (21) is connected with the steel wire rope catcher (20), the blowout prevention pipe (22) is connected with the pressure measuring blowout prevention joint (21), the steel wire rope blowout prevention box (23) is connected with the blowout prevention pipe (22), the crown block (24) is fixed on a workover rig, and a steel wire rope wound on the crown block (24) extends into a shaft and is connected with the weighting rod (19).

4. The multi-layer pressurized fracturing operation device for the medium and low pressure well according to claim 1, is characterized in that: 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 opening and a large-end pipe opening of the conical pipe section, a baffle (3.2) is arranged on the side of the large-end pipe opening in the check valve body (3.1), and a through opening with the width smaller than the diameter of the steel ball a (3.3) is formed in the baffle (3.2).

5. The multi-layer pressurized fracturing operation device for the medium and low pressure well as defined by 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 ejector main body (4.1), every two of the eight nozzles (4.2) are distributed on a radial quartering line of the ejector main body (4.1), adjacent nozzle groups are arranged in a staggered mode from top to bottom, and the drift diameter of the nozzles (4.2) is phi 6.3 mm.

6. The multi-layer pressurized fracturing operation device for the medium and low pressure well as defined by claim 5, wherein: 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 b (6.3), wherein one end of the upper joint (6.1) is provided with a plug nozzle, an axial line slot is arranged on the plug nozzle, a slot is arranged on the lower joint, the plug nozzle is inserted into the slot, the sliding sleeve (6.2) is inserted from the upper joint (6.1), the end stretches into in lower clutch (6.4), the external diameter of sliding sleeve (6.2) waist is less than both ends, the outline of spigot is by the link to free end convergent, the wall of slot with for spigot complex domatic, the lower tip of sliding sleeve (6.2), spigot, slot interference fit, worn shear pin (6.5) on the pipe wall of top connection (6.1), the end of shear pin (6.5) sinks to the heavy inslot of sliding sleeve (6.2) upper end outer wall, have the shoulder of interception steel ball b (6.3) in sliding sleeve (6.2), the fluid passage of steel ball b (6.3) shutoff sliding sleeve (6.2).

7. The multi-layer pressurized fracturing operation device for the medium and low pressure well as defined by claim 6, wherein: the circulating sliding sleeve (5) comprises a barrel body (5.5) and a steel ball c (5.3), two ends of the barrel body (5.5) are respectively connected with an upper connector (5.1) and a lower connector (5.2), an inlet and an outlet (5.6) are formed in the barrel wall of the barrel body (5.5), a sliding pipe (5.4) is inserted in the barrel body (5.5), the sliding pipe (5.4) seals the inlet and the outlet (5.6), a circumferential clamping ring is protruded on the outer pipe wall of the sliding pipe (5.4), the clamping ring is abutted to the inner wall of the barrel body and is positioned above the inlet and the outlet (5.6), a sunken section for accommodating the clamping ring is arranged on the inner wall of the barrel body at the inlet and the outlet (5.6), a shoulder for intercepting the steel ball c (5.3) is arranged in the sliding pipe (5.4), and the steel ball c (5.3.

8. The multi-layer pressurized fracturing operation device for the medium and low pressure well according to claim 7, wherein: the inlet and outlet (5.6) are uniformly distributed in three around the axis of the cylinder body (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 expanding section from the inner wall of the cylinder body, and a hard alloy layer (5.7) is spray-welded in the outer expanding section.

9. The multi-layer pressurized fracturing operation device for the medium and low pressure well according to claim 8, wherein: the guide head (1) is sleeved on the pipe orifice of the sieve pipe (2), and the end head of the guide head (1) is a ball head.

10. The application method of the medium and low pressure well multilayer pressurized fracturing operation device according to any one of the claims 1 to 9, characterized by comprising the following steps:

s1: washing and scraping a casing, and installing a wellhead four-way (12), a hydraulic single ram blowout preventer (13) and a hydraulic annular blowout preventer (14);

s2: the underground fracturing pipe string is put into the well, and an oil pipe (10) is hung and seated on a hydraulic annular blowout preventer (14); the ejector (4) is positioned at a first fracturing point position;

s3: installing a suspension upper flange (15) and a wellhead gate valve group (16), connecting the wellhead gate valve group upper flange with a ground fracturing pipeline, and carrying out pressure testing;

s4: closing the hydraulic single-ram blowout preventer (13), opening the hydraulic annular blowout preventer (14), performing sand blasting perforation in the oil pipe (10), and performing normal fracturing operation;

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

s6: opening a pressure relief valve of the wellhead cross (12) to perform annular pressure relief between the oil pipe and the casing pipe, and closing the pressure relief valve when the pressure is reduced to below 15 MPa;

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

s8: pumping the blanking plug (17) to a preset working barrel (9), opening a pressure relief valve of a wellhead gate valve group (16) for pressure relief, and checking whether the setting of the blanking plug (17) is good or not;

s9: opening a hydraulic single ram blowout preventer (13), closing a hydraulic annular blowout preventer (14) and disassembling a wellhead ram block (16);

s10: lifting the oil pipe (10) for operation, and moving the ejector (4) to a second fracturing point;

s11: installing a wellhead gate valve group (16), a steel wire rope catcher (20), a pressure measuring blowout joint (21), a blowout prevention pipe (22), a steel wire rope blowout prevention box (23) and a crown block (24);

s12: the fishing barrel (18) and the weighting rod (19) are connected by a steel wire and are put into a shaft to carry out fishing plug (17) operation;

s13: closing an upper valve of the wellhead gate valve group, opening a lower valve of the wellhead gate valve group, closing a lower valve of the wellhead gate valve group after the blanking plug (17) and the fishing barrel (18) move between the upper valve and the lower valve, opening the upper valve of the wellhead gate valve group, and fishing the blanking plug (17) into the lubricator (22);

s14: a steel wire rope catcher (20), a pressure measuring blowout joint (21), a blowout prevention pipe (22), a steel wire rope blowout prevention box (23) and a crown block (24);

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

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

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