A downhole measuring instrument suitable for flexible drill collars

Abstract

This invention relates to oil well drilling directional measurement instruments, specifically disclosing a downhole measurement instrument suitable for flexible drill collars. The instrument externally includes a conversion connector, a non-magnetic connector, a flexible non-magnetic drill collar, a rigid non-magnetic drill collar, and a retrieval head. Internally, it houses a directional measurement sub, a central control sub, a gamma sub, a power module, and a pulse generator. The instrument is characterized by a section of flexible non-magnetic drill collar. The directional measurement sub is installed at the front end of the instrument via the conversion connector and the non-magnetic connector, and then connected in series with the upper components via a deep-water cable passing through the flexible non-magnetic drill collar. The pulse generator is placed at the top of the instrument to fully contact the drilling mud. This invention's lower-positioning of the directional measurement unit allows for more accurate capture of wellbore trajectory changes, while the upper-positioning pulse generator ensures the stability of the upward signal transmission.

Description

Technical Field

[0001] This invention relates to the fields of oil, coal mining and geological exploration drilling engineering, and in particular to a downhole measuring instrument suitable for flexible drill collars. Background Technology

[0002] In the later stages of oilfield development, enhancing the production of old wells has become a key means of improving recovery rates. Short-radius / ultra-short-radius horizontal well technology can effectively activate inefficient well sections by drilling through lateral openings in the original wellbore. However, this technology places almost stringent requirements on the measurement-while-drilling (MWD) system. Traditional WWD instruments are limited by the wellbore curvature radius and the rigidity of the instrument structure, making it difficult to adapt to ultra-short-radius operating environments with curvature radii of less than 12 meters.

[0003] The current technical bottlenecks are mainly reflected in three aspects: First, spatial constraints. After the casing of old wells is opened, the diameter of the working channel is generally less than 50mm, which forces the outer diameter of the instrument to be compressed to less than 35mm. Second, dynamic bending requirements. The build-up rate of ultra-short radius wells is as high as 15-30° / meter. Therefore, the downhole drill collar adopts a "centipede-shaped" multi-joint connection, and each single section can bend up to 4°. However, traditional rigid connection measuring instruments cannot meet such a large bending angle. Third, signal transmission has also become a problem. Conventional wireless transmission methods have signal attenuation problems under strong bending conditions. Summary of the Invention

[0004] To address the aforementioned challenges, this invention provides a downhole measurement instrument suitable for flexible drill collars. This instrument enables ultra-short radius operations in wellbores with a curvature radius of less than 12 meters within a single drill collar with a 4° bend. The novel measurement instrument design innovatively employs a "split-type flexible connection" architecture, flexibly connecting the directional measurement unit and the power system via a long-distance tensile cable to form a freely bendable "string" structure. This design ensures the instrument's ability to traverse extremely curvature well sections and achieves long-term insulation (>100 hours) in mud environments through optimized cable armor, facilitating wellbore operations with a diameter of 35mm or less.

[0005] Of particular note is that the present invention’s scheme of placing the inclination measurement unit at the bottom can more accurately capture changes in the wellbore trajectory, while the pulse generator placed at the top ensures the stability of the signal uplink transmission. This spatial reconstruction reflects an important innovation in the design concept of downhole instruments.

[0006] The technical solution of this invention is as follows: A downhole measurement instrument suitable for flexible drill collars includes a conversion connector, a non-magnetic connector, a flexible non-magnetic drill collar, a rigid non-magnetic drill collar, and a retrieval head, which are sequentially connected to form an instrument housing. Inside the instrument housing is an instrument measurement string, including a slant measurement sub, a central control sub, a gamma ray sub, a power module, and a pulse generator.

[0007] The adapter and the non-magnetic connector are located at the front end of the instrument. The inclinometer section is installed inside the adapter and the non-magnetic connector. The inclinometer section is electrically connected to the device at the top of the instrument's measurement string via a deep-sea cable. The pulse generator is located at the top of the instrument's measurement string.

[0008] Furthermore: a positioning seat is provided in the central cavity of the conversion joint, the front end of the inclinometer section is connected to the guide head, and the guide head is seated in the positioning seat to stabilize the inclinometer section.

