CN111927373B - Threaded wellhead sealing detection pressure test load determination method, storage medium and equipment - Google Patents
Threaded wellhead sealing detection pressure test load determination method, storage medium and equipment Download PDFInfo
- Publication number
- CN111927373B CN111927373B CN202010797603.4A CN202010797603A CN111927373B CN 111927373 B CN111927373 B CN 111927373B CN 202010797603 A CN202010797603 A CN 202010797603A CN 111927373 B CN111927373 B CN 111927373B
- Authority
- CN
- China
- Prior art keywords
- pressure
- sealing
- load
- thread
- contact
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Classifications
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B33/00—Sealing or packing boreholes or wells
- E21B33/02—Surface sealing or packing
- E21B33/03—Well heads; Setting-up thereof
- E21B33/04—Casing heads; Suspending casings or tubings in well heads
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B17/00—Drilling rods or pipes; Flexible drill strings; Kellies; Drill collars; Sucker rods; Cables; Casings; Tubings
- E21B17/02—Couplings; joints
- E21B17/04—Couplings; joints between rod or the like and bit or between rod and rod or the like
- E21B17/042—Threaded
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B47/00—Survey of boreholes or wells
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/20—Design optimisation, verification or simulation
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
- G06F2119/14—Force analysis or force optimisation, e.g. static or dynamic forces
Landscapes
- Engineering & Computer Science (AREA)
- Mining & Mineral Resources (AREA)
- Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Physics & Mathematics (AREA)
- Environmental & Geological Engineering (AREA)
- Geochemistry & Mineralogy (AREA)
- Fluid Mechanics (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Theoretical Computer Science (AREA)
- General Physics & Mathematics (AREA)
- General Engineering & Computer Science (AREA)
- Evolutionary Computation (AREA)
- Computer Hardware Design (AREA)
- Geometry (AREA)
- Mechanical Engineering (AREA)
- Geophysics (AREA)
- Excavating Of Shafts Or Tunnels (AREA)
Abstract
The invention discloses a method for determining a pressure test load of threaded wellhead sealing detection, a storage medium and equipment, wherein an analysis sample is selected according to limit tolerance matching; establishing a material mechanics model; loading internal pressure on the oil sleeve, the inner wall of the thread and the end face of the shoulder, respectively calculating the sealing contact pressure and the length in the loading and unloading processes under different internal pressures, and analyzing the sealing contact pressure and the length; determining a sealing applicability criterion, namely controlling the lower pipe column within 20% reduction according to the basis that the envelope curve of the three-axis design safety coefficient of the underground pipe column is less than 80%; and determining the pressure test load of the wellhead according to the requirement of the internal pressure bearing capacity of the pipe body. The invention provides beneficial guidance for determining the pressure load in the wellhead tightness detection pressure test of the special thread connection of the airtight seal, and ensures safe and reliable use in the underground.
Description
Technical Field
The invention belongs to the technical field of petroleum and natural gas development, and particularly relates to a method for determining pressure test load of oil casing gas seal threaded wellhead seal detection, a storage medium and equipment.
Background
The oil sleeve gas-tight threaded connection is widely applied to high-temperature high-pressure high-corrosion gas wells. The abnormal rise of the threaded connection leakage, the production casing pressure and the technical casing pressure of the well completion pipe string easily causes the failure of the casing pipe, so that the natural gas leaks from a well head or the ground, and the hidden trouble is left for the safe production. The oil pipes used by 11 gas wells in the Di Na 2 gas field are all special threaded joint oil pipes, the phenomenon that the casing pressure of 9 wells is abnormally increased is not produced, the well with the casing pressure increased accounts for 81.8 percent of the total number of wells, and the 5 wells with the ratio of the casing pressure to the oil pressure exceeding 50 percent account for 55.6 percent. Therefore, after the threaded wellhead is buckled, airtightness detection is required. The detection pressure determines the use performance of the thread, and the detection pressure is too high to cause severe plastic deformation of the thread sealing structure, so that the underground subsequent use fails and the service life is reduced; the detection pressure testing is too low, and the integrity of the thread seal cannot be detected, so that the safety of later use in the well is ensured. Therefore, the pressure load determination of pressure test of airtightness detection of the wellhead by using special airtight threaded connection is required.
