One-trip double-layer fracturing pipe column without hydraulic anchor and capable of preventing sand blocking and operation method of one-trip double-layer fracturing pipe column

Abstract

The invention relates to a one-trip double-layer fracturing tubular column without a hydraulic anchor and capable of preventing sand blocking and an operation method, and the tubular column comprises a sleeve which is provided with at least two perforation sections; the oil pipe string is arranged in the sleeve; the first telescopic pipe and the second telescopic pipe are sequentially connected to the oil pipe string in series at intervals from top to bottom so that the oil pipe string can be divided into multiple sections. The double-slip anti-deblocking packer is arranged outside the oil pipe string in a sleeving manner, is positioned between the first telescopic pipe and the second telescopic pipe, and is used for forming upper-layer sealing between the oil pipe string and the sleeve; the non-rotating gravity type packer is arranged outside the oil pipe string in a sleeving mode, located between the bottom of the casing pipe and the second telescopic pipe and used for forming lower layer sealing between the oil pipe string and the casing pipe. The sand blocking risk of the pipe column can be reduced to the maximum extent.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas exploitation, and in particular to a one-pass double-layer fracturing pipe string without hydraulic anchors capable of preventing sand jamming and an operation method thereof. Background Art

[0002] For low porosity and permeability reservoirs, fracturing is an effective means of increasing production. At present, the number of fracturing layers in offshore low permeability oil fields is mostly two. Conventional simple fracturing strings mainly use a string to connect hydraulic anchors, multi-stage Y344 packers or Y441 packers and sliding sleeve sandblasters to perform layered fracturing on the reservoir. Although it has great advantages in pulling out and pulling out the string or operation, for large-size casings commonly used in offshore oil fields (such as 7in and 9-5 / 8in), the annulus section collects more sand, and the hydraulic anchor cannot be restored after fracturing, resulting in multiple sand jams in the string after fracturing, and subsequent well repair costs are high. If the hydraulic anchor is not connected, the conventional Y441 packer will be pushed up and unsealed during fracturing, and the Y344 packer will also be pushed up and slide, resulting in tearing of the rubber tube and sealing failure. Summary of the invention

[0003] In view of the above problems, the purpose of the present invention is to provide a one-trip double-layer fracturing string and an operating method that can prevent sand sticking without hydraulic anchors. The string is lowered in one trip, and two types of packers on the string are sealed by operations such as lifting, lowering and pressurizing. After fracturing, the two types of packers are gradually unsealed by lifting the string, thereby minimizing the risk of sand sticking in the string.

[0004] To achieve the above object, the present invention adopts the following technical solutions: The hydraulic anchor-free double-layer fracturing string capable of preventing sand jamming described in the present invention comprises: a casing having at least two perforation sections; a tubing string arranged in the casing; a first telescopic tube and a second telescopic tube, the first telescopic tube and the second telescopic tube being sequentially connected in series on the tubing string from top to bottom at intervals to divide the tubing string into multiple sections; a double-slip anti-unsealing packer, sleeved outside the tubing string and located between the first telescopic tube and the second telescopic tube, for forming an upper seal between the tubing string and the casing; a non-rotating gravity packer, sleeved outside the tubing string and located between the bottom of the casing and the second telescopic tube, for forming a lower seal between the tubing string and the casing.

[0005] In the double-layer fracturing string, preferably, the double slip anti-unsealing packer comprises a first slip and a second slip, wherein the first slip and the second slip are respectively arranged at the upper end and the lower end of the double slip anti-unsealing packer; The first slip and the second slip are respectively connected to the oil pipe string slips.

[0006] In the double-layer fracturing string, preferably, a third slip is provided at the upper end of the non-rotating gravity packer, and the third slip is connected to the tubing string slip.

[0007] The double-layer fracturing string preferably further includes a ball-dropping sleeve and a first sphere; the ball-dropping sleeve is arranged on the tubing string and is located between the second telescopic tube and the non-rotating gravity packer; the first sphere is arranged in the tubing string and is blocked by the ball-dropping sleeve.

[0008] The double-layer fracturing string preferably further comprises a shear ball seat and a second sphere; the shear ball seat is arranged on the oil pipe string and located at the lower end of the oil pipe string; the second sphere is arranged in the oil pipe string and blocked by the shear ball seat.

[0009] In the double-layer fracturing string, preferably, the radius of the first sphere is greater than the radius of the second sphere.

