A one-trip dual-layer fracturing pipe string and operation method capable of preventing sand from sticking to a hydraulic anchor

Abstract

The present application relates to a kind of hydraulic anchor sand prevention one-way double-layer fracturing pipe column and operating method, pipe column includes: casing, the casing has at least two perforating sections;Tubing string is arranged in the casing;First telescopic pipe and second telescopic pipe, the first telescopic pipe and the second telescopic pipe are sequentially spaced in series on the tubing string from top to bottom, to divide the tubing string into multiple sections;Double-grip anti-decapping packer, it is located between the first telescopic pipe and the second telescopic pipe and is sleeved on tubing string outer, for forming upper layer seal between tubing string and casing;Non-rotating gravity type packer, it is located between the bottom of the casing and the second telescopic pipe and is sleeved on tubing string outer, for forming lower layer seal between tubing string and casing.The present application can minimize the risk of pipe column sand sticking.

Description

Technical Field

[0001] This invention relates to the field of oil and gas extraction technology, specifically to a double-layer fracturing tubing string and operation method that can prevent sand jamming without hydraulic anchors. Background Technology

[0002] For low-porosity and permeability reservoirs, fracturing is an effective means of increasing production. Currently, most offshore low-permeability oilfields are fracturing two layers. Conventional simple fracturing tubing mainly uses a combination of hydraulic anchor, multi-stage Y344 packer or Y441 packer and sliding sleeve sandblasting device to perform layered fracturing of the reservoir. Although it has significant advantages in tubing tripping and operation, for the large-size casing commonly used in offshore oilfields (such as 7in and 9-5 / 8in), there is a large amount of sand accumulation in the annulus, and the hydraulic anchor cannot be restored after fracturing, resulting in multiple sand jams in the tubing after fracturing, and subsequent well workover 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 slip, causing the rubber sleeve to tear and the seal to fail. Summary of the Invention

[0003] To address the aforementioned problems, the purpose of this invention is to provide a hydraulically anchor-free, sand-block-resistant double-layer fracturing tubing string and its operation method. The tubing string is lowered in one run, and two types of packers on the tubing string are set by operations such as lifting, lowering, and pressurizing. After fracturing, the two packers are released step-by-step by lifting the tubing string, minimizing the risk of sand blockage in the tubing string.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] The present invention discloses a hydraulically anchor-free, sand-block-resistant, double-layer fracturing tubing string comprising: a casing having at least two perforated sections; a tubing string disposed within the casing; a first telescopic tube and a second telescopic tube, the first and second telescopic tubes being sequentially connected in series from top to bottom on the tubing string to divide the tubing string into multiple segments; a double-slip anti-unsealing packer, fitted outside the tubing string and located between the first and second telescopic tubes, for forming an upper seal between the tubing string and the casing; and a non-rotating gravity packer, fitted 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.

[0006] Preferably, in the aforementioned double-layer fracturing string, the double-slip anti-unsealing packer has a first slip and a second slip, the first slip and the second slip being respectively disposed at the upper end and the lower end of the double-slip anti-unsealing packer;

[0007] The first slip and the second slip are respectively connected to the slips of the oil pipe string.

[0008] Preferably, in the aforementioned double-layer fracturing tubing string, the upper end of the non-rotating gravity packer is provided with a third slip, which is connected to the tubing string slip.

[0009] Preferably, the double-layer fracturing string further includes a ball-throwing sleeve and a first ball; the ball-throwing sleeve is disposed on the tubing string and located between the second telescopic tube and the non-rotating gravity packer; the first ball is disposed inside the tubing string and is blocked by the ball-throwing sleeve.

[0010] Preferably, the double-layer fracturing tubing string further includes a shear ball seat and a second ball; the shear ball seat is disposed on the tubing string and located at the lower end of the tubing string; the second ball is disposed inside the tubing string and is blocked by the shear ball seat.

[0011] Preferably, in the aforementioned double-layer fracturing string, the radius of the first sphere is larger than the radius of the second sphere.

