Method for preventing sealing failure of sleeve thread

Abstract

The invention discloses a method for preventing sleeve thread sealing failure. The method comprises the step that sleeve quality control, field operation control, sleeve tripping-in quality control and volume fracturing parameter control are sequentially carried out to comprehensively prevent sleeve thread sealing failure. Wherein the casing pipe quality control sequentially comprises casing pipe processing quality control and casing pipe remote control; the on-site operation control sequentially comprises on-site casing discharge control, thread sealing grease smearing control, casing wellhead buckling control and casing screwing-on torque control. The casing pipe tripping-in quality control sequentially comprises casing pipe tripping-in resistance meeting frequency control, casing pipe resistance meeting tripping-in tonnage control, casing pipe thread bending amplitude control and casing pipe bending lateral force control. The volume fracturing parameter control sequentially comprises volume fracturing section number control and displacement pressure change vibration frequency control. According to the method, the casing thread failure can be effectively prevented under the complex working condition, higher practicability is achieved, and the use safety of the water casing is improved.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas well casing, and in particular to a method for preventing casing thread sealing failure. Background Art

[0002] Oil casing is an important tool in the exploration and development of oil and gas. A single oil and casing is connected by threaded joints to form a whole oil and casing string. Since the oil pipe string is the flow channel for high-pressure oil and gas from the bottom of the well to the wellhead, the oil pipe string must have sufficient sealing performance.

[0003] In recent years, as the geological conditions in the areas where oil and gas wells are located become more complex and the exploitation depth of oil and gas wells becomes deeper and deeper, the casing is increasingly affected by various complex working conditions in practical applications, and the problem of thread sealing failure is more likely to occur accordingly. Therefore, how to improve the sealing effect of casing threads to prevent their failure has become a technical problem that needs to be solved urgently.

[0004] In view of the problem that the casing thread is prone to sealing failure, the prior art proposes a solution to improve the casing thread connection structure, such as the patent document with publication number CN106382099A discloses a gas-tight oil casing thread connection structure and the patent document with publication number CN108868658A discloses a casing thread joint with multiple sealing surface thread positive angles. These two patent documents improve the sealing structure of the casing thread, so that the casing thread joint can be better protected, thereby achieving the purpose of improving the sealing effect and preventing sealing failure. However, there are many reasons for the failure of casing thread sealing in actual applications, such as processing quality, on-site operation conditions, casing stress conditions, etc., and the means of improving the sealing effect of the above-mentioned technology are relatively single, which cannot effectively cope with complex construction conditions, so its practicality is poor. Summary of the invention

[0005] The purpose of the present invention is to overcome the above-mentioned problems existing in the prior art and provide a method for preventing casing thread sealing failure. The method performs all-round control of the casing from four aspects: casing quality control, on-site operation control, casing running quality control, and volume fracturing parameter control. The method can effectively prevent casing thread failure under complex working conditions, and not only has higher practicality, but also improves the safety of casing use.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows: A method for preventing casing thread seal failure, characterized in that: it includes preventing casing thread seal failure by sequentially performing casing quality control, field operation control, casing running quality control and volume fracturing parameter control; wherein, The casing quality control includes casing processing quality control and casing pulling control in sequence; The field operation control includes field casing discharge control, thread sealing grease application control, casing wellhead buckling control and casing buckling torque control in sequence; The casing running quality control includes the following steps: controlling the number of times the casing is blocked, controlling the tonnage of the casing when it is blocked, controlling the bending amplitude of the casing thread, and controlling the lateral force of the casing bending. The volume fracturing parameter control includes volume fracturing stage number control and displacement pressure change vibration frequency control in sequence.

[0007] The casing processing quality control refers to the inspection of the processed casing threads using special tools and measuring tools according to the design drawings. If the inspection result meets the design requirements, the casing processing quality is judged to be qualified and transferred to the next process; if the inspection result is unqualified, it will be rectified again until it is qualified.

[0008] The casing pulling control refers to controlling the casing to be fixed intact during the pulling process to prevent casing thread damage.

[0009] The on-site casing discharge control refers to controlling the number of on-site casing discharge layers to not exceed two layers to prevent damage to the casing threads.

[0010] The thread sealing grease application control refers to wiping the sleeve thread clean with a towel and evenly applying special sealing grease with a thickness of 1-1.5mm on the thread surface.