[0010] The double-layer fracturing string described above preferably further includes a safety release; the safety release is arranged on the oil pipe string and is located between the first telescopic pipe and the double slip anti-unsealing packer.

[0011] The double-layer fracturing string preferably further comprises a backwash valve, which is arranged on the oil pipe string and located between the first telescopic pipe and the wellhead.

[0012] The method for operating a double-layer fracturing string without hydraulic anchors and capable of preventing sand jamming of the present invention comprises the following steps: The perforation of the two layers to be constructed is completed by TCP perforation. If it is an active production well or water injection well, there is no need to repeat the perforation; The pipe string is lowered into a predetermined position at the bottom of the well. At this time, the first sphere and the second sphere are not put in. The pipe string is first lifted up and then pressed down to complete the setting of the non-rotating gravity packer. At the same time, the wellhead needs to press down a set tonnage so that there is enough counterweight above the non-rotating gravity packer to ensure that the packer is completely set. While the pipe string is pressed down at the wellhead, the first telescopic tube and the second telescopic tube are in a fully recovered state under the action of the compression force; Put the second steel ball above the shear ball seat, apply hydraulic pressure to set the double slip anti-unsealing packer, and complete the sealing inspection operation by applying hydraulic pressure to the tubing string and casing annulus above the double slip anti-unsealing packer; When hydraulic pressure is applied to the tubing and exceeds the setting value of the packer's sealing force, the shear ball seat is driven into the bottom of the well to provide a channel for fracturing, and fracturing fluid is injected into the formation to fractur e the lowest layer; Put the first ball onto the ball-casting sleeve, hydraulically open the ball-casting sleeve, and perform fracturing of the upper layer, soaking the well and releasing the well, or fracturing and releasing the well; Lift the pipe string to the set value and release the double slip anti-unsealing packer; Continue to lift the tubing string to pull open the second telescopic tube, continue to lift the tubing string to release the non-rotating gravity packer, and lift the tubing string out of the wellhead as a whole.

[0013] The present invention adopts the above technical solution, which has the following advantages: (1) The present invention lowers two packers in one trip of tubing and completes the fracturing of two layers in one trip of tubing, thereby preventing well-sticking accidents caused by the superposition of sand burial risks of multiple packers when the tubing is lifted; (2) The present invention eliminates the shrinkage preload of the pipe string by adding a first telescopic tube and abandons the hydraulic anchor, thereby greatly reducing the risk of sand jamming in the pipe string; (3) The present invention installs a first telescopic tube on the double slip anti-unsealing packer to compensate for the contraction of the pipe string during fracturing and prevent the double slip anti-unsealing packer from being mistakenly sealed; (4) The present invention connects a second telescopic tube between the two packers, thereby realizing the step-by-step unsealing of the two packers; (5) The present invention uses a ball to press or lift the safety release to open the safety release. When the pipe string is stuck in sand, the pipe string above the safety release can be lifted out, thereby reducing the workload of well repair. (6) The present invention can open the backwash valve by means of annular space pressure to achieve backwashing of the well and well killing operations before wellhead removal. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Throughout the accompanying drawings, the same reference numerals are used to represent the same components. In the accompanying drawings: Figure 1 The present invention is a schematic structural diagram of a double-layer fracturing string without hydraulic anchors capable of preventing sand jamming.

[0015] The reference numerals in the figures are as follows: 1-tubing string; 2-backwash valve; 3-first telescopic pipe; 4-safety release; 5-double slip anti-unsealing packer; 5-1-first slip; 5-2-second slip; 6-second telescopic pipe; 7-first perforating section; 8-first sphere; 9-ball-throwing sliding sleeve; 10-non-rotating gravity packer; 10-1-third slip; 11-second sphere; 12-shear ball seat; 13-second perforating section; 14-casing. DETAILED DESCRIPTION

[0016] The exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0017] The present invention provides a one-trip double-layer fracturing string and an operation method which can prevent sand jamming without hydraulic anchors. Two packers are lowered into two-layer fracturing construction by one trip of the string, and a well jamming accident caused by the superposition of sand burial risks of multiple packers when the string is lifted is prevented. The shrinkage pre-tightening force of the string is eliminated by adding a first telescopic tube, and the hydraulic anchor is abandoned, thereby greatly reducing the risk of sand jamming of the string. The first telescopic tube is installed on the double-slip anti-unsealing packer to compensate for the shrinkage of the string during fracturing, thereby preventing the double-slip anti-unsealing packer from being mistakenly sealed. The second telescopic tube is connected between the two packers, thereby realizing the step-by-step unsealing of the two packers.

