Construction method for volume fracturing
By simulating and optimizing volumetric fracturing construction methods, and based on stress value sequence and wellbore trajectory, the problems of casing deformation and pressure channeling in shale gas resource extraction were solved, achieving more efficient reservoir stimulation and production enhancement.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-02
- Publication Date
- 2026-03-10
AI Technical Summary
Existing volumetric fracturing methods cannot effectively solve the problems of casing deformation and pressure channeling in shale gas resource development, especially in horizontal well development, which causes the wellbore trajectory to travel back and forth between the reservoir and the interlayer, affecting the reservoir stimulation effect and production.
Based on the actual stress conditions and wellbore trajectory of each horizontal well, the maximum displacement and fluid volume requirements of different horizontal sections are simulated. Volumetric fracturing operations are carried out in order of increasing stress value to establish a stress barrier, reduce the risk of casing deformation and pressure channeling, and optimize the construction sequence and wellbore deformation treatment by monitoring and adjusting construction parameters.
It effectively reduces casing deformation and fracturing fluid intrusion into non-target formations, improves reservoir stimulation and gas well production, and ensures the protection of fracturing results and production enhancement.
Smart Images
Figure CN121630337A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of oil and gas development technology, and in particular to a construction method for volumetric fracturing. Background Technology
[0002] For shale gas resource extraction, to reduce surface construction costs, the main development method currently adopted is horizontal well platforms, with a lateral distance of 300-450 meters between wells. Typically, shale's mineral composition mainly consists of 30%–39% clay, 29%–38% quartz, and 25%–30% other minerals such as calcite, dolomite, feldspar, and pyrite. Its mineral characteristics highlight the high brittleness of shale, resulting in good compressibility. Therefore, volumetric fracturing technology is generally used for shale gas extraction. Volumetric fracturing refers to the process of injecting fracturing fluid under high pressure during hydraulic fracturing, causing natural fractures to expand and brittle rocks to undergo shear slip, thus forming a fracture network of interwoven natural and artificial fractures. This fracture network can increase the reservoir's stimulation volume, improving initial production and ultimate recovery rate. Volumetric fracturing technology is characterized by large injection fluid volume, large sand volume, large pumping discharge volume, and high construction pressure. Taking a platform with 10 wells, each with a horizontal section length of 1500 meters, as an example, the platform is expected to be divided into 200 sections, with fracturing fluid expected to exceed 400,000 cubic meters and proppant expected to exceed 30,000 cubic meters. The construction sequence of volumetric fracturing technology is as follows: initial perforation, fracturing the first section, pumping in the first soluble bridge plug, fracturing the second section, pumping in the second bridge plug, fracturing the third section, and so on until the final section is completed, well opening for dissolution, drilling and cleaning the bridge plug, fluid drainage, and gas transmission. The construction sequence of volumetric fracturing technology can be one well at a time, or multiple wells can be fracturing in a "zipper-like" manner.
[0003] Because high-quality reservoirs are only 10-15 meters thick, which is relatively thin, and due to the presence of fracture structures in the formation, it is difficult to ensure that the wellbore trajectory of a horizontal well travels a long distance through the same reservoir. There are instances where the wellbore trajectory travels back and forth between the reservoir and adjacent layers, increasing the mutual influence between adjacent horizontal wells. Furthermore, under high fluid volume (exceeding 2000 cubic meters per section) and high displacement (greater than 18 cubic meters per minute), complex problems such as casing deformation and inter-well pressure channeling are prone to occur. The wellbore trajectory refers to the spatial orientation and shape of the borehole (i.e., the wellbore) formed by the drill bit underground during the drilling process. It describes the specific location, direction, and shape of the wellbore in the formation and is one of the important parameters in drilling engineering. Fracturing fluid or proppant accidentally migrates into non-target or adjacent formations during volumetric fracturing due to improper pressure control or complex formation conditions. This reduces the effectiveness of fracturing in the target formation, increases water production in adjacent wells, decreases gas production, and prevents the target formation's fracture network from expanding sufficiently, ultimately affecting the well's permeability and production. Casing deformation refers to the deformation or damage of the casing during volumetric fracturing.