[0012] Preferably, the aforementioned double-layer fracturing tubing string also includes a safety release mechanism; the safety release mechanism is installed on the tubing string and located between the first telescopic tube and the double slip anti-unsealing packer.

[0013] Preferably, the double-layer fracturing tubing string further includes a backwash valve, which is disposed on the tubing string and located between the first telescopic pipe and the wellhead.

[0014] The method for operating a double-layer fracturing tubing string without hydraulic anchors to prevent sand jamming, as described in this invention, includes the following steps:

[0015] The two sections to be constructed are perforated using the TCP perforation method. If the well is an in-service production well or a water injection well, it is not necessary to repeat the perforation process.

[0016] The tubing string is lowered to the predetermined position at the bottom of the well. At this time, neither the first ball nor the second ball has been deployed. The tubing string is first lifted and then pressed down to complete the setting of the non-rotating gravity packer. At the same time, the wellhead needs to be pressed down to a set tonnage so that there is enough counterweight above the non-rotating gravity packer to ensure that the packer is fully set. While the tubing string is being pressed down at the wellhead, the first telescopic tube and the second telescopic tube are in a fully retracted state under the action of compression force.

[0017] The second steel ball is placed above the shear ball seat, and hydraulic pressure is applied to set the double slip anti-unsealing packer. Hydraulic pressure is then applied to the oil pipe string and casing annulus above the double slip anti-unsealing packer to complete the seal verification operation.

[0018] When hydraulic pressure is pumped into the tubing and exceeds the set value of the packer's setting 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 perform fracturing of the lowest layer.

[0019] The first ball is dropped above the ball-dropping sleeve, hydraulic pressure is applied to open the ball-dropping sleeve, and fracturing is performed on the next layer, followed by well shut-in and blowout, or fracturing and blowout.

[0020] Raise the tubing string to the set value and release the double slip anti-unsealing packer;

[0021] Continue to lift the tubing string to open the second telescopic tube, continue to lift the tubing string to release the non-rotating gravity packer, and then lift the entire tubing string out of the wellhead.

[0022] The present invention has the following advantages due to the adoption of the above technical solutions:

[0023] (1) This invention allows two packers to be run in one tubing run, and two layers of fracturing construction to be completed in one tubing run; it prevents well jamming accidents caused by the superposition of risks of multiple packers being buried in sand when the tubing is pulled up.

[0024] (2) The present invention eliminates the shrinkage preload of the tubing by adding a first telescopic tube, and at the same time abandons the hydraulic anchor, thereby greatly reducing the risk of tubing sand jamming;

[0025] (3) The present invention compensates for the shrinkage of the tubing string during fracturing by installing a first telescopic tube on the double slip anti-unsealing packer, thereby preventing the double slip anti-unsealing packer from being missealed;

[0026] (4) The present invention connects a second telescopic tube between the two packers, thereby realizing the step-by-step unsealing of the two packers;

[0027] (5) The present invention opens the safety release by using ball-throwing pressure or over-lifting. When the tubing is stuck in sand, the tubing above the safety release can be lifted out, reducing the amount of well workover work.

[0028] (6) The present invention can open the backwash valve by annular pressure to realize the backwash well and the well control operation before dismantling the wellhead. Attached Figure Description

[0029] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts. In the drawings:

[0030] Figure 1 This is a schematic diagram of the structure of a double-layer fracturing tubing string that is free of hydraulic anchors and can prevent sand jamming, as described in this invention.

[0031] The labels for the attached figures are as follows:

[0032] 1-Tubing string; 2-Backwash valve; 3-First telescopic tube; 4-Safety release; 5-Double slip anti-dislodgement packer; 5-1-First slip; 5-2-Second slip; 6-Second telescopic tube; 7-First perforation section; 8-First sphere; 9-Throwing sleeve; 10-Non-rotating gravity packer; 10-1-Third slip; 11-Second sphere; 12-Shear ball seat; 13-Second perforation section; 14-Casing. Detailed Implementation

[0033] Exemplary embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art.

