A method for thermal recovery of oil from a low-efficiency well group

Abstract

The application provides a method for oil and heat simultaneous mining of a low-efficiency well group, and relates to the technical field of oil exploitation. The method comprises the following steps: obtaining geological parameters of a low-efficiency well group region and low-efficiency well parameters; determining candidate target wells according to the low-efficiency well parameters and preset reconstruction conditions; determining a target region by taking the low-efficiency well group region with the number of candidate target wells greater than or equal to two as the target region; obtaining corresponding geological indexes by evaluating the relationship according to the corresponding geological parameters of the target region; selecting two candidate target wells from the target region with the largest geological indexes as target wells; connecting the two target wells by a sidetracking method to construct a U-shaped horizontal well; and performing oil and heat simultaneous mining on the U-shaped horizontal well. The method can improve the efficiency of oil and heat simultaneous mining of the low-efficiency well group.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil exploitation, in particular to an oil and heat co-production method for a low-efficiency well group. BACKGROUND

[0002] Since the rise of the oil industry, the development of oil fields worldwide has undergone a long development process. From the early simple exploitation of shallow and high-permeability oil fields to the current deep excavation in the face of complex geological conditions, technology has been constantly innovated. Among the many types of oil fields, low-permeability old oil fields have been an important object of oil exploitation due to their abundant reserves and wide distribution.

[0003] However, after years of exploitation of these low-permeability old oil fields, the pressure of the oil reservoir gradually decreases, resulting in an increase in the flow resistance of the oil flow in the formation, which affects the exploitation efficiency. SUMMARY

[0004] The problem solved by the present application is how to improve the exploitation efficiency of low-permeability old oil fields.

[0005] To solve the above problems, the present application provides an oil and heat co-production method for a low-efficiency well group.

[0006] In a first aspect, the present application provides an oil and heat co-production method for a low-efficiency well group, comprising:

[0007] obtaining geological parameters of a low-efficiency well group area and low-efficiency well parameters therein;

[0008] determining a candidate target well according to the low-efficiency well parameters and a preset modification condition;

[0009] determining a target area from the low-efficiency well group area when the number of candidate target wells is greater than or equal to two;

[0010] obtaining a corresponding geological index through an evaluation relationship according to the geological parameters corresponding to the target area;

[0011] selecting two candidate target wells from the target area with the largest geological index as target wells;

[0012] connecting the two target wells to construct a U-shaped horizontal well through a sidetracking method;

[0013] conducting oil and heat co-production on the U-shaped horizontal well.

[0014] Optionally, the geological parameters include sandstone thickness, porosity, permeability, brittleness index, temperature, fracture pressure, water saturation, Poisson's ratio, and stress difference of the low-efficiency well group area; and the evaluation relationship satisfies:

[0015] ;

[0016] wherein, B is the geological index, b1 is the sandstone thickness, b2 is the porosity, b3 is the permeability, b4 is the brittleness index, b5 is the temperature, b6 is the fracture pressure, b7 is the water saturation, b8 is the Poisson's ratio, b9 is the stress difference, b1,max is the maximum sandstone thickness in all the target regions, b2,max is the maximum porosity in all the target regions, b3,max is the maximum permeability in all the target regions, b4,max is the maximum brittleness index in all the target regions, b5,max is the maximum temperature in all the target regions, b6,max is the maximum fracture pressure in all the target regions, b7,max is the maximum water saturation in all the target regions, b8,max is the maximum Poisson's ratio in all the target regions, b9,max is the maximum stress difference in all the target regions, W1 is the weight coefficient of the sandstone thickness, W2 is the weight coefficient of the porosity, W3 is the weight coefficient of the permeability, W4 is the weight coefficient of the brittleness index, W5 is the weight coefficient of the temperature, W6 is the weight coefficient of the fracture pressure, W7 is the weight coefficient of the water saturation, W8 is the weight coefficient of the Poisson's ratio, and W9 is the weight coefficient of the stress difference.

[0017] Optionally, the determining the alternative target well according to the low-efficiency well parameter and a preset reconstruction condition comprises:

[0018] When the low-efficiency well parameter meets the preset reconstruction condition, determining the low-efficiency well as the alternative target well.

[0019] Optionally, the low-efficiency well parameter comprises a casing parameter, a cement sheath parameter and a wellbore drift diameter parameter of the low-efficiency well; the preset reconstruction condition comprises a casing condition, a cement sheath condition and a wellbore drift diameter condition; and before the determining the low-efficiency well as the alternative target well, the method further comprises:

[0020] When the casing parameter of the low-efficiency well meets the casing condition, the cement sheath parameter meets the cement sheath condition and the wellbore drift diameter parameter meets the wellbore drift diameter condition, indicating that the low-efficiency well parameter meets the preset reconstruction condition.

[0021] Optionally, the constructing the U-shaped horizontal well by connecting two target wells through a sidetracking method comprises:

[0022] constructing a horizontal well section connecting the two target wells through the sidetracking method;

[0023] constructing the U-shaped horizontal well according to the horizontal well section and the two target wells.

[0024] Optionally, the method further comprises:

[0025] A fracture system in communication with the horizontal well section is formed by a staged fracturing technique centered on the horizontal well section.

[0026] Optionally, the oil-heat simultaneous production of the U-shaped horizontal well comprises:

[0027] The U-shaped horizontal well is developed by staged oil-heat simultaneous production, which comprises an elastic oil production stage, a water injection oil production and heat recovery stage, and a closed circulation heat exchange stage.

