A precise infinite segmented fracturing method for common oil pipes

Abstract

The present invention discloses a method for accurate infinite segmented fracturing of common oil pipes, including step S1, accurate division of horizontal well fracturing sections; step S2, accurate perforation by hydraulic jetting of common oil pipes; step S3, continuous multiple sand addition and accurate fracturing; step S4, accurate displacement and shut-in to measure pressure drop; step S5, lifting the pipe column and adding bottom seal to perform next segment fracturing. The accurate segmented wireless fracturing technology of the present invention does not require temporary plugging agents or other complex downhole tools during the entire process, and can be conveniently fracturing at any position of the horizontal well section, ultimately ensuring that each position to be fractured can form a main fracture and can be completely filled with proppant, so that each section of the reservoir to be transformed can be truly supported, forming a complete supporting fracture network system for the entire well section. The present invention has simple steps, fast construction speed, no need for lifting and lowering tools, no need for temporary plugging agents, low construction cost, reliable method, can effectively complete the accurate construction of each section, and improve construction efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas exploitation, and in particular to a method for precise infinite segmented fracturing of common oil pipes. Background Art

[0002] my country currently has a high degree of external dependence on oil and natural gas, and the development of conventional oil and gas resources is gradually depleting. Therefore, it is imperative to efficiently develop unconventional oil and gas resources, especially tight oil and gas resources. Since unconventional oil and gas reservoirs are low in porosity and extremely low in permeability, horizontal well staged fracturing technology must be used to effectively exploit such reservoirs. Therefore, it is necessary to conduct more in-depth research and discussion on horizontal well staged fracturing technology.

[0003] The multi-cluster fracturing of horizontal wells uses the principle of flow limiting method to ensure that each multi-cluster can be opened: when the fracturing fluid flows through the perforation at a very high flow rate, the friction between the holes increases significantly, and the magnitude of the friction increases with the increase in displacement, resulting in a significant increase in downhole pressure. If this pressure is higher than the fracture pressure of other fracturing layers, each layer can be opened. However, it is difficult to ensure that each cluster can be opened by the flow limiting method. Field tests show that in large-scale multi-cluster fracturing, only one or two clusters are often opened in the end, and it is difficult to achieve the requirement that all designed multi-cluster fractures are transformed. In addition, horizontal well fracturing generally uses continuous tubing, which is expensive; if a ball-casting sleeve is used, the diameter is affected, so that the displacement is limited. Therefore, it is urgent to provide a new type of ordinary tubing precise infinite segmented fracturing method, which can achieve infinite segmentation, and the displacement after segmentation is not limited, and at the same time, it can ensure that each segment can be opened. It is an important research content of horizontal well fracturing technology at this stage. Summary of the invention

[0004] The purpose of the present invention is to provide a method for precise infinite segmented fracturing of common oil pipes to solve the problems existing in the above-mentioned prior art.

[0005] To achieve the above object, the present invention provides the following solution: The present invention provides a precise infinite common oil pipe staged fracturing method, comprising:

[0006] Step S1, dividing the horizontal well fracturing section according to the geological engineering requirements, and then using ordinary oil pipe with bottom seal for isolation;

[0007] Step S2: According to the geological conditions of the formation, hydraulic sandblasting is performed in the horizontal well fracturing section to accurately align the perforation positions with appropriate parameters to establish a fluid flow channel between the formation and the casing;

[0008] Step S3: After perforation is completed, the perforated section is subjected to precise and continuous sand hydraulic fracturing according to the design, ensuring that the fracturing fluid and proppant enter the perforated section, forming a long fracture, controlling the fracture height, and enabling the entire fracture to be effectively supported;

[0009] Step S4, after each stage of multiple fracturing and sanding is completed, displacement is performed so that all the proppant in the ordinary oil casing enters the formation and then the well is shut down to reduce the pressure;

[0010] Step S5, when the pressure is reduced to close the formation, the continuous common pipe string is lifted to the next fracturing well section and a bottom seal is added;

[0011] Step S6, looping steps S1-S5 until the fracturing of all well sections of the horizontal well is completed, and finally forming a fracture network system of the entire horizontal well section.