[0004] When casing deformation occurs, the general approach is to run small bridge plugs for staged fracturing, use temporary plugging materials for long-stage temporary fracturing, or abandon fracturing altogether, depending on the wellbore's throughput capacity at the deformation location. Simultaneously, the fractured section before casing deformation faces the challenge of not being able to clear the plug, impacting single-well productivity. Plug clearing refers to removing incompletely dissolved bridge plugs after fracturing to ensure a completely unobstructed wellbore. When inter-well crossflow occurs, the common approach is to reduce fracturing parameters or strengthen temporary plugging. Therefore, for shale gas resource exploitation, it is crucial to optimize volumetric fracturing methods to minimize casing deformation or crossflow problems in horizontal well development. Summary of the Invention
[0005] The purpose of this invention is to overcome the shortcomings of existing technologies in the extraction of shale gas resources, where current volumetric fracturing construction methods cannot effectively solve the problems of casing deformation or pressure channeling in horizontal well development, and to provide a construction method for volumetric fracturing.
[0006] This invention provides a construction method for volumetric fracturing, comprising the following steps:
[0007] S1: Based on the actual stress conditions, actual wellbore trajectory, and actual relative positions of each horizontal well in each reservoir, simulate the maximum displacement and maximum fluid volume required for volumetric fracturing of different horizontal sections of each horizontal well without cross-linking with adjacent wells or casing deformation. Each horizontal well in each reservoir is located on the same platform. A platform well refers to a wellhead located on the same platform during oil and gas exploration and development, where multiple wellheads are concentrated to utilize surface space and resources more effectively. Directional drilling technology is used to drill into different target formations, enabling centralized management and operation of multiple wells. The actual relative positions refer to the vertical and horizontal relationships and distances between the horizontal wells within the formation.
[0008] S2: Based on the average stress value of all corresponding horizontal wells in each reservoir, volumetric fracturing operations are performed on each reservoir in ascending order of the average stress value. This order is the first-stage volumetric fracturing sequence. Based on the stress value of each horizontal well in a single reservoir, volumetric fracturing operations are performed on each horizontal well in ascending order of the stress value. This order is the second-stage volumetric fracturing sequence. When performing volumetric fracturing operations on a single horizontal well, segmented volumetric fracturing is performed according to the maximum displacement and maximum fluid volume required for each horizontal segment.
[0009] This invention provides a construction method for volumetric fracturing. Based on the conditions of each horizontal well in each reservoir, it simulates the maximum displacement and maximum fluid volume required for volumetric fracturing in different horizontal sections of each horizontal well, so as to avoid the displacement or fluid volume exceeding the required maximum value during volumetric fracturing, which could lead to casing deformation or pressure channeling problems.
[0010] Based on simulation calculations and construction verification, when the volumetric fracturing rate is 18-20 cubic meters per minute, it is difficult to connect two adjacent reservoirs with a stress difference exceeding 5 MPa when operating in deep shale gas formations at a vertical depth of 4000 meters. Therefore, based on the average stress of all corresponding horizontal wells in each reservoir, volumetric fracturing is performed on each reservoir in ascending order of stress. Reservoirs with lower average stress are fracturing first to increase their stress value and establish a stress barrier, thereby reducing the stress difference with subsequent reservoirs with higher average stress values. This helps reduce casing deformation or pressure channeling problems caused by excessive stress differences between different reservoirs and also helps to form a complex fracture network to provide gas production.
[0011] Furthermore, based on the stress values of each horizontal well in a single reservoir, volumetric fracturing is performed on each horizontal well in ascending order of stress value. Volumetric fracturing is first performed on the horizontal wells with lower stress values to increase their stress values, thereby reducing the stress difference with subsequent horizontal wells with higher stress values. This helps to reduce casing deformation or pressure channeling problems caused by excessive stress value differences between different horizontal wells.