[0011] The casing wellhead buckling control refers to using a casing thread buckler to control the casing thread to smoothly enter the casing coupling before starting buckling.

[0012] The casing make-up torque control refers to controlling the make-up torque value of the casing thread to reach 10000-11500nm according to design requirements.

[0013] The control of the number of times the casing encounters resistance during lowering means that when the casing encounters resistance during lowering, the number of times the casing is lifted and lowered at the same position is controlled to be less than 50 times.

[0014] The casing lowering tonnage control when encountering resistance means controlling the casing to continue to be lowered to a tonnage that is less than the total hanging weight of the casing string at the wellhead.

[0015] The casing thread bending amplitude control refers to controlling the bending amount of the casing underground to be greater than 58 mm.

[0016] The casing bending lateral force control refers to controlling the casing bending lateral force in the well to be less than 3.5 tons.

[0017] The volume fracturing stage number control refers to controlling the volume fracturing stage number of the casing to be less than 36 stages.

[0018] The casing bending lateral force control refers to controlling the vibration frequency of the casing underground to 1500-2000 times / minute.

[0019] The advantages of adopting the present invention are: 1. The present invention controls the casing in all directions from four aspects: casing quality control, on-site operation control, casing running quality control, and volume fracturing parameter control. It can effectively protect the casing threads from all aspects and prevent casing thread failure under complex working conditions. It not only has higher practicality, but also improves the safety of casing use.

[0020] 2. The present invention changes the current situation of a single means to prevent casing thread seal failure. It is not only a highly targeted technical means, but also a new technology and new measure for selecting horizontal well casing, which further improves the safety of horizontal well casing use.

[0021] 3. Through the application of this technology, the present invention can not only meet the requirements for safe casing lowering on site, but also reduce the cost of repairing casing string seal failure, thus also helping to reduce the cost of drilling and completion. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical scheme and advantages of the present application clearer, the present invention is further described below in conjunction with the accompanying drawings and embodiments, and the embodiments of the present invention include but are not limited to the following embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0024] In the present invention, the term "and / or" is merely a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may represent three situations: A exists alone, A and B exist at the same time, and B exists alone.

[0025] The terms "first" and "second" in the specification and claims of the present invention are used to distinguish different objects rather than to describe a specific order of objects. For example, a first target object and a second target object are used to distinguish different target objects rather than to describe a specific order of target objects.

[0026] In the present invention, words such as "exemplary" or "for example" are used to indicate examples, illustrations or explanations. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present invention should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present the relevant concepts in a specific way.

[0027] Example 1 like Figure 1 As shown, the present invention provides a method for preventing casing thread seal failure, which includes preventing casing thread seal failure by comprehensively improving the sealing effect by sequentially performing casing quality control, field operation control, casing running quality control and volume fracturing parameter control. The casing quality control includes casing processing quality control and casing pulling control in sequence.

[0028] The field operation control includes field casing discharge control, thread sealing grease application control, casing wellhead buckling control and casing buckling torque control in sequence.

[0029] The casing running quality control includes the control of the number of times the casing is blocked during running, the control of the tonnage of the casing when encountering blockage, the control of the bending amplitude of the casing thread and the control of the lateral force of the casing bending.

[0030] The volume fracturing parameter control includes volume fracturing stage number control and displacement pressure change vibration frequency control in sequence.

[0031] Example 2 like Figure 1 As shown, the present invention provides a method for preventing casing thread seal failure, which includes preventing casing thread seal failure by comprehensively improving the sealing effect by sequentially performing casing quality control, field operation control, casing running quality control and volume fracturing parameter control. Each control process is as follows: The casing quality control includes casing processing quality control and casing pulling control in sequence, wherein: Casing processing quality control refers to the inspection of the processed casing threads using special tools and measuring tools according to the design drawings. If the inspection results meet the design requirements, the casing thread processing quality is judged to be qualified and transferred to the next process; if the inspection results do not meet the design requirements, the casing thread processing quality is judged to be unqualified, and it will be rectified again until it is qualified.

[0032] Casing pulling control refers to controlling the casing to be fixed and intact during the pulling process, eliminating rough loading and unloading, and preventing casing thread damage. The on-site operation control includes on-site casing discharge control, thread sealing grease application control, casing wellhead buckling control and casing buckling torque control.

