Drill string and drilling method suitable for single barrel dual well

Abstract

The present application relates to the technical field of drilling, in particular to a drilling assembly and drilling method suitable for single-cylinder double-well, aiming at alleviating the technical problem of frequently worn casing when drilling along the casing in the related art. The drilling assembly suitable for single-cylinder double-well comprises a heavy drill pipe, a flexible ordinary drill pipe, a non-magnetic drill collar, a single-bend screw drill tool and a roller bit; the heavy drill pipe, the flexible ordinary drill pipe, the non-magnetic drill collar, the single-bend screw drill tool and the roller bit are connected in sequence. The drilling assembly is used for drilling along the casing without damaging the casing.

Description

Technical Field

[0001] This invention relates to the field of drilling technology, and in particular to a drill string assembly and drilling method suitable for single-tube dual-well drilling. Background Technology

[0002] Currently, drilling platforms commonly employ single-tube dual-well technology to increase the number of wells drilled. The conventional single-tube dual-well drilling technique involves first running a drill string assembly into a large-diameter guide pipe wellbore. Well A is drilled to a certain depth, and then surface casing is run into the large-diameter guide pipe to a certain depth before cementing. The staking drill string inside the large-diameter guide pipe is then retrieved. A conventional directional drill string is run into Well B. After the roller cone bit in Well B drills several meters out of the large-diameter guide pipe, a gyroscope instrument designed to prevent interference from the casing's magnetic field is used for positioning. The wellbore trajectory is drilled to an interference-free section. After the two wellbores are safely separated, the drill string is pulled out, and conventional drilling tools are used to control the wellbore trajectory.

[0003] It should be noted that the conventional directional drilling tool mentioned above includes, in sequence, a roller cone bit, a single-bend screw drill bit, a stabilizer, two non-magnetic drill collars, a weighted drill pipe, and a drill pipe. Among them, the stabilizer and the combination of multiple drill collars have high overall rigidity, which makes the overall flexibility of the drilling tool low. When drilling along the casing in long well sections, accidents of casing wear through often occur. Summary of the Invention

[0004] The purpose of this invention is to provide a drill string assembly and drilling method suitable for single-tube dual-well drilling, so as to alleviate the technical problem of casing wear-through that often occurs when rotating along the casing during drilling in related technologies.

[0005] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows: The present invention provides a drill string assembly suitable for single-tube dual-well configuration, comprising: a weighted drill pipe, a flexible conventional drill pipe, a non-magnetic drill collar, a single-bend screw drill string, and a roller cone drill bit; The weighted drill rod, the flexible ordinary drill rod, the non-magnetic drill collar, the single-bend screw drill bit, and the roller cone drill bit are connected in sequence.

[0006] Furthermore, drilling tool assemblies suitable for single-tube dual-well configurations also include drilling-while-drilling instruments; The drilling instrument is installed inside the non-magnetic drill collar.

[0007] Furthermore, the drilling instrument includes three gravity sensors; The combination of the three gravity sensors is used to measure three-component gravitational acceleration data in three mutually perpendicular directions.

[0008] Furthermore, the drilling instrument also includes three magnetic sensors; The combination of the three magnetic sensors is used to measure the three-component magnetic field strength data in three mutually perpendicular directions.

[0009] A drilling method employing a drill string assembly suitable for single-tube dual-well drilling includes the following steps: drilling the first well: the first well is drilled with a surface casing inside a large-diameter guide pipe and cemented, and the surface well depth reaches the design value. Drilling the second well: First, lower the drill string assembly and rotate it along the casing wall of the first well to apply pressure. Stop drilling when the well reaches the build-up point. The second step is to measure and calculate the orientation angle of the gravity tool using the drilling instrument, and then convert the obtained data into a pressure signal and upload it to the wellhead computer. The third step involves the ground construction personnel using the measured gravity tool direction angle data from the actual measuring points to rotate the drill string assembly at the wellhead and adjust the position of the single-bend screw drill string to 80° to the left or right of the gravity tool direction angle of the first well. The fourth step is to control the duration of sliding drilling until the target depth of the second well is reached.

[0010] Furthermore, if the first well is an inclined well, no pre-inclination treatment is required when drilling the first well. If the first well is a vertical well, when the first well is drilled to the preset distance from the start point of the second well, the inclined screw sliding drilling will be started to increase the inclination angle to 1.5° or more, and the well section with stable inclination will be maintained at the preset distance.

