CN110984937A - Fracturing-bearing casing and single-well SAGD development method based on fracturing-bearing casing - Google Patents

Abstract

The invention discloses a casing with fracturing and a single-well SAGD development method based on the casing with fracturing. The device has the advantages of reasonable structure, convenient use and strong tolerance under extreme working conditions. The perforation part can support the fracturing process and the long-time SAGD exploitation under the support of the fixed connection device, and the fixed connection device is connected with the outer wall of the casing through precision welding, so that the stable operation of the underground coal mine well casing under the long-time extreme working condition is ensured. The development method provided by the invention greatly improves the oil extraction speed of single-well SAGD and improves the stability of SAGD production under medium-high obstruction.

Description

Fracturing-bearing casing and single-well SAGD development method based on fracturing-bearing casing

Technical Field

The invention relates to the technical field of oil reservoir exploitation, in particular to a casing with fracturing and a single-well SAGD development method based on the casing with fracturing.

Background

SAGD (steam assisted gravity drainage), namely steam assisted gravity drainage, is a technology for developing a heavy oil reservoir and an effective technology for realizing the exploitation of heavy oil and oil sand, but the application effect of SAGD is greatly influenced by geological factors (reservoir thickness, shale interlayers, lean oil layers and the like). In order to overcome the influence of adverse geological factors and improve the application effect of the SAGD technology under different geological conditions, various modified SAGD technologies are proposed, and the single-well SAGD technology is one of the SAGD technologies.

The single well SAGD technology adopts a specially designed well completion pipe string, only one well is adopted in the production process, and the injection of steam and the extraction of crude oil are completed simultaneously. The single-well SAGD technology can effectively overcome the influence of adverse geological factors such as a thin reservoir and the like, and realize the economic and effective exploitation of the heavy oil reservoir under special geological conditions. The single-well SAGD technology is suitable for thinner oil reservoirs and can be used for thin-layer heavy oil reservoir exploitation with the reservoir thickness of 10-15 m. In the starting stage, the heat circulation channel can be formed more quickly, and the early production is higher.

When the vertical permeability of the reservoir is low or the reservoir is distributed with the interlayer, the vertical expansion of the steam cavity and the speed of gravity drainage can be influenced. Lean oil layers in the reservoir will increase heat loss and reduce economic benefits. These factors can affect the effectiveness of the application of single horizontal well SAGD technology.

Disclosure of Invention

The invention aims to provide a casing with fracturing and a single-well SAGD development method based on the casing with fracturing, which are used for solving the problems in the prior art, better overcoming the unfavorable conditions of low vertical permeability of a reservoir layer, poor oil layer and the like, and realizing high-efficiency high-speed exploitation of thick oil.

In order to achieve the purpose, the invention provides the following scheme: the invention provides a casing with a fracturing function, which comprises a casing and a welding support, wherein the casing is a four-wing casing, and when the casing is expanded mechanically, each wing is opened by the same amount and is kept in a locked opening state after being expanded; the welding bracket is arranged on the top of the four-wing sleeve and is arranged on the inner wall of the sleeve for limiting the opening width of each wing, and the conical shoulder of the four-wing sleeve is pulled into the welding bracket; and each wing surface of the four-wing casing is provided with a perforation, and the perforation is used for injecting fracturing fluid during fracturing operation.

Preferably, a steam injection pipe and a liquid production pipe are arranged in the inner cavity of the four-wing sleeve.

Preferably, the proppant of the fracturing fluid is garnet sand, and the expanded length of the four-wing casing is covered with gravel for the slotted liner.

Preferably, four perforating holes are uniformly arranged on the outer side of each airfoil, the perforating holes on the four airfoils form four perforating areas in total, and adjacent perforating areas are spaced from each other by a quarter of the circumference of the outer cylinder wall.

Preferably, the perforation is laser perforation.

Preferably, an associated device is arranged outside the perforation area.

A single-well SAGD development method based on a casing with a fracturing function comprises the casing with the fracturing function and further comprises the following steps:

the well is completed by adopting double-tubular columns in the deflecting section, a steam injection pipe and a liquid production pipe are parallelly arranged in the deflecting section of the well, and only the steam injection pipe is arranged in the horizontal section (fracturing section);

the four-wing casing is put into a fracturing section, and when fracturing construction is carried out, firstly, a mechanical method is adopted to expand the wing surface of the casing at the bottommost part to form uniformly distributed grooves, and then fracturing liquid is injected through perforation to carry out fracturing operation, so that a plurality of fracturing support surfaces in contact with an oil reservoir are formed;

and performing fracturing operation on the reservoir section at the front part section by section through the expanded four-wing casing by the same operation, and finally forming a fracturing support surface penetrating through the whole fracturing section.

Compared with the prior art, the invention has the following technical effects:

1. the device has reasonable structure and simple and convenient use, and can carry out high-speed and high-efficiency fracturing operation, steam injection operation and oil extraction operation by using one set of pipe column without repeatedly replacing the pipe column.

2. The present invention provides for the production performance (as net present value NPV) of a fractured single well SAGD in clean McMurray channel sand₁₀Measured) exceeds the conventional horizontal well by a factor of 2 for SAGD.

