Shale oil horizontal well radical drilling method

Abstract

The invention relates to the technical field of oil and gas well drilling and completion engineering design and construction, in particular to a shale oil horizontal well aggressive drilling method which comprises the steps that the actual torsion resistance value of a drill rod is measured; a safety coefficient is set, and the maximum allowable torque T of the drill rod is determined; selecting a drilling tool; aggressive drilling parameters are adjusted, so that the actual torque of the drill rod is close to and does not exceed the maximum allowable torque T; pulling out after aggressive drilling is completed; and during aggressive drilling next time, the safety coefficient is adjusted, and the steps are repeated. By means of the aggressive drilling method, the service life of the drilling tool of the shale oil horizontal well can be effectively prolonged, and the efficient development efficiency of the horizontal well can be guaranteed.

Description

Technical Field

[0001] This invention relates to the field of oil and gas well drilling and completion engineering design and construction technology, and in particular to a radical drilling method for shale oil horizontal wells. Background Technology

[0002] In current shale gas development, advanced speed-up tools and enhanced drilling measures, particularly aggressive drilling, have significantly increased drilling speed. Aggressive drilling aims to fully utilize the speed-up potential of each stage of drilling operations by employing high drilling pressure, high rotational speed, high displacement, and high pump pressure. This ensures that the drill bit, screw, drill collar, drill pipe, centralizer, and pump all function at their maximum potential, thereby increasing the mechanical drilling speed.

[0003] To address downhole safety issues during aggressive drilling, the following measures were taken: First, to address the technical challenges of poor PDC bit adaptability, difficulty in wellbore trajectory control, and poor wellbore stability in shale oil horizontal wells in different regions, aggressive parameter drilling was promoted, drill string assemblies were optimized, personalized PDC bit design was carried out, and drilling fluid systems were selected.

[0004] Second, we conducted research on the engineering geological characteristics of the drilling formation, including mineral composition and physicochemical properties, three-pressure profile, and formation drillability. We established a data model to select the best high-efficiency drill bit for actual drilling and clarified the types of drill bits to be used in each well section. We analyzed the application of drilling parameters through software simulation to clarify the aggressive drilling parameter schemes for different well types. At the same time, we also selected the best polyamine drilling fluid system through indoor evaluation and field tests to ensure the stability of the mudstone wellbore.

[0005] Third, by combining the selection of screw drilling tools and PDC drill bits that are suitable for different well types, wellbores, and formations to improve drilling speed and efficiency, and based on the theoretical understanding of improving mechanical drilling speed by the maximum bottom hole flow velocity and the sensitivity analysis of drilling pressure / rotation speed to mechanical drilling speed, we conducted field tests of aggressive drilling with large displacement, large drilling pressure, and high rotation speed. We established aggressive drilling parameter templates for different well types and well sections to achieve large-scale speed improvement in the same area.

[0006] Fourth, based on a series of technologies such as the adoption of well factory model and overall optimization design technology, well structure optimization technology, selection of personalized PDC drill bits + long-life equal wall thickness screw + high-pressure injection technology, friction reduction and drag reduction of complex well trajectory, and environmentally friendly starch-based drilling fluid system, a high-efficiency development technology integration suitable for Jiangsu Oilfield has been formed.

[0007] Fifth, we conducted research on optimizing the "factory-style" horizontal well drilling mode, the "high-efficiency PDC drill bit + high-power screw" aggressive parameter drilling technology, optimizing the well trajectory control mode with different offset distances, and segmented optimization of the strong-inhibition low-density CQSP-4 anti-collapse drilling fluid.

[0008] Based on the review and analysis of the above materials, it is believed that the methods and measures proposed for addressing the problem of aggressive drilling in shale oil horizontal wells mainly focus on drilling formation analysis, drilling fluid performance optimization, PDC bit customization, and screw selection, but do not systematically analyze the downhole safety of drilling tools. Summary of the Invention

[0009] To address the aforementioned technical problems, this invention proposes an aggressive drilling method for shale oil horizontal wells, which can not only effectively extend the service life of shale oil horizontal well drilling tools, but also ensure high-efficiency development of horizontal wells.