[0028] Optionally, the elastic oil production stage comprises:

[0029] Crude oil flowing into the U-shaped horizontal well through the fracture system is produced.

[0030] Optionally, the water injection oil production and heat recovery stage comprises:

[0031] High-pressure water is injected into low-efficiency vertical wells around the U-shaped horizontal well, and oil-water mixture flowing into the U-shaped horizontal well through the fracture system is produced.

[0032] Optionally, the closed circulation heat exchange stage comprises:

[0033] After production is stopped, an underground heat exchange circulation system is constructed with the U-shaped horizontal well as a channel.

[0034] The oil-heat simultaneous production method of the low-efficiency well group has the following beneficial effects: first, by obtaining low-efficiency well group regional geological parameters (clear oil and gas occurrence and development potential) and low-efficiency well parameters (locating single well low-efficiency causes), combined with preset conditions, the method screens and locks alternative target wells, avoids resource mismatch, and reduces invalid investment; second, according to the geological parameters, the method calculates geological indexes, and preferentially selects high-potential areas with the largest indexes, that is, from the alternative target wells in the low-efficiency well group area with the largest geological indexes, the final target well is selected, and higher output is achieved with the same construction cost; third, based on the two selected target wells, the method constructs a U-shaped horizontal well through sidetracking, maximizes the reservoir contact range, reduces dead oil zones, optimizes fluid flow paths through the U-shaped horizontal well structure, reduces resistance, and improves resource development degree and production stability; and finally, through oil-heat simultaneous production, the method reduces crude oil viscosity, reduces heat energy loss, breaks the low-efficiency bottleneck of difficult oil flow, and ultimately realizes the goal of activating low-efficiency well group resources at a lower cost and improving the production efficiency and recovery rate of low-efficiency well groups in old oilfields. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 A flowchart of an oil-heat simultaneous production method of a low-efficiency well group according to an embodiment of the present application;

[0036] Figure 2 Figure 1 is a structural schematic diagram of an oil and heat co-production system of a U-shaped horizontal well according to an embodiment of the present application.

[0037] Legend of reference signs:

[0038] 01 - target well; 02 - horizontal well section; 03 - fracture system; 04 - low-efficiency vertical well; 05 - rotating magnetic joint; 06 - magnetic steering tool assembly; 07 - metering station; 08 - oil transfer station; 09 - combination station; 10 - water injection station; 11 - oil production device. DETAILED DESCRIPTION

[0039] In order to make the above objectives, features and advantages of the present application more apparent, specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. Although some embodiments of the present application are shown in the drawings, it should be understood that the present application can be implemented in various forms, and should not be interpreted as being limited to the embodiments set forth herein, but rather, these embodiments are provided so as to more thoroughly and completely understand the present application. It should be understood that the drawings and embodiments of the present application are for illustrative purposes only, and are not intended to limit the scope of protection of the present application.

[0040] It should be understood that each of the steps recited in the method embodiments of the present application can be performed in different orders, and / or in parallel. In addition, the method embodiments can include additional steps and / or omit the steps shown. The scope of the present application is not limited in this respect.

[0041] The term "comprising" and variations thereof as used in the present application are open-ended, that is, "including but not limited to"; the term "based on" is "based, at least in part, on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments"; the term "optionally" means "optional embodiments". Related definitions are given throughout the detailed description. It should be noted that the concepts mentioned in the present application are merely used to distinguish different devices, modules or units, and are not intended to limit the functions performed by these devices, modules or units.

[0042] It should be noted that the modification of "one" or "multiple" mentioned in the present application is illustrative rather than limiting, and those skilled in the art should understand that, unless otherwise explicitly indicated in the context, it should be understood as "one or more".

[0043] The names of the messages or information exchanged between the multiple devices in the embodiments of the present application are merely for illustrative purposes, and are not intended to limit the scope of these messages or information.

[0044] In the related art, after years of exploitation, the pressure of the reservoir in the low permeability old oilfield gradually decreases, which causes a series of chain reactions and seriously affects the exploitation efficiency of the oilfield. The decrease of the reservoir pressure directly leads to a significant increase of the flow resistance of the oil flow in the formation, which greatly reduces the natural productivity of the oil well. Due to the complex pore structure and low permeability of the low permeability reservoir, the oil flow is difficult to flow smoothly, and the decrease of the pressure further weakens the power of the oil flow, so that the oil flow speed is more slow, and even stagnates in some areas. At the same time, long-term water injection exploitation not only cannot effectively supplement the reservoir pressure, but also may aggravate the heterogeneity of the reservoir due to uneven water injection and changes in the properties of the formation rock, further hindering the flow of the oil flow. In addition, the decrease of the reservoir pressure also leads to changes in the properties of the fluid, the complexity of the gas-liquid two-phase flow increases, and the flow resistance of the oil flow is further increased. These problems eventually lead to a significant decrease of the single well production, a significant increase of the exploitation cost, a more complex and difficult to exploit remaining oil distribution, and a great reduction of the recovery rate of the oilfield.

[0045] In view of the problems in the above related art, the embodiment of the present application provides an oil and heat co-production method for a low-efficiency well group.

[0046] As shown in Figure 1 The oil and heat co-production method for a low-efficiency well group provided by the embodiment of the present application comprises:

[0047] S100, obtaining geological parameters of a low-efficiency well group area and low-efficiency well parameters in the low-efficiency well group area.

