Construction method of multi-layer well bore structure and oil and gas exploitation method

Abstract

The invention relates to the field of oil and gas exploitation, in particular to a construction method of a multi-layer well bore structure and an oil and gas exploitation method.The construction method pays attention to early dynamic evaluation of an oil and gas reservoir in the drilling process, and the oil and gas content is calculated according to the oil and gas display condition in the drilling process, the reservoir quality and a well logging interpretation model after drilling is completed. Whether the reservoir has the condition of obtaining industrial oil gas flow or not is comprehensively analyzed, the advantages and disadvantages of the reservoir are evaluated before the oil-string casing is put in, and pipe waste and construction cost waste are avoided; by packing a deeper layer where the horizontal well is developed, oil and gas interference or safety risks during construction of a shallow layer are avoided; horizontal well development is conducted on the multiple exploitable reservoirs through the well bore structure, and effective utilization of underground oil gas is improved; according to the oil and gas exploitation method, oil and gas collection can be conducted on the multiple exploitable reservoirs through the existing shaft conditions, the risk that a shaft is scrapped after a single target falls down is reduced, the oil and gas collection efficiency is improved, and the oil and gas collection cost is saved.

Description

Technical Field

[0001] The present invention relates to the field of oil and gas exploitation, and particularly to a construction method for a multi-layer wellbore structure and an oil and gas exploitation method. Background Art

[0002] The Sichuan Basin is rich in oil and gas resources, and high-quality reservoirs are developed in multiple layers vertically. In order to develop natural gas resources in different layers by making more use of existing drilling sites, the vertical well or directional well development mode is generally adopted to drill through the target layer at one time. After casing cementing, packers are used for layered fracturing testing, or, after constructing horizontal wells for each target layer, the volume fracturing process is used for development.

[0003] However, the existing wellbore structure does not meet the development needs of other reservoirs during design and cannot achieve the exploitation of multiple target intervals. When the logging of the target layer of a vertical well or directional well shows unsatisfactory results or the stimulation effect is not ideal, the probability of achieving the expected production will be greatly reduced. It will be considered to seal and abandon the vertical well or directional well, and drill a new well to exploit other reservoirs; resulting in a substantial increase in the drilling cost of oil and gas collection.

[0004] Therefore, there is an urgent need for a technical solution to solve the technical problem that the existing wellbore structure cannot achieve the exploitation of multiple target intervals. Summary of the Invention

[0005] The purpose of the present invention is to provide a construction method for a multi-layer wellbore structure and an oil and gas exploitation method for solving the technical problem that the existing wellbore structure cannot achieve the exploitation of multiple target intervals.

[0006] In order to achieve the above purpose, the technical solution adopted by the present invention is as follows: A construction method for a multi-layer wellbore structure includes the following steps: Step 1: Analyze the three-pressure profile of the drilling area to determine the maximum depth of the technical casing setting depth; Step 2: Determine the positions of multiple exploitable reservoirs based on the maximum depth of the technical casing setting depth; Step 3: Implement horizontal well development for the exploitable reservoir with the greatest depth; Step 4: Judge whether the current reservoir meets the conditions for obtaining industrial oil and gas flow. If it meets the conditions for obtaining industrial oil and gas flow, lower the production casing and cement it; if it does not meet the conditions for obtaining industrial oil and gas flow, seal off the current reservoir, and take the upper reservoir of the current reservoir as the target reservoir in the depth direction to implement horizontal well development; Step 5: Repeat Step 4 until the exploitable reservoir with the shallowest seal-off depth is reached.