The existing method for detecting the pressure test sealing of the threaded connection wellhead has the following problems:
the oil field sets the standard of SY/T6872-2012 [ casing and oil pipe threaded connection airtight wellhead detection system ]. The standard specifies the mechanical structure composition of a wellhead pressure test detection system, the pressure index range required by the system work and an on-site pressure test operation method, and does not specify the tightness of gas-tight threaded connection wellheads of oil casings and materials with different specifications to detect the pressure test load and determine the method.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a method, a storage medium and equipment for determining the pressure test load of the oil casing gas-tight threaded wellhead sealing detection aiming at the defects in the prior art, so as to ensure the sealing integrity of an underground pipe column and solve the problem of sealing failure and leakage of threaded connection in the gas production and production process of the high-temperature and high-pressure gas well completion oil casing pipe column.
The invention adopts the following technical scheme:
a method for determining pressure test load of threaded wellhead sealing detection comprises the following steps:
s1, selecting an analysis sample according to limit tolerance matching;
s2, establishing a material mechanics model according to the analysis sample selected in the step S1;
s3, loading internal pressure on the oil sleeve, the inner wall of the thread and the end face of the shoulder according to the material mechanics model established in the step S2, respectively calculating the sealing contact pressure and the length in the loading and unloading processes under different internal pressures, and analyzing the sealing contact pressure and the length;
s4, determining the applicability criterion of the sealing performance according to the fact that the envelope curve of the safety factor of the triaxial design of the underground pipe column is less than 80%, and judging whether the reduced quantity of the change of the sealing performance meets the sealing integrity of the underground application of the working condition load of the subsequent oil field in the process that the contact pressure and the length of the threaded sealing surface change along with the load state in the step S3;
s5, determining pressure test load of a wellhead according to the requirement of the internal pressure bearing capacity of the pipe body, checking whether the screwing operation meets the sealing performance of the airtight thread, and checking whether the quality of the airtight thread product is qualified under the screwing torque condition.
Specifically, in step S1, the limit tolerance is as follows:
the interference fit of the internal and external threads is minimum; the sealing interference fit is maximum; the external thread taper is maximum; the taper of the internal thread is minimum; and (4) buckling the maximum torque.
Specifically, in step S2, the material mechanics model is as follows:
σF＝(1-c)σs+cY(εp)
wherein σFIs a plastic stress; sigmasIs the yield stress; y is plasticA stress-strain function; epsilonpAnd c is a hardening coefficient.
Specifically, step S3 specifically includes:
establishing an axisymmetric model by adopting a finite element numerical calculation simulation method; setting the interference of the diameter in the thread, the interference of the seal, the interference of the shoulder and the contact friction coefficient, and calculating the thread screwing torque; setting the mechanical property of the material by adopting a mixed hardening model, then applying internal pressure and pressure relief calculation and analysis steps on the inner wall of the thread, setting the internal pressure loading time rate by adopting a dynamic calculation mechanical model, adding the internal pressure to a preset analysis internal pressure, then carrying out load relief, and then carrying out sealing contact pressure and length analysis.
Specifically, in step S4, the application rule of the sealing property variation rule is as follows:
and comparing two numerical values of the axial contact area along the seal formed by the product of the maximum contact pressure of the seal and the contact pressure and the length with corresponding values generated by the seal in the initial make-up state, and taking the reduction of the two compared values after the pressure in the pressure test is unloaded as the pressure test control load, wherein the reduction is lower than 20%.
Specifically, in step S5, two loads are determined according to the lowest value and the further detection value safety coefficient 0.8 specified by the oil casing API 5CT standard, the pressure test detection value is improved, the pressure test load value is determined according to the 80% and 95% of the yield of the inner wall material under the defect-free internal pressure of the pipe body, the seal change rule and the applicability criterion.
Further, firstly, analyzing the distribution rule of the contact pressure and the length of the sealing surface in the buckling load step state, and extracting the maximum contact pressure and the contact sealing area required by the applicability criterion; analyzing a sealing contact distribution rule after internal pressure application and load retention, and extracting maximum contact pressure and contact sealing area; then analyzing the distribution rule of the unloaded sealing contact, and extracting the maximum contact pressure and the contact sealing area; comparing the relative variation of the maximum sealing contact pressure and the area after loading internal pressure and unloading internal pressure with the initial buckling state load step; and according to the seal applicability criterion, when the reduction of the pressure drop of the wellhead is lower than 20%, determining that the pressure test load of the wellhead finally receives the pressure test value of the internal pressure.
A storage medium having stored thereon computer-executable instructions for performing the load determination method.
An electronic device, comprising: at least one processor; and a memory communicatively coupled to the at least one processor; wherein the memory stores instructions executable by the at least one processor to enable the at least one processor to perform the load determination method.