[0012] Preferably, in step S2, during the secondary volumetric fracturing, when the stress difference among the horizontal wells in a single reservoir is less than a predetermined value, the volumetric fracturing of each horizontal well in the single reservoir is performed in the order of the middle well first, then the outer wells. The stress difference refers to the difference between the maximum and minimum stress values in each horizontal well within a single reservoir. As the middle horizontal well undergoes volumetric fracturing first, its stress value increases, establishing a stress barrier. Continuing to perform volumetric fracturing on the outer horizontal wells reduces the lateral intrusion of fracturing fluid along the main fracture, thereby reducing the possibility of inducing casing deformation or pressure channeling. This approach helps to form complex fracture networks and even better connects the upper and lower reservoirs.
[0013] The main fracture refers to the primary, dominant fracture channel formed during fracturing due to the fracturing of formation rocks and the injection of fluid. These main fractures typically develop along existing weak surfaces (such as faults, joints, bedding planes, etc.) or stress concentration areas in the formation. They have significant width and length, enabling efficient transport of fracturing fluid and proppant. During fracturing operations, if the fracturing fluid primarily propagates along these main fractures and fails to effectively form a complex fracture network, it may lead to poor fracturing results or even adverse consequences such as stratigraphic deformation or proppant channeling.
[0014] Preferably, the predetermined value is 1.0 MPa-2.0 MPa.
[0015] Preferably, in step S2, during the secondary volumetric fracturing, when a connected natural fracture passes through two or more adjacent horizontal wells in a single reservoir and each forms a fracture segment, synchronous volumetric fracturing is required for each fracture segment. That is, adjacent horizontal wells pierced by natural fractures need to undergo volumetric fracturing simultaneously to jointly cross the fracture segment. The natural fracture refers to a rupture caused by stress in the formation. The two sides of this fracture surface may have no significant displacement, meaning the rock mass or formation on both sides of the fracture surface remains relatively close after fracturing. Alternatively, the two sides of the fracture surface may have significant relative displacement, meaning the rock mass along both sides of the fracture surface undergoes significant displacement or loses continuity and integrity, forming a structural feature.
[0016] Preferably, during volumetric fracturing of the fractured section, the fracturing process is monitored. When an abnormal increase in wellhead pressure occurs in adjacent wells or microseismic events rapidly concentrate at a certain location along the wellbore of a horizontal well, measures such as temporary plugging within the fracture and reducing the discharge rate are taken for the volumetric fracturing of the fractured section. The monitoring process of volumetric fracturing includes: monitoring the wellhead pressure values of adjacent wells and monitoring microseismic event points. This scheme can avoid malignant fracturing. Malignant fracturing refers to more severe fracturing, which may lead to a significant decrease in gas well production, formation contamination, water flooding, and abandonment. Monitoring microseismic events refers to geophysical techniques that monitor the impact of microseismic events (i.e., microseismic events) generated during production activities, assess their effects, and understand the underground state by observing and analyzing them. The principle of microseismic monitoring is that when underground rocks fracture or move due to human factors (such as mining, excavation, fracturing, etc.) or natural factors, a weak seismic wave is generated and propagates to the surrounding area. By arranging multiple geophones in the space surrounding the rupture zone and collecting microseismic data in real time, the location of the rupture can be determined and displayed in three-dimensional space after data processing and vibration positioning principle.
[0017] Preferably, step S2 further includes, during volumetric fracturing of a single horizontal well, if wellbore deformation occurs in a certain horizontal section, the following measures should be taken for the deformed section:
[0018] When the wellbore deformation of the deformed section reaches a first predetermined deformation value, a bridge plug matching the first predetermined deformation value is used for the deformed section, and then volumetric fracturing is continued on the subsequent horizontal section.
[0019] When the wellbore deformation of the deformed section reaches the second predetermined deformation value, the fluid in the horizontal well is first drained, and then the section in the horizontal well that has been volumetrically fractured is swept and plugged. The deformed section is replaced with a bridge plug that matches the size of the second predetermined deformation value, and then the subsequent horizontal section is continued to be volumetrically fractured.
[0020] When the wellbore deformation of the deformed section reaches the third predetermined deformation value, the horizontal well is drained to dissolve the bridge plug in the fractured section, and the volumetric fracturing operation of the deformed section is abandoned. Then, volumetric fracturing is carried out on the subsequent horizontal sections.