[0007] A construction method for a multi-layer wellbore structure of the present invention designs the wellbore structure based on three pressure profiles, so that the setting depth range of the intermediate casing designed in the wellbore structure reaches the deepest well depth that can be reached, determines the position of the exploitable reservoir penetrated by the intermediate casing and the position of the exploitable reservoir at the bottom end of the intermediate casing; horizontally develops the exploitable reservoirs in sequence according to the principle from deep to shallow. First, horizontally develop the exploitable reservoir at the bottom of the intermediate casing, and during the horizontal well development process, judge whether the current reservoir meets the conditions for obtaining industrial oil and gas flows. If it meets the conditions for obtaining industrial oil and gas flows, run the production casing and cement it, and collect oil and gas from the current reservoir; if the current reservoir does not meet the conditions for obtaining industrial oil and gas flows or has been exploited, seal the current reservoir, and then turn to horizontally develop the upper exploitable reservoir in the depth direction of the current reservoir, and judge whether the reservoir currently undergoing horizontal well development meets the conditions for obtaining industrial oil and gas flows; horizontally develop the exploitable reservoirs in the intermediate casing in sequence from deep to shallow until the shallowest exploitable reservoir is sealed; in this construction method, after sealing the deeper exploitable reservoir, it will not affect the horizontal well development of the upper exploitable reservoir, and the horizontal well development of the exploitable reservoirs can be carried out in sequence from deep to shallow, so as to meet the development requirements of multiple-layer target reservoirs with one wellbore structure and can take into account the horizontal well development of different target reservoirs.

[0008] As a preferred solution of the present invention, the intermediate casing meets the window-opening conditions of the horizontal well bit, and the side wall of the intermediate casing can be provided with a window; the horizontal well development includes: drilling with a horizontal well bit, and the horizontal well bit can enter the target reservoir through the window or the bottom end of the intermediate casing. The cementing quality of the intermediate casing at the window-opening position is excellent to avoid wellbore collapse caused by window-opening operations; when horizontally developing the deepest reservoir, the horizontal well bit can be drilled and the production casing can be laid through the bottom of the intermediate casing; when horizontally developing the reservoir penetrated by the intermediate casing, it is necessary to first carry out window-opening operations on the side wall of the intermediate casing to make the side wall of the intermediate casing have a through window, and horizontally develop the target reservoir through the window; the size of the window should be designed according to the stroke, diameter, path of the horizontal well bit and the size of the production casing, so that the bit can drill through the window and then drill along the designed path, and the production casing can easily pass through the window. The sizes of the production casings in multiple layers are the same.

[0009] As a preferred embodiment of the present invention, the vertical distance between the window and the middle of the target reservoir is 200 - 350 m. When developing a horizontal well, the horizontal well bit needs to be bent from the vertical drilling state to the horizontal drilling state; due to the limited turning amplitude of the bit, the window needs to be opened on the wall of the technical casing at least 200 m away from the middle of the target reservoir, so that the horizontal well bit has enough turning space before entering the target reservoir, enabling the horizontal well bit to drill horizontally in the reservoir and ensuring that the production casing can be smoothly lowered.

[0010] As a preferred embodiment of the present invention, in step 4, the judgment of whether the current reservoir has the conditions to obtain industrial oil and gas flow includes: the oil and gas shows during drilling and the oil and gas content calculated by the logging interpretation model after drilling. The comprehensive judgment of whether the current reservoir has the conditions to obtain industrial oil and gas flow is made through the oil and gas shows during drilling and the oil and gas content calculated by the logging interpretation model after drilling. If the oil and gas shows are poor and the oil and gas content calculated by the logging interpretation model after drilling is low, and it does not have the conditions to obtain industrial oil and gas flow, then the horizontal well section drilled in the exploitable reservoir is sealed off; if it has the conditions to obtain industrial oil and gas flow, then the production casing is lowered and cemented, and the oil and gas are collected through the production casing.

[0011] As a preferred embodiment of the present invention, the oil and gas shows can judge the oil and gas production efficiency of the current reservoir, and the oil and gas content calculated by the logging interpretation model after drilling can calculate the oil and gas content of the current reservoir. The oil and gas shows can initially judge the oil and gas production efficiency during the drilling process. Combining the calculation results of the oil and gas content of the current reservoir by the logging interpretation model after drilling can judge whether the current reservoir has the conditions to obtain industrial oil and gas flow.