[0048] Specifically, the geological parameters of the low-efficiency well group area are obtained, which focuses on the oil and gas development potential of the area and covers parameters such as formation lithology, reservoir physical properties (porosity, permeability, etc.), structural features, sedimentary facies, formation pressure and temperature, which determine the oil and gas occurrence conditions and development potential boundary of the area; and the low-efficiency well parameters focus on a single well and include well body basic information, wellbore integrity (casing, cement sheath state), wellbore drift diameter, production performance and historical modification parameters, etc., which reflect the low-efficiency performance and potential causes of a single well, and the two types of parameters jointly provide core data support for determining whether the low-efficiency well meets the modification condition and formulating a modification scheme.

[0049] S200, determining a candidate target well according to the low-efficiency well parameters and a preset modification condition.

[0050] Specifically, the parameters of each low-efficiency well are compared according to the parameters of each low-efficiency well and the preset modification condition, and whether the low-efficiency well meets the modifiable condition is judged according to the comparison result, if it meets, the low-efficiency well can be determined as a candidate low-efficiency well.

[0051] S300, determining the low-efficiency well group area as a target area when the number of the candidate target wells is greater than or equal to two.

[0052] Specifically, the number of candidate inefficient wells in each inefficient well group region is counted, and when the number of candidate inefficient wells is greater than or equal to two, the region is determined as a target region, that is, two or more inefficient wells that meet the requirements of the reconstruction can be found in the region.

[0053] S400, obtaining a corresponding geological index through an evaluation relationship according to the geological parameter corresponding to the target region.

[0054] S500, selecting two candidate target wells in the target region with the largest geological index as target wells.

[0055] Specifically, a corresponding geological index is calculated through an evaluation relationship according to the geological parameter corresponding to the target region, which can include sandstone thickness, porosity, permeability, brittleness index, temperature, fracture pressure, water saturation, Poisson's ratio, stress difference and other data information of the inefficient well group region. Finally, the target region with the largest geological index is determined as the final reconstruction region, and two candidate target wells are selected from it as the final target wells of the reconstruction. Since the candidate target wells in the target region all meet the requirements of the reconstruction, two suitable candidate target wells can be selected as the final target wells according to the distance of the two candidate target wells. For example, the well spacing of the two candidate target wells is selected to be between 300 and 500 meters as the most suitable target wells for reconstruction.

[0056] It should be noted that the final target well selection needs to follow the principles of geological index priority and well condition adaptation. First, the target region with the largest geological index is selected from all target regions. The target region can be divided into a first type region or a second type region according to the geological index, for example, the geological index greater than or equal to 100 is a first type region, and the geological index between 60 and 100 is a second type region. The larger the geological index, the better the reservoir conditions (such as high porosity, high oil saturation), the rich geothermal resources (high formation temperature), and the low difficulty of fracturing reconstruction (high brittleness index, low fracture pressure), which can maximize the efficiency and benefits of subsequent oil-heat co-production. Then, two final target wells are selected from the candidate target wells in the target region with the largest geological index. The well spacing threshold, for example, the well spacing is between 300 and 500 meters, also needs to be met when selecting, and the well condition (such as casing integrity, wellbore smoothness) is verified again to ensure that both wells have ultra-short radius sidetracking conditions (curvature radius ≤ 30 m, build-up rate > 90° / 30 m), which lays a foundation for subsequent construction of U-shaped horizontal wells and implementation of fracturing operations, and finally realizes the dual goals of precise targeting of remaining oil enrichment areas and adaptation of oil-heat co-development.

[0057] Exemplarily, the inefficient wells are screened according to the parameters of the inefficient wells in each inefficient well group region, that is, at least two or more than two inefficient vertical wells with good casing, good cementing quality and unobstructed wellbore are selected as the preliminary screening candidate target wells. For example, the well spacing of the two candidate target wells is controlled between 300 meters and 500 meters, and the two candidate target wells are arranged in a region with stable geology, simple structure and few faults. This process is mainly a preliminary screening of the inefficient well group region, and the region in which the number of the candidate target wells does not meet the demand is proposed, so that the inefficient well group region meeting the demand of the candidate target well is taken as a target region. At the same time, the final target well meeting the demand is obtained by further screening according to the corresponding geological parameters of each target region. For example, the target regions are classified according to the geological parameters of each target region, and the target region with the optimal geological condition is selected as the final selection region, and the candidate target wells in the region are taken as the final target well for reconstruction.

[0058] S600, the two target wells are connected by a sidetracking method to construct a U-shaped horizontal well.

[0059] Specifically, a horizontal well section is constructed between two target wells using sidetracking, connecting the two wells and forming a modified U-shaped horizontal well. Sidetracking involves drilling laterally from a point in the existing wellbore towards the other target well using specific tools and techniques, thus creating a horizontal well section connecting the two wells. Sidetracking methods can include ultra-short radius sidetracking (USRD), medium-radius sidetracking (MRD), and long-radius sidetracking (LRD), with the specific method chosen based on the actual operating conditions. To achieve wellbore orientation changes over short distances, ultra-short radius sidetracking technology can be prioritized. Its curvature radius is typically controlled within 30 meters, corresponding to a build-up rate exceeding 90° / 30 meters. This design meets the need for rapid turning within confined downhole spaces, making it particularly suitable for scenarios such as sidetracking old wells to extract remaining oil and developing thin reservoirs. To achieve high-precision trajectory control, this technology is equipped with a Measurement While Drilling (MWD) system, which can collect key data such as downhole inclination angle, azimuth angle, and formation parameters in real time and rapidly transmit the data to the surface control system. This allows operators to monitor the downhole situation in real time. Simultaneously, it is paired with titanium alloy flexible drill pipe, which combines high strength and good flexibility to adapt to the bending requirements of high-curvature wellbore trajectories. This effectively avoids trajectory deviation or drill string damage caused by excessive drill pipe rigidity. Through the synergistic effect of both, the drill bit can accurately traverse complex formations and precisely reach the preset target production area or wellbore repair area, significantly improving operational efficiency and resource utilization while reducing new well drilling costs.