[0011] Furthermore, in the first step, when drilling to the build-up point, stop rotating the drill string assembly and move it up and down to release the torque of the drill string assembly. Place the roller cone bit at a preset distance from the bottom of the well, stop the pump and stop the drill string, start the pump, and then begin the second step.

[0012] Furthermore, in the second step, the gravity tool orientation angle GTF is calculated, GTF = Tan⁻¹GX / GY, where GX and GY are the three-component gravitational acceleration data.

[0013] Furthermore, in the fourth step, the drilling time is controlled by sliding drilling, with the time being three times the normal drilling time. The two wellbores are separated by sliding. When drilling to a certain depth, the inclination angle and magnetic field at the measuring point are measured by the drilling instrument to measure abnormal parameters. If the inclination angle of the well increases by more than 0.5° compared to the original inclination angle, and the anomaly ratio of magnetic field strength and the anomaly ratio of geomagnetic angle (anomaly ratio = 100 × measured value / theoretical value of the region) are both less than 4%, then it is determined that the two wells have been separated.

[0014] Furthermore, after confirming that the two wellbores had been separated, the construction personnel continued to measure the direction angle of the gravity tool and carried out directional well trajectory operations according to the trajectory control requirements of the second well, until the target well depth of the second well was reached by drilling with the drill string assembly.

[0015] In summary, the technical effects achieved by the drilling tool assembly for single-tube dual-well configuration provided by this invention are as follows: In this application, the drill string assembly includes a weighted drill pipe, a flexible ordinary drill pipe, a non-magnetic drill collar, a single-bend screw drill string, and a roller cone bit. The flexible ordinary drill pipe is connected after the non-magnetic drill collar, followed by the weighted drill pipe, which reduces the rigidity of the drill string above the non-magnetic drill collar and enhances the overall flexibility. In this assembly, the drill pipe and bottom drill string are inverted, reducing the number of non-magnetic drill collars and the number of weighted drill pipes, and no rigid stabilizer is used separately. The flexible ordinary drill pipe has a small diameter and weak rigidity. When connected to the non-magnetic drill collar, it undergoes bending deformation during pressurized drilling. When the roller cone bit is in the rotating drilling state, the roller cone bit can drill in a relatively large deformation space, realizing drilling along the casing without damaging the casing, and can also be used for sidetracking separation and trajectory control operations.

[0016] During rotary drilling along the casing, the drill string assembly rotates and applies pressure along the casing wall of the first well. The roller cone bit drills along the water-bearing formation, mud sheath, and part of the casing. Due to the large deformability of the roller cone bit and the entire assembly, when the roller cone bit contacts the casing, the axis of the roller cone bit in the second well is parallel to the wellbore axis of the casing in the first well. There is no angle of entry where the roller cone bit axially cuts into the axis of the first well. Therefore, the roller cone bit will not penetrate deeply into the casing wall. The rotating roller cone bit mainly cuts into the relatively soft cement sheath and formation of the first well, and the roller cone bit only partially collides with the harder casing wall. Since the angle of entry is 0°, the self-rotating roller cone bit only slides across the casing surface, causing minimal damage to the casing well. This achieves drilling along the casing without abrading the casing of the first well. Attached Figure Description

[0017] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the drill string assembly suitable for single-tube dual-well configuration provided in an embodiment of the present invention; Figure 2 A schematic diagram of the structure of a drilling instrument for a single-tube dual-well assembly provided in an embodiment of the present invention; Figure 3 This is a schematic diagram illustrating the application of a drill string assembly suitable for single-tube dual-well configurations provided in an embodiment of the present invention.

[0019] Icons: 100 - Heavyweight drill pipe; 200 - Flexible standard drill pipe; 300 - Non-magnetic drill collar; 400 - Single-bend screw drill bit; 500 - Roller cone drill bit; 600 - Drilling instrument; 610 - Gravity sensor; 620 - Magnetic sensor; 700 - Large diameter conduit; 800 - Surface sheath; 900 - Cement ring. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0021] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0022] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0023] Existing directional drilling tools have high overall rigidity but low flexibility. When drilling along the casing in long well sections, accidents often occur where the casing is worn through.