[0021] This plan aims to protect the fracturing results of the fractured well section and increase production. The wellbore refers to the entire well passage from the surface to the oil and gas reservoir, including vertical, inclined, or horizontal sections. It is usually formed by tools such as drill bits and drill pipes during the drilling process, and its main functions are to provide fluid channels, isolate the formation, and protect the wellbore.
[0022] Preferably, the first predetermined deformation value is that the ratio of the inner diameter of the deformed wellbore to the inner diameter of the wellbore before deformation is greater than 70% and less than or equal to 85%; the second predetermined deformation value is that the ratio of the inner diameter of the deformed wellbore to the inner diameter of the wellbore before deformation is greater than 50% and less than or equal to 70%; and the third predetermined deformation value is that the ratio of the inner diameter of the deformed wellbore to the inner diameter of the wellbore before deformation is less than or equal to 50%.
[0023] Preferably, step S2 further includes, when there is a producing gas well near the horizontal well requiring volumetric fracturing, shutting down the producing gas well 5-7 days before volumetric fracturing of the horizontal well to establish a stress barrier. Then, during volumetric fracturing of the horizontal well, the volumetric fracturing parameters are adjusted based on changes in the wellhead pressure of the producing gas well. This approach can reduce the adverse effects of the producing gas well on the fracturing well.
[0024] Preferably, step S2 further includes, before performing volumetric fracturing on the horizontal well, maintaining pressure on other unfractured horizontal wells in the same platform well as the other unfractured horizontal wells in the same platform well as the horizontal well adjacent to the horizontal well. The pressure maintenance value is 60-70% of the highest pump pressure during volumetric fracturing to establish a stress barrier. The wellhead pressure changes of the unfractured horizontal wells are monitored periodically. When the wellhead pressure is lower than 60%, pressure should be replenished, and the volumetric fracturing parameters are adjusted according to the wellhead pressure changes.
[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0026] 1. This invention provides a construction method for volumetric fracturing. By determining the maximum displacement and maximum fluid volume required for different horizontal sections in each horizontal well, and performing volumetric fracturing construction in order of the average stress value of all corresponding horizontal wells in each reservoir from smallest to largest, and performing volumetric fracturing construction in order of the stress value of each horizontal well in a single reservoir from smallest to largest, it is possible to reduce casing deformation or pressure channeling problems in platform horizontal well development. Attached Figure Description
[0027] Figure 1 This is a schematic diagram of the wellbore trajectory for a horizontal well.
[0028] Figure 2 This is a schematic diagram of the formation profile of each horizontal well in different reservoirs.
[0029] Figure 3 This is a schematic diagram of the horizontal wells in a single reservoir.
[0030] Figure 4 This is a schematic diagram of multiple horizontal wells in a single reservoir that are penetrated by natural fractures.
[0031] Marked in the image:
[0032] 1-Wellbore trajectory,
[0033] 2-First partition,
[0034] 3-First high-quality reservoir,
[0035] 4-Second partition,
[0036] 5-Second high-quality reservoir,
[0037] 6- The third high-quality reservoir,
[0038] 7-Horizontal well,
[0039] 8. Natural cracks. Detailed Implementation
[0040] The present invention will now be described in further detail with reference to specific embodiments. However, this should not be construed as limiting the scope of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.
[0041] Unless otherwise specified, the use of terms such as "upper," "lower," "left," "right," "center," "inner," and "outer" to indicate orientation or positional relationships in the description of specific embodiments of the present invention is based on the orientation or positional relationships shown in the accompanying drawings, or the orientation or positional relationship in which the product / equipment / device is typically placed during use. These terms are merely for the purpose of facilitating the description of the present invention or simplifying the description in specific embodiments, enabling those skilled in the art to quickly understand the solution, and do not indicate or imply that a particular device / component / element must have a specific orientation, or be constructed and operated in a specific positional relationship. Therefore, they should not be construed as limitations on the present invention.
