CN104373103A - A temporary plugging and repeated fracturing pipe string in old well fractures capable of large displacement construction and its method - Google Patents

Abstract

The invention belongs to the technical field of oilfield fracturing, and particularly relates to a temporary plugging repeated fracturing string in an old well fracture capable of being constructed at a large displacement, which comprises an oil pipe, a hydraulic anchor and a packer connected with the hydraulic anchor, wherein the lower end of the packer is connected with a straight nozzle sub sliding sleeve throttleer, and the oil pipe is 3¹/₂The oil pipe is connected with the hydraulic anchor through the buckle-changing adapter. The invention also provides a fracturing process, which comprises the following steps: 1) connecting a fracturing string; 2) setting a fracturing string; 3) temporarily blocking and fracturing; 4) large displacement fracturing; 5) after the construction is finished, open flow is controlled from the oil pipe, then the well is washed in a reverse circulation mode, the repeated transformation is finished, and finally the liquid drainage stage is carried out. Has the advantages that: within the size limit of the casing, compared with conventional 2⁷/₈Comparing fracturing oil pipe columns, adopting 3¹/₂The oil pipe and straight nozzle sub-sliding sleeve throttleer realizes continuous operation of a pipe column in construction with small displacement and large displacement, meets the requirement of temporary blocking and fracturing in a small displacement lower joint, and also realizes large displacement continuous operation.

Description

A temporary plugging and repeated fracturing pipe string in old well fractures capable of large displacement construction and its method

technical field

The invention belongs to the technical field of oilfield fracturing, and specifically relates to a pipe string for temporary plugging and repeated fracturing in old well fractures that can be constructed with a large displacement and a method, mainly for low-permeability reservoirs in old oilfield vertical wells with a large displacement (6 m ³ /min) for intra-fracture temporary plugging and refracturing, which is suitable for refracturing wells (well depth less than 2000m) with casing completion in formations with relatively small horizontal and two-dimensional stress differences and relatively developed natural fractures.

Background technique

At present, most oilfields in China have entered the medium-high water cut period, and the situation of stable production is severe. Refracturing of old wells has become one of the indispensable offensive measures for stable production of old oilfields.

For a medium-low water-cut well that only exploits one main layer, the current refracturing of old wells mainly involves refracturing techniques such as increasing the scale of sand addition, temporarily plugging old fractures and pressing new fractures. Since the fracturing process of temporarily plugging old fractures and pressing new fractures combines lateral creation of new fractures and improvement of old fracture conductivity, it has the advantages of communicating lateral residual oil in fractures, controlling the extension length of old fractures, and reducing the risk of water breakthrough. It has been widely used in oilfield refracturing stimulation.

Studies have shown that for low-permeability oilfields, where the reservoir is tight, relying solely on temporary plugging and pressure of new fractures, the fracture turning radius is small, the measures to increase production are low and the validity period is short. Transformation effects, such as light casing and large displacement hybrid fracturing. However, the bare casing high-volume fracturing technology in the early stage can only be used for wells with intact casings. At the same time, it is extremely difficult to implement the process of temporarily plugging and pressing new fractures in fractures under large-scale displacement, and blindly pursues to increase construction displacement to increase net fracturing. The magnitude of pressure is small. Therefore, there is a need for an integrated process string that can meet both temporary plugging fracturing under conventional displacement and large displacement construction.

Contents of the invention

The purpose of the present invention is to overcome the problem that the existing fracturing string cannot satisfy the large displacement construction at the same time under the temporary plugging fracturing under the conventional displacement.

For this reason, the present invention provides a temporary plugging refracturing string in old well fractures that can be constructed with a large displacement, including a tubing, a hydraulic anchor, and a packer connected to the hydraulic anchor. The lower end of the packer is connected with a Straight nozzle sliding sleeve restrictor, the oil pipe is 3 ¹ / ₂ "oil pipe, the oil pipe is connected with the hydraulic anchor through the buckle conversion joint.

The packer is a k344 type 2 ^7/8 _" packer.

The variable buckle conversion joint is a 3 ¹ / ₂ "-2 ⁷ / ₈ " variable buckle conversion joint.

The lower end of the packer is connected with the straight nozzle sliding sleeve restrictor through a 2 ^7/8 _" tubing nipple.