[0024] In view of this, the present invention provides a drill string assembly suitable for single-tube dual-well configuration, comprising a weighted drill pipe 100, a flexible ordinary drill pipe 200, a non-magnetic drill collar 300, a single-bend screw drill string 400, and a roller cone drill bit 500; the weighted drill pipe 100, the flexible ordinary drill pipe 200, the non-magnetic drill collar 300, the single-bend screw drill string 400, and the roller cone drill bit 500 are connected in sequence.

[0025] In this application, the drill string assembly includes a heavy-duty drill pipe 100, a flexible ordinary drill pipe 200, a non-magnetic drill collar 300, a single-bend screw drill string 400, and a roller cone bit 500. The flexible ordinary drill pipe 200 is connected after the non-magnetic drill collar 300, followed by the heavy-duty drill pipe 100, which reduces the rigidity of the drill string above the non-magnetic drill collar 300 and enhances the overall flexibility. In this assembly, the drill pipe and bottom drill string are inverted, reducing the number of non-magnetic drill collars 300 and the number of heavy-duty drill pipes 100, and a rigid stabilizer is not used separately. The flexible ordinary drill pipe 200 has a small diameter and weak rigidity. When connected to the non-magnetic drill collar 300, it undergoes bending deformation during pressurized drilling. When the roller cone bit 500 is in the rotating drilling state, it can drill in a relatively large deformation space, achieving drilling along the casing without damaging the casing, and can also be used for sidetracking separation and trajectory control operations.

[0026] During rotary drilling along the casing, the drill string assembly rotates and applies pressure along the casing wall of the first well. The roller cone bit 500 drills along the water formation, mud sheath, and part of the casing. Due to the large deformability of the roller cone bit 500 and the entire assembly, when the roller cone bit 500 contacts the casing, the axis of the roller cone bit 500 in the second well is parallel to the wellbore axis of the casing in the first well. There is no angle of entry where the roller cone bit 500 cuts into the axis of the first well. Therefore, the roller cone bit 500 will not penetrate deeply into the casing wall. The rotating roller cone bit 500 mainly cuts into the relatively soft cement sheath 900 and formation in the first well, and the roller cone bit 500 only partially collides with the harder casing wall. Since the angle of entry is 0°, the self-rotating roller cone bit 500 only slides across the casing surface, causing minimal damage to the casing well. This achieves drilling along the casing without abrading the casing of the first well.

[0027] The following combination Figures 1 to 3 The structure and shape of the drill string assembly suitable for single-tube dual-well configuration provided in this embodiment are described in detail below: Further reference Figure 1 and Figure 2 The drill string assembly suitable for single-tube dual-well configuration also includes a drilling instrument 600; the drilling instrument 600 is housed within the non-magnetic drill collar 300.

[0028] Continue to refer to Figure 1 and Figure 2 The drilling instrument 600 includes three gravity sensors 610 and three magnetic sensors 620; wherein, the combination of the three gravity sensors 610 is used to measure three-component gravitational acceleration data in three mutually perpendicular directions; the combination of the three magnetic sensors 620 is used to measure three-component magnetic field strength data in three mutually perpendicular directions.

[0029] refer to Figure 3 During drilling of Well B, a drill string assembly is lowered, containing a drilling instrument 600. Once the designed trajectory separation point is reached, rotary drilling is stopped, and a sliding directional drilling mode is activated. Utilizing the magnetic interference-free characteristics of three gravity sensors 610, the gravity tool orientation angle is measured under a certain well inclination direction. When Well B reaches the designed sidetracking separation depth, the drilling instrument 600 measures the gravity tool orientation angle. The data is transmitted via mud medium as a pressure signal to a surface computer for decoding. After decoding the data at the wellhead, technicians adjust the direction of the forward drilling screw on the surface, adjusting the gravity tool orientation angle to 80° to the left (right) of the Well A casing for easy sidetracking separation. After adjustment, a pressurized single-bend screw drill string 400 is lowered for sliding drilling. During sliding, the drilling speed is controlled to be three times the normal drilling time, enhancing the separation capability of the single-bend screw drill string 400 and achieving rapid separation of the Well B and Well A casings. After successful separation, this assembly is used to continue trajectory control of Well B to the target depth.