[0012] As a preferred embodiment of the present invention, in step 4, if the production casing is lowered and cemented, after the oil and gas collection is completed, the production casing exposed in the technical casing is removed, and then the current reservoir is sealed off. After the oil and gas collection is completed, the uncemented production casing is removed to avoid the influence of the production casing on the horizontal well development of the upper exploitable reservoir; sealing off the current reservoir can avoid the formation of oil and gas interference during the horizontal well development of the upper exploitable reservoir.

[0013] As a preferred embodiment of the present invention, in step 4, the method of cementing and / or the method of sealing off both include pouring cement slurry in the technical casing or the production casing, and the top depth of the cement slurry is lower than the window depth during the development of the upper layer. After the cement slurry solidifies, it has a good sealing effect; moreover, the cement slurry has fluidity and can flow from the technical casing into the wellbore of the horizontal well, enabling the horizontal wellbore to be better sealed; during the sealing operation, the pouring height of the cement slurry in the technical casing exceeds the top of the sealed-off reservoir by 50 m.

[0014] As a preferred embodiment of the present invention, in step 3, there is a gap between the deepest exploitable reservoir and the bottom end of the technical casing, and the technical casing penetrates through at least one layer of exploitable reservoir. When the horizontal well bit conducts horizontal well development on the deepest exploitable reservoir, the horizontal well bit can drill through the opening at the bottom end of the technical casing; the more exploitable reservoirs the technical casing penetrates through, the more reservoirs that can be developed by horizontal well in this drilling operation.

[0015] An oil and gas production method uses the construction method of a multi-layer wellbore structure described in any one of the above to design the wellbore structure, and includes the following steps: A1: Conduct drilling operations and lower the surface casing and the technical casing. A2: Conduct horizontal well construction of the exploitable reservoir according to the construction method of a multi-layer wellbore structure. A3: After lowering the production casing, conduct oil and gas production operations on the exploitable reservoir The oil and gas production method of the present invention uses the construction method of a multi-layer wellbore structure to design the wellbore structure; when conducting oil and gas production operations, lower the surface casing to stabilize the wellbore, drill the bit to the maximum depth that the technical casing can reach, and then lower the technical casing so that there is a gap between the bottom end of the technical casing and the exploitable reservoir and it penetrates through at least one layer of exploitable reservoir; conduct horizontal well construction of the exploitable reservoir according to the construction method of a multi-layer wellbore structure, and conduct horizontal well development on the exploitable reservoirs in sequence from deep to shallow. When encountering an exploitable reservoir that meets the conditions for obtaining industrial oil and gas flow, lower the production casing to conduct oil and gas collection operations; the oil and gas production method of the present invention can collect oil and gas from multiple exploitable reservoirs with the existing wellbore conditions, reduce the risk of wellbore abandonment after a single target fails, improve the oil and gas collection efficiency, and save the oil and gas collection cost.

[0016] As a preferred embodiment of the present invention, fracturing construction is carried out after the production casing is lowered. Fracturing construction can accelerate oil and gas production.

[0017] In summary, due to the adoption of the above technical solutions, the beneficial effects of the present invention are: 1. A construction method for a multi-layer wellbore structure of the present invention designs the wellbore structure based on a three-pressure profile, so that the interval depth of the production casing section designed in the wellbore structure reaches the deepest well depth that can be reached, determines the position of the exploitable reservoir penetrated by the production casing path and the position of the exploitable reservoir at the bottom of the production casing; successively conducts horizontal well development on the exploitable reservoirs according to the principle from deep to shallow. First, conducts horizontal well development on the exploitable reservoir at the bottom of the production casing, and during the horizontal well development process, determines whether the current reservoir meets the conditions for obtaining industrial oil and gas flows. If it meets the conditions for obtaining industrial oil and gas flows, then runs the production tubing and cementing is carried out to collect oil and gas from the current reservoir; if the current reservoir does not meet the conditions for obtaining industrial oil and gas flows or has been exploited, then seals the current reservoir and turns to conduct horizontal well development on the upper exploitable reservoir in the depth direction of the current reservoir, and determines whether the reservoir where the current horizontal well development is carried out meets the conditions for obtaining industrial oil and gas flows; successively conducts horizontal well development on the exploitable reservoirs in the production casing from deep to shallow until the shallowest exploitable reservoir is sealed; in this construction method, after sealing the deeper exploitable reservoir, it does not affect the horizontal well development of the upper exploitable reservoir, and can successively conduct horizontal well development on the exploitable reservoirs from deep to shallow, so as to meet the development requirements of multi-layer target reservoirs with one wellbore structure, and can take into account the horizontal well development of different target reservoirs.

