A method of preventing casing thread seal failure

Abstract

The application discloses a method for preventing casing thread sealing failure, which comprises preventing casing thread sealing failure by sequentially performing casing quality control, field operation control, casing running quality control and volume fracturing parameter control; wherein the casing quality control comprises casing processing quality control and casing pulling control; the field operation control comprises field casing discharge control, thread sealing grease application control, casing wellhead make-up control and casing make-up torque control; the casing running quality control comprises casing running resistance encountering times control, casing running resistance encountering tonnage control, casing thread bending amplitude control and casing bending lateral force control; and the volume fracturing parameter control comprises volume fracturing section number control and displacement pressure change vibration frequency control. The method can effectively prevent casing thread failure under complex working conditions, has higher practicability, and improves the safety of casing use.

Description

TECHNICAL FIELD

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

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

[0003] In recent years, as the geological conditions of the area where the oil and gas well is located are more complex and the exploitation depth of the oil and gas well is deeper, the casing is affected by various complex working conditions in actual application more and more, and the problem of thread sealing failure is more and more likely to occur. Therefore, how to improve the sealing effect of the casing thread to prevent its failure has become a technical problem that needs to be solved at present.

[0004] In view of the problem that the casing thread is prone to sealing failure, the prior art proposes a scheme for improving the casing thread connection structure, such as the patent document with publication number CN106382099A which discloses a gas-tight oil casing thread connection structure and the patent document with publication number CN108868658A which discloses a casing thread joint with a plurality of sealing surfaces and a right angle. The two patent documents improve the sealing structure of the casing thread, which can better protect the casing thread joint, thereby achieving the purpose of improving the sealing effect and preventing sealing failure. However, since there are various reasons for the sealing failure of the casing thread in actual application, such as processing quality, on-site operation, casing stress, etc., the above-mentioned means for improving the sealing effect is relatively single, which cannot effectively cope with complex construction conditions, and thus its practicality is poor. SUMMARY

[0005] The present application aims to overcome the above-mentioned problems in the prior art and provides a method for preventing casing thread sealing failure, which comprehensively controls the casing from four aspects of casing quality control, on-site operation control, casing running quality control and volume fracturing parameter control, which can effectively prevent casing thread failure under complex conditions, not only has higher practicality, but also improves the safety of casing use.

[0006] To achieve the above-mentioned purpose, the technical solution adopted by the present application is as follows:

[0007] A method for preventing casing thread sealing failure, characterized in that: it comprises preventing casing thread sealing failure by sequentially performing casing quality control, on-site operation control, casing running quality control and volume fracturing parameter control; wherein,

[0008] The casing quality control includes casing machining quality control and casing pulling control in sequence;

[0009] The field operation control includes field casing discharge control, thread sealant application control, casing wellhead make-up control and casing make-up torque control in sequence;

[0010] The casing running quality control includes casing running resistance number control, casing resistance running tonnage control, casing thread bending amplitude control and casing bending lateral force control in sequence.

[0011] The volume fracturing parameter control includes volume fracturing segment number control and displacement pressure change vibration frequency control in sequence.

[0012] The casing machining quality control refers to using special tools and measuring tools to inspect the machined casing thread according to the design drawing, if the inspection result meets the design requirement, the casing machining quality is determined to be qualified, and the next process is transferred; if the inspection result is unqualified, it is reformed until it is qualified.

[0013] The casing pulling control refers to controlling the casing to be fixed well during pulling to prevent casing thread damage.

[0014] The field casing discharge control refers to controlling the field casing discharge layer number not to exceed two layers to prevent casing thread damage.

[0015] The thread sealant application control refers to using a towel to wipe the casing thread clean, and uniformly applying a special sealant with a thickness of 1-1.5mm on the thread surface.

[0016] The casing wellhead make-up control refers to using a casing thread make-up device to control the casing thread to smoothly enter the casing coupling before starting to make up.

[0017] The casing make-up torque control refers to controlling the casing thread make-up torque value to reach 10000-11500nm according to the design requirement.

[0018] The casing running resistance number control refers to controlling the casing to be lifted and lowered at the same position less than 50 times when the casing meets resistance during running.