[0010] This invention is achieved by adopting the following technical solution:

[0011] An aggressive drilling method for shale oil horizontal wells includes the following steps:

[0012] S1. Measure the actual torsional resistance T′ of the drill pipe;

[0013] S2. Set a safety factor α and determine the maximum permissible torque T of the drill pipe:

[0014] T = T′ / α

[0015] S3. Select drilling tools;

[0016] S4. Adjust the aggressive drilling parameters so that the actual torque of the drill pipe is close to and does not exceed the maximum allowable torque T;

[0017] S5. Aggressive drilling completed; tripping out of the well.

[0018] S6. For the next aggressive drilling operation, adjust the safety factor and repeat steps S2 to S5; the adjusted safety factor is:

[0019] α′=α-(n-1)β

[0020] In the formula, α′ is the adjusted safety factor, α is the safety factor when the drill string is used for the first time, n is the number of times the drill string is used, and β is the safety threshold.

[0021] The safety factor is determined based on the measured outer diameter of the drill pipe joint during the drilling process.

[0022] The aggressive drilling parameters include wellhead rotational pressure and drill pipe rotational speed.

[0023] Adjusting aggressive drilling parameters also involves conducting multiple pre-drilling operations in the drilling block to obtain the correspondence between aggressive drilling parameters and drill string torque.

[0024] During aggressive drilling, when the drill bit encounters a gravel layer 30-50m above the surface, reduce the wellhead pressure and drill pipe rotation speed.

[0025] Drill through gravel layers or highly abrasive formations for 10-20m; restore aggressive drilling parameters and continue aggressive drilling.

[0026] During the tripping process, identify the locations of obvious damage to the drill string and determine the appropriate parameters for drilling string entry into the well based on the extent of the damage.

[0027] The method for measuring the actual torsional resistance of drill pipe is as follows: randomly select drill pipes for overload uncoupling tests, and obtain the actual maximum uncoupling torque, which is the actual torsional resistance of the drill pipe.

[0028] When measuring the actual torsional resistance of the drill pipe, at least two drill pipes should be randomly selected.

[0029] When selecting drilling tools, ensure that the weakest point in the drill string structure that bears torque is on the drill pipe.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] 1. This drilling method can reduce the occurrence of drill string falling into the well and leakage; eliminate the phenomenon of thread sticking and puncture in drill string threads; effectively extend the service life of shale oil horizontal well drill string and ensure a high overall drilling speed; and provide theoretical support for field construction.

[0032] Specifically, based on the actual torsional resistance of the drill pipe, the present invention designs a safety factor to further obtain the maximum allowable torque of the drill pipe, so that the drill bit and drill tool can work under full load without damaging the threads of the drill pipe joint, thereby maximizing the rotational speed.

[0033] In subsequent drilling operations, the safety factor decreases sequentially to ensure the safety of the drilling tools entering the well.

[0034] 2. By conducting multiple pre-drilling operations in the drilling block, the correlation between aggressive drilling parameters and drill pipe torque can be obtained, enabling faster and more accurate adjustment of the most suitable parameters when adjusting the aggressive drilling parameters.

[0035] 3. When drilling encounters a gravel layer 30-50m above the surface, reducing the wellhead pressure and drill pipe speed can prevent overload damage to the drill pipe joint.

[0036] 4. The safety factor is determined based on the outer diameter of the drill pipe joint during the drilling process, making the determination of the safety factor more accurate and targeted.

[0037] 5. When selecting drilling tools, ensure that the weakest point of the drill tool structure in terms of torque is on the drill pipe, so as to identify the location of well sections with reduced diameter or gravel formations encountered during drilling, and ensure that the drilling torque variation is within a reasonable range.