[0018] 2. An oil and gas production method of the present invention designs the wellbore structure by using a construction method for a multi-layer wellbore structure; when carrying out oil and gas production operations, runs the surface casing to stabilize the wellbore, drills the bit to the maximum depth that the production casing can reach, and then runs the production casing, so that the bottom of the production casing is provided with exploitable reservoirs at intervals and penetrates at least one exploitable reservoir; conducts horizontal well construction of the exploitable reservoirs by using a construction method for a multi-layer wellbore structure, successively conducts horizontal well development on the exploitable reservoirs from deep to shallow, and when encountering an exploitable reservoir that meets the conditions for obtaining industrial oil and gas flows, runs the production tubing to carry out oil and gas collection operations; an oil and gas production method of the present invention can collect oil and gas from multi-layer exploitable reservoirs with the existing wellbore conditions, reduces the risk of wellbore abandonment after a single target fails, improves the oil and gas collection efficiency, and saves the oil and gas collection cost.

[0019] 3. A construction method for a multi-layer wellbore structure of the present invention focuses on the early dynamic evaluation of oil and gas reservoirs during the drilling process. By comprehensively analyzing the oil and gas shows, reservoir quality, and the calculated oil and gas content from the well logging interpretation model after drilling, it determines whether the reservoir has the conditions to obtain industrial oil and gas flows. After the production casing is run in, the reservoir quality is re-evaluated, avoiding waste of pipe materials and construction costs. By isolating the deeper drilled intervals, it can prevent oil and gas interference during the construction of shallower intervals. Using the wellbore structure for horizontal well construction of multiple exploitable reservoirs reduces the risk of wellbore abandonment after a single target fails, lowers the oil and gas production cost, and improves the oil and gas production efficiency, having good economic and practical values. 3. A construction method for a multi-layer wellbore structure of the present invention focuses on the early dynamic evaluation of oil and gas reservoirs during the drilling process. By comprehensively analyzing the oil and gas shows, reservoir quality, and the calculated oil and gas content from the well logging interpretation model after drilling, it determines whether the reservoir has the conditions to obtain industrial oil and gas flows. After the production casing is run in, the reservoir quality is re-evaluated, avoiding waste of production casing materials and construction costs. By isolating the deeper drilled intervals, it can prevent oil and gas interference during the construction of shallower intervals. Using the wellbore structure for horizontal well construction of multiple exploitable reservoirs reduces the risk of wellbore abandonment after a single target fails, lowers the oil and gas production cost, and improves the oil and gas production efficiency, having good economic and practical values. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a schematic flow chart of a construction method for a multi-layer wellbore structure; Figure 2 is a schematic diagram of the horizontal well development of Reservoir A in Example 1; Figure 3 is a schematic diagram of the horizontal well development of Reservoir B in Example 1; Figure 4 is a schematic diagram of the horizontal well development of Reservoir C in Example 1.

[0021] ICON: 1 - Reservoir A, 2 - Reservoir B, 3 - Reservoir C, 4 - technical casing, 5 - surface casing, 6 - horizontal well bit. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The present invention will be described in detail below with reference to the accompanying drawings.

[0023] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0024] Example 1 As Figure 1A construction method for a multi-layer wellbore structure shown in the figure includes the following steps: S1: Explore the geology of the drilling area to obtain geological exploration data; S2: Based on the obtained geological exploration data, conduct a three-pressure profile modeling of the geology of the drilling area, analyze the three-pressure profile of the geology of the drilling area, and determine the maximum depths of the surface casing and the production casing setting depth; S3: According to the maximum depth of the production casing setting depth, determine the position of the exploitable reservoir at the bottom of the production casing and the position of the exploitable reservoir penetrated by the production casing.