[0019] The casing resistance running tonnage control refers to controlling the tonnage of the casing that can continue to run to be less than the total hanging weight of the casing string at the wellhead.

[0020] The casing thread bending amplitude control refers to controlling the bending amount of the casing in the well to be less than 58mm.

[0021] The casing bending lateral force control refers to controlling the bending lateral force of the casing in the well to be less than 3.5 tons.

[0022] The volume fracturing section number control refers to controlling the volume fracturing section number of the casing to be less than 36 sections.

[0023] The casing bending lateral force control refers to controlling the vibration frequency of the casing in the well to be 1500-2000 times / minute.

[0024] The advantages of the present application are as follows:

[0025] 1. The present application can effectively protect the casing thread and prevent the casing thread from failing in various aspects under complex working conditions through the overall control of the casing from four aspects of casing quality control, field operation control, casing running quality control and volume fracturing parameter control, thereby having higher practicability and improving the safety of casing use.

[0026] 2. The present application changes the current single means of preventing casing thread sealing failure, and is not only a targeted technical means, but also a new technology and measure for horizontal well casing selection, thereby further improving the safety of horizontal well casing use.

[0027] 3. The present application can not only meet the requirement of safe casing running on site, but also reduce the repair cost of casing string sealing failure, thereby being beneficial to reducing the cost of drilling and completion. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The flowchart of the present application. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application will be further described below in combination with the drawings and examples, and the implementation of the present application includes but is not limited to the following examples. Based on the examples in the present application, all other examples obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0030] In the present application, the term "and / or" is only used to describe the association relationship of the associated objects, which means that there can be three kinds of relationships, for example, A and / or B, which can represent the three cases of A alone, A and B together, and B alone.

[0031] The terms "first" and "second" and the like in the specification and claims of the present application are used to distinguish different objects, and are not used to describe the specific order of the objects. For example, the first target object and the second target object are used to distinguish different target objects, and are not used to describe the specific order of the target objects.

[0032] In the present application, the word "exemplary" or "for example" is used to mean serving as an example, instance, or illustration. Any embodiment or design described in this application as "exemplary" or "for example" should not be construed to mean that it is preferred or advantageous over other embodiments or designs. Rather, the word "exemplary" or "for example" is used in this application to present concepts in a concrete manner.

[0033] Embodiment 1

[0034] As shown in the Figure 1 , the present application provides a method for preventing casing thread sealing failure, which comprises preventing casing thread sealing failure by improving sealing effect through casing quality control, field operation control, casing running quality control and volume fracturing parameter control in sequence. Among them,

[0035] The casing quality control comprises casing machining quality control and casing pulling control in sequence.

[0036] The field operation control comprises field casing discharge control, thread sealing grease application control, casing wellhead make-up control and casing make-up torque control in sequence.

[0037] The casing running quality control comprises casing running resistance number control, casing running resistance tonnage control, casing thread bending amplitude control and casing bending lateral force control in sequence.

[0038] The volume fracturing parameter control comprises volume fracturing segment number control and displacement pressure change vibration frequency control in sequence.

[0039] Embodiment 2

[0040] As shown in the Figure 1 , the present application provides a method for preventing casing thread sealing failure, which comprises preventing casing thread sealing failure by improving sealing effect through casing quality control, field operation control, casing running quality control and volume fracturing parameter control in sequence. Each control process is as follows:

[0041] The casing quality control comprises casing machining quality control and casing pulling control in sequence, wherein,

[0042] The casing machining quality control refers to inspecting the machined casing thread according to the design drawing using special tools and measuring tools. If the inspection result meets the design requirement, it is determined that the casing thread machining quality is qualified, and the next process is entered. If the inspection result does not meet the design requirement, it is determined that the casing thread machining quality is unqualified, and then it is re-adjusted until it is qualified.

[0043] The casing pulling operation control refers to controlling the casing to be fixed well during the pulling operation, preventing rough loading and unloading, and preventing casing thread damage. The field operation control successively includes field casing discharge control, thread sealing grease application control, casing wellhead make-up control, and casing make-up torque control.