[0060] S700, the U-shaped horizontal well is used for simultaneous oil and heat production.

[0061] Specifically, by the special trajectories of the injection well section, the horizontal reservoir well section and the production well section of the U-shaped horizontal well, thermal recovery and crude oil recovery are simultaneously promoted. During the operation, the target well at one end of the U-shaped horizontal well can be used as the injection well section to continuously inject hot medium such as steam and high-temperature hot water, and the hot medium is uniformly diffused in the reservoir along the horizontal section, thereby reducing the viscosity of the crude oil and breaking the bonding state of the crude oil and the formation, and greatly improving the flowability of the crude oil. At the same time, the target well at the other end of the U-shaped horizontal well is used as the production well section to simultaneously start production, and the easily flowing crude oil after heating is efficiently collected by means of the long reservoir contact length of the horizontal section. This technology can reduce the loss of hot medium and improve the efficiency of heat utilization, and is especially suitable for heavy oil reservoirs, high condensate oil reservoirs and remaining oil tapping of old wells, and can significantly improve the recovery efficiency of the reservoir and realize the synergistic and efficient thermal injection and crude oil production. Moreover, a fracture system including a main fracture and multiple branch fractures can be constructed around the horizontal well section through fracturing construction (such as a small-diameter bridge plug multi-section and multi-cluster process), and the structure is complex and has high conductivity.

[0062] In this embodiment, first, the geological parameters of the low-efficiency well group region (clear oil and gas occurrence and development potential) and the low-efficiency well parameters (locating the low-efficiency causes of single well) are obtained, and the selected target wells are screened and locked in combination with preset conditions, so as to avoid resource mismatch and reduce invalid investment; then, the geological index is calculated according to the geological parameters, and the well is selected in the high-potential region with the largest index, that is, the selected target well in the low-efficiency well group region with the largest geological index is the final target well, so that higher output is realized at the same construction cost; subsequently, based on the two selected target wells, the U-shaped horizontal well is constructed through sidetracking, the reservoir contact range is maximized, the dead oil area is reduced, and the fluid flow path is optimized through the structure of the U-shaped horizontal well to reduce the resistance, thereby improving the resource producing degree and the production stability; finally, the viscosity of the crude oil is reduced, the heat energy loss is reduced, the low-efficiency bottleneck of the difficult oil flow is broken, and the target of activating the low-efficiency well group resources at a lower cost and improving the recovery efficiency and the recovery rate of the low-efficiency well group in the old oilfield is finally realized.

[0063] Alternatively, the geological parameters include the sandstone thickness, porosity, permeability, brittleness index, temperature, fracture pressure, water saturation, Poisson's ratio and stress difference of the low-efficiency well group region; and the evaluation relationship satisfies:

[0064] ;

[0065] B = b1 * W1 + b2 * W2 + b3 * W3 + b4 * W4 + b5 * W5 + b6 * W6 + b7 * W7 + b8 * W8 + b9 * W9, wherein B is the geological index, b1 is the sandstone thickness, b2 is the porosity, b3 is the permeability, b4 is the brittleness index, b5 is the temperature, b6 is the fracture pressure, b7 is the water saturation, b8 is the Poisson's ratio, b9 is the stress difference, b1,max is the maximum sandstone thickness in all the target regions, b2,max is the maximum porosity in all the target regions, b3,max is the maximum permeability in all the target regions, b4,max is the maximum brittleness index in all the target regions, b5,max is the maximum temperature in all the target regions, b6,max is the maximum fracture pressure in all the target regions, b7,max is the maximum water saturation in all the target regions, b8,max is the maximum Poisson's ratio in all the target regions, b9,max is the maximum stress difference in all the target regions, W1 is the weight coefficient of the sandstone thickness, W2 is the weight coefficient of the porosity, W3 is the weight coefficient of the permeability, W4 is the weight coefficient of the brittleness index, W5 is the weight coefficient of the temperature, W6 is the weight coefficient of the fracture pressure, W7 is the weight coefficient of the water saturation, W8 is the weight coefficient of the Poisson's ratio, and W9 is the weight coefficient of the stress difference.

[0066] Optionally, the determining the candidate target well according to the low-efficiency well parameter and a preset reconstruction condition comprises:

[0067] When the low-efficiency well parameter meets the preset reconstruction condition, determining the low-efficiency well as the candidate target well.

[0068] Optionally, the low-efficiency well parameter comprises a casing parameter, a cement sheath parameter and a wellbore drift diameter parameter of the low-efficiency well; the preset reconstruction condition comprises a casing state condition, a cement sheath state condition and a wellbore drift diameter condition; and before the determining the low-efficiency well as the candidate target well, the method further comprises:

[0069] When the casing parameter of the low-efficiency well meets the casing state condition, the cement sheath parameter meets the cement sheath state condition and the wellbore drift diameter parameter meets the wellbore drift diameter condition, indicating that the low-efficiency well parameter meets the preset reconstruction condition.