[0025] S4: Implement horizontal well development for the deepest exploitable reservoir (i.e., the exploitable reservoir at the bottom of the production casing) in a conventional production process. ]

[0026] S5: When implementing horizontal well development, determine whether the exploitable reservoir where the horizontal well drilling is currently carried out meets the conditions for obtaining industrial oil and gas flows. If it meets the conditions for obtaining industrial oil and gas flows, run in the production casing, and carry out cementing and fracturing operations; if the current reservoir does not meet the conditions for obtaining industrial oil and gas flows or the oil and gas in the current reservoir have been collected, seal the current reservoir, and take the upper exploitable reservoir of the current reservoir in the depth direction of the production casing as the target reservoir, and implement horizontal well development for the target reservoir.

[0027] S6: Repeat S5 until the shallowest exploitable reservoir is sealed off.

[0028] Specifically, the production casing meets the window-opening conditions of the horizontal well bit. The horizontal well development is carried out by drilling with a horizontal well bit. The horizontal well bit bends from the vertical direction into the exploitable reservoir and conducts horizontal drilling in the exploitable reservoir; in S4, there is a gap between the deepest exploitable reservoir and the bottom end of the production casing, and the reserved vertical depth, that is, the vertical distance interval between the kick-off point and the middle of the target reservoir is greater than 200 m, so that the horizontal well bit has enough space for bending; when implementing horizontal well development for the deepest exploitable reservoir, the horizontal well bit drills from the opening at the bottom end of the production casing, finally reaches the deepest exploitable reservoir, and can conduct horizontal drilling in the exploitable reservoir; in S5, a window is opened on the side wall of the production casing, and the horizontal well bit enters the target reservoir from the window. The window is vertically 200-350 m different from the middle of the target reservoir.

[0029] Specifically, in S5, it is determined whether the current reservoir has the conditions to obtain industrial oil and gas flow based on the oil and gas shows during the drilling of the horizontal well bit and the oil and gas content calculated by the logging interpretation model after drilling is completed; the oil and gas shows judge the oil and gas production efficiency of the current reservoir through the oil and gas production situation during the horizontal well drilling process; the oil and gas content calculated by the logging interpretation model after drilling can calculate the oil and gas content of the current reservoir, and based on the oil and gas production efficiency and the oil and gas content of the current reservoir, it is determined whether to install a casing in the current reservoir, avoiding waste of the materials and construction of the production casing.

[0030] Specifically, in S5, if a production casing is installed for oil and gas collection, after the oil and gas collection is completed, it is necessary to first remove the production casing exposed in the intermediate casing, and then seal off the current reservoir. The exposed production casing is the section of the production casing that is not submerged by the cementing material; the cementing method and / or the sealing method both include injecting cement slurry into the intermediate casing or the production casing, and the pouring height of the cement slurry in the casing exceeds the top of the current reservoir to be sealed off by 50 m, so as to avoid affecting the horizontal well development of the upper exploitable reservoir after the cement slurry solidifies; when cementing the production casing, the cement slurry seals off the gap between the outer wall of the production casing and the horizontal well wellhead, preventing oil and gas from leaking into the intermediate casing to form oil and gas interference; when sealing off, it is necessary to first cut the production casing and remove the production casing that has not been solidified by cement from the intermediate casing to prevent the production casing from interfering with the horizontal well bit.