[0044] The casing running quality control successively includes casing running resistance encountering number control, casing resistance encountering running tonnage control, casing thread bending amplitude control, and casing bending lateral force control.

[0045] The volume fracturing parameter control successively includes volume fracturing segment number control and displacement pressure variation vibration frequency control.

[0046] Embodiment 3

[0047] As shown in Figure 1 The present application provides a method for preventing casing thread sealing failure on the basis of Embodiment 2, which comprises preventing casing thread sealing failure by comprehensively improving the sealing effect through successively performing casing quality control, field operation control, casing running quality control, and volume fracturing parameter control. Each control procedure is as follows:

[0048] The casing quality control successively includes casing processing quality control and casing pulling operation control.

[0049] The field operation control successively includes field casing discharge control, thread sealing grease application control, casing wellhead make-up control, and casing make-up torque control, wherein,

[0050] The field casing discharge control refers to controlling the field casing discharge layer number to be no more than two layers, preventing casing thread damage due to too many discharge layers.

[0051] The thread sealing grease application control refers to first wiping the casing thread surface clean with a clean towel, and then uniformly applying special sealing grease on the thread surface, with the thickness of the special sealing grease being controlled to be 1-1.5 mm.

[0052] The casing wellhead make-up control refers to using a casing thread make-up device specially designed by the manufacturer to control the casing thread to smoothly enter the casing coupling before starting to make up.

[0053] The casing make-up torque control refers to controlling the casing thread make-up torque value to be 10000-11500 nm according to the design requirements of the manufacturer. If the make-up torque value is lower than 10000 nm or higher than 11500 nm, it is regarded as unqualified, which is easy to cause casing thread sealing failure.

[0054] The casing running quality control successively includes casing running resistance encountering number control, casing resistance encountering running tonnage control, casing thread bending amplitude control, and casing bending lateral force control.

[0055] The volume fracturing parameter control successively comprises volume fracturing section number control and displacement pressure variation vibration frequency control.

[0056] Embodiment 4

[0057] As shown in Figure 1 The present application provides a method for preventing casing thread sealing failure on the basis of Embodiment 2 or 3, which comprises preventing casing thread sealing failure by comprehensively improving sealing effect through sequentially performing casing quality control, field operation control, casing running quality control and volume fracturing parameter control. Each control procedure is as follows:

[0058] The casing quality control successively comprises casing machining quality control and casing pulling control.

[0059] The field operation control successively comprises field casing discharge control, thread sealing grease application control, casing wellhead make-up control and casing make-up torque control.

[0060] The casing running quality control successively comprises casing running resistance number control, casing resistance running tonnage control, casing thread bending amplitude control and casing bending lateral force control, wherein,

[0061] The casing running resistance number control refers to controlling the number of rapid pulling and running of the casing at the same position to be less than 50 times when the casing meets resistance during running. If the number of rapid pulling and running is greater than 50 times, it indicates that the casing thread is prone to failure and cannot continue to run.

[0062] The casing resistance running tonnage control refers to controlling the tonnage of the casing that can continue to run to be less than the total hanging weight of the wellhead casing string.

[0063] The casing thread bending amplitude control refers to controlling the bending amount of the casing in the well. The casing string in the well is inevitably bent due to the bending of the wellbore during the running process. Therefore, when the wellhead casing meets resistance, the casing thread is inevitably excessively bent by axial overload through rapid running. Therefore, the present application preferably controls the bending amount of the casing in the well to be less than 58 mm, so as to effectively prevent casing thread sealing failure,

[0064] The casing bending lateral force control refers to controlling the bending lateral force of the casing in the well to be less than 3.5 tons. The lateral force can be calculated according to the conventional calculation model in the art.

[0065] The volume fracturing parameter control successively comprises volume fracturing section number control and displacement pressure variation vibration frequency control.

[0066] Embodiment 5

[0067] As shown in Figure 1As shown, the present application provides a method for preventing casing thread sealing failure on the basis of any one of embodiments 2-4, which comprises preventing casing thread sealing failure by improving sealing effect through casing quality control, site operation control, casing running quality control and volume fracturing parameter control in sequence.