The present invention also provides a method for temporary plugging and repeated fracturing in old well fractures that can be constructed with a large displacement, comprising the following steps:

Step 1) Connect the fracturing string _: connect the 3 ^1/2 _" tubing, the 3 ^1/2 _" —2 ^7/8 " variable buckle adapter, the hydraulic anchor, the packer, and the 2 ^7/8 _" from top to bottom. "Oil pipe pup joint, straight nozzle sliding sleeve restrictor;

Step 2) Running the fracturing string: run the well through flushing, and run the temporarily blocked repeated fracturing string in the old well fractures that can be operated with a large displacement to the designed position, so that the straight nozzle sliding sleeve restrictor is located in the perforation Section top boundary 3-5m;

Step 3) Temporary plugging and fracturing stage: Sit on the fracturing wellhead, start the fracturing unit, and flush the well with a displacement of 0.3-0.5 cubic meters per minute. After the low displacement cycle is normal, the displacement is raised, and the conventional displacement of 1 ~2 cubic meters per minute to open the fracture after the packer is set normally, inject fracturing fluid from the wellhead tubing, and carry out temporary plugging and fracturing construction to realize temporary plugging and pressurization to create new fractures;

Step 4) Large-displacement fracturing stage: After the temporary plugging and pressing of new fractures is completed, steel balls are put in from the oil pipe, and the steel balls are sent to the ball seat of the straight nozzle sliding sleeve restrictor at a displacement of 0.3-0.5m ³ /min. After suppressing the pressure and cutting off the ball seat pin of the straight nozzle sliding sleeve restrictor, the steel ball and the straight nozzle sliding sleeve restrictor ball seat fall into the pocket at the bottom of the well, realizing the straight nozzle sliding sleeve restrictor and 2 ⁷ / ₈ " The full diameter of the tubing pup joint; after the ball seat sliding sleeve has obvious opening characteristics, increase the displacement to meet the design requirements for large-displacement main fracturing construction;

Step 5) After the construction is completed, first control the blowout from the oil pipe, then reverse circulation to wash the well, repeat the reconstruction, and finally transfer to the liquid drainage stage.

The beneficial effects of the present invention have the following points:

First, under the limitation of the casing size, compared with _the conventional 2 ^7/8 _" fracturing tubing string, the 3 ^1/2 " tubing and the straight nozzle sliding sleeve restrictor are used to realize the The continuous operation in construction with large displacement and large displacement not only meets the requirements of temporary plugging and fracturing in fractures with small displacement, but also realizes continuous operation with large displacement, which promotes the process of temporary plugging and repeated fracturing under large displacement. accomplish.

Second, integrating the advantages of temporarily plugging and pressing new fractures in fractures and increasing the complexity of fractures and increasing the bandwidth of fractures by large displacement, expanding the range of remaining oil in the lateral direction of fractures, and improving the effect of repeated stimulation. Crack 2 times.

Third, the string is equipped with a packer and a hydraulic anchor to protect the casing and fracturing string, so the construction safety is high.

Fourth, this string is also suitable for wells with corroded and perforated wellbore casings, and saves the engineering logging costs before large-volume hybrid fracturing with bare casings, and shortens the construction time while restoring the productivity of old wells. The cycle saves the construction cost and shows a strong economy.

Description of drawings

Fig. 1 is a structural schematic diagram of the present invention.

In the figure: 1, 3 ¹ / ₂ "oil pipe; 2, variable buckle adapter; 3, hydraulic anchor; 4, packer; _5. ^Straight nozzle sliding sleeve restrictor; 7. Casing.

Further details will be described below in conjunction with the accompanying drawings.

Detailed ways

Example 1:

In order to solve the problem that the existing fracturing string cannot satisfy the large-displacement operation under the temporary plugging fracturing under the conventional displacement, this embodiment provides a temporary plugging in the old well fracture that can be operated with a large displacement Refracturing string, including tubing, hydraulic anchor 3, and packer 4 connected to hydraulic anchor 3. The lower end of the packer 4 is connected with a straight nozzle sliding sleeve restrictor 5, and the tubing is 3 ¹ / ₂ "oil tubing 1. The oil pipe is connected to the hydraulic anchor 3 through the buckle conversion joint 2.