[0009] Furthermore: a groove is provided on the inner wall of the central cavity of the conversion connector, and a positioning groove is provided on the outer surface of the positioning seat. A flat key is embedded in the positioning groove on one side and in the groove on the other side, so that the positioning seat is fixed in the conversion connector.

[0010] Furthermore, the outer surface of the positioning seat is provided with a directional hole that penetrates the central cavity, and a directional key passes through the directional hole and contacts the surface of the guide head to radially limit the guide head.

[0011] Furthermore: the center cavity of the positioning seat has a stepped hole at its end, a retaining ring is movably seated in the stepped hole, and a lock nut is threaded onto the end of the stepped hole, the lock nut blocking the retaining ring in the stepped hole; when the guide head passes through the positioning seat, the annular groove on the guide head locks the retaining ring in the annular groove; the end of the guide head is provided with a shoulder, which blocks the outside of the lock nut.

[0012] Furthermore, the diameter of the retaining ring is smaller than the annular groove on the guide head, and an axial notch is formed on the retaining ring.

[0013] Furthermore, the end of the retaining ring facing the lock nut is designed as an outward-flaring flared shape.

[0014] Furthermore: the inclinometer section includes an inclinometer platform and an outer cylinder;

[0015] One end of the outer cylinder is threadedly connected to the guide head, and the other end is threadedly connected to the connecting sleeve;

[0016] The inclined plane is fitted with a straightening rubber ring on its outside, and is supported in the outer cylinder by the straightening rubber ring.

[0017] The guide head has a blind hole at its tail end, and a buffer spring is installed in the blind hole. One end of the inclinometer platform extends into the blind hole and presses against the buffer spring. The other end of the inclinometer platform makes buffer contact with the end face of the connecting sleeve through an elastic pad.

[0018] One end of the deep-water cable has a first cable plug, which is threaded inside the connecting sleeve and electrically connected to the measuring device on the inclinometer platform.

[0019] Furthermore, a support wing is provided at one end of the outer cylinder near the guide head. The support wing provides downward mud pressure to the instrument, so that the guide head sits in the positioning seat.

[0020] Furthermore: the deep-water cable passes through the flexible non-magnetic drill collar, one end of the deep-water cable has a first cable plug that is electrically connected to the inclination section, and the other end has a second cable plug that is electrically connected to the upper device of the instrument measuring string located in the rigid non-magnetic drill collar.

[0021] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention solves the industry problem of structural failure in wells with ultra-short bending radii by adopting a split-type flexible connection architecture through innovative design; through the unique "lower-positioned inclination measurement unit + upper-positioned pulse unit" structure, the inclination measurement unit is closer to the measurement interface, and the wellbore trajectory measurement error is controlled within ±0.1°, improving accuracy by 35% compared to traditional structures; the flexible cable connection design effectively eliminates the measurement signal distortion problem caused by rigid connections, achieving a data acquisition integrity rate of 99.7%. Compared with conventional sidetracking technology, this solution increases single-well oil recovery rate by 15-20%, bringing significant economic benefits to oilfield development.

[0022] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall connection structure of the measuring instrument of the present invention;

[0024] Figure 2 This is a schematic diagram of the front end structure of the measuring instrument of the present invention;

[0025] Figure 3 This is a schematic diagram of the positioning seat structure of the present invention;

[0026] Figure 4 This is a schematic diagram showing the connection between the positioning seat and the flat key, directional key, retaining ring, and lock nut of the present invention;

[0027] Figure 5 This is a schematic diagram of the guide head structure of the present invention;

[0028] Figure 6 This is a schematic diagram of the retaining ring structure of the present invention;

[0029] Figure 7 This is a schematic diagram of the lock nut structure of the present invention;

[0030] Figure 8 This is a schematic diagram of the assembly of the guide head and the retaining ring of the present invention;

[0031] Figure 9 This is a schematic diagram of the inclinometer section structure of the present invention.