[0042] Furthermore, the use of terms such as "horizontal," "vertical," "suspended," and "parallel" does not imply that the corresponding device / component / element must be absolutely horizontal, vertical, suspended, or parallel, but rather that it can be slightly tilted or have a deviation. For example, "horizontal" merely means that its direction is more horizontal relative to "vertical," not that the structure must be completely horizontal, but that it can be slightly tilted. Alternatively, it can be simplified to mean that the corresponding device / component / element, when set in a "horizontal," "vertical," "suspended," or "parallel" direction, can have an error / deviation of ±10% relative to the corresponding direction, more preferably within ±8%, more preferably within ±6%, more preferably within ±5%, and more preferably within ±4%. As long as the corresponding device / component / element is within the error / deviation range, it can still achieve its function in the present invention.
[0043] Furthermore, the use of terms such as "first," "second," and "third" in terminology is merely for distinguishing descriptions of identical or similar components and should not be interpreted as emphasizing or implying the relative importance of a particular component.
[0044] Furthermore, in the description of the embodiments of the present invention, "several", "more than", and "a number of" represent at least two. The number can be any number, such as 2, 3, 4, 5, 6, 7, 8, or 9, and can even exceed nine.
[0045] Furthermore, in the description of the technical solution of this invention, unless otherwise explicitly specified / limited / restricted, the terms "set up," "install," "connect," "link," "provided with," "laid out," and "arranged" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to common connection methods in the art, such as welding, riveting, bolting, and threaded connections. Such connections can be mechanical, electrical, or communication connections; they can be direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components.
[0046] Example 1
[0047] like Figure 1 As shown, the wellbore trajectory 1 of a horizontal well 7 travels through the formation. The first high-quality reservoir 3 is adjacent to the first interlayer 2 above it, and the second interlayer 4 is adjacent to the first high-quality reservoir 3 below it. When the first high-quality reservoir 3 is relatively thin, for example, only 10-15 meters thick, the wellbore trajectory 1 cannot be in a completely horizontal state when traveling through the horizontal section of the horizontal well 7. It may be curved upward or downward, and thus the wellbore trajectory 1 may travel back and forth between the reservoir and the interlayer.
[0048] like Figure 2 The diagram illustrates the arrangement of horizontal wells 7 within each reservoir. Above the first high-quality reservoir 3 is the first interlayer 2, above the first interlayer 2 is the second high-quality reservoir 5, below the first high-quality reservoir 3 is the second interlayer 4, and below the second interlayer 4 is the third high-quality reservoir 6. Several horizontal wells 7 are arranged horizontally within the first high-quality reservoir 3, the second high-quality reservoir 5, and the third high-quality reservoir 6. Furthermore, the horizontal wells 7 in adjacent high-quality reservoirs are staggered vertically. Figure 2 The example only shows three reservoirs and three horizontal wells 7 arranged in each reservoir. In reality, there can be one or more reservoirs, such as four, five, six, seven, eight, etc. The number of horizontal wells 7 in each reservoir can be one or more, such as four, five, six, seven, eight, etc.
[0049] A construction method for volumetric fracturing includes the following steps:
[0050] S1: Based on the actual stress conditions, actual wellbore trajectory 1, and actual relative positions of each horizontal well 7 in each reservoir, the maximum displacement and maximum fluid volume required for volumetric fracturing of different horizontal sections of each horizontal well 7 without displacement into adjacent wells or casing deformation are simulated. The simulation refers to calculation using corresponding formulas, which are existing technologies known to those skilled in the art.
[0051] S2: Based on the average stress value of all corresponding horizontal wells 7 in each reservoir, volumetric fracturing operations are carried out in each reservoir in ascending order of the average stress value. This order is the first-stage volumetric fracturing sequence. Based on the stress value of each horizontal well 7 in a single reservoir, volumetric fracturing operations are carried out in each horizontal well 7 in a single reservoir in ascending order of the stress value. This order is the second-stage volumetric fracturing sequence. When carrying out volumetric fracturing operations on a single horizontal well 7, segmented volumetric fracturing is performed according to the maximum displacement and maximum fluid volume required for each horizontal segment.
