Gas lift reverse circulation wire-line coring device suitable for large-diameter geothermal well

Abstract

The invention relates to the technical field of drilling, in particular to a gas lift reverse circulation wire-line coring device suitable for a large-diameter geothermal well and a gas lift reverse circulation wire-line coring method. The device comprises a drill rod assembly, an outer core barrel and a drill bit which are sequentially connected, an inner core barrel is arranged in the outer core barrel, the inner core barrel and the outer core barrel are coaxially arranged, and the inner core barrel and the outer core barrel are detachably connected; the annular gap width between the inner core barrel and the outer core barrel is greater than a preset value; wherein the annular gap width between the inner core barrel and the outer core barrel is equal to the difference between the inner radius of the outer core barrel and the outer radius of the inner core barrel. By adopting the device and the method provided by the invention, the drilling efficiency can be improved, and the working intensity of workers can be reduced.

Description

Technical Field

[0001] The present application relates to the field of drilling technology, and in particular to a gas lift reverse circulation rope coring device suitable for large-diameter geothermal wells and a gas lift reverse circulation rope coring method. Background Art

[0002] In geothermal drilling, to reserve sufficient space for submersible pumps and reduce construction risks, large-diameter, multi-pass wellbore structures are often used, with the lower casing not returned to the wellhead, resulting in a large upper wellbore annulus. When using positive circulation drilling, large drilling fluid volumes are required to meet the rock-carrying requirements of the upper, large-diameter wellbore section. This not only places high demands on the pump (and equipment) configuration, but also can lead to wellbore erosion and instability in the smaller-diameter wellbore sections due to excessive mud return velocities. Especially during coring drilling, excessive pumping rates can reduce the coring rate. However, reducing pumping rates makes it difficult to return cuttings from the large-diameter wellbore section, causing them to fall back underground, leading to repeated fragmentation, reduced drilling rates, and even drill bit burial, shortening drill bit life. Summary of the Invention

[0003] The purpose of the embodiments of the present application is to provide a gas lift reverse circulation rope coring device and a gas lift reverse circulation rope coring method suitable for large-diameter geothermal wells.

[0004] In order to achieve the above-mentioned objectives, the first aspect of the present application provides an air lift reverse circulation rope coring device suitable for large-diameter geothermal wells, the device comprising a drill pipe assembly, an outer core barrel and a drill bit connected in sequence; an inner core barrel is provided in the outer core barrel, the inner core barrel and the outer core barrel are coaxially arranged, and the inner core barrel and the outer core barrel are detachably connected; the annular gap width between the inner core barrel and the outer core barrel is greater than a preset value; wherein the annular gap width between the inner core barrel and the outer core barrel is equal to the inner radius of the outer core barrel minus the outer radius of the inner core barrel.

[0005] Based on the first aspect, in some embodiments of the present application, the drill rod assembly includes a double-wall drill rod, an air-water mixer and a single-wall drill rod connected in sequence; wherein, the single-wall drill rod is connected to the outer core tube; wherein, the inner diameter of the inner tube of the double-wall drill rod is larger than the outer diameter of the inner core tube, the inner diameter of the core tube of the air-water mixer is larger than the outer diameter of the inner core tube, and the inner diameter of the single-wall drill rod is larger than the outer diameter of the inner core tube.

[0006] Based on the first aspect, in some embodiments of the present application, the device further includes: a coring device for extracting the inner core tube from the outer core tube or lowering the inner core tube to a predetermined position in the outer core tube; the coring device includes: a fixing component fixedly connected to the top of the inner core tube; an extraction component adapted to the fixing component and detachably connected to the fixing component.

[0007] Based on the first aspect, in some embodiments of the present application, the preset value is not less than one third of the inner diameter of the inner core barrel.

[0008] Based on the first aspect, in some embodiments of the present application, the device also includes: an air box, which is connected to the end of the double-wall drill pipe away from the air-water mixer; and an air compressor, whose air outlet is connected to the air inlet of the air box.

[0009] Based on the first aspect, in some embodiments of the present application, the specification of the double-arm drill rod is ø168mm / 100mm.