[0038] 6. This invention provides an upper limit standard for rapid drilling by measuring the actual torsional resistance of the drill pipe. Attached Figure Description

[0039] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments, wherein:

[0040] Figure 1 This is a schematic diagram of the drill pipe joint structure in this invention. Figure 1 ;

[0041] Figure 2 This is a schematic diagram of the drill pipe joint structure in this invention. Figure 2 . Detailed Implementation

[0042] Example 1

[0043] As a basic embodiment of the present invention, the present invention includes a radical drilling method for shale oil horizontal wells, comprising the following steps:

[0044] Step S1. Measure the actual torsional resistance T′ of the drill pipe.

[0045] Step S2. Set the safety factor α and determine the maximum allowable torque T of the drill pipe:

[0046] T = T′ / α.

[0047] Step S3. Select the drilling tool.

[0048] Step S4. Adjust the aggressive drilling parameters so that the actual torque of the drill pipe is close to but does not exceed the maximum allowable torque T.

[0049] Step S5. Aggressive drilling completed, trip the drill string.

[0050] Step S6. During the next aggressive drilling operation, adjust the safety factor and repeat steps S2 to S5; the adjusted safety factor is:

[0051] α′=α-(n-1)β.

[0052] In the formula, α′ is the adjusted safety factor, α is the safety factor when the drill string is used for the first time, n is the number of times the drill string is used, and β is the safety threshold.

[0053] Example 2

[0054] As a preferred embodiment of the present invention, the present invention includes a radical drilling method for shale oil horizontal wells, comprising the following steps:

[0055] Step S1. Measure the actual torsional resistance T′ of the drill pipe.

[0056] Step S2. Set the safety factor α and determine the maximum allowable torque T of the drill pipe:

[0057] T = T′ / α.

[0058] The safety factor is determined based on the outer diameter of the drill pipe joint measured during the drilling process.

[0059] Step S3. Select the drilling tool.

[0060] Step S4. Adjust the aggressive drilling parameters so that the actual drill pipe torque is close to but does not exceed the maximum permissible torque T. The aggressive drilling parameters include wellhead spin and drill pipe rotation speed.

[0061] Step S5. Aggressive drilling completed, trip the drill string. During aggressive drilling, when encountering a gravel layer 30-50m above the surface, reduce the wellhead rotational pressure and drill pipe rotation speed. Drill through the gravel layer or highly abrasive formation for 10-20m; restore the aggressive drilling parameters and continue aggressive drilling.

[0062] Step S6. During the next aggressive drilling operation, adjust the safety factor and repeat steps S2 to S5; the adjusted safety factor is:

[0063] α′=α-(n-1)β.

[0064] In the formula, α′ is the adjusted safety factor, α is the safety factor when the drill string is used for the first time, n is the number of times the drill string is used, and β is the safety threshold.

[0065] Example 3

[0066] In another preferred embodiment of the present invention, the present invention includes a radical drilling method for shale oil horizontal wells, comprising the following steps:

[0067] Step S1. Randomly select drill pipes for overload uncoupling tests to obtain the actual maximum uncoupling torque, which is the actual torsional resistance value T′ of the drill pipe.

[0068] Step S2. Set the safety factor α and determine the maximum allowable torque T of the drill pipe:

[0069] T = T′ / α.

[0070] Step S3. Select the drilling tool.

[0071] Step S4. Adjust the aggressive drilling parameters so that the actual drill pipe torque is close to but does not exceed the maximum allowable torque T. The aggressive drilling parameters include wellhead spin and drill pipe rotation speed. When adjusting the aggressive drilling parameters, multiple pre-drilling operations can be performed in the drilling block to obtain the correspondence between the aggressive drilling parameters and the drill pipe torque, thereby enabling the rapid selection of the most appropriate aggressive drilling parameters.

[0072] Step S5. Aggressive drilling completed, trip the drill string.

[0073] Step S6. During the next aggressive drilling operation, adjust the safety factor and repeat steps S2 to S5; the adjusted safety factor is:

[0074] α′=α-(n-1)β.

[0075] In the formula, α′ is the adjusted safety factor, α is the safety factor when the drill string is used for the first time, n is the number of times the drill string is used, and β is the safety threshold.