[0031] Such as Figures 2 - 4 shown in the construction method of a multi-layer wellbore structure: Based on the three-pressure modeling of the drilling area, the setting depth of the intermediate casing 4 is determined to be 1500 m, and the surface casing 5 and the intermediate casing 4 are installed. The exploitable reservoirs within the interval of the intermediate casing 4 are three layers: the A reservoir 1 at a depth of 1800 m, the B reservoir 2 at a depth of 1300 m, and the C reservoir 3 at a depth of 1000 m. Among them, the A reservoir 1 is located at the bottom end of the intermediate casing 4 and has a gap with the intermediate casing 4. The B reservoir 2 and the C reservoir 3 are penetrated by the intermediate casing 4. The depths of the A reservoir 1, the B reservoir 2, and the C reservoir 3 decrease in sequence; the intermediate casing 4 is a casing with a diameter of 219 - 244.5 mm, the production casing is a casing with a diameter of 139.7 mm, and the diameter of the horizontal well bit 6 is 190.5 - 215.9 mm.

[0032] Such as Figure 2As shown in the figure, after the production casing 4 is run in, horizontal well development is first carried out on the A reservoir 1. The horizontal well bit 6 drills from the opening at the bottom end of the production casing 4. During the drilling process, the bit gradually inclines from the vertical direction to the horizontal direction until it finally drills horizontally in the reservoir. When carrying out horizontal well development on the A reservoir 1, the oil and gas show situation of the A reservoir 1 is collected and the probability of obtaining an industrial oil and gas flow is initially judged. After the drilling is completed, a logging interpretation model is established for the A reservoir 1, and the oil and gas content of the A reservoir 1 is calculated through the logging interpretation model of the A reservoir 1. The probability of obtaining an industrial oil and gas flow is comprehensively judged through the oil and gas content and the oil and gas show situation. If the probability of obtaining an industrial oil and gas flow is relatively high, the production casing is run in and cement slurry is injected for cementing, and then the operation is transferred to fracturing construction for oil and gas production. After the oil and gas production from the A reservoir 1 is completed, the part of the production casing in the production casing 4 that is not sealed by the cementing material is taken out, and then the A reservoir 1 is isolated. If it is judged that the probability of the A reservoir 1 obtaining an industrial oil and gas flow is low, cement slurry is directly injected to isolate the A reservoir 1 with the cement slurry.

[0033] As Figure 3 shown, after waiting for the cement slurry used to isolate the A reservoir 1 to solidify, an oval window 1 is opened on the wall of the production casing 4 about 300 m above the top of the B reservoir 2. The diameter of the window 1 needs to be larger than the diameter of the horizontal well bit 6 to enable the horizontal well bit 6 to pass through smoothly. The distance of about 300 m from the top of the B reservoir 2 can ensure that the horizontal well bit has enough bending distance to change from vertical drilling to horizontal drilling, and finally the horizontal well bit drills horizontally in the B reservoir 2. After the horizontal well bit 6 enters the B reservoir 2, the oil and gas show situation of the B reservoir 2 is collected and the probability of obtaining an industrial oil and gas flow is initially judged. After the drilling is completed, a logging interpretation model is established for the B reservoir 2, and the oil and gas content of the B reservoir 2 is calculated through the logging interpretation model of the B reservoir 2. The probability of obtaining an industrial oil and gas flow is comprehensively judged through the oil and gas content and the oil and gas show situation. If the probability of obtaining an industrial oil and gas flow is relatively high, the production casing is run in and cement slurry is injected for cementing, and then the operation is transferred to fracturing construction for oil and gas production. After the oil and gas production from the B reservoir 2 is completed, the part of the production casing in the production casing 4 that is not sealed by the cementing material is taken out, and then the B reservoir 2 is isolated. If it is judged that the probability of the B reservoir 2 obtaining an industrial oil and gas flow is low, cement slurry is directly injected again to isolate the B reservoir 2 with the cement slurry.