[0018] like Figure 1 As shown, the hydraulic anchor-free double-layer fracturing string for preventing sand jamming provided by the present invention comprises: a casing 14, the casing 14 having at least two perforation sections, namely a first perforation section 7 and a second perforation section 13; an oil pipe string 1, arranged in the casing 14; a first telescopic tube 3 and a second telescopic tube 6, the first telescopic tube 3 and the second telescopic tube 6 are sequentially connected in series on the oil pipe string 1 from top to bottom, so as to divide the oil pipe string 1 into multiple sections; a double-slip anti-unsealing packer 5, sleeved outside the oil pipe string 1 and located between the first telescopic tube 3 and the second telescopic tube 6, for forming an upper seal between the oil pipe string 1 and the casing 14; a non-rotating gravity packer 10, sleeved outside the oil pipe string 1 and located between the bottom of the casing 14 and the second telescopic tube 6, for forming a lower seal between the oil pipe string 1 and the casing 14.

[0019] Among them, it should be noted that the first telescopic tube has a telescopic function and can be stretched 1.5 meters or even longer. During the process of lowering the tubing string, due to the deadweight of the tubing string, the first telescopic tube is in a fully stretched state. When the tubing string reaches a predetermined depth and the tubing string is pressed down to seal the non-rotating gravity type packer, the stretched part of the first telescopic tube will be in a state of maximum contraction. During fracturing, the tubing string will shrink as a whole due to reduced temperature. At this time, the contracted part of the first telescopic tube begins to be stretched, which plays a compensating role for the tubing string. If there is no first telescopic tube, the tubing string will tend to shorten, resulting in a large pre-tightening force on the tubing string, which may unseal the double-slip anti-unsealing packer. Due to the existence of the first telescopic tube, there is no pre-tightening force on the tubing string above the double-slip anti-unsealing packer, and there is no risk of the double-slip anti-unsealing packer being unsealed.

[0020] The second telescopic tube has the same principle as the first telescopic tube. When the tubing string is pressed down to seal the non-rotating gravity packer below, the second telescopic tube is also in the shortest state. When the double slip packer is unsealed after fracturing, due to the existence of the second telescopic tube, the unsealing force of the lifting string is only used to unseal the double slip anti-unsealing packer. After unsealing the packer, the tubing string is continued to be lifted, and the second telescopic tube will be extended and retracted, and then the tubing string is continued to be lifted to unseal the non-rotating gravity packer below, thereby realizing the step-by-step unsealing of the packers. After fracturing, due to sand jamming, the lifting and unsealing force required for the two packers is about 20 tons. If there is a second telescopic tube, the two packers can be unsealed step by step, and the lifting force required to unseal each packer is 20 tons. If there is no second telescopic tube, a lifting force of 40 tons is required to unseal the double slip anti-unsealing packer above, and when the packer is unsealed, the non-rotating gravity packer below will also be unsealed at the same time.

[0021] In the above embodiment, preferably, the double slip anti-unsealing packer 5 comprises a first slip 5-1 and a second slip 5-2, and the first slip 5-1 and the second slip 5-2 are respectively arranged at the upper end and the lower end of the double slip anti-unsealing packer 5; The first slip 5-1 and the second slip 5-2 are connected to the slips of the oil pipe string 1 respectively.

[0022] It should be noted that the double-slip anti-unsealing packer 5 is set by hydraulic pressure at the wellhead and is unsealed by lifting the tubing. The packer has a first slip and a second slip. When there is high pressure in the annulus below the rubber tube of the double-slip anti-unsealing packer 5, the upper slip (i.e., the first slip) can offset the piston force caused by the annulus below the rubber tube. Therefore, the packer will not be unsealed when there is high pressure in the annulus below the rubber tube. This is the biggest difference between this packer and the conventional Y441 packer, so it is called an anti-unsealing packer. However, the unsealing method of this packer is the same as that of the conventional Y441 packer, that is, lifting to unseal.

[0023] In the above embodiment, preferably, a third slip 10 - 1 is provided at the upper end of the non-rotating gravity packer 10 , and the third slip 10 - 1 is connected to the slip of the oil pipe string 1 .