Connect the 3 ¹ / ₂ "oil pipe 1, variable buckle adapter 2, hydraulic anchor 3, packer 4, straight nozzle sliding sleeve restrictor 5 in order from top to bottom to form a fracturing string; the fracturing pipe The working process and principle of the string: Run the fracturing string into the downhole so that the straight nozzle sliding sleeve restrictor 5 is located at the top boundary of the perforation section 3-5m, because the straight nozzle sliding sleeve restrictor 5 (such as the aperture 25mm), the packer 4 is set, and then the fracturing fluid is injected from the wellhead tubing according to the design, and the temporary plugging and fracturing stage is carried out, so as to realize the temporary plugging and pressurization to create new fractures.

When the temporary plugging and pressing of the new seam is completed, put steel balls (such as ￠38mm, matching the ball seat) from the oil pipe, and send the ball to the 5 ball seat of the straight nozzle sliding sleeve restrictor at a displacement of 0.3-0.5m ³ /min. After suppressing the pressure and cutting off the ball seat pin of the straight nozzle sliding sleeve restrictor 5, the steel ball and the straight nozzle sliding sleeve restrictor 5 ball seat fall into the pocket at the bottom of the well, realizing the straight nozzle sliding sleeve restrictor 5 and 2 ⁷ / ₈ "full diameter of the tubing pup joint; after the opening characteristics of the ball seat sliding sleeve are obvious, increase the displacement to the design requirement for large displacement main fracturing construction, because the pipe string is in the stage of temporary plugging and pressing of new fractures to the stage of large displacement construction With continuity, the wellhead does not release pressure, ensuring safe construction.

The straight nozzle sliding sleeve restrictor 5 can realize the temporary plugging and fracturing operation in the fracture during the small displacement construction in the early stage; The 5 ball seats of the sliding sleeve choke are dropped into the pocket at the bottom of the hole together to ensure the full diameter of the choke body and the tubing string. With the help of the large diameter of 3 ^1/2 _" tubing string 1 string, large displacement fracturing operations are realized.

Example 2:

_This embodiment provides a ^temporary plugging repeated fracturing pipe string in old well fractures _that can ^be operated in large displacement as shown in Figure 1 ^. / ₈ "Variable buckle adapter 2, hydraulic anchor 3, packer 4, 2 ⁷ / ₈ " tubing nipple 6, straight nozzle sliding sleeve restrictor 5 are connected in sequence, and packer 4 is k344 type 2 ⁷ / ₈ "packer 4.

Since the variable buckle conversion joint 2 is a 3 ^1/2 _" -2 ^7/8 _" variable buckle conversion joint 2 _, the 3 ^1/2 "joint end is connected with the 3 ^1/2 "oil pipe 1, and the 2 ^7/8 _{" connector} is connected with the 2 ⁷ / ₈ "hydraulic anchor 3 is connected, and then sequentially connected to packer 4, 2 ⁷ / ₈ " tubing sub-joint 6, and straight nozzle sliding sleeve restrictor 5. In this embodiment, packer 4 is k344 type 2 ⁷ / ₈ "Packer 4.

The working process and principle of the fracturing string in this embodiment: run the fracturing string downhole so that the straight nozzle sliding sleeve throttle 5 is located at the top boundary of the perforation section 3-5m, due to the straight nozzle sliding sleeve throttling The throttling effect of the packer 5 (for example, the pore diameter ￠25mm), the packer 4 is set, and then the fracturing fluid is injected from the wellhead tubing according to the design, and the construction of the temporary plugging fracturing stage is carried out to realize the temporary plugging and pressurization to create new fractures.

When the temporary plugging and pressing of the new seam is completed, put steel balls (such as ￠38mm, matching the ball seat) from the oil pipe, and send the ball to the 5 ball seat of the straight nozzle sliding sleeve restrictor at a displacement of 0.3-0.5m ³ /min. After suppressing the pressure and cutting off the ball seat pin of the straight nozzle sliding sleeve restrictor 5, the steel ball and the straight nozzle sliding sleeve restrictor 5 ball seat fall into the pocket at the bottom of the well, realizing the straight nozzle sliding sleeve restrictor 5 and 2 ⁷ / ₈ "tubing sub-joint 6 full diameter; after the ball seat sliding sleeve has obvious opening characteristics, increase the displacement to the design requirements for large displacement main fracturing construction, because the pipe string is in the stage of temporary plugging and pressing of new fractures to large displacement construction The phases are continuous, the wellhead does not release pressure, and the variable diameter conversion of the construction string 3 ^1/2 _" to 2 ^7/8 _" tubing has a certain throttling effect under the large displacement to ensure that the packer 4 is always Keep setting to ensure safe construction.