[0034] This invention provides a single-run, double-layer fracturing tubing string and operation method that prevents sand jamming without hydraulic anchors. Two packers are run in a single run, completing two layers of fracturing in one run. This prevents well jamming accidents caused by the cumulative risk of sand burial from multiple packers during tubing string retraction. The addition of a first telescopic pipe eliminates the tubing string's contraction pre-tightening force, while simultaneously eliminating the need for hydraulic anchors, thus significantly reducing the risk of tubing string sand jamming. The installation of a first telescopic pipe on the double-slip anti-unsealing packer compensates for tubing string contraction during fracturing, preventing the double-slip anti-unsealing packer from being mis-sealed. A second telescopic pipe connects the two packers, enabling step-by-step unsealing of the two packers.

[0035] like Figure 1 As shown, the present invention provides a hydraulically anchor-free, sand-resistant, double-layer fracturing string, comprising: a casing 14 having at least two perforated sections, namely a first perforated section 7 and a second perforated section 13; a tubing string 1 disposed within the casing 14; a first telescopic tube 3 and a second telescopic tube 6, which are sequentially connected in series from top to bottom on the tubing string 1 to divide the tubing string 1 into multiple segments; a double-slip anti-unsealing packer 5, fitted outside the tubing string 1 and located between the first telescopic tube 3 and the second telescopic tube 6, for forming an upper seal between the tubing string 1 and the casing 14; and a non-rotating gravity packer 10, fitted outside the tubing string 1 and located between the bottom of the casing 14 and the second telescopic tube 6, for forming a lower seal between the tubing string 1 and the casing 14.

[0036] It should be noted that the first telescopic tube has a telescopic function and can be stretched to 1.5 meters or even longer. During the lowering of the tubing string, due to the weight of the tubing string itself, the first telescopic tube is in a fully extended state. When the tubing string reaches the predetermined depth and is pressed down to set the non-rotating gravity packer, the stretched part of the first telescopic tube will be in a state of maximum contraction. When fracturing occurs, the tubing string temperature decreases and it contracts as a whole. At this time, the contracted part of the first telescopic tube begins to stretch, which plays a compensating role for the tubing string. Without the first telescopic tube, the tubing string would tend to shorten, resulting in a large preload. This preload could potentially unseal the double slip anti-unsealing packer. Due to the presence of the first telescopic tube, there is no preload on the tubing string above the double slip anti-unsealing packer, and the double slip anti-unsealing packer is not at risk of being unsealed.

[0037] The second telescopic tube operates on the same principle as the first telescopic tube. When the downcompression string sets the lower non-rotating gravity packer, the second telescopic tube is also in its shortest extension state. When the double-slip packer is released after fracturing, due to the presence of the second telescopic tube, the release force of lifting the string is only used to release the double-slip anti-release packer. After releasing this packer, the string is lifted again, and the second telescopic tube will extend and retract. Then, the string is lifted again to release the lower non-rotating gravity packer, thus achieving step-by-step release of the packers. Due to sand jamming after fracturing, the required lifting force for both packers is approximately 20 tons. With the presence of the second telescopic tube, the release of the two packers can be carried out step-by-step, with each packer requiring a lifting force of 20 tons. Without the second telescopic tube, a lifting force of 40 tons is required to release the upper double-slip anti-release packer, and the lower non-rotating gravity packer will also be released simultaneously.

[0038] In the above embodiment, preferably, the double slip anti-unsealing packer 5 has a first slip 5-1 and a second slip 5-2, the first slip 5-1 and the second slip 5-2 being respectively disposed at the upper end and the lower end of the double slip anti-unsealing packer 5;

[0039] The first slip 5-1 and the second slip 5-2 are respectively connected to the slip of the oil pipe string 1.