[0010] Based on the first aspect, in some embodiments of the present application, the model of the inner core tube is Sichuan 5-4, and the model of the outer core tube is Sichuan 8-4 or Sichuan 9-4.

[0011] Based on the first aspect, in some embodiments of the present application, the length of the inner core barrel ranges from 1.2 m to 1.4 m.

[0012] Based on the first aspect, in some embodiments of the present application, the device further includes: a faucet, which is connected to the drill rod assembly and is used to bear the weight of the suspended drill rod assembly.

[0013] In the second aspect, the present application provides an air lift reverse circulation rope coring method, which is applied to the above-mentioned air lift reverse circulation rope coring device. The method includes: using the air lift reverse circulation rope coring device to drill and coring. During the drilling process, the core enters the inner core tube, and the cuttings are returned to the ground along with the mud through the drill bit, the annular gap between the inner core tube and the outer core tube, and the drill pipe assembly.

[0014] Based on the second aspect, in some embodiments of the present application, the device further includes a vibrating screen; and the method includes: using the vibrating screen to purify the mud returned from the bottom of the well.

[0015] Based on the second aspect, in some embodiments of the present application, the method includes: determining the depth of the double-wall drill rod; and calculating the number of double-wall drill rods required in the drill rod assembly according to the depth of the double-wall drill rod.

[0016] Based on the second aspect, in some embodiments of the present application, the depth of the double-wall drill pipe is determined based on the following calculation formula: :

[0017] In the above formula, in the above formula, Indicates the length of the single-wall drill pipe; h indicates the head height from the end of the double-wall drill pipe; Indicates the density of the mud; Indicates the average density of gas, liquid and solid phases in the double-walled tube; Indicates the density of liquid and solid phases in single-wall drill pipe; Indicates the pressure drop caused by frictional resistance.

[0018] The gas lift reverse circulation rope coring device and gas lift reverse circulation rope coring method provided in this application have at least the following beneficial effects: 1) Compared with achieving positive circulation, less mud is required and the mud has a stronger rock-carrying capacity; 2) Underbalanced drilling can be achieved. When the bottomhole pressure is less than the formation pore pressure, the formation fluid (mud) flows into the wellbore instead of entering the formation. This solution can effectively protect the reservoir. 3) Wireline coring does not require the drill pipe assembly to be lifted out of the well, thus greatly reducing the time for tripping and untripping the drill bit, effectively increasing the pure drilling time and improving the drilling efficiency. At the same time, the number of tripping and untripping the drill bit is reduced, thus reducing the labor intensity.

[0019] Other features and advantages of the embodiments of the present application will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings are used to provide a further understanding of the embodiments of the present application and constitute a part of the specification. Together with the following detailed description, they are used to explain the embodiments of the present application but do not constitute a limitation on the embodiments of the present application. In the accompanying drawings: Figure 1 The schematic diagram of the structure of the gas lift reverse circulation rope coring device is shown schematically. DETAILED DESCRIPTION

[0021] To make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. It should be understood that the specific implementation methods described herein are only used to illustrate and explain the embodiments of the present application and are not used to limit the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0022] It should be noted that if the embodiments of the present application involve directional indications (such as up, down, left, right, front, back, etc.), such directional indications are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0023] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present application, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the fact that they can be implemented by ordinary technicians in this field. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0024] Example 1 This embodiment provides a gas lift reverse circulation rope coring device suitable for large-diameter geothermal wells, the device comprising a drill pipe assembly, an outer core barrel, and a drill bit connected in sequence; an inner core barrel is disposed within the outer core barrel, the inner core barrel and the outer core barrel are coaxially arranged, and the inner core barrel and the outer core barrel are detachably connected; the annular gap width between the inner core barrel and the outer core barrel is greater than a preset value (satisfying the requirement for returning cuttings); wherein the annular gap width between the inner core barrel and the outer core barrel is equal to the inner radius of the outer core barrel minus the outer radius of the inner core barrel.