Compared with the conventional 2 ⁷ / ₈ ″ fracturing tubing string, this string can not only temporarily plug old fractures and press new fractures in the fracture under conventional displacement, but also can perform large-volume fracturing under the same string. Through temporary The lateral fractures are created by plugging and boosting, and then the net pressure of the fractures is increased by large-scale construction, the complexity of the lateral fractures is increased, the fracture bandwidth is increased, and the residual oil in the lateral fractures is communicated to the greatest extent, ensuring the same well and the same layer refracturing effect. At the same time, because the string has packer 4 to protect the casing 7 above the perforation section, it not only saves the cost of engineering logging of casing 7 before using bare casing 7 for large displacement refracturing in old wells In addition, it is also applicable to old wells with corrosion and perforation in the casing 7, which not only saves construction costs, but also restores the productivity of old wells and improves the transformation effect.

Example 3:

The method for temporarily plugging repeated fracturing in old well fractures that can be constructed with a large displacement of the present invention comprises the following steps:

Step 1) Connect the fracturing string: Connect the 3 ^1/2 " tubing 1, ³ _1/2 " _—2 ^7/8 " variable buckle adapter 2, hydraulic anchor ₃ , packer 4, 2 ⁷ / ₈ "Oil pipe nipple 6, straight nozzle sliding sleeve restrictor 5;

Step 2) Running the fracturing string: Run the well flushing, and run the temporarily blocked repeated fracturing string in the old well fractures that can be operated with a large displacement to the designed position, so that the straight nozzle sliding sleeve restrictor 5 is located at the injection site. The top boundary of the hole section is 3-5m;

Step 3) Temporary plugging and fracturing stage: Sit on the fracturing wellhead, start the fracturing unit, wash the well with small displacement positive circulation and low replacement cycle, increase the displacement after the low replacement cycle is normal, and use the conventional displacement to make the packer 4 sit normally After sealing, the fractures are opened, and the fracturing fluid is injected from the wellhead tubing, and the construction of the temporary plugging and fracturing stage is carried out, so as to realize the temporary plugging and pressurization to create new fractures;

Step 4) Large-displacement fracturing stage: After the temporary plugging and pressing of new fractures is completed, steel balls are put into the tubing, and the steel balls are sent to the 5-ball seat of the straight nozzle sliding sleeve restrictor at a displacement of 0.3-0.5m ³ /min , after suppressing the pressure and cutting off the ball seat pin of the straight nozzle sliding sleeve restrictor 5, the steel ball and the straight nozzle sliding sleeve restrictor 5 ball seat fall into the pocket at the bottom of the well, realizing the straight nozzle sliding sleeve restrictor 5 and 2 ⁷ / ₈ "tubing sub-joint 6 full diameter; after the ball seat sliding sleeve has obvious opening characteristics, increase the displacement to the design requirements for large-displacement main fracturing construction;

Step 5) After the construction is completed, first control the blowout from the oil pipe, then reverse circulation to wash the well, repeat the reconstruction, and finally transfer to the liquid drainage stage.

In summary, under the limitation of the size of the casing 7, compared _with the conventional 2 ^7/8 _" fracturing tubing string, the present invention uses a 3 ^1/2 " tubing 1 and a straight nozzle sliding sleeve restrictor 5 to realize The continuous operation of one string in the construction of small displacement and large displacement not only meets the requirements of temporary plugging and fracturing in fractures with small displacement, but also realizes the effect of increasing the complexity of fractures and increasing the bandwidth of large displacement. It has the advantages of controlling the length of old fractures and reducing the risk of water breakthrough. It realizes continuous operation with large displacement, improves construction efficiency and stimulation effect, and facilitates the realization of temporary plugging and repeated fracturing under large displacement. At the same time, because the string has packer 4 to protect the casing 7 above the perforation section, it not only saves the cost of engineering logging of casing 7 before using bare casing 7 for large displacement refracturing in old wells In addition, it is also applicable to old wells with corrosion and perforation in the casing 7, which not only saves construction costs, but also restores the productivity of old wells and improves the transformation effect.