[0070] Specifically, first, the candidate target well is screened through the comparison result of the inefficient well parameters and the preset reconstruction condition, that is, whether the casing meets the preset casing state condition according to the casing parameter in the inefficient well parameter, whether the cement sheath meets the preset cement sheath state condition according to the cement sheath parameter, and whether the wellbore drift diameter condition is met according to the wellbore drift diameter parameter. When the above three conditions are met at the same time, it indicates that the inefficient well meets the preset reconstruction condition, and the inefficient well can be determined as the candidate target well. In the method, the inefficient well with a good casing state, a cementing quality up to the standard and a smooth wellbore (excluding the wellbore damaged and lost, which cannot be reconstructed) is selected as the candidate target well. For example, the casing state condition includes: whether the residual wall thickness of the casing meets the preset threshold value, when the residual wall thickness of the casing of the inefficient well at any position is greater than or equal to 80% of the design wall thickness (including the corrosion and wear position), if it is a casing for high-pressure formation, the residual wall thickness needs to be greater than or equal to 85% of the design wall thickness (to avoid pressure collapse); the structural condition of the casing is detected by a multi-arm caliper or a downhole television (CCTV), the casing has no radial shrinkage, bending and cracking, if there is slight deformation, the maximum shrinkage amount is less than or equal to 5% of the nominal inner diameter of the casing (for example, the minimum inner diameter of the 139.7mm casing is greater than or equal to 132.7mm after shrinkage), and there is no axial crack (the crack length greater than 50mm is determined as not meeting the standard); the material performance condition, if it is a metal casing (such as J55, N80 steel grade), the material has no “hydrogen embrittlement, stress corrosion cracking” (verified by metallographic analysis or magnetic powder detection); if it is a non-metal casing (such as a glass steel casing), there is no aging, delamination and brittle cracking phenomenon. The cement sheath state condition includes: whether the cement return height meets the design requirement, the cement return height (the filling height of the cement slurry outside the casing) is greater than or equal to the design isolation section height, if it is a production casing, the cement return height needs to be higher than the top boundary of the production layer by greater than or equal to 50m (to prevent the production layer fluid from flowing into the upper formation), if it is a abandoned well casing, the cement return height needs to be higher than the uppermost layer to be isolated by greater than or equal to 100m, or return to the ground (full well section isolation); the pressure test verification, the casing annulus (such as the oil casing annulus) is pressed to 1.1 times of the design isolation pressure, and the pressure is stabilized for 60 minutes, and the pressure drop is less than or equal to 0.3MPa (no pressure leakage, indicating that the cement sheath has no through crack). The wellbore drift diameter condition: the wellbore minimum drift diameter is greater than or equal to 90% of the nominal inner diameter of the casing (or meets the tool size requirement of subsequent operation) through the well caliper full well section detection, for example, the minimum drift diameter of the 177.8mm (7inch) casing is greater than or equal to 160mm, which is determined as smooth, and when the single section shrinkage length is greater than 1m and the drift diameter after shrinkage is less than 85% of the casing inner diameter, it is determined as not smooth.The running / hoisting of the well-through gauge (size = 90% of the inner diameter of the casing, length = 3 times the inner diameter of the casing) in the whole well section is free of jamming and resistance (the resistance is less than 5 kN, which is normal), and the CCTV detection shows that there are no obstacles such as falling objects (such as broken drill pipe sections, cement blocks), scaling (thickness > 5 mm), and casing deformation jamming in the wellbore.

[0071] In this optional embodiment, by comparing the low-efficiency well parameters (such as the casing state, cementing quality, and wellbore patency) with the preset reconstruction conditions, the optional target wells with reconstruction potential are accurately screened out, the low-efficiency wells that cannot meet the subsequent sidetracking and fracturing requirements are excluded, invalid operations are avoided, and it is ensured that there are sufficient well body resources in the target region to support the construction of U-shaped horizontal wells, without the need to add new drilling, which greatly reduces the cost of old well reconstruction and well pattern construction, and activates low-efficiency well resources; according to the geological parameters of the target region (such as sandstone thickness, porosity, permeability, formation temperature, and brittleness index), the geological indexes are obtained through the evaluation relationship, the remaining oil enrichment degree, thermal reservoir potential, and fracturing adaptability of the region are quantitatively evaluated, subjective selection bias is avoided, and the target region with high oil storage, high heat conduction, and easy fracturing is finally screened out, which lays a resource foundation for subsequent efficient oil production and geothermal development.

[0072] Optionally, the U-shaped horizontal well is constructed by connecting two target wells through the sidetracking method, and the method comprises the following steps:

[0073] A horizontal well section connecting the two target wells is constructed by the sidetracking method.

[0074] The U-shaped horizontal well is constructed according to the horizontal well section and the two target wells.