[0076] Example 4

[0077] As a preferred embodiment of the present invention, the present invention includes a radical drilling method for shale oil horizontal wells, comprising the following steps:

[0078] Step S1. Measure the actual torsional resistance T′ of the drill pipe.

[0079] Two drill pipes were randomly selected from the existing drill pipe stock. The outer diameter and thread type of the drill pipe joint were measured. The steel grade and wall thickness of the drill pipe were checked. The two selected drill pipes were subjected to an overload turn-on / off test on a testing machine. The actual maximum turn-on torque was obtained (e.g., 48,000 Nm for an outer diameter of 127 mm, steel grade G105, thread type NC46, wall thickness of 9.19 mm, and drill pipe joint outer diameter of 168 mm); that is, the threads did not stick under a turn-on torque of 48,000 Nm; this provides an upper limit standard for rapid drilling in this block.

[0080] Step S2. Set the safety factor α and determine the maximum allowable torque T of the drill pipe:

[0081] T = T′ / α.

[0082] The safety factor is determined based on the measured outer diameter of the drill pipe joint during drilling. Specifically, the determination and application of the drill pipe safety factor in aggressive horizontal drilling of shale oil wells can be shown in the table below:

[0083] Outer diameter of drill pipe joint (mm) Safety factor 168 1.20 166 1.16 164 1.12 162 1.08 160 1.04 158 1

[0084] That is, when the outer diameter of the drill pipe joint is 168mm, and the safety factor is set to 1.2, the maximum allowable torque T of the drill pipe can be: 48000 / 1.2=40000Nm.

[0085] Step S3. Selecting the drilling tools. Due to the characteristics of rotary steerable tools, the outer diameter of the drill pipe wears severely. To ensure safe and rapid drilling, drill pipe fatigue safety is selected as the evaluation criterion. When selecting the drilling tools, the weakest point in the drill tool structure in terms of torque bearing capacity is on the drill pipe. This allows for the identification of well sections encountered during drilling, such as those with reduced diameter or gravel formations, ensuring that drilling torque variations remain within a reasonable range. In this embodiment, the drilling tools can be: 215.9 PDC drill bit + 165 screw + 165 rotary steerable tool + centralizer + weighted drill pipe + drill pipe.

[0086] Step S4. Refer to the instruction manual appendix. Figure 1 Included with instruction manual Figure 2 In aggressive drilling, due to the large number of drill pipes used (400-600 per well), drill pipe joints are prone to problems, making joint safety crucial. The end face of the drill pipe joint is the primary sealing surface. Therefore, aggressive drilling parameters are adjusted so that the actual torque of the drill pipe is close to but does not exceed the maximum permissible torque T. This allows for real-time consideration of the actual capabilities of the drill pipe and equipment during aggressive drilling, rather than solely focusing on speed without considering safety.

[0087] The aggressive drilling parameters include wellhead rotational pressure and drill pipe rotational speed. More specifically, it involves pre-understanding the formation characteristics of the drilling block, analyzing the technical difficulties of the wellbore structure, understanding the wellbore trajectory design, and mastering the actual performance of the drilling rig. Multiple pre-drilling operations are conducted in the drilling block. This includes understanding the existing drill pipe type, thread type, and wear degree; the maximum service life of the existing screw; the maximum service life of the existing PDC drill bit; and the actual condition of the existing pump (displacement, pump stroke, cylinder liner diameter). The correlation between the aggressive drilling parameters and the drill pipe torque is obtained. While ensuring that the actual drill pipe torque does not exceed the maximum allowable torque T, the rotational speed is maximized to provide a foundation for subsequent drilling speed increases.

[0088] In this embodiment, the mud pump displacement can be 38-42 L / s; the pump pressure can be 30-35 MPa; the wellhead drill bit speed can be 65-70 rpm; and the downhole screw speed can be 120-150 rpm, ensuring that the downhole drill bit and drill string operate under full load.

[0089] Step S5. Aggressive drilling completed, trip the drill string.

[0090] During aggressive drilling, when encountering a gravel layer 30-50m above the surface, reduce the wellhead torque and drill pipe rotation speed. Specifically, reduce the wellhead torque to 10-12 tons; reduce the rotation speed to 55-60 rpm; monitor changes in wellhead torque data to prevent overload damage to the drill pipe joints; and simultaneously monitor well leakage and pump pressure changes to prevent complications in the downhole environment.

[0091] When drilling through gravel layers or highly abrasive formations for 10-20m, revert to aggressive drilling parameters and continue aggressive drilling. During tripping out, observe changes in the overall drill string diameter and morphology to identify locations of significant damage. This information will help determine the operating parameters for the next drill string entry based on the damage condition.

[0092] Step S6. During the next aggressive drilling operation, adjust the safety factor and repeat steps S2 to S5; the adjusted safety factor is:

[0093] α′=α-(n-1)β.

[0094] In the formula, α′ is the adjusted safety factor, α is the safety factor when the drill string is used for the first time, n is the number of times the drill string is used, and β is the safety threshold. The value of β can be 0.04 or 0.02, etc., and can be selected according to the actual situation. The smaller the reduction in the drill string safety factor, the higher the safety of aggressive drilling.

[0095] In summary, any other corresponding modifications made by those skilled in the art after reading this invention document, without requiring creative mental effort, based on the technical solutions and concepts of this invention, are all within the scope of protection of this invention.

Claims

1. A radical drilling method for shale oil horizontal wells, characterized in that: Includes the following steps: S1. Measure the actual torsional resistance T′ of the drill pipe; S2. Set a safety factor α and determine the maximum permissible torque T of the drill pipe: T = T′ / α S3. Select drilling tools; S4. Adjust the aggressive drilling parameters so that the actual torque of the drill pipe is close to and does not exceed the maximum allowable torque T; S5. Aggressive drilling completed; tripping out of the well. S6. For the next aggressive drilling operation, adjust the safety factor and repeat steps S2 to S5; the adjusted safety factor is: α′＝α-(n-1)β In the formula, α′ is the adjusted safety factor, α is the safety factor when the drill string is used for the first time, n is the number of times the drill string is used, and β is the safety threshold.

2. The radical drilling method for shale oil horizontal wells according to claim 1, characterized in that: The safety factor is determined based on the measured outer diameter of the drill pipe joint during the drilling process.

3. The radical drilling method for shale oil horizontal wells according to claim 2, characterized in that: The aggressive drilling parameters include wellhead rotational pressure and drill pipe rotational speed.

4. The radical drilling method for shale oil horizontal wells according to claim 3, characterized in that: Adjusting aggressive drilling parameters also involves conducting multiple pre-drilling operations in the drilling block to obtain the correspondence between aggressive drilling parameters and drill string torque.

5. The radical drilling method for shale oil horizontal wells according to claim 3, characterized in that: During aggressive drilling, when the drill bit encounters a gravel layer 30-50m above the surface, reduce the wellhead pressure and drill pipe rotation speed.

6. The radical drilling method for shale oil horizontal wells according to claim 5, characterized in that: Drill through gravel layers or highly abrasive strata for 10-20m; Restore aggressive drilling parameters and continue aggressive drilling.

7. A radical drilling method for shale oil horizontal wells according to any one of claims 1 to 6, characterized in that: During the tripping process, identify the locations of obvious damage to the drill string and determine the appropriate parameters for drilling string entry into the well based on the extent of the damage.

8. A radical drilling method for shale oil horizontal wells according to any one of claims 1 to 6, characterized in that: The method for measuring the actual torsional resistance of drill pipe is as follows: randomly select drill pipes for overload uncoupling tests, and obtain the actual maximum uncoupling torque, which is the actual torsional resistance of the drill pipe.

9. The radical drilling method for shale oil horizontal wells according to claim 8, characterized in that: When measuring the actual torsional resistance of the drill pipe, at least two drill pipes should be randomly selected.

10. A radical drilling method for shale oil horizontal wells according to any one of claims 1 to 6, characterized in that: When selecting drilling tools, ensure that the weakest point in the drill string structure that bears torque is on the drill pipe.

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