[0024] It should be noted that the non-rotating gravity type packer 10 belongs to the Y221 packer, and the packer is sealed by lifting the tubing string and pressing the tubing string down. The force of pressing the tubing string down needs to be large enough to fully compress the rubber tube of the packer. The packer has a lower anchor shoe with a one-way anchoring effect, which can ensure that the packer will not slide down the casing during the downward pressure process. When fracturing, the third shoe will open under the pressure difference of the casing annulus to prevent the packer from being pushed up and unsealed.

[0025] In the above embodiment, preferably, the present invention also includes a ball-throwing sleeve 9 and a first sphere 8; the ball-throwing sleeve 9 is arranged on the tubing string 1 and is located between the second telescopic tube 6 and the non-rotating gravity-type packer 10; the first sphere 8 is arranged in the tubing string 1 and is blocked by the ball-throwing sleeve 9.

[0026] In the above embodiment, preferably, the present invention further includes a shear ball seat 12 and a second sphere 11; the shear ball seat 12 is arranged on the tubing string 1 and located at the lower end of the tubing string 1; the second sphere 11 is arranged in the tubing string 1 and is blocked by the shear ball seat 12.

[0027] The radius of the first sphere 8 is greater than the radius of the second sphere 11 .

[0028] It should be noted that when it is necessary to seal the double-slip anti-unsealing packer, hydraulic pressure is required. In order to allow high pressure to be maintained in the tubing string, the second steel ball is put into the tubing string, and hydraulic pressure is applied to the tubing string to the set value to seal the double-slip anti-unsealing packer. Then the pressure value is continued to be increased to drive the ball seat part of the shear ball seat into the bottom of the well to provide a channel for fracturing.

[0029] When the bottom layer is fracturing, the first steel ball 8 can be thrown in, the ball throwing sleeve 9 can be opened, and the second layer can be fracturing. In the above embodiment, preferably, the present invention further comprises a safety release 4; the safety release 4 is arranged on the oil pipe string 1 and is located between the first telescopic tube 3 and the double slip anti-unsealing packer 5. Therefore, the safety release does not work during fracturing. When there is a problem with the pipe string and it cannot be pulled out of the wellhead, a steel ball can be put into the safety release to apply hydraulic pressure, and the safety joint will be separated from the inside and outside, that is, the pipe string above the safety release will be separated from the pipe string below it and pulled out of the wellhead.

[0030] In the above embodiment, preferably, the present invention further comprises a backwash valve 2, which is arranged on the oil pipe string 1 and is located between the first telescopic pipe 3 and the wellhead. Thus, the backwash valve can realize backwashing of the well, and when the annular pressure reaches the opening value of the backwash valve, the valve inside the backwash valve opens, the passage of the oil casing annular space is opened, and the liquid in the annular space can enter the oil pipe from the annular space to realize backwashing and well killing, thereby ensuring the safety of well control when the subsequent pipe string is pulled up.

[0031] The present invention also provides a method for operating a double-layer fracturing string without hydraulic anchors and capable of preventing sand jamming, comprising the following steps: (1) The perforation of the two layers to be constructed is completed by TCP perforation. If it is an active production well or water injection well, there is no need to repeat the perforation; (2) The tubing string is lowered into the predetermined position at the bottom of the well. At this time, the first sphere and the second sphere are not put in. The tubing string is first lifted up and then pressed down to complete the setting of the non-rotating gravity packer. At the same time, the wellhead needs to press down a set tonnage so that there is enough counterweight above the non-rotating gravity packer to ensure that the packer is completely set. While the tubing string is pressed down at the wellhead, the first telescopic tube and the second telescopic tube are in a fully recovered state under the action of the compression force; (3) Place the second steel ball above the shear ball seat, apply hydraulic pressure to set the double slip anti-unsealing packer, and complete the sealing test operation by applying hydraulic pressure to the tubing string and casing annulus above the double slip anti-unsealing packer; (4) Apply hydraulic pressure to the tubing, and drive the shear ball seat into the bottom of the well when the sealing force of the packer exceeds 8-10 MPa to provide a channel for fracturing, and inject fracturing fluid into the formation to fractur e the lowest layer; (5) Place the first ball on top of the ball-casting sleeve, apply hydraulic pressure to open the ball-casting sleeve, and perform fracturing of the upper layer, then soak the well and perform blowout or perform fracturing and blowout; (6) Lift the tubing string to the set value and unseal the double slip anti-unseal packer; (7) Continue to lift the tubing string and pull open the second telescopic tube, continue to lift the tubing string to release the non-rotating gravity packer, and lift the tubing string out of the wellhead as a whole.