[0032] In the diagram, 1-adapter connector, 2-non-magnetic connector, 3-flexible non-magnetic drill collar, 4-hard non-magnetic drill collar, 5-retrieval head, 6-inclination measuring section, 7-central control section, 8-gamma section, 9-power module, 10-pulse generator, 11-centralizer, 12-telescopic rod, 13-positioning seat, 14-guide head, 15-flat key, 16-directional key, 17-ring, 18-lock nut;

[0033] 20 - Deep-sea cable, 21 - First cable plug, 22 - Second cable plug, 23 - Socket, 24 - Adapter;

[0034] 61- Inclinometer platform body, 62- Outer cylinder, 63- Straightening rubber ring, 64- Buffer spring, 65- Elastic pad, 66- Support wing, 67- Connecting sleeve. Detailed Implementation

[0035] The present invention will now be described in detail with reference to the accompanying drawings and embodiments, wherein the drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the present invention. However, those skilled in the art should understand that the following embodiments are not the only limitation on the technical solutions of the present invention, and any equivalent transformations or modifications made under the spirit and essence of the technical solutions of the present invention should be considered as falling within the protection scope of the present invention.

[0036] This invention provides a downhole measuring instrument suitable for flexible drill collars. On the one hand, it aims to adopt a split-type flexible connection architecture for the measuring instrument string to adapt to the structural requirements of the flexible drill collar with its variable angles. On the other hand, it aims to adopt a scheme in which the inclination measurement unit is placed at the bottom and the pulse unit is placed at the top, and to solve the problem of signal attenuation or distortion by combining wired and wireless transmission.

[0037] like Figure 1 As shown, the measuring instrument of the present invention includes: a conversion connector 1, a non-magnetic connector 2, a flexible non-magnetic drill collar 3, a rigid non-magnetic drill collar 4, and a retrieval head 5. These components are connected in sequence (generally by threaded connection) to form the instrument housing. Each component has a central cavity, and the cavities are interconnected after connection. The instrument measuring string is arranged in the cavity. The instrument measuring string includes a slant section 6, a central control section 7, a gamma section 8, a power module 9, a pulse generator 10, and corresponding support components and connecting components such as a centralizer 11 and a telescopic rod 12. These modules are used for measurement and are conventional in the field. Their functions will not be described in detail here. The present invention aims to improve the structure and connection relationship of the instrument.

[0038] like Figure 2As shown, the present invention has two components, a conversion connector 1 and a non-magnetic connector 2, at the front end of the instrument. The conversion connector 1 and the non-magnetic connector 2 are threaded together and serve as rigid connectors to the front end of the flexible non-magnetic drill collar 3 to meet the instrument's downhole keying requirements. At the same time, it is also for installing the inclination measuring sub 6 inside the conversion connector 1 and the non-magnetic connector 2. The inclination measuring sub 6 is used to measure well inclination and azimuth data, so the ideal position is as close to the front end of the instrument as possible. The conversion connector 1 and the non-magnetic connector 2 are rigid connectors used to protect the inclination measuring sub 6.

[0039] Specifically, the present invention provides a positioning seat 13 in the central cavity of the conversion joint 1, and connects a guide head 14 to the front end of the inclination measuring sub 6. The guide head 14 is keyed into the positioning seat 13 and connected to the inclination measuring sub 6 to achieve the stability of the inclination measuring sub 6 downhole.

[0040] Specifically, the structure of positioning seat 13 is as follows: Figure 3 As shown, it includes a large end and a small end. A positioning groove is provided on the outer surface of the large end of the positioning seat 13, and a corresponding groove is provided on the inner wall of the central cavity of the adapter 1. Figure 4 As shown, a flat key 15 is embedded in the positioning groove of the positioning seat 13 on one side and in the groove of the inner wall of the adapter 1 on the other side. Through the connection of the flat key 15, the positioning seat 13 is fixed in the central cavity of the adapter 1.

[0041] The positioning seat 13 is also a component with a central cavity. A directional hole penetrating the central hole is provided on the outer surface of the small end of the positioning seat 13. A directional key 16 is disposed within the directional hole, such as... Figure 4 As shown, the directional key 16 is fixedly connected to the positioning seat 13 by a cylindrical pin. The inner end of the directional key 16 extends into the central cavity of the positioning seat 13 and is used to contact and limit the outer surface of the guide head 14. When the guide head 14 is seated in the positioning seat 13, the directional key 16 presses against the guide head 14 to perform radial limiting.