[0075] In this optional embodiment, a horizontal well section is constructed between two target wells through the sidetracking method, and the horizontal well section can be constructed from a proper position of one target well along the horizontal direction towards the other target well, so as to connect the two target wells through the horizontal well section, and thus the U-shaped horizontal well is constructed. Figure 2As shown, for example in the process of ultra-short radius sidetracking, the ultra-short radius technical parameters of a build-up angle greater than 90° / 30m and a curvature radius less than or equal to 30m can be strictly followed, real-time data of well inclination angle, azimuth angle, etc. can be collected by a measurement-while-drilling system, and the high flexibility of the titanium alloy flexible drill pipe can be combined to realize precise control of the drilling trajectory. Drilling starts from a preset build-up point of one target well 01 and extends to a horizontal section. When drilling to a preset docking area between the two target wells 01, the relative spatial positions of the two wells are calculated in real time by the magnetic guidance docking technology and dynamic deviation is corrected to ensure that the horizontal section 02 precisely connects the two target wells 01. That is, a rotating magnetic joint 05 is provided as a magnetic source in the horizontal section 02, and a magnetic guidance drilling assembly (including a through-well probe (including a magnetic field receiving device, a gyromagnetic signal probe rod, and a non-magnetic drill pipe) is provided in the target well. The docking accuracy can be less than 1% within 30 meters, the azimuth error can be less than 0.5%, and the docking success rate can be greater than 95%. When the U-shaped horizontal well is finally constructed, the original vertical sections of the two target wells 01 are used as the two vertical ends of the U-shaped structure, and the horizontal section 02 precisely connected by the sidetracking method is used as the horizontal side of the U-shaped structure, forming a complete U-shaped horizontal well structure. This structure not only makes full use of the existing wellbore resources of the target well 01 to avoid additional drilling costs, but also relies on the horizontal section 02 to expand the contact range with the reservoir, laying a stable well pattern foundation for subsequent implementation of small-diameter bridge plug multi-section and multi-cluster fracturing and development of staged oil and heat production (elastic oil production, water injection oil production, and heat injection).

[0076] Optionally, the method further comprises:

[0077] A fracture system in communication with the horizontal section is formed by a staged fracturing technique.

[0078] In this optional embodiment, as Figure 2As shown, a connected fracture system 03 is formed through the horizontal section 02 by using a staged fracturing technique, for example, a small-diameter bridge plug multi-stage and multi-cluster fracturing process can be used, which is based on the wellbore structure design of the horizontal section 02, and the horizontal section 02 is first segmented and isolated by using a staged bridge plug, and then a plurality of fracturing clusters are arranged in each section by combining perforating operation, so as to ensure that the fracturing energy can accurately act on different regions of the reservoir. During the fracturing process, a rapid gel breaking guanidium gel system can be selected as the fracturing fluid, which can quickly break the gel after fracturing, reduce the plugging and damage to the reservoir pores, and 20 to 40 mesh quartz sand can be used as a proppant at the same time, so as to ensure that the fracture has long-term stable high conductivity after being formed. High-pressure injection of fracturing fluid can also be used to expand the surrounding reservoirs around the horizontal section 02, forming a complex fracture system 03 with the main fracture as the skeleton and the multi-branch fracture as the extension, and the fracture system 03 not only communicates closely with the horizontal section 02, but also effectively communicates with the surrounding low-efficiency vertical well 04, thereby constructing the point-to-line seepage channel mentioned in the patent, improving the seepage efficiency, providing an efficient channel for the reservoir elastic energy to drive the crude oil to flow to the horizontal section 02 in the subsequent elastic oil production stage, and providing a stable path for the displacement and heat transfer of the injected water in the water injection oil production stage and the heat exchange and circulation of the cold water in the hot water injection stage, thereby achieving the dual improvement of the reservoir producing range and the heat exchange efficiency.

[0079] Optionally, the oil and hot simultaneous production of the U-shaped horizontal well comprises:

[0080] The U-shaped horizontal well is developed by stage oil and hot simultaneous production, and the stage oil and hot simultaneous production comprises an elastic oil production stage, a water injection oil production and heat recovery stage, and a closed cycle heat exchange stage.

[0081] Optionally, the elastic oil production stage comprises:

[0082] The crude oil flowing into the U-shaped horizontal well through the fracture system is produced.

[0083] In this optional embodiment, as shown in the figure, Figure 2 The point-to-line fracture system 03 with the main fracture as the skeleton and the multi-branch fracture as the extension has been formed around the U-shaped horizontal section 02 by using a small-diameter bridge plug multi-stage and multi-cluster fracturing technique, the fracture system 03 not only communicates with the horizontal section 02 of the U-shaped horizontal well, but also penetrates into the remaining oil enrichment area of the reservoir, and the long-term high conductivity of the fracture can be ensured by using 20 to 40 mesh quartz sand proppant, and the plugging of the reservoir pores can be avoided by using a rapid gel breaking guanidium gel fracturing fluid, thereby clearing the obstacles for the flow of crude oil. The hot oil simultaneous production mainly comprises three stages, the first stage is the elastic oil production stage, the second stage is the water injection oil production and heat recovery stage, and the third stage is the closed cycle heat exchange stage.

[0084] Specifically, in the elastic oil production stage, its core driving force comes from the elastic energy released by the reservoir after fracturing. The original pressure balance of the reservoir is broken through fracturing operations, and the frozen rock elastic expansion force and the fluid expansion force in the pore are released. Under the driving of this energy, the dispersed remaining oil in the reservoir will gather along the main fracture and branch fracture of the fracture system 03 to the horizontal section 02 of the U-shaped horizontal well with lower pressure, and due to the large contact area between the horizontal section 02 and the reservoir, the oil from the fractures in all directions can be efficiently collected, and then the oil flows along the horizontal section 02 to the vertical end of the U-shaped horizontal well (i.e. the original vertical well section of the two target wells 01), and finally the oil is produced through the oil production device 11 at the wellhead and transported to the metering station 07. This stage does not require additional energy injection (such as water injection and heating), relies on the energy of the reservoir itself to achieve spontaneous oil production with low cost and no energy consumption, which not only quickly develops the remaining oil in the fracturing area, but also lays a stable oil flow channel foundation for the subsequent water injection and heat recovery stage, and avoids the waste of resources caused by early external energy injection, which meets the needs of low permeability old oilfield development with high efficiency and low cost.