Compared with the prior art, the invention has at least the following beneficial effects:
the invention discloses a method for determining a pressure test load of oil casing gas seal thread wellhead seal detection, which establishes attenuation analysis of the contact pressure and length of a seal structure caused by load change in wellhead pressure test loading and unloading processes under the condition of maximum make-up torque based on maximum seal interference, and determines the pressure test load. According to the method, a mechanical analysis thread structure geometric model is determined according to the design tolerance and the upper buckling torque control range of the airtight special thread structure, and the maximum stress and plastic strain of the thread in the processing and manufacturing tolerance range are ensured; a method for determining pressure load of pressure test of a threaded wellhead is established based on the principle, and a basis is provided for detecting the sealing integrity of oil casing threads in an oil field after the oil casing threads are buckled.
Further, establishing a geometric model of maximum stress of the threads: the interference fit of the internal and external threads is minimum; the sealing interference fit is maximum; the external thread taper is maximum; the taper of the internal thread is minimum; shoulder interference generated by maximum make-up torque. Through the establishment of the thread screwing geometric model, all processed thread products of the thread structure in the design tolerance and the specified screwing torque range can be ensured not to cause serious sealing deformation in the pressure test of the wellhead of the oil field to influence the subsequent use.
Furthermore, after the material is subjected to plastic deformation, the mechanical property of the material is softened and reduced along with the repetition of loading and unloading, and the stress change rule of sealing along with load alternation can be better analyzed by adopting a material mechanical mixing and hardening constitutive model. Therefore, the integral area change of the sealing structure deformation contact pressure and the length of the thread structure in the loading and unloading process can be effectively analyzed.
Furthermore, the thread sealing change law is applied to a judgment index, two numerical values of the axial contact area along the sealing formed by the product of the maximum sealing contact pressure and the length are compared with corresponding values generated by the sealing in the initial make-up state, and the reduction of the two numerical values after the pressure in the pressure test is unloaded is lower than 20% to serve as a pressure test control load. According to the fact that the envelope curve of the safety factor of the triaxial design of the underground pipe column is less than 80%, the follow-up underground safe and reliable use of the thread can be effectively guaranteed by controlling the envelope curve within 20% of the reduction amount.
Further, the criterion of thread air tightness is as follows: by adopting the comparison of the maximum contact pressure of the sealing surface and the internal pressure of the seal, whether the seal is leaked or not can be effectively reflected; the contact area formed by the contact pressure distribution of the sealing surface can effectively reflect the contact length of the seal and the residual seal strength including the length and the pressure after the internal pressure load penetrates through the seal under the contact pressure distribution state, and the reliability of the seal can be further explained.
Further, determining the pressure test load of the oil casing gas seal special thread wellhead. Firstly, selecting possible pressure test loads according to the following selection criteria of 1) initial values: detecting the pressure test value of the defect of the API 5CT oil sleeve body produced by the production plant; 2) further improvement is achieved; the internal yield pressure value of the bearing capacity of the pipe body is 80 percent; 3) further options are: the internal yield pressure value of the bearing capacity of the pipe body; 4) and finally, selecting: the oil casing material measured VME 80% and VME 95% critical values for the composite stress of material yield strength (Von MISES abbreviated as VME). Through progressively rising analysis to above-mentioned pressure testing load, can select the biggest pressure testing load, both guaranteed to have effectively to detect well head leakproofness can guarantee the safe reliability of follow-up use in the pit.
In conclusion, the invention ensures that the thread has maximum stress and plastic strain within the processing and manufacturing tolerance range by selecting the limit tolerance matching sample, and can ensure that the gas-tight special thread which conforms to the manufacturing tolerance range and the screwing-up control torque range can ensure effectiveness and ensure that the sealing surface does not generate serious plastic deformation damage to ensure the subsequent safe use in the well in the pressure test load tightness detection process of the well head. By adopting the material mechanics mixed hardening constitutive model, the integral area change of the sealing plastic deformation contact pressure and the length of the thread structure in the loading and unloading processes can be effectively analyzed and reflected, and a basis is provided for further judgment of the thread sealing applicability. The reduction of the unloaded pressure in the pressure test compared with the initial screwing-in is lower than 20% as a pressure test control load, so that the follow-up underground safe and reliable use of the thread can be effectively ensured. The maximum contact pressure of the sealing surface is adopted, so that whether the sealing is leaked or not can be effectively reflected; the reliability of the seal can be further explained by adopting the contact area formed by the contact pressure distribution of the sealing surface and the residual sealing strength including the length and the pressure. The gradual rise analysis of the pressure test load of the wellhead can select the maximum pressure test load, thereby ensuring that the sealing performance of the wellhead can be effectively detected, and the safety and the reliability of the follow-up use in the well can be ensured. The method has the advantages that the beneficial guidance is provided for determining the pressure load in the wellhead tightness detection pressure test of the special airtight threaded connection, and the underground safe and reliable use is ensured.