3. Except early, in homogeneous sandstones where the vertical permeability fluctuates in the range of 0.4 to 2.0 darcy, no loss in performance of the fractured single well SAGD occurred.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

FIG. 1 is a front view of a four-winged casing string configuration design for a single well SAGD fracturing section;

FIG. 2 is a schematic top view of a single well SAGD fracturing section tubular column structural design after completion;

FIG. 3 is a schematic diagram of a single well SAGD development mode after completion of a fracturing operation;

FIG. 4 is a schematic illustration of an airfoil formed after a four wing sleeve fracturing operation;

wherein, 1, a four-wing sleeve; 2 associating means; 3, perforating; 4, a steam injection pipe; 5 producing oil pipe; 6, welding a bracket; 7 oil reservoir; 8 oil-well pump.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The invention aims to provide a casing with fracturing and a single-well SAGD development method based on the casing with fracturing, which are used for solving the problems in the prior art, better overcoming the unfavorable conditions of low vertical permeability of a reservoir layer, poor oil layer and the like, and realizing high-efficiency high-speed exploitation of thick oil.

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.

As shown in fig. 1-4, the invention provides a casing with fracturing and a single-well SAGD development method based on the casing with fracturing.

The fracturing sleeve with the pressure comprises a four-wing sleeve 1 and a welding support 6, wherein the wing surface position of the four-wing sleeve 1 is provided with a perforation 3, and the perforation 3 is arranged on the outer wall of the sleeve and used for injecting fracturing fluid during fracturing operation; the top of the four-wing sleeve 1 is provided with a welding bracket 6, the welding bracket 6 being provided on the inner wall of the sleeve for limiting the opening width of each wing, its tapered shoulder being drawn into the bracket, preventing the housing from closing once fully deployed.

Four perforation 3 zones are evenly arranged along the outer wall of the casing to realize airfoil molding, and the adjacent zones are separated from each other by a distance 1/4 from the circumference of the outer cylinder wall; the position of the perforation 3 is superposed with the position of the airfoil surface; the size of the perforation 3 is 5mm, and the two perforations are arranged in parallel and sparsely to realize fracturing better; and selecting laser perforation as the perforation mode. And the outer side of the perforation 3 area is reinforced by the associated device 2, so that stable operation is ensured without damage during fracturing. The diameter of the casing is 31.12 cm, and the position of the outer flank perforation 3 is connected with the shaft by precision welding. The tube contains a steam injection tube 4 of 11.5 cm diameter and the annular space is filled with a cover gas. During expansion, the high pressure gas drives the formation to mechanically expand with about 10% radial strain.

On mechanical expansion of the four-wing sleeve 1, the airfoil will separate along the pre-aligned planes, all wings open by the same amount and remain locked open after expansion. A four-wing casing 1 for cased holes may be used to stimulate the airfoil. The multi-directional housing of the four-wing sleeve 1 has a series of laser cuts to form pre-aligned flats, and a weld bracket 6 limits the width of the opening of each wing, with its tapered shoulder being drawn into the bracket, preventing the housing from closing once fully deployed. The casing string is cemented in place with hot cement through the inner string bore. Independent stimulation of each wing in the cannula system is achieved by a special azimuthally aligned treatment tool. Upon mechanical expansion, the four-winged sleeve 1 has four grooves in its outer surface to form pre-aligned planes.

The casing, cement and formation are mechanically expanded to a radial strain of about 10% to split the casing and cement along pre-aligned planes of weakness. During fracturing operation, one fracturing fluid is injected into the wings in each direction in sequence, a penetration surface is completely installed in the whole thickness of the oil reservoir 7, and gravels are filled in the penetration surface.

Each azimuth wing is independently stimulated by a dedicated azimuth alignment treatment tool, and a high viscosity clean fracturing fluid carrying garnet sand proppant is injected into each azimuth wing in turn, forming a highly permeable airfoil. After the innermost section is completed, the next level is expanded and stimulated, and the pore pressure relief helps to ensure coalescence with deeper regions of the airfoil. This process is repeated until the permeable surface is fully installed throughout the length of the fracture.

Wherein, the single well is filled with garnet sand in the casing and is covered with slotted liner gravel on the expansion length thereof to strengthen the well, thereby adapting to the heat load.

The single-well SAGD development method based on the casing with the fracturing comprises the following steps:

the well deflecting section adopts double-string well completion, and a steam injection pipe 4 and an oil production pipe 5 are parallelly arranged; the horizontal section (fracturing section) is only provided with a steam injection pipe 4; the annular space is filled with a cover gas. A specially designed four-wing casing 1 is set in the fracturing section and is arranged at the rear 2/5 of the horizontal section. When in fracturing construction, firstly, a mechanical method is adopted to expand the bottommost sleeve wing surface to form uniformly distributed grooves, and then fracturing fluid is injected to perform fracturing operation to form a plurality of fracturing support surfaces which are in contact with the oil reservoir 7. And sequentially fracturing the front reservoir section by adopting the same method to finally form a fracturing support surface penetrating through the whole fracturing section.