[0034] As Figure 4As shown in the figure, after waiting for the cement slurry used to seal the B reservoir 2 to solidify, a window two is opened on the pipe wall of the production casing 4 about 300 m above the top of the C reservoir 3, and the horizontal well bit 6 drills into the C reservoir 3 from the window two; after the horizontal well bit 6 enters the C reservoir 3, the oil and gas shows in the C reservoir 3 are collected and the probability of obtaining an industrial oil and gas flow is preliminarily judged. After the drilling is completed, a logging interpretation model of the C reservoir 3 is established, and the oil and gas content of the C reservoir 3 is calculated through the logging interpretation model of the C reservoir 3. The probability of obtaining an industrial oil and gas flow in the C reservoir 3 is comprehensively judged based on the oil and gas content and the oil and gas shows; if the probability of obtaining an industrial oil and gas flow in the C reservoir 3 is relatively high, the production casing is run in, and cement slurry is injected for well cementing, and then the fracturing construction is carried out for oil and gas production; after the oil and gas production is completed, the uncemented part of the production casing is removed, and the C reservoir 3 is sealed; if the probability of obtaining an industrial oil and gas flow is low, cement slurry is injected to seal the C reservoir 3.

[0035] Preferably, the production casing penetrates through more than three exploitable reservoirs, enabling horizontal well development of multiple target reservoirs within the same production casing.

[0036] A construction method for a multi-layer wellbore structure of the present invention, based on the analysis of the formation pressure profiles of three formations (formation pore pressure, formation fracture pressure, formation collapse pressure), adopts the "from bottom to top" method for horizontal well development of multiple reservoirs. The setting depth of the production casing preferably meets the development needs of the deepest target layer, and different development target layers can be taken into account; during horizontal well development, attention is paid to the early dynamic evaluation of the oil and gas layers during the horizontal well drilling process. Through the oil and gas shows, reservoir quality, and logging interpretation after drilling during the horizontal well drilling process, the reservoir effect is comprehensively analyzed to judge whether the current reservoir has the conditions to obtain an industrial oil and gas flow, guiding the running in of the production casing, thereby avoiding losses caused by blindly running in the production casing; when switching from the A reservoir to developing the B reservoir or the C reservoir, since the sizes of the casing and bit for each opening are the same, the construction cost is reduced; effective sealing is achieved between the horizons of different reservoirs, and sequential development can avoid oil and gas interference.

[0037] A construction method for a multi-layer wellbore structure of the present invention designs the wellbore structure based on three pressure profiles, so that the interval of the depth where the designed production casing is run into the well reaches the deepest well depth that can be reached, determines the position of the exploitable reservoir penetrated by the production casing path and the position of the exploitable reservoir at the bottom end of the production casing; successively conducts horizontal well development on the exploitable reservoirs according to the principle from deep to shallow. First, conducts horizontal well development on the exploitable reservoir at the bottom of the production casing. During the horizontal well development process, determines whether the current reservoir meets the conditions for obtaining industrial oil and gas flows. If it meets the conditions for obtaining industrial oil and gas flows, runs in the production casing and cement bonds it, and conducts oil and gas collection on the current reservoir; if the current reservoir does not meet the conditions for obtaining industrial oil and gas flows or has been exploited, seals the current reservoir, and then conducts horizontal well development on the upper exploitable reservoir in the depth direction of the current reservoir, and determines whether the reservoir where the current horizontal well development is carried out meets the conditions for obtaining industrial oil and gas flows; successively conducts horizontal well development on the exploitable reservoirs in the production casing from deep to shallow until the shallowest exploitable reservoir is sealed; in this construction method, after sealing the deeper exploitable reservoir, it will not affect the horizontal well development of the upper exploitable reservoir, and can successively conduct horizontal well development on the exploitable reservoirs from deep to shallow, so as to meet the development requirements of a multi-layer target reservoir with one wellbore structure, and can take into account the horizontal well development of different target reservoirs.

[0038] Example 2 An oil and gas production method uses the construction method of a multi-layer wellbore structure in Example 1 for wellbore design, including the following steps: A1: Conduct drilling operations, and run in the surface casing and the production casing; A2: Conduct horizontal well construction on the exploitable reservoirs according to the construction method of a multi-layer wellbore structure; A3: Conduct oil and gas production operations on the exploitable reservoirs after running in the production casing.

[0039] Specifically, in A3, after the production casing is run in, fracturing construction is carried out.