The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.
Drawings
FIG. 1 illustrates a seal maximum interference fit and maximum stab shoulder interference in an embodiment of the present invention; wherein, (a) is the integral interference fit of the thread upper buckle, and (b) is the maximum interference fit of the seal and the maximum interference fit of the shoulder upper buckle;
FIG. 2 is a composite MISES stress distribution after threading in an embodiment of the present invention; wherein, (a) threading and sealing MISES stress distribution; (b) sealing the local MISES stress profile;
FIG. 3 shows the equivalent plastic strain after pressure test internal pressure loading and internal pressure unloading in the embodiment of the present invention, wherein (a) is the pressure test internal pressure loading equivalent plastic strain; (b) unloading the equivalent plastic strain for the internal pressure;
FIG. 4 shows the contact pressure and length distribution of the sealing surfaces after loading and unloading of internal pressure of different pressure tests in the embodiment of the invention; wherein (a) prescribes a pressure test hydrostatic pressure for API 5CT standard; (b) a coefficient of 0.8 is specified for API 5CT to replace the pressure test pressure; (c) API specifies the yielding pressure in the pipe body; (d) the composite equivalent stress of the pipe body is 80 percent; (e) the composite equivalent stress of the pipe body is 95 percent.
Detailed Description
The invention discloses a method for determining pressure test load of oil casing gas seal thread wellhead seal detection, which comprises the following steps:
s1, selecting an analysis sample;
the limit tolerance is used for reflecting main parameters of the thread structure, such as thread pitch diameter, thread taper, sealing surface diameter and ovality, and selecting a limit matching value (see tables 1 and 2) within a product design tolerance range, so that the maximum sealing interference is ensured after the thread is buckled, namely, the tested thread product is ensured to be in a qualified machining tolerance range, and after three steps of internal pressure loading, load protection and unloading of wellhead pressure test, good sealing integrity is still ensured to ensure the safe use of the subsequent oil field underground working condition load.
The maximum interference fit of the seal in the tolerance range enables the seal surface to have maximum plastic strain and stress under the conditions of upper buckle, internal pressure and load retention, the reduction of the seal contact pressure and length caused by the maximum deformation of the seal surface can be detected after the internal pressure is unloaded, and whether the seal meets the use of subsequent loads can be effectively determined. Under the conditions of geometrical model building and limit tolerance matching of the back coating yellow and a case matching table.
The thread structure parameter matching is based on the selection and analysis requirements of the sample:
the maximum stress and strain, namely the maximum equivalent plastic strain, of the sealing structure is ensured under the conditions that the thread parameters selected in the specified processing tolerance range of the product are matched with the maximum torque upper buckle and the internal pressure load state. Therefore, after the threaded products are all operated and executed in a wellhead pressure test, the residual sealing performance after the contact pressure and the length of the sealing surface are reduced can be ensured to ensure the safe use of the subsequent working condition load in the oil field.
Sample selection limit tolerance fit:
the interference fit of the pitch diameters of the internal thread and the external thread is minimum; the sealing interference fit is maximum; the external thread taper is maximum; the taper of the internal thread is minimum; and (4) buckling the maximum torque.
The thread has the minimum low interference stress, the maximum plastic strain is generated by the maximum sealing high interference stress, the sealing contact pressure and the length attenuation are maximum in the pressure test loading and unloading process, and the subsequent use safety of the sealing can be reflected to the greatest extent.
S2 model of material mechanics
The material mechanics model is the basis for analyzing the stress-strain distribution of the structure of the thread under a load state. The material mechanics model has different models under different stress states; the main flow model is a stress-strain model of the material under the unidirectional tensile load, and only the stress change of the structure under one load state of tension or compression can be analyzed; the mechanical model of the material under the tensile and compressive alternating load state can analyze the change development of the stress strain of the structure under the coexistence of various loads and the alternating dynamic state of the load.
After plastic deformation of the material, the plastic hardening behavior of the material during loading and unloading has a significant effect on the contact pressure and length of the thread seal. The mechanical behavior of the material is as follows:
σF＝(1-c)σs+cY(εp)
wherein c is a hardening coefficient, and c is 1 isotropic hardening; c is 0 follow-up hardening, c is between 0 and 1 is called hybrid hardening, sigmaFIs a plastic stress; sigmasIs the yield stress; y is a plastic stress strain function; epsilonpIs a plastic strain.