[0042] Furthermore, such as Figure 5 As shown, the outer surface of the guide head 14 is provided with a guide groove A, and the directional key 16 is limited in the guide groove. Due to the presence of the directional key 16, the positioning seat 13 and the guide head 14 cannot rotate relative to each other, and only the guide head 14 is allowed to move axially.

[0043] The guide head 14 not only achieves radial limiting through the directional key 16, but also achieves axial keying function through the retaining ring 17 and the lock nut 18. For example... Figure 4 As shown, the end of the positioning seat 13 is provided with a stepped hole, and a retaining ring 17 is movably disposed in the stepped hole. The retaining ring 17 can sit in the stepped hole. A lock nut 18 is threadedly connected to the end of the stepped hole. The lock nut 18 can block the retaining ring 17 in the hole. The structure of the retaining ring 17 and the lock nut 18 is as follows. Figure 6 , 7 As shown.

[0044] When the guide head 14 passes through the positioning seat 13, the guide groove A of the head of the guide head 14 must first be aligned with the orientation key 16 before it can be inserted; otherwise, it cannot enter. Then, when the annular groove on the guide head 14 passes through the retaining ring 17, the retaining ring 17 is engaged in the groove. Figure 8 As shown, because the retaining ring 17 is confined in the stepped hole, the axial displacement of the guide head 14 is also limited, thus realizing the key-seating function of the guide head 14.

[0045] Furthermore, a shoulder is provided at the end of the guide head 14 to block the outside of the lock nut 18, which also restricts the further extension of the guide head 14.

[0046] Furthermore, the diameter of the retaining ring 17 can be made smaller, smaller than the annular groove on the guide head 14, and an axial notch can be made on the retaining ring 17 so that the guide head 14 can pass through the retaining ring 17 by opening the notch. When the retaining ring 17 is locked in the groove, the notch retracts, so that the retaining ring 17 and the guide head 14 are tightly bound together. This is more conducive to the guide head 14 and the retaining ring 17 becoming a whole.

[0047] Furthermore, to prevent key disengagement, the end of the retaining ring 17 facing the lock nut 18 can be designed as an outward-flaring flared mouth. When the guide head 14 tends to retract, the outward-flaring flared mouth is tightened in the lock nut 18, preventing the guide head 14 from being pulled out together with the retaining ring 17. The small end of the retaining ring 17 is stuck in the annular groove of the guide head 14, which also prevents the guide head 14 from coming out of the retaining ring. Through the ingenious connection between the positioning seat 13 and the guide head 14, the present invention makes the inclinometer section 6 sit firmly in the drill collar, which is conducive to signal acquisition.

[0048] Inclinometer section 6 is located at the front of the instrument, such as... Figure 9 As shown, the device includes a ramp body 61 and an outer cylinder 62. Measuring devices are arranged on the ramp body 61, and the outer cylinder 62 protects the ramp body 61. One end of the outer cylinder 62 is threadedly connected to the guide head 14. A straightening rubber ring 63 is fitted at both ends of the ramp body 61, with its outer wall fitting against the outer cylinder 62. The straightening rubber ring 63 supports the ramp body 61 within the outer cylinder 62, maintaining the stability of the ramp body 61 during movement and providing straightening and radial vibration damping. Additionally, a blind hole is provided at the tail end of the guide head 14, and a buffer spring 64 is installed inside the blind hole. One end of the ramp body 61 extends into the blind hole of the guide head 14, pressing against the buffer spring 64. Simultaneously, an elastic pad 65 is provided at the contact point between the end faces of the ramp body 61 and the guide head 14. Both the buffer spring 64 and the elastic pad 65 assist in axial vibration damping of the ramp body 61. The present invention does not fix the inclinometer platform 61 to the outer cylinder 62 and the guide head 14, in order to reduce the impact on the inclinometer platform 61 during instrument vibration and avoid damage to the measuring device.

[0049] Furthermore, a support wing 66 is provided at the outer end of the outer cylinder 62 near the guide head 14. The support wing 66 is fitted onto the outer cylinder 62 and fixedly connected to it. The support wing 66 is mainly for assisting the key seat. When the pump is started downhole, the mud at the top of the instrument will continuously impact the end face of the support wing, giving the support wing a downward pressure, so that the retaining ring 17 can retract more quickly under the guidance of the lock nut 18 until the key seat is fully in place.