[0012] Preferably, in step S2, the length of the horizontal well fracturing segment is 3 to 50 m, the length of the perforation segment is 0.1 to 0.5 m, and the number of precise perforations is 2 to 10.

[0013] Preferably, in step S3, precise fracturing is performed to form a single main fracture at the perforation position, and then multiple sand fracturing is continued, the number of times is 2-5 times, and each complete sand fracturing is carried out in the order of pre-fracture creation, sand support, displacement, and well shut-in. The well shut-in time between each fracturing is 30-60 minutes, and then the next sand fracturing is carried out, and it is repeated 2-5 times.

[0014] Preferably, there are three types of proppants for precision fracturing: the first type is to use micro-particle proppants to support micro-cracks and secondary cracks; the second type is to use medium-particle proppants to support secondary cracks and main cracks; the third type is to use large-particle proppants to support main cracks and crack ends.

[0015] Preferably, the micro-particle proppant combination accounts for 10%-20%, and its particle size is 140-400 mesh; the medium-particle proppant combination accounts for 40%-60%, and its particle size is 40-70 mesh; the large-particle proppant combination accounts for 20%-40%, and its particle size is 16-30 mesh.

[0016] Preferably, the cracks include microcracks, secondary cracks and main cracks; the micro-particle proppant is used to support microcracks and secondary cracks; the medium-particle proppant is used to support secondary cracks and main cracks; and the large-particle proppant is used to support main cracks.

[0017] Preferably, during the precise perforation process in step S2, each perforation section can generate a main fracture, and during the precise fracturing process, the pipe string does not move, ensuring that each section of the fracture can be opened and the amount of sand added to the fracture can be determined.

[0018] The present invention discloses the following technical effects:

[0019] 1. Ordinary tubing fracturing is simple and convenient. So far, using ordinary tubing to replace coiled tubing is low-cost, effective, and easy to use. The length of the coiled tubing is fixed. For operations at different well depths, the length of the coiled tubing used must be greater than the operating well depth. The excess length during fracturing will consume a lot of energy. If ordinary tubing is used, the situation is completely different. Ordinary tubing is connected by a 10-meter-long tubing. You can connect as many tubings as the well depth. It is simple and convenient.

[0020] 2. Short perforation sections and fewer perforations make it easier to open the formation; long perforation sections and more perforations make the hydraulic force more dispersed, which makes it easier to filter out and form multiple cracks in the near-wellbore area. It is difficult to form long cracks and communicate with the distant reservoir, and the effect of fracturing transformation cannot be achieved.

[0021] 3. The present invention adds sand, lifts the tubing string, and adds a bottom seal to carry out precise fracturing in the next section. It can efficiently carry out precise stratified or segmented fracturing and achieve precise positioning, thereby achieving fracturing of multiple layers in a vertical well or multiple horizontal sections in a horizontal well, ensuring that each layer or section forms a supporting fracture network system; when operating on different construction layers or sections, an isolation design with a bottom seal is implemented for the sections outside the operating layers or sections, ensuring that the non-operating sections are not affected by inappropriate operations and avoiding layer channeling caused by different pressure differences. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 This is a flow chart of the method for precise infinite segmented fracturing of common oil pipes of the present invention; DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] Reference Figure 1 The present invention provides a precise infinite staged fracturing method, comprising:

[0027] Step S1, dividing the horizontal well fracturing section according to the geological engineering requirements, and then using ordinary oil pipe with bottom seal for isolation;

[0028] Step S2: According to the geological conditions of the formation, hydraulic sandblasting is performed in the horizontal well fracturing section to accurately align the perforation positions with appropriate parameters to establish a fluid flow channel between the formation and the casing;