[0033] The casing running quality control includes the control of the number of times the casing is blocked during running, the control of the tonnage of the casing when encountering blockage, the control of the bending amplitude of the casing thread and the control of the lateral force of the casing bending.

[0034] The volume fracturing parameter control includes volume fracturing stage number control and displacement pressure change vibration frequency control in sequence.

[0035] Example 3 like Figure 1 As shown, the present invention provides a method for preventing casing thread seal failure based on Example 2, which includes preventing casing thread seal failure by comprehensively improving the sealing effect by sequentially performing casing quality control, field operation control, casing running quality control and volume fracturing parameter control. Each control process is as follows: The casing quality control includes casing processing quality control and casing pulling control in sequence.

[0036] The field operation control includes field casing discharge control, thread sealing grease application control, casing wellhead buckling control and casing buckling torque control, wherein: On-site casing discharge control refers to controlling the number of on-site casing discharge layers to no more than two layers, to prevent damage to the casing threads due to excessive discharge layers.

[0037] Thread sealing grease application control means first using a clean towel to wipe the surface of the casing thread clean, and then evenly applying special sealing grease on the thread surface. The thickness of the special sealing grease is controlled at 1-1.5mm.

[0038] Casing wellhead threading control refers to using the manufacturer's special casing thread threading device to control the casing threads to smoothly enter the casing coupling before starting threading.

[0039] Casing make-up torque control refers to controlling the make-up torque value of the casing thread to 10000-11500nm according to the manufacturer's design requirements. If the make-up torque value is lower than 10000nm or higher than 11500nm, it is considered unqualified and may easily lead to failure of the casing thread seal.

[0040] The casing running quality control includes the control of the number of times the casing is blocked during running, the control of the tonnage of the casing when encountering blockage, the control of the bending amplitude of the casing thread and the control of the lateral force of the casing bending.

[0041] The volume fracturing parameter control includes volume fracturing stage number control and displacement pressure change vibration frequency control in sequence.

[0042] Example 4 like Figure 1As shown, the present invention provides a method for preventing casing thread seal failure based on Example 2 or 3, which includes preventing casing thread seal failure by comprehensively improving the sealing effect by sequentially performing casing quality control, field operation control, casing running quality control and volume fracturing parameter control. Each control process is as follows: The casing quality control includes casing processing quality control and casing pulling control in sequence.

[0043] The field operation control includes field casing discharge control, thread sealing grease application control, casing wellhead buckling control and casing buckling torque control in sequence.

[0044] The casing running quality control includes the control of the number of times the casing is blocked, the control of the tonnage of the casing when it is blocked, the control of the bending amplitude of the casing thread and the control of the lateral force of the casing bending, wherein: The control of the number of times the casing encounters resistance during running means that when the casing encounters resistance during running, the number of times the casing is quickly lifted and lowered at the same position is controlled to be less than 50 times. If the number of times the casing is quickly lifted and lowered is greater than 50 times, it indicates that the casing thread is prone to failure and cannot be run further.

[0045] The tonnage control of casing lowering when encountering resistance means that the tonnage of casing that can continue to be lowered is controlled to be less than the total hanging weight of the casing string at the wellhead.

[0046] Casing thread bending amplitude control refers to controlling the bending amount of the casing in the well. During the casing lowering process, the casing string in the well will inevitably bend due to the bending of the wellbore. Therefore, when the casing at the wellhead encounters resistance, the casing thread will be excessively bent by the axial overload through rapid lowering. For this reason, the present invention preferably has a bending amount of the casing in the well greater than 58mm, so as to effectively prevent the casing thread seal from failing. Casing bending lateral force control refers to controlling the casing bending lateral force in the well to be less than 3.5 tons. The lateral force can be calculated according to a conventional calculation model in the art.

[0047] The volume fracturing parameter control includes volume fracturing stage number control and displacement pressure change vibration frequency control in sequence.

[0048] Example 5 like Figure 1 As shown, the present invention provides a method for preventing casing thread seal failure based on any one of embodiments 2-4, which includes preventing casing thread seal failure by comprehensively improving the sealing effect by sequentially performing casing quality control, field operation control, casing running quality control and volume fracturing parameter control. Each control process is as follows: The casing quality control includes casing processing quality control and casing pulling control in sequence.

[0049] The field operation control includes field casing discharge control, thread sealing grease application control, casing wellhead buckling control and casing buckling torque control in sequence.