[0050] The other end of the outer cylinder 62 is threadedly connected to a connecting sleeve 67; the other end of the inclinometer platform 61 is also supported in the outer cylinder 62 by a straightening rubber ring 63, and is in buffer contact with the end face of the connecting sleeve 67 by an elastic pad 65. The connecting sleeve 67 is internally threadedly connected to a first cable plug 21. One end of the first cable plug 21 is electrically connected to the measuring device on the inclinometer platform 61, and the other end is connected to the deep-water cable 20. The signal from the inclinometer sub 6 is transmitted outward through the deep-water cable 20.

[0051] The deep-water cable 20 is prone to disturbance, so when the key is not in place, the inclinometer section 6, along with the guide head 14, is movable. When the key is successfully engaged, the guide head 14 locks into the positioning seat 13, thus fixing the inclinometer section 6. This invention uses the deep-water cable 20 for linear transmission because, on the one hand, it leverages the structural advantages of flexible non-magnetic drill collars, allowing for flexible long-distance cable connections; on the other hand, it utilizes the advantages of wired signal transmission, making signal transmission more stable. All of these factors make it possible for the inclinometer section 6 to be lowered for close-range measurement.

[0052] One end of the deep-water cable 20 is connected to the inclinometer section 6, and the other end passes through the flexible non-magnetic drill collar 3 and enters the rigid non-magnetic drill collar 4 to connect with the measuring device at the top of the instrument. For example... Figure 2 As shown, the other end of the deep-sea cable 20 is provided with a second cable plug 22, which is threaded into the adapter 24. The other end of the adapter 24 is also fixedly connected to the socket 23, which is connected to the second cable plug 22. The other end of the socket 23 is connected to the upper part of the instrument measuring string to transmit the signal of the deep-sea cable 20 upward.

[0053] The lower end of the instrument uses a flexible non-magnetic drill collar 3, which adopts a "centipede-shaped" multi-section structure. A single section can bend up to 4°, which can meet the dynamic bending requirements of the wellbore. The deep water cable 20 is also flexible, which can adapt to the dynamic changes of the flexible non-magnetic drill collar 3. At the same time, the deep water cable 20 can upload the signal of the sinking inclination measuring section 6.

[0054] The upper part of the instrument uses a rigid non-magnetic drill collar 4 to meet the requirements for downhole operation and equipment installation. Inside the rigid non-magnetic drill collar 4, components such as the central control sub 7, gamma sub 8, and pulse generator 10 are tightly connected, allowing for wireless transmission. This invention also places the pulse generator 10 at the very top of the instrument, in closest contact with the mud, to meet the requirements for generating mud pulse signals.

[0055] When the drilling team is drilling, after connecting the drill collar, the instrument measuring string is lowered into the well along the drill collar by the retrieval head. During the lowering process, the inclination measurement sub connected to the front end of the deepwater cable is dropped along the flexible drill collar. Under the action of gravity, the inclination measurement sub gradually slides to the position of the adapter joint. The guide head passes through the middle of the positioning seat along the guide. At this time, the pump is turned on to pressurize the mud, which continuously impacts the end face of the support wing, so that the guide head is fully embedded in the positioning seat, and the inclination measurement sub is stabilized. The upper end of the drill collar is the pulse generator, and the lower end is the inclination measurement sub. Data is transmitted through the cable in the middle. As the drill string advances, the inclination measurement sub continuously collects the well inclination and azimuth, and the pulse generator continuously emits mud pulse signals, transmitting the current data in the form of mud pressure waves. When the wellbore bends, the flexible drill collar changes angle with the wellbore, causing the entire instrument to change direction. The cable in the drill collar adapts to the change in direction of the flexible drill collar. The conversion connector, non-magnetic connector, positioning seat, and guide head at the front end of the instrument ensure the stability of the inclination measurement sub, always pointing in front of the wellbore.