[0085] Optionally, the water injection and heat recovery stage includes:

[0086] High-pressure water is injected into the low-efficiency vertical well around the U-shaped horizontal well, and the oil-water mixture flowing into the U-shaped horizontal well from the fracture system is produced.

[0087] In this optional embodiment, as shown in Figure 2 The low-efficiency vertical well 04 around the U-shaped horizontal well with good well conditions (good casing condition, good cementing quality, and unobstructed wellbore) is selected as the water injection well (without the need for new drilling, and the demand for cost reduction through old well modification), and high-pressure water is injected from the water injection station 10 into these low-efficiency vertical wells 04. The injected high-pressure water not only supplements the reservoir energy consumed in the elastic oil production stage to avoid the yield decline caused by the sudden drop of reservoir pressure, but also uniformly diffuses along the main fracture and branch fracture to the deep part of the reservoir through the high-conductivity point linear fracture system 03 formed by the previous small-bore bridge plug multi-section and multi-cluster fracturing, and efficiently displaces the dispersed remaining oil that has not been completely developed. After the displaced remaining oil and high-pressure water form an oil-water mixture, the oil-water mixture will continuously flow along the fracture system 03 to the horizontal section 02 of the U-shaped horizontal well due to the low-pressure advantage of the horizontal section 02 of the U-shaped horizontal well (the horizontal section 02 has a large contact area with the reservoir, and can efficiently collect the mixture from all directions), and then is produced through the oil production device 11 at the vertical end of the U-shaped horizontal well (i.e. the straight well section of the target well 01 connected by the previous ultra-short radius sidetracking), and transported to the metering station 07. The whole process not only relies on the low-efficiency vertical well 04 to achieve low-cost energy supplement, but also ensures continuous oil production through the high-permeability flow capacity of the fracture system 03, and lays a foundation for the subsequent separated liquid heat recovery (utilizing the formation temperature and fracture heat conduction characteristics) and the transition to the closed cycle heat recovery stage.

[0088] Optionally, the closed-loop heat exchange stage includes:

[0089] After oil production ceases, an underground heat exchange and circulation system is constructed using the U-shaped horizontal well as a channel.

[0090] In this optional embodiment, such as Figure 2 As shown, in the closed-loop heat exchange stage, oil production must be stopped as a prerequisite, and the underground heat exchange circulation system should be constructed by fully utilizing the U-shaped horizontal wells constructed in the early stage as the core channel. First, the inefficient vertical well 04 (which can be an inefficient vertical well 04 with good well conditions or an inefficient vertical well 04 that meets the requirements after modification) around the U-shaped horizontal well used in the early stage of water injection and oil production is identified as a water injection well. The U-shaped horizontal well itself serves as a water production well, and the surface end is connected to the water injection station 10 to form a closed loop with the heat exchange system. Subsequently, cold water is injected from the surface injection station 10 into the injection well. The cold water, through the fracture system 03, fully contacts the reservoir, absorbing formation heat (e.g., a regional geothermal gradient ≥ 5.0℃ / 100m, indicating sufficient geothermal resources), and then heats up to become hot water. The heated hot water flows along the fracture system 03 to the horizontal section 02 of the U-shaped horizontal well, and then through the vertical end of the U-shaped horizontal well (the vertical section of the original target well 01, with good well conditions and unobstructed wellbore) to the surface heat exchange system. The surface heat exchange system extracts heat from the hot water for related biological processes. After production or living needs are met, the cooled water is transported back to the water injection station 10 and re-injected underground to complete the circulation. The entire system achieves a closed operation mode of heat extraction without water extraction, which avoids disturbing the formation water environment and makes full use of the existing U-shaped horizontal well and fracture system 03. There is no need to add new dedicated geothermal wells, which greatly reduces the cost of geothermal development. At the same time, relying on the connectivity of the U-shaped horizontal well and the high thermal conductivity and high permeability of the fracture system 03, the heat exchange efficiency and system stability are guaranteed, realizing the efficient and sustainable development of geothermal energy.

[0091] It should be noted that the main function of the water injection station 10 is to supply the key medium for the underground reservoir, and the treated water is pressurized and delivered to the injection well (such as the low-efficiency vertical well 04 with good well conditions) around the U-shaped horizontal well in the water injection and oil production stage, and the reservoir energy is supplemented through the fracture system 03 to displace the remaining oil, and the circulating cold water is delivered to the injection well in the closed cycle heat recovery stage to provide medium for underground heat exchange; the metering station 07 belongs to the mechanical recovery system, located between the U-shaped horizontal well and the oil transfer station 08, responsible for real-time metering of key parameters such as flow, pressure and temperature of the oil-water mixture (in the water injection and oil production stage) or hot circulating water (in the closed cycle heat recovery stage) recovered by the U-shaped horizontal well, which not only provides data basis for subsequent ground treatment, but also real-time monitors the development dynamics of the underground reservoir; the oil transfer station 08 is the transfer hub of the gathering system, which receives the produced liquid delivered by the metering station 07, completes preliminary sand removal, gas removal and other pretreatment work to avoid solid impurities blocking the subsequent equipment, and stably delivers the preliminary treated liquid to the joint station 09, playing the role of connecting the upstream and downstream of the produced liquid pretreatment and transfer; the joint station 09 is the core of the treatment system, which is the key node of the whole process treatment and energy recovery of the produced liquid, in the water injection and oil production stage, the oil-water mixture is deeply separated by the three-phase separator (to obtain qualified crude oil, hot sewage and associated gas), and the heat recovery is realized by extracting the formation heat in the hot sewage with the help of the heat exchange system, in the closed cycle heat recovery stage, the heat in the hot circulating water is extracted, and at the same time, the cooled cold water is delivered back to the water injection station 10 to complete the closed cycle of heat recovery without water, and the separated qualified crude oil is delivered to the ground oil and gas gathering system, and the four stations and warehouses cooperate to provide ground support for the continuous promotion of the staged oil and heat recovery.