[0025] In this embodiment, under the premise of meeting the core diameter, the inner core tube with the smallest outer diameter is selected. The smallest inner core tube is Sichuan 5-4 type, and the size of its steel inner tube is: 85×72×6.5 (outer diameter×inner diameter×wall thickness). Then, for the design of the outer core tube, since the cuttings and flushing fluid need to be returned from the gap between the inner and outer core tubes during gas lift reverse circulation drilling, it is necessary to select an outer core tube with a larger inner diameter as much as possible (the size of the cuttings formed during the drilling process is usually not larger than For cores with an outer core tube size of 180 × 144 × 18 or 203 × 169 × 17 (outer diameter × inner diameter × wall thickness), choose the Sichuan 8-4 or Sichuan 9-4 outer core tube. The outer core tube dimensions are 180 × 144 × 18 or 203 × 169 × 17 (outer diameter × inner diameter × wall thickness). When the outer core tube dimensions are 180 × 144 × 18, the annular gap width is 29.5 mm, and when the outer core tube dimensions are 203 × 169 × 17, the annular gap width is 42 mm, both of which are greater than one-third of the inner core tube's inner diameter (72 mm). In actual applications, due to the air compressor's air pressure, a larger annular gap width is not necessarily better (a larger annular gap width requires higher actual air compressor pressure capacity). Therefore, the most appropriate outer core tube size should be selected based on the air compressor's air pressure capacity.

[0026] Specifically, the drill pipe assembly includes a double-wall drill pipe, a gas-water mixer and a single-wall drill pipe connected in sequence; wherein one end of the single-wall drill pipe is connected to the outer core tube, and the other end is connected to the gas-water mixer through a reducer (such as Figure 1To ensure that the inner core tube can be smoothly returned during core extraction, the inner diameter of the inner tube of the double-wall drill pipe must be larger than the outer diameter of the inner core tube. The inner diameter of the core tube of the air-water mixer must be larger than the outer diameter of the inner core tube. The inner diameter of the single-wall drill pipe must be larger than the outer diameter of the inner core tube.

[0027] Currently, the most commonly used coring tool for geothermal wells is the Sichuan-4 type. Conventional coring tools are ideal for routine coring operations in petroleum and geological exploration drilling. These tools offer a comprehensive suite of specifications and advanced technology, making them suitable for coring soft, medium, hard, and fractured formations. The smallest of the Sichuan-4 types is the Sichuan 5-4, with a steel inner barrel measuring 85×72×6.5 (outer diameter × inner diameter × wall thickness). However, the double-wall drill pipe commonly used in geothermal gas lift reverse circulation is 127mm, with a through-hole diameter of only 70mm, which is insufficient for the return of the inner core barrel. The inner through-hole of a ø168mm double-wall drill pipe is ø100mm, so a double-wall drill pipe with specifications of ø168mm / 100mm is recommended.

[0028] Furthermore, the device also includes an air compressor, which is connected to the air-water mixer through the double-wall drill pipe. The air compressor sends compressed air to the air-water mixer through the annular channel between the inner and outer tubes of the double-wall drill pipe, causing the air to mix with the flushing fluid in the drill pipe, forming a relatively low-density mixed gas liquid column. This creates a pressure difference between the column and the liquid column outside the drill pipe, creating a reverse circulation under the action of this pressure difference, causing the mixed gas liquid in the inner drill pipe to carry rock cuttings out of the hole. As the external pressure gradually decreases during the ascent, the bubbles in the mixed gas liquid continue to expand, causing the mixed gas liquid to rise faster and faster (the expansion work of the compressed air is converted into kinetic energy of the liquid), thereby achieving air lift reverse circulation.

[0029] like Figure 1 As shown, the device also includes: a coring device, which is used to extract the inner core tube from the outer core tube or lower the inner core tube to a predetermined position in the outer core tube; specifically, the coring device includes: a fixing component (such as a core tube handle), which is fixedly connected to the top of the inner core tube; and an extraction component (such as a salvage device), which is adapted to the fixing component and is detachably connected to the fixing component.

[0030] The coring device consists of a retaining ring, retaining ring, retaining ring, and core tube adapter connected to the inner core tube. When coring, the force of breaking the core causes the inner tube and retaining ring to move downward onto the drill bit step. The force of breaking the core is then transferred from the drill bit to the outer tube, protecting the inner tube from damage.