S3 analysis of sealing contact pressure and length
An analysis model is established according to the geometric dimension tolerance of the analysis selected sample as shown in figure 1, and a material mechanics model is set according to the actually measured material stress-strain curve. Internal pressure is loaded on the oil sleeve, the inner wall of the thread and the end face of the shoulder, sealing contact pressure and length in the loading and unloading processes under different internal pressures are calculated respectively, and the sealing contact pressure and the length are compared with an initial upper buckling value. The seal contact variation is shown in tables 4 and 5.
Because the complexity of the thread structure cannot adopt an analytic calculation method, the fine structures such as chamfer arcs and the like with the complex thread structure can be perfectly reflected by adopting a finite element numerical calculation simulation method.
Firstly, finite element modeling is carried out, and the axial symmetry model has the advantages of high precision and high calculation efficiency; the thread pitch diameter interference, the sealing interference, the shoulder interference and the contact friction coefficient are set, so that the thread screwing-in process and the change of alternating load can be fully reflected, and the thread screwing-in torque can be accurately calculated;
the method comprises the steps of setting the mechanical property of a material by adopting a hybrid hardening model, namely the mechanical property of the material under tension and compression load changes along with the change of the yield strength of the load, fully reflecting the change of structural stress and strain distribution in the loading and unloading process, then applying internal pressure and pressure relief on the inner wall of a thread, calculating and analyzing, setting the internal pressure loading time rate such as 30MPa/min pressurization per minute and adding the internal pressure to a preset analysis internal pressure for 10 seconds, setting the pressure relief rate at 35MPa/min per minute, fully reflecting the three steps of pressurization, load retention and pressure relief and the time length in the wellhead thread tightness detection process, truly and effectively simulating all details of practical field operation, and perfectly analyzing the changes of sealing contact pressure and length under the application of different loads.
S4, sealing applicability criterion;
the application rule of the change rule of the sealing property is as follows:
and comparing two numerical values of the axial contact area along the seal formed by the product of the maximum contact pressure of the seal and the contact pressure and the length with corresponding values generated by the seal in the initial make-up state, and taking the reduction of the two compared values after the internal pressure of the pressure test is unloaded as the pressure test control load, wherein the reduction is lower than 20%. According to the fact that the envelope curve of the safety factor of the triaxial design of the underground pipe column is less than 80%, the follow-up underground safe and reliable use of the thread can be effectively guaranteed by controlling the envelope curve within 20% of the reduction amount.
And the sealing performance applicability criterion is used for analyzing and judging whether the reduction of the change of the sealing performance meets the sealing integrity of the underground application of the subsequent oil field under the working condition load in the process that the contact pressure and the length of the thread sealing surface change along with the load state after the calculation and analysis in the step S3.
S5, carrying out pressure test sealing detection load analysis;
determining pressure test loads of a wellhead according to the requirements of the internal pressure bearing capacity of the pipe body, detecting the internal pressure value required by the bearing capacity of the pipe body under the upper limit of specified defects in production, and determining 2 loads according to the lowest value specified by the API 5CT standard of the oil casing pipe and the safety coefficient of further detection values of 0.8;
in order to further determine a wider application range and improve a pressure test detection value, the pressure test load value of the wellhead thread sealing detection is finally determined according to the applicability criterion by further analyzing 80% and 95% of the yield of the inner wall material under the defect-free internal pressure of the pipe body and the sealing change rule.
Firstly, analyzing the distribution rule of the contact pressure and the length of a sealing surface in a buckling load step state, and extracting the maximum contact pressure and the contact sealing area required by the applicability criterion, namely the integral Newton per millimeter N/mm formed by the contact pressure and the length; continuously analyzing the sealing contact distribution rule after internal pressure application and load retention, and extracting the maximum contact pressure and the contact sealing area; then analyzing the distribution rule of the unloaded sealing contact, and extracting the maximum contact pressure and the contact sealing area; the sealing maximum contact pressure and the relative variation of the area after loading internal pressure and unloading internal pressure are compared with the loading step in the initial state of buckling so as to be convenient for comparison; according to the seal applicability criterion, the reduction amount of the two is lower than 20%, and the final internal pressure test value of the wellhead pressure test load is determined.
The pressure test load is shown in table 1, and the change of the sealing performance of the pressure test load is shown in fig. 4.