[0040] An oil and gas production method of the present invention designs the wellbore structure by using a construction method of a multi-layer wellbore structure; during the oil and gas production operation, a surface casing is lowered to stabilize the wellbore, the drill bit is drilled to the maximum depth where the technical casing can be lowered, and then the technical casing is lowered, so that the bottom end of the technical casing is spaced from the exploitable reservoir and at least penetrates one exploitable reservoir; the horizontal well construction of the exploitable reservoir is carried out by using a construction method of a multi-layer wellbore structure, and the exploitable reservoirs are developed by horizontal wells in sequence from deep to shallow. When an exploitable reservoir with the condition of obtaining industrial oil and gas flow is encountered, an oil layer casing is lowered for oil and gas collection operation; an oil and gas production method of the present invention can collect oil and gas from multi-layer exploitable reservoirs with the existing wellbore conditions, reduces the risk of wellbore abandonment after a single target fails, improves the oil and gas collection efficiency, and saves the oil and gas collection cost.

[0041] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A construction method for a multi-layer wellbore structure, characterized in that It includes the following steps: Step 1: Conduct a tri-pressure profile analysis of the drilling area to determine the maximum depth of the production casing setting depth. Step 2: Determine the positions of multiple exploitable reservoirs based on the maximum depth of the production casing setting depth. Step 3: Implement horizontal well development for the exploitable reservoir with the greatest depth. Step 4: Determine whether the current reservoir meets the conditions for obtaining industrial oil and gas flows. If it meets the conditions for obtaining industrial oil and gas flows, run the production casing and cement it in place. If it does not meet the conditions for obtaining industrial oil and gas flows, seal off the current reservoir and conduct horizontal well development for the upper reservoir of the current reservoir in the depth direction as the target reservoir. Step 5: Repeat Step 4 until the exploitable reservoir with the shallowest sealing depth is reached.

2. The construction method of a multi-layer wellbore structure according to claim 1, characterized in that The production casing meets the window-opening conditions for the horizontal well bit, and a window can be opened on the sidewall of the production casing; the horizontal well development includes: drilling with a horizontal well bit, and the horizontal well bit can enter the target reservoir through the window or the bottom end of the production casing.

3. The construction method of a multi-layer wellbore structure according to claim 2, characterized in that, The window is vertically spaced 200 - 350 m from the middle of the target reservoir.

4. The construction method of a multi-layer wellbore structure according to claim 3, characterized in that In Step 4, the determination of whether the current reservoir meets the conditions for obtaining industrial oil and gas flows includes: the oil and gas shows during drilling and the oil and gas content calculated by the well logging interpretation model after drilling.

5. The construction method of a multi-layer wellbore structure according to claim 4, characterized in that The oil and gas shows can determine the oil and gas production efficiency of the current reservoir, and the well logging interpretation model after drilling can calculate the oil and gas content of the current reservoir.

6. The construction method of a multi-layer wellbore structure according to claim 5, characterized in that, In Step 4, if the production casing is run and cemented in place, after the oil and gas are collected, the production casing exposed in the production casing is removed, and then the current reservoir is sealed off.

7. The construction method of a multi-layer wellbore structure according to claim 6, characterized in that, In Step 4, the cementing method and / or the sealing method both include pouring cement slurry in the production casing or the production casing, and the top depth of the cement slurry is lower than the window depth during the development of the upper layer.

8. The construction method of a multi-layer wellbore structure according to claim 7, characterized in that, In Step 3, there is a gap between the exploitable reservoir with the greatest depth and the bottom end of the production casing, and the production casing penetrates at least one exploitable reservoir.

9. An oil and gas production method, characterized in that, Based on the construction method of a multi-layer wellbore structure according to any one of claims 1 - 8, conduct wellbore structure design, including the following steps: A1: Conduct drilling operations and run the surface casing and the production casing. A2: Conduct horizontal well construction for the exploitable reservoir according to a construction method of a multi-layer wellbore structure. A3: Conduct oil and gas production operations for the exploitable reservoir after running the production casing.

10. A method for oil and gas extraction according to claim 9, characterized in that, In A3, fracturing construction is carried out after the production casing is run.

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