[0029] Step S3, after the perforation is completed, the perforated section is accurately and repeatedly hydraulically fractured with sand according to the design to ensure that the fracturing fluid and the proppant enter the perforated well section, and the sand fracturing process is completed multiple times, so that the sand added for each fracturing is settled at the bottom of the crack, so that the cross-sectional area of ​​the fracturing fluid is reduced; the reduction in cross-sectional area will increase the flow rate of the fracturing fluid in the crack for the next fracturing, so that the fracturing fluid can bring the proppant into the far end of the fracturing crack, forming a long crack, controlling the crack height, and effectively supporting the entire crack;

[0030] Step S4, after each stage of multiple fracturing and sanding is completed, displacement is performed so that all the proppant in the ordinary oil casing enters the formation and then the well is shut down to reduce the pressure;

[0031] Step S5, when the pressure is reduced to close the formation, the continuous common pipe string is lifted to the next fracturing well section and a bottom seal is added;

[0032] Step S6, looping steps S1-S5 until the fracturing of all well sections of the horizontal well is completed, and finally forming a fracture network system of the entire horizontal well section.

[0033] Furthermore, common tubing is a key step in ensuring the success of the process during the fracturing construction design; the equipment and reliability of common tubing systems play a pivotal role in improving the safety of operations and the success rate of operations. The development prospects of common tubing to replace coiled tubing technology are good, and it can be used to improve the shortcomings of conventional fracturing technology, so that the efficiency, safety factor and benefits of coiled tubing segmented fracturing methods can be improved, making the fracturing operation engineering simpler, with a shorter cycle and lower costs.

[0034] Further optimize the scheme, in step S2, the segment length of the horizontal well fracturing well is 3-50m, the length of the perforation section is 0.1-0.5m, and the number of holes for precise perforation is 2-10. Precise perforation is to use the high-pressure pump equipment or fracturing vehicle group on the ground to input grinding fluid into the ordinary oil pipe. At this time, the high-pressure fluid of the nozzle will change the high-pressure fluid flowing through the nozzle into a high-energy high-speed grinding fluid under the throttling and acceleration of the nozzle. The high-speed grinding fluid has concentrated energy and strong impact and destruction ability. The energy of the high-speed grinding fluid breaks the casing and reservoir rock to form a hole. In addition, the fluid flow rate of the grinding fluid at the nozzle mouth is large. According to the Bernoulli equation, the kinetic energy is large, so the pressure energy is small. Therefore, a low-pressure area is formed at the entrance of the perforation hole, which has a large pressure difference. Under the action of this pressure difference, the surrounding fluid will be sucked into the hole entry area under the action of the pressure difference, forming a hydraulic isolation area, which can be automatically isolated. The high-pressure grinding fluid uses its own high kinetic energy to penetrate the well wall and achieve the fracturing goal. It is convenient and efficient in layered and segmented operations, does not require mechanical isolation, can realize the process of multi-stage fracturing in one trip of the tubing string, and can achieve the advantages of accurate fracture creation and effective isolation; the precise perforation of the present application is that only one cluster is shot in the target layer or segment, the cluster length is generally 0.1-0.5 meters, and the number of perforations is 2-8; for horizontal wells, it is necessary to ensure that the perforations are on the same plane as much as possible, and the artificial fractures in four directions merge into a main fracture, reduce the appearance of multiple fractures in the near-well area, and provide the best channel for the extension of subsequent fractures and sand addition; the purpose is to control the height of the fracture. After the proppant settles after one sand addition, the proppant is piled at the bottom of the fracture, and the piled sand bank reduces the cross-sectional area of ​​the fracture mouth for liquid inlet. The next fracturing uses the same displacement as the previous one to increase the flow rate of the fracturing fluid, so that the next proppant can be transported to a farther position of the fracture under the same pumping displacement, which is conducive to creating long fractures and supporting long fractures and their secondary and micro fractures around the main fractures.