[0031] Taking into account the influence of the length of the reverse circulation center channel on the reverse circulation effect and the influence of the length of the round footage in the actual formation drilling production, the designed length of the inner core tube is most suitable to be 1.2m~1.4m.

[0032] Furthermore, the device further comprises: The faucet is connected to the drill pipe assembly and is used to support the weight of the suspended drill pipe assembly. A lifting ring is installed on the top of the faucet, and the entire assembly can be raised or lowered by hooking and pulling the lifting ring. During drilling, the faucet supports the weight of the drill string (the general term for the steel pipe below the faucet, including the drill pipe assembly, (inner and outer) core barrel, and drill bit) and provides upper bearing support for the rotating drill string. The faucet is also used to introduce high-pressure drilling fluid into the rotating drill string. Air box, the air compressor is connected to the double-wall drill pipe through the air box. The air box provides an air inlet channel for high-pressure air as a drilling medium to enter the annular gap of the double-wall drill tool. The compressed air enters the annular gap of the double-wall drill pipe through the air box, reaches the bottom hole drill tool along the annular gap, flows through the bottom hole drill tool to the inner tube of the double-wall drill pipe, and carries rock cuttings back to the ground from the inner tube.

[0033] Example 2 This embodiment provides a gas lift reverse circulation rope coring method, which is applied to the gas lift reverse circulation rope coring device described in Example 1. The method includes: The gas lift reverse circulation rope coring device is used for drilling and coring. During the drilling process, the core enters the inner core tube, and the rock cuttings are returned to the ground along with the mud through the drill bit, the annular gap between the inner core tube and the outer core tube, the single-wall drill pipe, the air-water mixer and the inner tube of the double-wall drill pipe.

[0034] For the reuse of the returned mud, the device further includes a vibrating screen, which is connected to the inner tube of the double-wall drill pipe through a faucet to purify the mud returned from the bottom of the well (filter out rock cuttings from the mud).

[0035] The process flow of wireline coring is as follows: assemble the drilling tool on the surface - check the fit between the retaining ring, retaining ring seat and the inner diameter of the drill bit - lower the drill bit (the inner tube assembly can be lowered without the drilling tool) - supply water to flush the hole - insert the inner tube assembly - drill - break the core - lower the fishing device to fish out the inner core tube - pull out the inner core tube and take the core - check the inner core tube - insert (or lower) the inner tube assembly into the inner hole of the drill pipe - continue drilling.

[0036] The process flow of gas lift reverse circulation is as follows: the gas lift reverse circulation coring drill bit, the outer core tube of the gas lift reverse circulation wireline coring drill tool, the drill collar, the single-wall drill pipe, the gas-water mixer and the double-wall drill pipe are successively lowered.

[0037] In the rope coring process, when assembling the drill string on the surface, the drilling depth must be determined in advance. The number of double-wall drill rods required in the drill rod assembly is then calculated based on the drilling depth. The number of double-wall drill rods required depends on the drilling depth. Based on the principle of reverse circulation coring, when the system reaches equilibrium, the following conditions must be met: (1) In the above formula, Indicates the length of the single-wall drill pipe; h indicates the head height from the end of the double-wall drill pipe; Indicates the density of the mud; Indicates the average density of gas, liquid and solid phases in the double-walled tube; Indicates the density of liquid and solid phases in single-wall drill pipe; Indicates the pressure drop caused by frictional resistance.

[0038] When other resistance, inertia, etc. are not considered, in order to form the entire reverse circulation process, (2) Analyze the four terms in the above inequality, The item is the main item. When compressed air is delivered to the end of the double-wall drill pipe, Only when the double-wall drill pipe is lowered to a certain depth, a pressure difference is generated between the internal and external liquid columns of the entire pipeline, and the circulation movement can be carried out.

[0039] After determining the depth (H) of the double-wall drill pipe according to formula (2), the number of double-wall drill pipes required is determined based on the length of a single double-arm drill pipe.