[0040] It should be noted that the double-slip anti-unsealing packer 5 is set by hydraulic pressure at the wellhead and unsealed by lifting the tubing string. This packer has a first slip and a second slip. When there is high pressure in the lower annulus of the rubber sleeve of the double-slip anti-unsealing packer 5, the upper slip (i.e., the first slip) can counteract the piston force caused by the lower annulus of the rubber sleeve. Therefore, this packer will not be unsealed when there is high pressure in the lower annulus of the rubber sleeve. This is the biggest difference between this packer and the conventional Y441 packer, hence the name anti-unsealing packer. However, the unsealing method of this packer is the same as that of the conventional Y441 packer, which is to lift the tubing string to unseal.

[0041] In the above embodiments, preferably, the upper end of the non-rotating gravity packer 10 is provided with a third slip 10-1, which is connected to the slip of the tubing string 1.

[0042] It should be noted that the non-rotating gravity packer 10 belongs to the Y221 packer. The packer is set by lifting the tubing string and pressing down the tubing string. The force of the pressing down tubing string needs to be large enough to fully compress the rubber sleeve of the packer. The packer has a lower anchor shoe, which has a unidirectional anchoring function and can ensure that the packer will not slide down the casing during the pressing process. When fracturing, the third slip will open under the pressure difference of the annulus and prevent the packer from being unsealed by the upper push.

[0043] In the above embodiments, preferably, the present invention further includes a ball-throwing slide 9 and a first ball 8; the ball-throwing slide 9 is disposed on the oil pipe string 1 and located between the second telescopic pipe 6 and the non-rotating gravity packer 10; the first ball 8 is disposed inside the oil pipe string 1 and is blocked by the ball-throwing slide 9.

[0044] In the above embodiments, preferably, the present invention further includes a shear ball seat 12 and a second ball 11; the shear ball seat 12 is disposed on the oil pipe string 1 and located at the lower end of the oil pipe string 1; the second ball 11 is disposed inside the oil pipe string 1 and is blocked by the shear ball seat 12.

[0045] The radius of the first sphere 8 is greater than the radius of the second sphere 11.

[0046] It should be noted that when it is necessary to set the double slip anti-unsealing packer, hydraulic pressure needs to be applied. In order to build up high pressure in the tubing string, a second steel ball is inserted, and hydraulic pressure is applied into the tubing string to the set value to set the double slip anti-unsealing packer. Then, the pressure value is increased to drive the ball seat part of the shear ball seat into the bottom of the well, providing a channel for fracturing.

[0047] Once the bottom layer of fracturing is complete, the first steel ball 8 can be dropped, and the dropping sleeve 9 can be opened to begin the second layer of fracturing.

[0048] In the above embodiments, preferably, the present invention further includes a safety release handle 4; the safety release handle 4 is disposed on the tubing string 1 and located between the first telescopic pipe 3 and the double slip anti-unsealing packer 5. Thus, the safety release handle does not function during fracturing. When the tubing string encounters a problem and cannot be pulled out of the wellhead, a steel ball can be inserted into the safety release handle to apply hydraulic pressure. This causes the safety joint to detach from the tubing string above the safety release handle, allowing it to be pulled out of the wellhead.

[0049] In the above embodiments, preferably, the present invention further includes a backwash valve 2, which is disposed on the tubing string 1 and located between the first telescopic pipe 3 and the wellhead. Thus, the backwash valve can achieve backwashing. When the annular pressure reaches the opening value of the backwash valve, the internal valve of the backwash valve opens, the passage of the annulus is opened, and the fluid in the annulus can enter the tubing to achieve backwashing and well control, ensuring well control safety during subsequent tubing string tripping.

[0050] This invention also provides a method for operating a double-layer fracturing tubing string without hydraulic anchors to prevent sand jamming, comprising the following steps:

[0051] (1) The perforation of the two sections to be constructed is completed by TCP perforation. If it is an in-service production well or water injection well, it is not necessary to repeat the perforation.

[0052] (2) The tubing string is lowered to the predetermined position at the bottom of the well. At this time, neither the first ball nor the second ball is put in. The tubing string is first lifted and then pressed down to complete the setting of the non-rotating gravity packer. At the same time, the wellhead needs to be pressed down to 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 retracted state under the action of compression force.