[0035] In step S3 of the further optimization scheme, precise fracturing forms a single main fracture at the perforation position, and then continues to fractur with sand for 2-5 times. Each complete hydraulic fracturing with sand is carried out in the order of pre-fracture creation, sand support, displacement, and well shut-in. The well shut-in time between each fracturing is 30-60 minutes, and then the next fracturing with sand is carried out, which is repeated 2-5 times. Continuous precise fracturing mainly lies in the fact that segmentation and fracture spacing are not restricted, which can avoid the complex downhole tool lifting and lowering operation during the fracturing process. Fracturing to generate fractures and adding sand are carried out alternately to ensure that the fractures in the sub-column are properly supported, and the scope of the fractures is further expanded, the surrounding formations are connected with the horizontal well, and the mining efficiency is guaranteed.

[0036] To further optimize the plan, there are three types of proppants for precision fracturing: the first is to use micro-particle proppants to support micro-cracks and secondary cracks; the second is to use medium-particle proppants to support secondary cracks and main cracks; the third is to use large-particle proppants to support main cracks and crack ends; the combination of micro-particle proppants accounts for 10%-20%, and the particle size is 140-400 mesh; the combination of medium-particle proppants accounts for 40%-60%, and the particle size is 40-70 mesh; the combination of large-particle proppants accounts for 20%-40%, and the particle size is 16-30 mesh; cracks include micro-cracks, secondary cracks and main cracks; micro-particle proppants are used to support micro-cracks and secondary cracks; medium-particle proppants are used to support secondary cracks and main cracks; large-particle proppants are used to support main cracks. Fracturing ultimately forms a supported main fracture and a fracture system consisting of secondary fractures and micro fractures surrounding the main fracture. Proppants of different particle sizes are filled into the generated fracture system to support fractures of different sizes and prevent the closure of the fractures due to formation pressure.

[0037] To further optimize the solution, during the precise perforation process in step S2, each perforation section can generate a main fracture. During the precise fracturing process, the tubing string does not move; it ensures that each section of the fracture can be opened, and the amount of sand added to the fracture can be determined. Precise perforation can ensure the formation of a main fracture extending far away without the tubing string moving. At the same time, the high-pressure fracturing fluid in the main fracture will spread from the main fracture to the surrounding areas to form secondary fractures and micro fractures in the formation, and finally form a branch-like fracture network. This process does not require the movement of the tubing string, which improves work efficiency, does not require complex downhole operation procedures, reduces operating costs, and has the advantages of low risk and high efficiency.

[0038] Furthermore, the tubing is lifted up and a bottom seal is added to further segment the oil well. After precise positioning, a bottom seal is added to protect the well section that has been fracturing. Then, the fracturing operation of the next well section does not require any extra downhole tools, and the goal of unlimited segmentation can be achieved with just one trip of tubing.

[0039] Furthermore, unlimited segmented continuous precise fracturing is completed through the cooperation of common oil pipes, bottom seals, etc., with the aim of accurately positioning different well sections, realizing unlimited segmentation, and efficiently performing precise layered (segment) fracturing, thereby achieving fracturing of multiple horizontal sections, ensuring that each layer (segment) forms a three-dimensional supporting fracture network system, and ensuring that multiple well sections with different parameters can be independently fracturable.

[0040] The present invention does not require the use of temporary plugging agents or other complex downhole tools during the entire fracturing process, but can achieve fracturing at any position in the horizontal well section, and each well section can be accurately positioned, and can be completely isolated from the remaining well sections during the fracturing operation, ultimately ensuring that each well section to be fractured can form a main fracture and can be completely filled with proppant, so that the transformed formation truly forms a supported volume fracture. In addition, this invention is designed with a fast construction speed, does not require lifting tools, does not require temporary plugging agents, and greatly saves costs. The technical invention has simple steps, and the methods adopted in each step are reliable, can effectively complete the construction, and improve construction efficiency.