[0040] It should also be noted that the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, commodity, or apparatus that includes a series of elements includes not only those elements but also other elements not explicitly listed, or includes elements inherent to such process, method, commodity, or apparatus. In the absence of further limitations, an element defined by the phrase "comprises a ..." does not exclude the presence of other identical elements in the process, method, commodity, or apparatus that includes the element.

[0041] The above are merely embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should all be included within the scope of the claims of the present application.

Claims

1. A gas lift reverse circulation rope coring device suitable for large-diameter geothermal wells, characterized by: The device comprises a drill rod assembly, an outer core barrel and a drill bit connected in sequence; An inner core tube is provided in the outer core tube, the inner core tube and the outer core tube are coaxially arranged, and the inner core tube and the outer core tube are detachably connected; The annular gap width between the inner core tube and the outer core tube is greater than a preset value; wherein the annular gap width between the inner core tube and the outer core tube is equal to the inner radius of the outer core tube minus the outer radius of the inner core tube.

2. The gas lift reverse circulation rope coring device suitable for large-diameter geothermal wells according to claim 1, characterized in that: The drill rod assembly includes a double-wall drill rod, an air-water mixer and a single-wall drill rod connected in sequence; Wherein, the single-wall drill pipe is connected to the outer core barrel; The two ends of the core tube of the gas-water mixer are respectively connected to the inner tube of the double-wall drill pipe and the single-wall drill pipe; The inner diameter of the inner tube of the double-wall drill pipe is larger than the outer diameter of the inner core tube, the inner diameter of the core tube of the gas-water mixer is larger than the outer diameter of the inner core tube, and the inner diameter of the single-wall drill pipe is larger than the outer diameter of the inner core tube.

3. The gas lift reverse circulation rope coring device suitable for large-diameter geothermal wells according to claim 2, characterized in that: The device further comprises: An air box is connected to an end of the double-wall drill pipe away from the air-water mixer; An air compressor, wherein the air outlet of the air compressor is connected to the air inlet of the air box.

4. The gas lift reverse circulation rope coring device suitable for large-diameter geothermal wells according to claim 1, characterized in that: The preset value is not less than one third of the inner diameter of the inner core tube.

5. The gas lift reverse circulation rope coring device suitable for large-diameter geothermal wells according to claim 1, characterized in that: The device further comprises: The faucet is connected to the drill pipe assembly and is used to bear the weight of the suspended drill pipe assembly.

6. The gas lift reverse circulation rope coring device suitable for large-diameter geothermal wells according to claim 1, characterized in that: The device further comprises: A coring device is used to extract the inner core tube from the outer core tube or to lower the inner core tube to a predetermined position in the outer core tube; The coring device comprises: A fixing component fixedly connected to the top of the inner core tube; The extraction component is adapted to the fixing component and is detachably connected to the fixing component.

7. A gas lift reverse circulation rope coring method, applied to the gas lift reverse circulation rope coring device according to any one of claims 1 to 6, characterized in that: The method comprises: The gas lift reverse circulation rope coring device is used for drilling and coring. During the drilling process, the core enters the inner core tube, and the cuttings are returned to the surface along with the mud through the drill bit, the annulus between the inner core tube and the outer core tube, and the drill pipe assembly.

8. The air lift reverse circulation rope coring method according to claim 7, characterized in that: The device further includes a vibrating screen; and the method includes: Use vibrating screen to purify the mud returning from the bottom of the well.

9. The air lift reverse circulation rope coring method according to claim 7, characterized in that: The method comprises: Determine the depth of double-wall drill pipe; Calculate the number of double-wall drill rods required in the drill rod assembly based on the depth to which the double-wall drill rods are lowered.

10. The air lift reverse circulation rope coring method according to claim 9, characterized in that: Determine the depth of the double-wall drill pipe based on the following calculation formula : In the above formula, Indicates the length of the single-wall drill pipe; h indicates the head height from the end of the double-wall drill pipe; Indicates the density of the mud; Indicates the average density of gas, liquid and solid phases in the double-walled tube; Indicates the density of liquid and solid phases in single-wall drill pipe; Indicates the pressure drop caused by frictional resistance.

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