The well was 31.12 cm in diameter with a 24.45 cm diameter casing string of K55 cemented in place by hot cement through the bore of the inner string. The wings in each azimuth are stimulated independently by a dedicated azimuth alignment treatment tool, and a high viscosity clean fracturing fluid with a proppant of 12/20 mesh garnet sand is injected into each azimuth wing in turn to form a high permeability penetration surface about 40 meters long and 2.5 centimeters wide. The steam injection planes need to have high permeability throughout the life cycle of the well, so that a garnet sand proppant with better steam resistance is selected. After the bottommost portion is completed, the next level is expanded and stimulated, and pore pressure relief helps ensure coalescence with the vertical plane of the deeper region. This process is repeated until the permeable surface is installed for the entire length of the fracture.

The 24.5 cm casing was filled with 12/20 resin coated garnet sand and covered with 17.78 cm slotted liner gravel over its expanded length to strengthen the wellbore wall to accommodate thermal loading. The well contained a vacuum insulated tube 11.5 cm in diameter for steam injection. The proppant was selected as an 12/20 mesh garnet sand because the injected flat surface needs to have high permeability throughout the life of the well, and this material has high steam resistance.

During SAGD production, steam is injected into the fracturing section, the steam diffuses towards the top of the oil reservoir 7 and the periphery of the shaft, the oil reservoir 7 is heated to reduce the viscosity of crude oil, and hot oil and condensate water flow into the front section of the shaft from the oil drainage channel under the action of gravity and are lifted to the ground by the oil well pump 8, so that the purpose of thick oil exploitation is achieved.

The single well SAGD production with fracturing provides another completion system than traditional horizontal well pair SAGD. The support plane contains 12/20 steam resistant garnet sand to maintain high permeability around the well over the life cycle. Compared with traditional SAGD, single well SAGD is almost unaffected by the vertical permeability of the formation.

Performance of fractured single well SAGD in clean McMurray channel sands (NPV as net present value) by constructing multiple permeable planes throughout the fracture length₁₀Measured) exceeds the conventional horizontal well by a factor of 2 for SAGD. Except early, in homogeneous sandstones where the vertical permeability fluctuates in the range of 0.4 to 2.0 darcy, no loss in performance of the fractured single well SAGD occurred. Also, the performance of the fractured single well SAGD is not affected at medium to high impediments. In such cases, however, significant performance losses occur with oil production and CSOR for conventional horizontal SAGD well pairs.

The principle and the implementation mode of the invention are explained by applying a specific example, and the description of the embodiment is only used for helping to understand the method and the core idea of the invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.

Claims (6)

1. The utility model provides a take fracturing sleeve pipe which characterized in that: the welding device comprises a sleeve and a welding bracket, wherein the sleeve is a four-wing sleeve, and when the sleeve is expanded mechanically, each wing is opened by the same amount and keeps a locking opening state after the sleeve is expanded; the welding bracket is arranged on the top of the four-wing sleeve and is arranged on the inner wall of the sleeve for limiting the opening width of each wing, and the conical shoulder of the four-wing sleeve is pulled into the welding bracket; and each wing surface of the four-wing casing is provided with a perforation, and the perforation is used for injecting fracturing fluid during fracturing operation.

2. The fracturing sleeve with a fracturing function of claim 1, wherein: and a steam injection pipe and an oil production pipe are arranged in the inner cavity of the four-wing sleeve. The steam injection pipe is connected with the steam injection boiler through a ground steam injection pipeline to realize the injection of steam into the stratum; the oil production pipe is connected with an electric submersible pump or a screw pump to lift produced liquid.

3. The fracturing sleeve with a fracturing function of claim 1, wherein: the proppant of the fracturing fluid is garnet sand, and gravel for slotting the liner tube covers the expansion length of the four-wing sleeve tube along the radial direction.

4. The fracturing sleeve with a fracturing function of claim 1, wherein: four perforating holes are uniformly distributed on the outer side of each wing surface, the perforating holes on the four wing surfaces form four perforating areas in total, and the distance between every two adjacent perforating areas is a quarter of the circumference of the outer cylinder wall.

5. The fracturing sleeve with a fracturing function of claim 4, wherein: the perforation adopts laser perforation.

6. A single well SAGD development method based on a fractured casing, comprising the fractured casing according to any one of claims 1 to 6, further comprising the steps of:

the well deflecting section adopts double-tubular column completion, a steam injection pipe and an oil production pipe are parallelly arranged, and a horizontal section (a fracturing section) is only arranged in the steam injection pipe;

the four-wing casing is put into a fracturing section, and when fracturing construction is carried out, a ball throwing method is adopted to trigger a launching hole mechanism to enable the wing surface of the casing at the bottommost to expand to form uniformly distributed grooves, and then fracturing fluid is injected through a perforation to carry out fracturing operation to form a plurality of fracturing supporting surfaces which are in contact with an oil reservoir;

and performing fracturing operation on the reservoir section at the front part section by section through the expanded four-wing casing by the same operation, and finally forming a fracturing support surface penetrating through the whole fracturing section.

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