[0052] In an optional implementation, during step S2, when the stress difference between the horizontal wells 7 in a single reservoir is less than a predetermined value, the volumetric fracturing of each horizontal well 7 in a single reservoir can be carried out in the order of the middle and then the two sides of the horizontal well 7.
[0053] In an optional implementation, the predetermined value is 1.0 MPa-2.0 MPa, specifically 1.0 MPa, 1.2 MPa, 1.5 MPa, 1.8 MPa, or 2.0 MPa. For example... Figure 3 The diagram illustrates six horizontal wells 7 within a single reservoir, with the two innermost wells representing the middle positions and the leftmost and rightmost wells representing the outer positions. For example, when the stress difference among the horizontal wells 7 in the single reservoir is 0.8 MPa (less than 1 MPa), fracturing can be performed on the middle wells first, followed by the outer wells. As fracturing fluid is injected into the middle wells, the stress value gradually increases, establishing a stress barrier. Then, fracturing continues from the middle wells outwards, finally fracturing the leftmost and rightmost wells.
[0054] In an optional implementation, during step S2, when performing the secondary volumetric fracturing, if a connected natural fracture 8 penetrates two or more adjacent horizontal wells 7 in a single reservoir and each forms a fracture segment, simultaneous volumetric fracturing can be performed on each fracture segment. The fracture segment refers to the fracturing segment penetrated by the natural fracture 8. For example... Figure 4As shown, the natural fracture 8 obliquely crosses the two rightmost horizontal wells 7. During the volumetric fracturing operation, the two horizontal wells 7 are fracturing in segments, alternating between left and right. The segment fracturing operation of the rightmost horizontal well 7 can proceed faster than that of the second horizontal well 7 from the right, so that the fracture segments in the two horizontal wells 7 crossed by the natural fracture 8 can be fracturing simultaneously, so as to cross the natural fracture 8 synchronously and avoid the fracturing fluid communicating between the two wells along the natural fracture 8.
[0055] In an optional implementation, during volumetric fracturing of the fractured segment, the fracturing process can be monitored. If an abnormal increase in wellhead pressure occurs in an adjacent well, or if microseismic events rapidly concentrate at a certain location along the wellbore of horizontal well 7, measures such as temporary plugging within the fracture and reducing the fracturing flow rate can be taken for the volumetric fracturing of the fractured segment. Temporary plugging within the fracture refers to temporarily blocking the interior of the fracturing fracture, preventing it from propagating in one direction, thereby controlling and guiding the direction and pattern of fracture propagation.
[0056] In an optional implementation, step S2 further includes, if wellbore deformation occurs in a certain horizontal section during volumetric fracturing of a single horizontal well 7, the following measures can be taken for the deformed section:
[0057] When the wellbore deformation of the deformed section reaches a first predetermined deformation value, a bridge plug matching the first predetermined deformation value is used for the deformed section, and then volumetric fracturing is continued on the subsequent horizontal section.
[0058] When the wellbore deformation of the deformed section reaches the second predetermined deformation value, the fluid in the horizontal well 7 is first drained, and then the section in the horizontal well 7 that has been volumetrically fractured is swept and plugged. The deformed section is replaced with a bridge plug that matches the size of the second predetermined deformation value, and then the subsequent horizontal section is continued to be volumetrically fractured.
[0059] When the wellbore deformation of the deformed section reaches the third predetermined deformation value, fluid is drained from the horizontal well 7 to dissolve the bridge plug in the fractured section, and the volumetric fracturing operation of the deformed section is abandoned. Then, volumetric fracturing is continued on the subsequent horizontal section.
[0060] In an optional embodiment, the first predetermined deformation value may be that the ratio of the deformed wellbore inner diameter to the original wellbore inner diameter is greater than 70% and less than or equal to 85%; the second predetermined deformation value may be that the ratio of the deformed wellbore inner diameter to the original wellbore inner diameter is greater than 50% and less than or equal to 70%; and the third predetermined deformation value may be that the ratio of the deformed wellbore inner diameter to the original wellbore inner diameter is less than or equal to 50%.