[0056] This invention innovatively employs a combined wired and wireless transmission approach, solving the industry problem that traditional hard-connected instruments cannot operate normally in wells with ultra-short bending radii. Furthermore, through its unique "lower-positioned inclination measurement unit + upper-positioned pulse" structure, it controls the wellbore trajectory measurement error within ±0.1°. Although embodiments of the invention have been shown above, it will be understood by those skilled in the art that various equivalent changes, modifications, or substitutions can be made to these embodiments without departing from the principles and spirit of the invention. The scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A downhole measuring instrument suitable for flexible drill collars, comprising a conversion connector (1), a non-magnetic connector (2), a flexible non-magnetic drill collar (3), a rigid non-magnetic drill collar (4), and a retrieval head (5), which are sequentially connected to form an instrument housing. The instrument housing contains an instrument measuring series, including a slant section (6), a central control section (7), a gamma section (8), a power module (9), and a pulse generator (10), characterized in that: The conversion connector (1) and the non-magnetic connector (2) are located at the front end of the instrument. The inclinometer section (6) is installed inside the conversion connector (1) and the non-magnetic connector (2). The inclinometer section (6) is electrically connected to the device at the upper end of the instrument's measuring string via a deep-water cable (20). The pulse generator (10) is placed at the top of the instrument measurement string; The conversion connector (1) has a positioning seat (13) in its central cavity. The front end of the inclinometer section (6) is connected to the guide head (14). The guide head (14) is seated in the positioning seat (13) to stabilize the inclinometer section (6). The conversion connector (1) has a groove on the inner wall of the central cavity, and the positioning seat (13) has a positioning groove on the outer surface. A flat key (15) is embedded in the positioning groove on one side and in the groove on the other side, so that the positioning seat (13) is fixed in the conversion connector (1). The outer surface of the positioning seat (13) is provided with a directional hole that penetrates the central cavity. A directional key (16) passes through the directional hole and contacts the surface of the guide head (14) to radially limit the guide head (14). The positioning seat (13) has a stepped hole at the end of the central cavity. A retaining ring (17) is movably seated in the stepped hole. A lock nut (18) is threaded onto the end of the stepped hole. The lock nut (18) blocks the retaining ring (17) in the stepped hole. When the guide head (14) passes through the positioning seat (13), the annular groove on the guide head (14) will lock the retaining ring (17) in the annular groove; the end of the guide head (14) is provided with a shoulder, which blocks the outside of the lock nut (18).

2. The downhole measuring instrument for flexible drill collars according to claim 1, characterized in that: The diameter of the retaining ring (17) is smaller than the annular groove on the guide head (14), and an axial notch is provided on the retaining ring (17).

3. The downhole measuring instrument for flexible drill collars according to claim 1, characterized in that: The end of the retaining ring (17) facing the lock nut (18) is designed as an outward-flaring flared shape.

4. The downhole measuring instrument for flexible drill collars according to claim 1, characterized in that: The inclinometer section (6) includes an inclinometer platform (61) and an outer cylinder (62); One end of the outer cylinder (62) is threadedly connected to the guide head (14), and the other end is threadedly connected to the connecting sleeve (67); The inclined platform (61) is fitted with a straightening rubber ring (63) on the outside, and is supported in the outer cylinder (62) by the straightening rubber ring (63); The guide head (14) has a blind hole at its tail end, and a buffer spring (64) is installed in the blind hole. One end of the inclinometer (61) extends into the blind hole and presses against the buffer spring (64); the other end of the inclinometer (61) is in buffer contact with the end face of the connecting sleeve (67) through an elastic pad (65). One end of the deep-water cable (20) has a cable first plug (21), which is threaded inside the connecting sleeve (67) and electrically connected to the measuring device on the inclinometer platform (61).

5. The downhole measuring instrument for flexible drill collars according to claim 4, characterized in that: The outer cylinder (62) is provided with a support wing (66) at one end near the guide head (14). The support wing (66) provides downward mud pressure to the instrument, so that the guide head (14) sits in the positioning seat (13).

6. The downhole measuring instrument for flexible drill collars according to claim 1, characterized in that: The deep-water cable (20) passes through the flexible non-magnetic drill collar (3). One end of the deep-water cable (20) has a first cable plug (21) that is electrically connected to the inclinometer section (6), and the other end has a second cable plug (22) that is electrically connected to the upper device of the instrument measuring string located in the rigid non-magnetic drill collar (4).

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