[0068] The casing quality control comprises casing processing quality control and casing pulling control in sequence.

[0069] The site operation control comprises site casing discharge control, thread sealing grease application control, casing wellhead make-up control and casing make-up torque control in sequence.

[0070] The casing running quality control comprises casing running resistance number control, casing running resistance tonnage control, casing thread bending amplitude control and casing bending lateral force control in sequence.

[0071] The volume fracturing parameter control comprises volume fracturing segment number control and displacement pressure change vibration frequency control in sequence, wherein,

[0072] The volume fracturing segment number control refers to controlling the volume fracturing segment number of the casing to be less than 36 segments, and if the volume fracturing segment number of the casing is greater than 36 segments, the casing thread sealing failure will be obviously caused.

[0073] The casing bending lateral force control refers to controlling the vibration frequency of the casing in the well. In the process of horizontal well multi-segment volume fracturing, the displacement pressure change causes the vibration of the tubing in the well, and the tubing vibration will drive the casing vibration, and if the frequency of the casing vibration is too high, the casing thread will be operated to cause the sealing failure. Therefore, the present application preferably controls the vibration frequency of the casing in the well to be 1500-2000 times / minute, which can effectively prevent the damage to the casing thread and achieve the effect of preventing the thread sealing failure.

[0074] In summary, the present application controls the casing from four aspects of casing quality control, site operation control, casing running quality control and volume fracturing parameter control, which is equivalent to protecting the casing thread from the production source to the actual application and preventing the casing thread failure, and has higher practicability, improves the safety of the casing use, meets the requirement of the site casing safe running, reduces the repair cost of the casing string sealing failure, and is beneficial to reducing the cost of drilling and completion.

[0075] The above is only a specific embodiment of the present application, and any feature disclosed in the specification can be replaced by other equivalent or similar purpose replacement features unless specifically described; all features disclosed or steps in all methods or processes can be combined in any way except for mutually exclusive features and / or steps.

Claims

1. A method of preventing seal failure in a casing thread, characterized by: The casing thread sealing failure is prevented by sequentially performing casing quality control, field operation control, casing running quality control and volume fracturing parameter control. The casing quality control sequentially comprises casing processing quality control and casing pulling control. The field operation control sequentially comprises field casing discharge control, thread sealing grease application control, casing wellhead make-up control and casing make-up torque control. The casing running quality control sequentially comprises casing running resistance number control, casing resistance running tonnage control, casing thread bending amplitude control and casing bending lateral force control. The volume fracturing parameter control sequentially comprises volume fracturing segment number control and displacement pressure variation vibration frequency control. The casing thread bending amplitude control refers to controlling the bending amount of the casing in the well to be less than 58mm. The casing bending lateral force control refers to controlling the vibration frequency of the casing in the well to be 1500-2000 times per minute.

2. A method of preventing seal failure in a tubular thread as defined in claim 1, characterized in that: The thread sealing grease application control refers to using a towel to wipe the casing thread clean and uniformly applying a special sealing grease with a thickness of 1-1.5mm on the thread surface.

3. A method of preventing seal failure in a tubular thread as defined by claim 1, characterized in that: The casing wellhead make-up control refers to using a casing thread make-up device to control the casing thread to smoothly enter into the casing coupling and then start make-up.

4. A method of preventing seal failure in a tubular thread as defined by 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 the design requirement.

5. A method of preventing seal failure in a tubular thread as defined by claim 1, characterized by: The casing running resistance number control refers to controlling the lifting and lowering number of the casing at the same position to be less than 50 times when the casing meets resistance during running.

6. A method of preventing seal failure in a tubular thread as defined by claim 1, characterized by: The casing resistance running tonnage control refers to controlling the tonnage of the casing that can continue to run to be less than the total hanging weight of the casing string at the wellhead.

7. A method of preventing seal failure in a tubular thread as defined by claim 1, characterized by: The casing bending lateral force control refers to controlling the bending lateral force of the casing in the well to be less than 3.5 tons.

8. A method of preventing seal failure in a tubular thread as defined by claim 1, characterized by: The volume fracturing segment number control refers to controlling the volume fracturing segment number of the casing to be less than 36 segments.

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