[0061] The deformed wellbore inner diameter is determined by the size of the bridge plug or well-drilling tool; that is, the deformed wellbore inner diameter must be just large enough to allow the bridge plug or well-drilling tool to pass through. For example, if the deformed wellbore inner diameter allows a well-drilling tool with a diameter of 90mm to pass through, then the deformed wellbore inner diameter is equal to 90mm. Taking volumetric fracturing inside a casing with a diameter of 139.7mm and a wall thickness of 12.7mm as an example, the original inner diameter of the wellbore is 114.3mm. When the deformed wellbore inner diameter is 97mm, the deformation value is 84.86%, which is within the range of the first predetermined deformation value and is considered slight deformation. In this case, a small-size standard bridge plug of 83-95mm should be used, and volumetric fracturing should continue on the subsequent horizontal section. When the deformed wellbore inner diameter is 79mm, the deformation value is 69.12%, which is within the range of the second predetermined deformation value and is considered slight deformation. For significant deformation, fluid should first be drained from horizontal well 7, followed by a plugging operation on the already volumetrically fractured section of horizontal well 7. After replacing the plug with a 73mm small-sized bridge plug, volumetric fracturing should continue on the subsequent horizontal sections. When the inner diameter of the deformed wellbore is 54mm, the deformation value is 47.24%, which is within the range of the third predetermined deformation value and is considered severe deformation. In this case, fluid should first be drained from horizontal well 7 to accelerate the dissolution of the bridge plug in the already fractured section, and the volumetric fracturing operation on the deformed section should be abandoned. Instead, volumetric fracturing should continue on the subsequent horizontal sections.
[0062] When the wellbore deforms, it may cause the inner diameter of the wellbore to shrink or its shape to become irregular. This can cause the setting or scavenging tools to encounter resistance, making it impossible to effectively deliver fracturing fluid and proppant to the intended formation location, or even to carry out scavenging operations. Therefore, when wellbore deformation or a tendency to deform is detected, construction can be carried out according to this embodiment to reduce the negative impact of wellbore deformation on oil and gas production.
[0063] In an optional implementation, step S2 further includes, when there is a producing gas well near the horizontal well 7 requiring volumetric fracturing, the producing gas well can be shut down 5-7 days before volumetric fracturing of the horizontal well 7 to establish a stress barrier. During volumetric fracturing of the horizontal well 7, the volumetric fracturing parameters are adjusted based on the changes in the wellhead pressure of the producing gas well. The main purpose of shutting down the producing gas well in advance is to reduce or eliminate the dynamic stress generated by gas flow in the area before fracturing operations by stopping gas production activities. This reduction in dynamic stress helps to form a relatively stable "stress barrier" around the fracturing well, thereby reducing unpredictable behaviors that may occur during fracturing due to stress changes, such as unexpected fracture propagation or gas leakage. The construction parameters refer to the fracturing fluid discharge rate, fluid volume, construction pressure, and proppant addition intensity, etc.
[0064] In an optional implementation, step S2 further includes, before volumetric fracturing of the horizontal well 7, maintaining pressure on other unfractured horizontal wells 7 in the same platform well as the target horizontal well 7, and on other unfractured horizontal wells 7 adjacent to the target horizontal well 7 in the same platform well, with the pressure set at 60-70% of the highest pump pressure during volumetric fracturing, to establish a stress barrier. Simultaneously, the wellhead pressure changes of these unfractured horizontal wells 7 are monitored periodically. If the wellhead pressure is found to be below 60%, a pressure replenishment operation should be performed, and the volumetric fracturing parameters should be adjusted according to the wellhead pressure changes. The fracturing parameters refer to the fracturing fluid discharge rate, fluid volume, fracturing pressure, and proppant addition intensity, etc.