The pressure test load value of the airtight threaded wellhead is calculated and analyzed and is based on a guarantee value for ensuring safe and reliable use of the subsequent oil field underground; meanwhile, after the oil casing pipe column air-tight threaded connection is buckled on an oil field wellhead, whether the buckling operation effectively achieves the tightness required by the air-tight thread is checked, and whether the quality of the air-tight thread product is qualified under the condition of reasonably standardizing the buckling torque is checked. The standard SY/T6872-2012 'casing and oil pipe threaded connection airtight wellhead detection system' is executed in the pressure test of the wellhead for the oil field, an airtight internal pressure value to be controlled is provided, the standard does not stipulate the pressure test load internal pressure value, and only a pressure test operation process is provided, so that the problem of how to determine the pressure test load is effectively solved.
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of the embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The present invention will be further described with reference to the accompanying drawings, and it should be noted that the present embodiment is based on the technical solution, and a detailed implementation manner and a specific analysis process are provided, and the protection scope of the present invention includes the present embodiment.
This embodiment is as follows
The method is used for analyzing and determining the pressure testing load of the wellhead of the thread sealing detection by taking the material steel grade 110SS gas sealing special thread oil pipe as an example.
1. Thread seal analysis geometric model building
The thread limit tolerance fit requirements are shown in table 1, and the modeled thread limit parameter fit is shown in table 2
TABLE 1
TABLE 2
2. Screw thread analysis finite element model
The thread assembly and internal pressure loading are shown in figure 1, and the composite stress MISES stress distribution after the threads are buckled is shown in figure 2; the equivalent plastic strain after the internal pressure loading and the internal pressure unloading of the sealing pressure test is shown in figure 3. And under the condition of maximum torque upper buckling, the coupling shoulder and the external thread sealing surface both enter plastic yield.
3. Thread pressure test load analysis
According to the specification of the pipe body (the outer diameter is 88.9mm, the wall thickness is 6.45mm) and the actually measured yield strength of the material is 845MPa, the pressure test analysis load is determined and is shown in Table 3.
TABLE 3
4. Thread seal suitability load determination
The sealing contact pressure and the length distribution under different pressure test loads of wellhead sealing detection are shown in figure 4. The pressure test load and unload seal maximum contact pressure changes are shown in table 4. The pressure test loading and unloading seal contact pressure and length area changes are shown in table 5. The internal pressure load controlled by VME 80% pressure test under the conditions of nominal material yield strength and different effective wall thicknesses is shown in Table 6.
TABLE 4
TABLE 5
TABLE 6
Table 4 when the composite equivalent stress of the pipe body is within 80%, the maximum contact pressure of the main seal increases with the increase of the internal pressure; the maximum contact pressure reduction of the seal after unloading is less than 20%; when the increase of the internal pressure exceeds 80%, the internal pressure increase maximum contact pressure is decreased, and the decrease of the contact pressure after unloading exceeds 20%; table 5 when the composite equivalent stress of the pipe body is within 80%, the sealing contact pressure area increases with the increase of the internal pressure; the area of the sealing contact pressure after unloading is larger than the area of the upper buckle; when the increase of the internal pressure exceeds 80%, the contact pressure area of the internal pressure increasing encryption seal is reduced, and the reduction of the contact pressure area after unloading is 1%; and (4) recommending the pressure testing pressure of the wellhead not to exceed 80% of the composite equivalent stress of the pipe body based on the worst contact pressure reduction amount. Table 6 suggests controlling wellhead pressure testing at 85.7MPa at 80% pipe body composite equivalent (VME stress) based on 90% of nominal material yield strength and wall thickness.
In summary, the invention provides a method for determining a pressure test load of oil casing gas seal thread wellhead seal detection, which comprises the steps of firstly establishing a finite element geometric model by using the limit tolerance provided by the invention patent, applying an interference magnitude and material mechanical property model, and analyzing three wellhead pressure test implementation processes of buckling, internal pressure loading and load retention and unloading by using a dynamic load model; analyzing the sealing contact pressure and length distribution rule of different internal pressures; and then comparing the sealing change rules of the three load steps in the pressure test process according to a sealing applicability criterion to determine a reasonable internal pressure value finally received by the pressure test load of the wellhead. The scheme fully reflects all patent right requirements of technical innovation of the invention patent, perfectly explains the effectiveness and the feasibility of the invention patent, and provides a clear guidance process for field application of an oil field. The invention case further illustrates that the invention patent has reliable scientific principle, creatively solves the technical problem in oil and gas engineering, and provides an innovative solution for the engineering technical development in the field.