[0030] In the above, utilizing the principle that the three magnetic sensors 620 and three gravity sensors 610 are aligned, when the well inclination exceeds 1.5 degrees, even if the magnetic tool orientation angle MTF is distorted due to casing magnetic interference, the gravity sensor 610 is unaffected by the magnetic field, and the calculated gravity tool orientation angle GTF can accurately locate the downhole single-bend screw drill string at 40°. This design solves the problem of magnetic tool orientation angle positioning failure under casing magnetic interference, realizing accurate orientation operation in small well inclinations with a single-tube dual-well setup; and compared to the current practice of using gyroscope instruments unaffected by magnetic interference to measure the orientation angle of the downhole bent screw tool face, it reduces costs. It should be noted that GTF = Tan⁻¹GX / GY, MTF = Tan⁻¹BX / BY, for reference... Figure 2 GX and GY are three-component gravitational acceleration data, and BX and BY are three-component magnetic field strength data.

[0031] The present invention also provides a drilling method, which is implemented based on the above-described drill string assembly suitable for single-tube dual-well drilling, and includes the following steps: Drilling the first well: The first well is drilled with a surface casing of 800mm inside the large-diameter guide pipe of 700mm and cemented. The surface well depth reaches the design value. Drilling the second well: First, the drill string assembly is run in and rotated along the casing wall of the first well for pressure drilling. Drilling is stopped when the build-up point is reached. Second, the gravity tool orientation angle is measured and calculated using the drilling instrument 600, and the obtained data is converted into a pressure signal and uploaded to the wellhead computer. Third, based on the gravity tool orientation angle data measured at the actual measuring points, the surface construction personnel rotate the drill string assembly at the wellhead and adjust the position of the single-bend screw drill string 400mm to the left or right 80° to the side of the gravity tool orientation angle of the first well. Fourth, sliding drilling is controlled during drilling until the target well depth of the second well is reached.

[0032] Specifically, the following are examples Figure 3 For example, two wells, A and B, are drilled. Well A has a 339.7mm surface casing installed inside a 700mm diameter guide pipe and cemented, with a surface well depth of 900m. Well B is the second well to be drilled, with a surface well depth of 1000m. Both wells use 500mm roller cone bits with a diameter of 406.4mm. Well A has a vertical wellbore at 900m, while well B has a build-up point at 400m.

[0033] For well A, the minimum inclination angle of 1.5° is activated on the 600 gravity tool face of the drilling instrument. Therefore, when well A is about 50m before reaching the starting point of well B's directional drilling, the inclined screw sliding drilling is initiated to increase the inclination angle to 1.5° or higher, and a stable inclination is maintained for 100m. If well A is an inclined well, no lateral inclination treatment is required.

[0034] The drilling assembly in well B, from bottom to top, consists of: a 406.4mm roller cone bit (500), a 244mm single-bend screw drill bit (400), a 203mm non-magnetic drill collar (300) (with a drilling instrument (600) installed inside each non-magnetic drill collar (300)), a 127mm flexible ordinary drill pipe (200-200m), followed by a 127mm heavy-duty drill pipe (100-300m), and finally a 127mm drill pipe assembly at the wellhead.

[0035] Rotary drilling along the casing: In well B, the drill string assembly rotates and applies pressure along the casing wall of well A. The roller cone bit 500 drills along the water formation, the cement sheath 900, and part of the casing. Because the roller cone bit 500 and the flexible drill string assembly are highly deformable, when the roller cone bit 500 contacts the casing, the axis of the roller cone bit 500 in well B is parallel to the wellbore axis of the casing in well A. Therefore, there is no axial cutting angle between the roller cone bit 500 in well B and the axis of well A. As a result, the roller cone bit 500 will not penetrate deeply into the casing wall. The rotating roller cone bit 500 mainly cuts into the relatively soft cement sheath 900 and formation in well A. Moreover, the roller cone bit 500 only partially collides with the harder casing wall. Since the cutting angle is 0°, the self-rotating roller cone bit 500 only slides over the casing surface, causing less damage to the casing well. This achieves drilling along the casing without wearing down the casing of well A.