[0092] Although the present application is disclosed as above, the protection scope of the present application is not limited to this. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present application, and these changes and modifications will fall within the protection scope of the present application.

Claims

1. A method for simultaneous oil and heat recovery in inefficient well groups, characterized in that, include: Geological parameters of the inefficient well group area and parameters of the inefficient wells therein were obtained; Based on the parameters of the inefficient wells and the preset stimulation conditions, candidate target wells are determined; The region of the inefficient well group with two or more candidate target wells is defined as the target region. Based on the geological parameters corresponding to the target area, the corresponding geological indicators are obtained through evaluation relationships; Two candidate target wells are selected as target wells from the target area with the highest geological index. A U-shaped horizontal well was constructed by connecting the two target wells using the side-drilling method. The U-shaped horizontal well is used for both oil and heat recovery. The geological parameters include sandstone thickness, porosity, permeability, brittleness index, temperature, fracture pressure, water saturation, Poisson's ratio, and stress difference in the inefficient well group area; the evaluation relationship satisfies: ； Wherein, B is the geological index, b1 is the sandstone thickness, b2 is the porosity, b3 is the permeability, b4 is the brittleness index, b5 is the temperature, b6 is the fracture pressure, b7 is the water saturation, b8 is the Poisson's ratio, b9 is the stress difference, and b 1，max b is the maximum thickness of the sandstone in the entire target area. 2，max b is the maximum porosity in all the target regions. 3，max b is the maximum penetration rate in all the target regions. 4，max b is the largest of the brittleness index in all the target regions. 5，max b is the maximum temperature in all the target regions. 6，max b is the maximum rupture pressure in all the target regions. 7，max b represents the maximum water saturation in all the target regions. 8，max b is the largest Poisson's ratio in all the target regions. 9，max The maximum stress difference across all target regions is defined by the following factors: W1 is the weighting factor for sandstone thickness; W2 is the weighting factor for porosity; W3 is the weighting factor for permeability; W4 is the weighting factor for brittleness index; W5 is the weighting factor for temperature; W6 is the weighting factor for fracture pressure; W7 is the weighting factor for water saturation; W8 is the weighting factor for Poisson's ratio; and W9 is the weighting factor for stress difference.

2. The method for simultaneous oil and heat recovery of inefficient well groups according to claim 1, characterized in that, The step of determining candidate target wells based on the parameters of the inefficient wells and preset stimulation conditions includes: When the parameters of the inefficient well meet the preset modification conditions, the inefficient well is determined to be the candidate target well.

3. The method for simultaneous oil and heat recovery of inefficient well groups according to claim 2, characterized in that, The parameters of the inefficient well include the casing parameters, cement sheath parameters, and wellbore diameter parameters; the preset modification conditions include the casing condition conditions, cement sheath condition conditions, and wellbore diameter conditions. Before determining the inefficient well as a candidate target well, the method further includes: When the casing parameters, cement sheath parameters, and wellbore diameter parameters of the inefficient well meet the casing condition, the parameters of the inefficient well are indicated to meet the preset modification conditions.

4. The method for simultaneous oil and heat recovery of inefficient well groups according to claim 1, characterized in that, The method of connecting the two target wells to construct a U-shaped horizontal well using side-drilling includes: A horizontal well section connecting the two target wells is constructed using the side-drilling method described above. The U-shaped horizontal well is constructed based on the horizontal well section and the two target wells.

5. The method for simultaneous oil and heat recovery of inefficient well groups according to claim 4, characterized in that, Also includes: Using segmented fracturing technology, a fracture system is formed centered on the horizontal well section and connected to the horizontal well section.

6. The method for simultaneous oil and heat recovery of inefficient well groups according to claim 5, characterized in that, The U-shaped level Wells undergoing simultaneous oil and heat recovery include: The U-shaped horizontal well is exploited through staged oil and heat recovery, which includes flexible oil recovery. The stages include water injection for oil production and heat recovery, and closed-loop heat exchange.

7. The method for simultaneous oil and heat recovery of inefficient well groups according to claim 6, characterized in that, The resilient oil recovery stage includes: Oil is extracted from the crude oil flowing into the U-shaped horizontal well through the fracture system.

8. The method for simultaneous oil and heat recovery of inefficient well groups according to claim 6, characterized in that, The water injection oil recovery and heat tracing recovery stage includes: High-pressure water is injected into the inefficient vertical wells surrounding the U-shaped horizontal well, and oil-water mixture flowing into the U-shaped horizontal well from the fracture system is used for oil production.

9. The method for simultaneous oil and heat recovery of inefficient well groups according to claim 6, characterized in that, The closed-loop heat exchange stage includes: After oil production ceases, an underground heat exchange and circulation system is constructed using the U-shaped horizontal well as a channel.

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