[0053] (3) The second steel ball is placed above the shear ball seat, and hydraulic pressure is applied to set the double slip anti-unsealing packer. Hydraulic pressure is applied to the oil pipe string and casing annulus above the double slip anti-unsealing packer to complete the sealing operation.

[0054] (4) Pump hydraulic fluid into the tubing and drive the shear ball seat into the bottom of the well, exceeding the packer's setting force by 8-10 MPa, to provide a channel for fracturing. Inject fracturing fluid into the formation to perform fracturing of the lowest layer.

[0055] (5) Drop the first ball above the ball-dropping sleeve, apply hydraulic pressure to open the ball-dropping sleeve, and perform fracturing of the next layer, then shut the well and release the blowout, or perform fracturing and release the blowout.

[0056] (6) Raise the tubing to the set value and release the double slip anti-unsealing packer;

[0057] (7) Continue to lift the tubing string to open the second telescopic tube, continue to lift the tubing string to unseal the non-rotating gravity packer, and pull the entire tubing string out of the wellhead.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A double-layer fracturing tubing string without hydraulic anchors to prevent sand jamming, characterized in that, include: A casing having at least two perforated sections; The tubing string is installed inside the casing; The first telescopic tube and the second telescopic tube are connected in series from top to bottom at intervals on the oil pipe string to divide the oil pipe string into multiple segments; The double slip anti-unsealing packer 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. A non-rotating gravity packer is fitted 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; The double slip anti-unsealing packer has a first slip and a second slip, which are respectively disposed 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 tubing string slip; The upper end of the non-rotating gravity packer is provided with a third slip, which is connected to the tubing string slip; It also includes a pitching slide and a first ball; the pitching slide is disposed on the oil pipe string and located between the second telescopic pipe and the non-rotating gravity packer; the first ball is disposed inside the oil pipe string and is blocked by the pitching slide; It also includes a shear ball seat and a second ball; the shear ball seat is disposed on the tubing string and located at the lower end of the tubing string; the second ball is disposed inside the tubing string and is blocked by the shear ball seat; It also includes a safety release mechanism; the safety release mechanism is installed on the tubing string and is located between the first telescopic tube and the double slip anti-unsealing packer.

2. The double-layer fracturing string according to claim 1, characterized in that, The radius of the first sphere is greater than the radius of the second sphere.

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

4. A method for operating a double-layer fracturing tubing string without hydraulic anchors to prevent sand jamming, based on any one of claims 1 to 3, characterized in that, Includes the following steps: The two sections to be constructed are perforated using the TCP perforation method. If the well is an in-service production well or a water injection well, it is not necessary to repeat the perforation process. The tubing string is lowered to the predetermined position at the bottom of the well. At this time, neither the first ball nor the second ball has been deployed. The tubing string is first lifted and then pressed down to complete the setting of the non-rotating gravity packer. At the same time, the wellhead needs to be pressed down to a set tonnage so that there is enough counterweight above the non-rotating gravity packer to ensure that the packer is fully set. While the tubing string is being pressed down at the wellhead, the first telescopic tube and the second telescopic tube are in a fully retracted state under the action of compression force. The second steel ball is placed above the shear ball seat, and hydraulic pressure is applied to set the double slip anti-unsealing packer. Hydraulic pressure is then applied to the oil pipe string and casing annulus above the double slip anti-unsealing packer to complete the seal verification operation. When hydraulic pressure is pumped into the tubing and exceeds the set value of the packer's setting 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 perform fracturing of the lowest layer. The first ball is dropped above the ball-dropping sleeve, hydraulic pressure is applied to open the ball-dropping sleeve, and fracturing is performed on the next layer, followed by well shut-in and blowout, or fracturing and blowout. Raise the tubing string to the set value and release the double slip anti-unsealing packer; Continue to lift the tubing string to open the second telescopic tube, continue to lift the tubing string to release the non-rotating gravity packer, and then lift the entire tubing string out of the wellhead.

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