[0036] Gravity tool orientation angle measurement and control: When drilling B along the casing of well A to 400m from the build-up point, stop rotating the drill string assembly, release the torque of the drill string assembly by moving it up and down, place the roller cone bit 500 2m from the bottom of the well, stop the pump, and stationary the drill string assembly; start the pump, and the drilling instrument 600 measures the three-axis data of the gravity accelerometer GX, GY, and GZ at a measuring point 383m above the non-magnetic drill collar 300 above the drill bit, calculate the gravity tool orientation angle, GTF = Tan-1GX / GY; during the measurement, the drilling instrument 600 converts the data signal into a pressure signal and uploads it to the wellhead computer for decoding. Based on the measured gravity tool orientation angle data at the actual measuring point, the surface construction personnel rotate the drill string assembly at the wellhead to position the downhole single-bend screw drill string 400. Adjust the azimuth angle of the gravity tool to 80° to the left of the side of Well A. Here, the left and right positions depend on the trajectory of Well B and the anti-collision drilling requirements. Control the sliding drilling during drilling, with the time being three times the normal drilling time. Slide to separate the two wellbores. Drill to 430m. Through the 600-meter measurement while drilling instrument, it was found that there were significant changes in the inclination angle and magnetic field measurement abnormal parameters at the measuring point 413m. The inclination angle increased by more than 0.5° compared with the original inclination angle. The abnormal ratio of magnetic field strength and the abnormal ratio of geomagnetic angle (abnormal ratio = 100 × measured value / theoretical value of the area) were both less than 4%, which confirmed that the two wellbores had been separated. Afterwards, the construction personnel continued to measure the azimuth angle of the gravity tool and carried out directional well trajectory operation according to the trajectory control requirements of Well B until the target well depth of Well B was reached using this drilling tool combination.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A drilling method for a drill string assembly suitable for single-tube dual-well drilling, characterized in that, The drill string assembly includes: a weighted drill pipe, a flexible standard drill pipe, a non-magnetic drill collar, a single-bend screw drill string, and a roller cone drill bit; The weighted drill pipe, the flexible ordinary drill pipe, the non-magnetic drill collar, the single-bend screw drill string, and the roller cone drill bit are connected in sequence; the drill string assembly suitable for single-tube dual-well also includes a drilling instrument; The drilling instrument is installed inside the non-magnetic drill collar; the drilling instrument includes three gravity sensors; The combination of the three gravity sensors is used to measure three-component gravitational acceleration data in three mutually perpendicular directions; the drilling instrument also includes three magnetic sensors; The combination of the three magnetic sensors is used to measure the three-component magnetic field strength data in three mutually perpendicular directions; The drilling method includes the following steps: Drilling the first well: The first well is drilled with a surface casing inside a large-diameter guide pipe and cemented. The surface well depth reaches the design value. Drilling the second well: First, lower the drill string assembly and rotate it along the casing wall of the first well to apply pressure. Stop drilling when the well reaches the build-up point. The second step is to measure and calculate the orientation angle of the gravity tool using the drilling instrument, and then convert the obtained data into a pressure signal and upload it to the wellhead computer. The third step involves the ground construction personnel using the measured gravity tool direction angle data from the actual measuring points to rotate the drill string assembly at the wellhead and adjust the position of the single-bend screw drill string to 80° to the left or 80° to the right of the gravity tool direction angle of the first well. The fourth step is to control the sliding drilling time until the target well depth of the second well is reached; if the first well is an inclined well, no pre-inclination treatment is required when drilling the first well. If the first well is a vertical well, when the first well is drilled to a preset distance from the start point of the second well, start the inclined drilling with the bent screw to increase the inclination angle to 1.5° or more, and maintain the stable inclination at a preset distance in the well section; in the first step, when drilling to the start point, stop rotating the drill string assembly and move it up and down to release the torque of the drill string assembly, place the roller cone bit at a preset distance from the bottom of the well, stop the pump and stop the drill string, start the pump, and then start the second step; In the fourth step, the drilling time is controlled by sliding drilling, with the time being three times the normal drilling time. The two wellbores are separated by sliding. When drilling to a certain depth, the inclination angle and magnetic field at the measuring point are measured by the drilling instrument to measure abnormal parameters. If the inclination angle of the well increases by more than 0.5° compared to the original inclination angle, and the ratio of magnetic field strength anomaly and the ratio of geomagnetic angle anomaly are both less than 4%, then it is determined that the two wells have been separated.

2. The drilling method for a single-tube dual-well drill string assembly according to claim 1, characterized in that, In the second step, the orientation angle of the gravity tool, GTF, is calculated as GTF = Tan⁻¹GX / GY, where GX and GY are the three-component gravitational acceleration data.

3. The drilling method for a single-tube dual-well drill string assembly according to claim 1, characterized in that, After confirming that the two wellbores had been separated, the construction personnel continued to measure the direction angle of the gravity tool and carried out directional well trajectory operations according to the trajectory control requirements of the second well, until the target well depth of the second well was reached by drilling with the drill string assembly.

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