The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.
Claims (7)
1. A method for determining a pressure test load in threaded wellhead sealing detection is characterized by comprising the following steps:
s1, selecting an analysis sample according to limit tolerance matching;
s2, establishing a material mechanics model according to the analysis sample selected in the step S1;
s3, loading internal pressure on the oil sleeve, the inner wall of the thread and the end face of the shoulder according to the material mechanics model established in the step S2, respectively calculating the sealing contact pressure and the length in the loading and unloading processes under different internal pressures, and analyzing the sealing contact pressure and the length;
s4, determining the sealing applicability criterion based on that the envelope curve of the safety coefficient of the triaxial design of the underground pipe column is less than 80%, and judging whether the reduction of the change of the sealing performance meets the sealing integrity of the underground application of the subsequent oil field under the working condition load in the process that the contact pressure and the length of the threaded sealing surface change along with the load state in the step S3;
s5, determining pressure test load of a wellhead according to the requirement of the internal pressure bearing capacity of the pipe body, and checking whether the screwing operation meets the sealing performance of the airtight thread and whether the quality of the airtight thread product is qualified under the screwing torque condition;
determining two loads according to a lowest value specified by an oil casing API 5CT standard and a further detection value safety coefficient of 0.8, improving a pressure test detection value, further analyzing according to 80% and 95% of yield of an inner wall material under non-defective internal pressure of a pipe body, determining a pressure test load value of wellhead thread tightness detection according to an applicability criterion according to a sealing change rule and a pressure test load value of the inner wall material under non-defective internal pressure of the pipe body;
firstly, analyzing the distribution rule of the contact pressure and the length of a sealing surface in a buckling load step state, and extracting the maximum contact pressure and the contact sealing area required by the applicability criterion; analyzing a sealing contact distribution rule after internal pressure application and load retention, and extracting maximum contact pressure and contact sealing area; then analyzing the distribution rule of the unloaded sealing contact, and extracting the maximum contact pressure and the contact sealing area; comparing the relative variation of the maximum sealing contact pressure and the area after loading internal pressure and unloading internal pressure with the initial buckling state load step; and according to the seal applicability criterion, when the reduction of the pressure drop of the wellhead is lower than 20%, determining that the pressure test load of the wellhead finally receives the pressure test value of the internal pressure.
2. The method according to claim 1, wherein in step S1, the limit tolerance fit is as follows:
the interference fit of the internal and external threads is minimum; the sealing interference fit is maximum; the external thread taper is maximum; the taper of the internal thread is minimum; and (4) buckling the maximum torque.
3. The method of claim 1, wherein in step S2, the material mechanics model is as follows:
σF＝(1-c)σs+cY(εp)
wherein σFIs a plastic stress; sigmasIs the yield stress; y is a plastic stress strain function; epsilonpThe plastic strain and c the hardening coefficient.
4. The method according to claim 1, wherein step S3 is specifically:
establishing an axisymmetric model by adopting a finite element numerical calculation simulation method; setting the interference of the diameter in the thread, the interference of the seal, the interference of the shoulder and the contact friction coefficient, and calculating the thread screwing torque; setting the mechanical property of the material by adopting a mixed hardening model, then applying internal pressure and pressure relief on the inner wall of the thread, setting the internal pressure loading time rate by adopting a dynamic calculation mechanical model, adding the internal pressure to a preset analysis internal pressure, then carrying out load retention, then relieving the pressure, and carrying out sealing contact pressure and length analysis.
5. The method according to claim 1, wherein in step S4, the rule of application of the sealing variation rule is as follows:
and comparing two numerical values of the axial contact area along the seal formed by the product of the maximum contact pressure of the seal and the contact pressure and the length with corresponding values generated by the seal in the initial make-up state, and taking the reduction of the two compared values after the pressure in the pressure test is unloaded as the pressure test control load, wherein the reduction is lower than 20%.
6. A storage medium having stored thereon computer-executable instructions, the computer being operable
The execution instructions are for performing the load determination method of any one of claims 1-5.