[0050] The casing running quality control includes the control of the number of times the casing is blocked during running, the control of the tonnage of the casing when encountering blockage, the control of the bending amplitude of the casing thread and the control of the lateral force of the casing bending.

[0051] The volume fracturing parameter control includes volume fracturing stage number control and displacement pressure change vibration frequency control in sequence, wherein: Volume fracturing stage number control refers to controlling the volume fracturing stage number of the casing to be less than 36 stages. If the volume fracturing stage number of the casing is greater than 36 stages, it will obviously lead to failure of the casing thread seal.

[0052] Casing bending lateral force control refers to controlling the vibration frequency of the casing underground. During the multi-stage volume fracturing process of horizontal wells, the displacement pressure changes cause the downhole tubing to vibrate, and the tubing vibration will drive the casing to vibrate. If the casing vibration frequency is too high, it will operate the casing thread and cause the seal to fail. For this reason, the present invention preferably controls the casing vibration frequency underground to 1500-2000 times / minute, which can effectively prevent damage to the casing thread and achieve the effect of preventing thread seal failure.

[0053] In summary, the present invention controls the casing in all directions from four aspects: casing quality control, on-site operation control, casing lowering quality control, and volume fracturing parameter control. This is equivalent to protecting the casing threads and preventing casing thread failure from production source to actual application. It not only has higher practicality, but also improves the safety of casing use. It can meet the requirements for safe casing lowering on site, and reduce the cost of repairing casing string sealing failure, thereby also helping to reduce the cost of drilling and completion.

[0054] The above description is only a specific implementation mode of the present invention. Any feature disclosed in this specification, unless otherwise stated, can be replaced by other alternative features that are equivalent or have similar purposes; all the disclosed features, or all the steps in the methods or processes, except for mutually exclusive features and / or steps, can be combined in any way.

Claims

1. A method for preventing casing thread seal failure, characterized in that: It includes preventing casing thread seal failure by sequentially carrying out casing quality control, field operation control, casing running quality control and volume fracturing parameter control; among which, The casing quality control includes casing processing quality control and casing pulling control in sequence; The field operation control includes field casing discharge control, thread sealing grease application control, casing wellhead buckling control and casing buckling torque control in sequence; The casing running quality control includes the following steps: controlling the number of times the casing is blocked, controlling the tonnage of the casing when it is blocked, controlling the bending amplitude of the casing thread, and controlling the lateral force of the casing bending. The volume fracturing parameter control includes volume fracturing stage number control and displacement pressure change vibration frequency control in sequence.

2. A method for preventing casing thread seal failure according to claim 1, characterized in that: The thread sealing grease application control refers to wiping the sleeve thread clean with a towel and evenly applying special sealing grease with a thickness of 1-1.5mm on the thread surface.

3. A method for preventing casing thread seal failure according to claim 1, characterized in that: The casing wellhead buckling control refers to using a casing thread buckler to control the casing thread to smoothly enter the casing coupling before starting buckling.

4. A method for preventing casing thread seal failure according to claim 1, characterized in that: The casing make-up torque control refers to controlling the make-up torque value of the casing thread to reach 10000-11500nm according to design requirements.

5. A method for preventing casing thread seal failure according to claim 1, characterized in that: The control of the number of times the casing encounters resistance during lowering means that when the casing encounters resistance during lowering, the number of times the casing is lifted and lowered at the same position is controlled to be less than 50 times.

6. A method for preventing casing thread seal failure according to claim 1, characterized in that: The casing lowering tonnage control when encountering resistance means controlling the casing to continue to be lowered to a tonnage that is less than the total hanging weight of the casing string at the wellhead.

7. A method for preventing casing thread seal failure according to claim 1, characterized in that: The casing thread bending amplitude control refers to controlling the bending amount of the casing underground to be greater than 58 mm.

8. A method for preventing casing thread seal failure according to claim 1, characterized in that: The casing bending lateral force control refers to controlling the casing bending lateral force in the well to be less than 3.5 tons.

9. A method for preventing casing thread seal failure according to claim 1, characterized in that: The volume fracturing stage number control refers to controlling the volume fracturing stage number of the casing to be less than 36 stages.

10. A method for preventing casing thread seal failure according to claim 1, characterized in that: The casing bending lateral force control refers to controlling the vibration frequency of the casing underground to 1500-2000 times / minute.

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