[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A one-pass double-layer fracturing string without hydraulic anchors and capable of preventing sand jamming, characterized in that: include: a casing having at least two perforated sections; An oil pipe string is arranged in the casing; A first telescopic tube and a second telescopic tube, wherein the first telescopic tube and the second telescopic tube are sequentially connected to the oil pipe string from top to bottom in sequence and at intervals, so as to divide the oil pipe string into multiple sections; A double-slip anti-unsealing packer, which is sleeved outside the tubing string and located between the first telescopic tube and the second telescopic tube, and is used to form an upper seal between the tubing string and the casing; The non-rotating gravity packer is sleeved outside the tubing string and located between the bottom of the casing and the second telescopic tube, and is used to form a lower layer seal between the tubing string and the casing.

2. The double-layer fracturing string according to claim 1, characterized in that: The double slip anti-unsealing packer comprises a first slip and a second slip, wherein the first slip and the second slip are respectively arranged at the upper end and the lower end of the double slip anti-unsealing packer; The first slip and the second slip are respectively connected to the oil pipe string slips.

3. The double-layer fracturing string according to claim 1, characterized in that: A third slip is arranged at the upper end of the non-rotating gravity packer, and the third slip is connected to the oil pipe string slip.

4. The double-layer fracturing string according to claim 1, characterized in that: Also included is a pitching slide and a first ball; The ball-dropping sliding sleeve is arranged on the tubing string and is located between the second telescopic tube and the non-rotating gravity packer; The first sphere is disposed in the oil pipe string and is blocked by the ball-casting sliding sleeve.

5. The double-layer fracturing string according to claim 4, characterized in that: Also included is a shear ball seat and a second ball; The shear ball seat is arranged on the oil pipe string and is located at the lower end of the oil pipe string; The second ball is disposed in the oil pipe string and is blocked by the shear ball seat.

6. The double-layer fracturing string according to claim 5, characterized in that: The radius of the first sphere is greater than the radius of the second sphere.

7. The double-layer fracturing string according to claim 1, characterized in that: It also includes safe hand-dropping; The safety release is arranged on the oil pipe string and is located between the first telescopic pipe and the double slip anti-unsealing packer.

8. The double-layer fracturing string according to claim 1, characterized in that: It also includes a backwash valve, which is arranged on the oil pipe string and located between the first telescopic pipe and the wellhead.

9. An operation method of a double-layer fracturing string without hydraulic anchors and capable of preventing sand jamming based on any one of claims 1 to 8, characterized in that: The steps include: The perforation of the two layers to be constructed is completed by TCP perforation. If it is an active production well or water injection well, there is no need to repeat the perforation; The pipe string is lowered into a predetermined position at the bottom of the well. At this time, the first sphere and the second sphere are not put in. The pipe string is first lifted up and then pressed down to complete the setting of the non-rotating gravity packer. At the same time, the wellhead needs to press down a set tonnage so that there is enough counterweight above the non-rotating gravity packer to ensure that the packer is completely set. While the pipe string is pressed down at the wellhead, the first telescopic tube and the second telescopic tube are in a fully recovered state under the action of the compression force; Put the second steel ball above the shear ball seat, apply hydraulic pressure to set the double slip anti-unsealing packer, and complete the sealing inspection operation by applying hydraulic pressure to the tubing string and casing annulus above the double slip anti-unsealing packer; When hydraulic pressure is applied to the tubing and exceeds the setting value of the packer's sealing force, the shear ball seat is driven into the bottom of the well to provide a channel for fracturing, and fracturing fluid is injected into the formation to fractur e the lowest layer; Put the first ball onto the ball-casting sleeve, open the ball-casting sleeve by hydraulic pressure, and perform fracturing of the upper layer, soak the well and release the well, or perform fracturing and release the well; Lift the pipe string to the set value and release the double slip anti-unsealing packer; Continue to lift the tubing string to pull open the second telescopic tube, continue to lift the tubing string to release the non-rotating gravity packer, and lift the tubing string out of the wellhead as a whole.

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