[0041] The above embodiments are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for precise infinite segmented fracturing of common oil pipes, characterized by: include Step S1, dividing the horizontal well fracturing section according to the geological engineering requirements, and then using ordinary oil pipe with bottom seal for isolation; Step S2: According to the geological conditions of the formation, hydraulic sandblasting is performed in the horizontal well fracturing section to accurately align the perforation positions with appropriate parameters to establish a fluid flow channel between the formation and the casing; Step S3: After perforation is completed, the perforated section is subjected to precise and continuous sand hydraulic fracturing according to the design, ensuring that the fracturing fluid and proppant enter the perforated section, forming a long fracture, controlling the fracture height, and enabling the entire fracture to be effectively supported; Step S4, after each stage of multiple fracturing and sanding is completed, displacement is performed so that all the proppant in the ordinary oil casing enters the formation and then the well is shut down to reduce the pressure; Step S5, when the pressure is reduced to close the formation, the continuous common pipe string is lifted to the next fracturing well section and a bottom seal is added; Step S6, looping steps S1-S5 until the fracturing of all well sections of the horizontal well is completed, and finally forming a fracture network system of the entire horizontal well section; In the step S3, precise fracturing forms a single main fracture at the perforation position, and then continues to fractur with sand for 2-5 times. Each complete hydraulic fracturing with sand is carried out in the order of pre-fracture creation, sand support, displacement, and well shut-in. The well shut-in time between each fracturing is 30-60 minutes, and then the next fracturing with sand is carried out, which is repeated 2-5 times. In the step S3, after the perforation is completed, the perforated section is accurately and repeatedly hydraulically fractured with sand according to the design to ensure that the fracturing fluid and the proppant enter the perforated well section. The sand addition and fracturing process is completed multiple times, so that the sand added for each fracturing is settled at the bottom of the crack, so that the cross-sectional area of ​​the fracturing fluid is reduced; the reduction in the cross-sectional area will increase the flow rate of the fracturing fluid in the crack for the next fracturing, so that the fracturing fluid can bring the proppant into the far end of the fracturing crack, so as to form a long crack, control the crack height, and effectively support the entire crack; After the proppant settles after the first sand addition, the proppant is piled at the bottom of the crack. The piled sand bank reduces the cross-sectional area of ​​the fluid entering the crack mouth. The next fracturing with the same displacement as the previous one can increase the flow rate of the fracturing fluid, so that the next proppant can be transported to a farther position in the crack at the same pumping displacement, which is conducive to the formation of long cracks and the support of long cracks and their secondary and micro cracks around the main cracks. There are three types of proppants for precision fracturing: the first type uses micro-sized proppants to support micro-cracks and secondary cracks; the second type uses medium-sized proppants to support secondary cracks and main cracks; the third type uses large-sized proppants to support main cracks and crack ends. The micro-particle proppant combination accounts for 10%-20%, and its particle size is 140-400 mesh; the medium-particle proppant combination accounts for 40%-60%, and its particle size is 40-70 mesh; the large-particle proppant combination accounts for 20%-40%, and its particle size is 16-30 mesh.

2. The common oil pipe precise infinite staged fracturing method according to claim 1, characterized in that: In step S2, the length of the horizontal well fracturing segment is 3 to 50 m, the length of the perforation segment is 0.1 to 0.5 m, and the number of precise perforations is 2 to 10.

3. The common oil pipe precise infinite staged fracturing method according to claim 1, characterized in that: The cracks include micro cracks, secondary cracks and main cracks; the micro-particle proppant is used to support micro cracks and secondary cracks; the medium-particle proppant is used to support secondary cracks and main cracks; and the large-particle proppant is used to support main cracks.

4. The common oil pipe precise infinite staged fracturing method according to claim 3, characterized in that: During the precise perforation process in step S2, each perforation section can generate a main fracture, and during the precise fracturing process, the pipe string does not move, ensuring that each section of the fracture can be opened and the amount of sand added to the fracture can be determined.

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