The fracturing pipe string and process of the present invention can be used for temporary plugging and repeated fracturing in fractures under the condition of large displacement of vertical wells in old oilfields with low permeability reservoirs, the well depth is less than 2000m, and the construction displacement is greater than 6m ³ /min.

The components and structures not described in detail in this embodiment belong to the known components and common structures or common means in this industry, and are not described here one by one.

The above examples are only illustrations of the present invention, and do not constitute a limitation to the protection scope of the present invention. All designs that are the same as or similar to the present invention fall within the protection scope of the present invention.

Claims (5)

1. A pipe string for temporary plugging and repeated fracturing in old well fractures that can be constructed with a large displacement, including tubing, a hydraulic anchor (3), and a packer (4) connected to the hydraulic anchor (3), characterized in that: The lower end of the packer (4) is connected with a straight nozzle sliding sleeve restrictor (5), and the oil pipe is a 3 ¹ / ₂ "oil pipe (1), and the oil pipe is connected to the hydraulic anchor through the variable buckle conversion joint (2) (3) Connection. 2. A pipe string for temporary plugging and repeated fracturing in old well fractures that can be constructed with a large displacement according to claim 1, characterized in that: the variable buckle adapter (2) is 3 ¹ / ₂ "-2 ⁷ / ₈ 〞change buckle adapter. 3. According to claim 2, a pipe string for temporary plugging and repeated fracturing in old well fractures capable of large displacement construction, characterized in that: the packer (4) is a K344 type 2 ⁷ / ₈ ″ packer separator. 4. A temporary plugging and repeated fracturing string in old well fractures that can be constructed with a large displacement according to claim 3, characterized in that: the lower end of the packer (4) passes through a short 2 ⁷ / ₈ ″ tubing Joint (6) is connected with the straight nozzle sliding sleeve restrictor (5). 5. A method for temporarily plugging and repeated fracturing in old well fractures capable of large displacement construction, characterized in that it comprises the following steps: Step 1) Connect the fracturing string _: connect the 3 ^1/2 _" tubing (1), 3 ^1/2 _" -2 ^7/8 " variable buckle adapter (2), hydraulic anchor (3) in order from top to bottom , Packer (4), 2 ⁷ / ₈ "tubing nipple (6), straight nozzle sliding sleeve restrictor (5); Step 2) Running the fracturing string: run the well flushing, and run the temporarily blocked repeated fracturing string in the old well fractures that can be operated with a large displacement to the designed position, so that the straight nozzle sliding sleeve restrictor (5) 3-5m at the top of the perforation section; Step 3) Temporary plugging and fracturing stage: Sit on the fracturing wellhead, start the fracturing unit, and flush the well with a displacement of 0.3-0.5 cubic meters per minute. After the low displacement cycle is normal, the displacement is raised, and the conventional displacement of 1 ~2 cubic meters per minute to open the fracture after the packer (4) is set normally, inject fracturing fluid from the wellhead tubing, and carry out temporary plugging and fracturing construction to realize temporary plugging and pressurization to create new fractures; Step 4) Large-displacement fracturing stage: After the temporary plugging and pressing of new fractures is completed, steel balls are put in from the oil pipe, and the steel balls are sent to the straight nozzle sliding sleeve restrictor (5) at a displacement of 0.3-0.5m ³ /min Ball seat, pressurize and cut off the ball seat pin of the straight nozzle sliding sleeve restrictor (5), the steel ball and the straight nozzle sliding sleeve restrictor (5) ball seat fall into the pocket at the bottom of the well to realize the straight nozzle sliding sleeve The restrictor (5) and the 2 ⁷ / ₈ "tubing nipple (6) are full-bore; after the ball seat sliding sleeve has obvious opening characteristics, the displacement is increased to the design requirement for large-displacement main fracturing construction; Step 5) After the construction is completed, first control the blowout from the oil pipe, then reverse circulation to wash the well, repeat the reconstruction, and finally transfer to the liquid drainage stage.