[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method of construction for volumetric fracturing, characterized in that, The method comprises the following steps: S1: according to the actual stress condition, the actual borehole trajectory (1) passing condition and the actual mutual position relationship of each horizontal well (7) in each reservoir, simulating the maximum discharge and the maximum liquid volume required for volume fracturing of each horizontal section of each horizontal well (7) without channeling to adjacent wells and without casing deformation; S2: according to the stress average value of all corresponding horizontal wells (7) in each reservoir, performing volume fracturing construction of each reservoir in the order from small to large according to the stress average value, which is a primary volume fracturing sequence; according to the stress value of each horizontal well (7) in a single reservoir, performing volume fracturing construction of each horizontal well (7) in the single reservoir in the order from small to large according to the stress value, which is a secondary volume fracturing sequence; when performing volume fracturing construction of a single horizontal well (7), performing segmented volume fracturing according to the maximum discharge and the maximum liquid volume required for each horizontal section.
2. The method of claim 1, wherein, In the S2 step, when the stress value difference of each horizontal well (7) in a single reservoir is less than a predetermined value during the secondary volume fracturing, the volume fracturing construction of each horizontal well (7) in the single reservoir is performed in the order from the middle to the two sides according to the position of the horizontal well (7).
3. The method of claim 2, wherein, The predetermined value is 1.0-2.0 MPa.
4. The method of claim 1, wherein, In the S2 step, when there are connected natural fractures (8) passing through 2 or more adjacent horizontal wells (7) in a single reservoir and each forming a fracture section, synchronous volume fracturing needs to be performed on each fracture section.
5. The method of claim 4, wherein, During the volume fracturing of the fracture section, the process of volume fracturing is monitored, and when abnormal wellhead pressure rise of adjacent wells or rapid concentration of microseismic event points along a certain position of the wellbore of the horizontal well (7) occurs, measures such as temporary plugging in the fracture and reducing the construction discharge are taken for the volume fracturing of the fracture section.
6. The method of claim 1-5, wherein, The S2 step further comprises, when volume fracturing is performed on a single horizontal well (7), if wellbore deformation of a certain horizontal section occurs, the following measures need to be taken for the deformed well section: When the wellbore deformation of the deformed well section reaches a first predetermined deformation value, a bridge plug matched with the size of the first predetermined deformation value is used for the deformed well section, and then volume fracturing is continued for the subsequent horizontal section; When the wellbore deformation of the deformed well section reaches a second predetermined deformation value, the horizontal well (7) is first drained, then the swept plug operation is performed on the volume-fractured well section of the horizontal well (7), a bridge plug matched with the size of the second predetermined deformation value is used for the deformed well section, and then volume fracturing is continued for the subsequent horizontal section; When the wellbore deformation of the deformed well section reaches a third predetermined deformation value, the horizontal well (7) is drained to promote the dissolution of the bridge plug of the fractured well section, and the volume fracturing construction of the deformed well section is abandoned, and then volume fracturing is continued for the subsequent horizontal section.
7. A method of construction for volumetric fracturing according to claim 6, wherein, The first predetermined deformation value is that the ratio of the deformed wellbore inner diameter to the original wellbore inner diameter is greater than 70% and less than or equal to 85%; the second predetermined deformation value is that the ratio of the deformed wellbore inner diameter to the original wellbore inner diameter is greater than 50% and less than or equal to 70%; and the third predetermined deformation value is that the ratio of the deformed wellbore inner diameter to the original wellbore inner diameter is less than or equal to 50%.
8. The method of claim 6, wherein, The S2 step further comprises, when there is a producing gas well near the horizontal well (7) needing volume fracturing, closing the gas well 5-7 days before volume fracturing of the horizontal well (7) to establish a stress barrier, and then adjusting the volume fracturing construction parameters according to the wellhead pressure change of the gas well during volume fracturing of the horizontal well (7).
9. The method of claim 6, wherein, The S2 step further comprises, before volume fracturing of the horizontal well (7), pressure maintaining of other horizontal wells (7) in the same platform well as the horizontal well (7) and not subjected to volume fracturing and horizontal wells (7) adjacent to the horizontal well (7) in other platform wells and not subjected to volume fracturing, with a pressure maintaining value of 60-70% of the highest pump pressure during volume fracturing to establish a stress barrier, and regularly monitoring the wellhead pressure change of the horizontal wells (7) not subjected to volume fracturing, supplementing pressure when the wellhead pressure is less than 60%, and adjusting the volume fracturing construction parameters according to the wellhead pressure change.