7. An electronic device, comprising: at least one processor; and a memory communicatively coupled to the at least one processor; wherein the memory stores instructions executable by the at least one processor to enable the at least one processor to perform the load determination method of any one of claims 1-5.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010797603.4A CN111927373B (en) | 2020-08-10 | 2020-08-10 | Threaded wellhead sealing detection pressure test load determination method, storage medium and equipment |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010797603.4A CN111927373B (en) | 2020-08-10 | 2020-08-10 | Threaded wellhead sealing detection pressure test load determination method, storage medium and equipment |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN111927373A CN111927373A (en) | 2020-11-13 |
| CN111927373B true CN111927373B (en) | 2022-07-05 |
Family
ID=73307208
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202010797603.4A Active CN111927373B (en) | 2020-08-10 | 2020-08-10 | Threaded wellhead sealing detection pressure test load determination method, storage medium and equipment |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN111927373B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112761542B (en) * | 2021-01-21 | 2023-04-21 | 衡阳华菱钢管有限公司 | Design method of sealing structure of threaded joint of oil casing |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102678064A (en) * | 2011-11-09 | 2012-09-19 | 中国石油天然气集团公司 | Control method for improving anti-sticking performance and connection strength of round thread oil pipe and bushing |
| CN108982076A (en) * | 2018-04-11 | 2018-12-11 | 中国石油天然气集团有限公司 | A kind of gas well at HTHP oil pipe hermetic seal screw thread assay method |
-
2020
- 2020-08-10 CN CN202010797603.4A patent/CN111927373B/en active Active
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102678064A (en) * | 2011-11-09 | 2012-09-19 | 中国石油天然气集团公司 | Control method for improving anti-sticking performance and connection strength of round thread oil pipe and bushing |
| CN108982076A (en) * | 2018-04-11 | 2018-12-11 | 中国石油天然气集团有限公司 | A kind of gas well at HTHP oil pipe hermetic seal screw thread assay method |
Non-Patent Citations (3)
| Title |
|---|
| 外压作用对特殊螺纹接头内压密封性影响分析;申昭熙等;《石油工业技术监督》;20120820;第28卷(第08期);全文 * |
| 特殊螺纹气密封性能评价研究;马艳琳等;《石油管材与仪器》;20160815;第02卷(第04期);全文 * |
| 特殊螺纹油管与套管的上扣扭矩构成与密封性能研究;王新虎等;《石油矿场机械》;20101225;第39卷(第12期);全文 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN111927373A (en) | 2020-11-13 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN108982076B (en) | Analysis and evaluation method for gas sealing threads of oil pipe of high-temperature and high-pressure gas well | |
| US5212885A (en) | High gas sealibility makeup for API buttress connections | |
| US20190271621A1 (en) | Method and device for determining elasticity of cement stone utilized in well cementing of oil-gas well | |
| Van Wittenberghe et al. | Experimental determination of the fatigue life of modified threaded pipe couplings | |
| CN111927373B (en) | Threaded wellhead sealing detection pressure test load determination method, storage medium and equipment | |
| CN111767614A (en) | Evaluation and analysis method for vibration fatigue failure test of air-tight seal special thread | |
| Hertelé et al. | Effects of pipe steel heterogeneity on the tensile strain capacity of a flawed pipeline girth weld | |
| JPH0565756B2 (en) | ||
| Zhang et al. | Research on probabilistic assessment method based on the corroded pipeline assessment criteria | |
| Uribe et al. | Leakage resistance envelopes of API 8 round casing connections using fe analysis | |
| US11156526B1 (en) | Triaxial leak criterion for optimizing threaded connections in well tubulars | |
| US11513027B1 (en) | Triaxial leak criterion with thread shear for optimizing threaded connections in well tubulars | |
| CN114544081A (en) | Method and device for determining safety load of threaded pipe | |
| CN111324985B (en) | Method for evaluating fatigue life of continuous pipe containing groove-shaped scratch defects | |
| Van Wittenberghe et al. | Modeling of preloaded threaded pipe connections | |
| Xie et al. | Methodology for reliability-based design and assessment of tubular connection sealability in HPHT wells | |
| CN117823058A (en) | Three-axis safety coefficient determination method, system, equipment and storage medium for tubular column design based on air seal integrity | |
| US11739594B2 (en) | Testing and validation of connectors for subsea intervention riser systems | |
| Song et al. | Numerical and Experimental Qualification of Seal Integrity of Rotary Shouldered Connections Under Combined Loads | |
| Cahyati et al. | Design and process plan of hydroforming casing patch using virtual manufacturing method | |
| Day et al. | New makeup method for API connections | |
| Van Wittenberghe et al. | Numerical and experimental study of the fatigue of threaded pipe couplings | |
| US20240151136A1 (en) | Well Integrity Safety Factor for Evaluating Threaded Connections During Well Operations | |
| CN111177879B (en) | Method for designing strength of deep well ultra-deep well full life cycle casing string | |
| CN117852199A (en) | Seal integrity analysis method for airtight threaded joint |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |