A full-size non-metallic reinforced flexible composite pipe life prediction method

Abstract

The application discloses a kind of full-size non-metal reinforced flexible composite pipe life prediction method, belong to non-metal reinforced flexible composite pipe life prediction and its evaluation technical field, solve the technical problem that when flexible composite pipe life prediction is carried out in prior art, great workload, test cycle is long, effective data is uncontrollable in test process.It is disclosed in the method that six pressures are selected under each temperature condition at three temperature conditions, the pipe failure time under each pressure value is obtained, then the pipe failure time and pressure curve under different temperature conditions and corresponding linear equation are made, 50% of the limit pressure strength of non-metal pipe in full-size oil and gas field environment under room temperature condition is taken as threshold and substituted into the above linear equation, corresponding time is obtained, finally non-metal reinforced composite pipe temperature-time Arrhenius relationship diagram is established, and the service life of pipe material can be accurately predicted through service temperature, to provide basic support for long-term safe application of full-size oil and gas field environment non-metal pipe.

Description

Technical Field

[0001] This invention belongs to the technical field of life prediction and evaluation of non-metallic reinforced flexible composite pipes, specifically relating to a method for predicting the life of full-size non-metallic reinforced flexible composite pipes. Background Technology

[0002] Currently, traditional oil and gas transportation mainly relies on metal pipelines. However, metal pipelines are susceptible to perforation and leakage under corrosive media in oil fields, such as hydrogen sulfide (H2S) and carbon dioxide (CO2). In recent years, thermoplastic pipes have been gradually applied to acidic environments. However, due to the limited pressure resistance of these materials when used alone, they are typically only suitable for pressure pipelines below 1.6 MPa, failing to meet the on-site requirements of oil fields. Therefore, to improve the transportation pressure of thermoplastic pipes, non-metallic reinforced thermoplastic pipes have emerged and are gaining increasingly widespread application. Non-metallic reinforced thermoplastic pipes are composite material pipes with a multi-layered structure, typically including an inner lining, a non-metallic reinforcing layer, and an outer cladding layer. Generally, the design life of both non-metallic and composite pipes is over 20 years. However, under the combined effects of high temperature and high pressure, the aging process of thermoplastics in direct contact with oil and gas media accelerates, resulting in diverse material failure morphologies (cracks, holes, blistering, etc.) and complex alternating failure modes (toughness, brittleness, degradation, etc.).

[0003] In existing technologies, the pressure rating assessment test methods for full-size non-metallic composite pipes, referencing standard API 15S 5.3.3, stipulate that the MPR of the PFR should be determined through a series of creep rupture tests under assessment test temperature and constant pressure conditions. The tests should be conducted according to procedure B specified in ASTM D2992-12, excluding data points with failure times less than 10 hours in regression calculations. Specific test protocols are shown in Table 1. The assessment test temperature is selected by the manufacturer and should not be lower than the design temperature of the product under any application conditions; a recommended assessment test temperature is 65°C (for polyester fiber reinforced polyethylene composite pipes). The permissible failure mode is tensile fracture of the reinforcement. If, during the assessment test, the failure mode is not tensile fracture of the reinforcement, such as when the pipe body detaches from the joint or sleeve, the test result should be discarded when calculating the average value or using data plots. Some data collection for the pressure rating assessment tests of flexible composite pipes in existing technologies is shown in Table 1. Figure 1 .

[0004] Table 1. Distribution of MPR failure points (referencing ASTM D2992-12)

[0005] Failure time (h) Failure Point Design failure points 10～1000 At least 4 11 1000～6000 At least 3 3 Greater than 6000 At least 3 3 Greater than 10000 At least 1 1 total At least 18 18 pcs

[0006] The specific implementation scheme of the existing technology is as follows:

[0007] a) The test sample tube was subjected to a 65℃ water pressure burst strength test to obtain the ultimate strength value;

[0008] b) Based on the ultimate strength value, estimate the pressure value corresponding to the failure time of 10-1000h, and complete the collection of data from 11 failure points for two specifications within 2 months.

[0009] c) Based on the failure point distribution from 10 to 1000 hours, a preliminary regression curve is plotted, and the correspondence between subsequent test time and pressure distribution is calculated, giving the pressure value corresponding to the failure point in the subsequent test.

[0010] d) Conduct data collection at 3 test sites over a period of 6000–10000 hours;

[0011] e) Conduct data collection at 1000-6000h test sites, totaling 3 sites.

[0012] The above implementation steps and appendix Figure 1 As can be seen, the pressure rating test specified by API 15S includes the collection of 18 valid data points, with a maximum test time of 10,000 hours. Therefore, this rating method involves a huge workload, a long test cycle, and uncontrollable valid data during the test. Summary of the Invention

[0013] In order to overcome the shortcomings of the prior art, the present invention aims to provide a method for predicting the life of full-size non-metallic reinforced flexible composite pipes, so as to solve the technical problems of huge workload, long test cycle and uncontrollable effective data in the existing technology for predicting the life of flexible composite pipes.

[0014] To achieve the above objectives, the present invention employs the following technical solution:

[0015] This invention discloses a method for predicting the lifespan of a full-size non-metallic reinforced flexible composite tube, comprising the following steps:

[0016] S1: Cut test samples from a section of full-size non-metallic reinforced flexible composite pipe and process the test samples into standard specimens.

[0017] S2: Under room temperature conditions, a water immersion compression burst test is performed on a standard specimen to obtain the ultimate compressive strength P of the standard specimen at room temperature. y ;

[0018] Then, three different test temperatures T1, T2, and T3 were selected, and six test pressures P1, P2, P3, P4, P5, and P6 were selected for each test temperature.

[0019] S3: Using three different test temperatures T1, T2 and T3, and six test pressures P1, P2, P3, P4, P5 and P6 corresponding to each test temperature as the conditions for immersion pressure burst test, the standard sample is subjected to immersion pressure burst test to obtain the failure time t1, t2, t3, t4, t5 and t6 of the standard sample under the corresponding test pressure at the three different test temperatures;

[0020] S4: Based on the six test pressures P1, P2, P3, P4, P5, P6 and the failure times t1, t2, t3, t4, t5, and t6, a linear fit is performed to establish a linear formula for failure time and test pressure at different test temperatures; the ultimate bearing strength P of the standard specimen at room temperature is then used as the basis for this formula. y Substituting 50% of the value into the linear formula for failure time and test pressure at different test temperatures, the ultimate bearing strength P of the full-size non-metallic reinforced flexible composite pipe at different test temperatures is obtained. y Failure time t when reduced by 50% 501 t 502 t 503 ;

[0021] S5: Based on three different test temperatures T1, T2, and T3, and the obtained t 501 t 502 t 503 By performing fitting, the ultimate bearing strength P of the full-size non-metallic reinforced flexible composite pipe under different test temperatures was established. y Arrhenius formula for reducing failure time by 50%;

[0022] S6: When the actual working temperature of the full-size non-metallic reinforced flexible composite pipe is T, substitute the actual working temperature T into the Arrhenius formula obtained in S5 to predict the life of the full-size non-metallic reinforced flexible composite pipe.

[0023] Furthermore, in S1, the standard sample meets the requirements of the hydrostatic burst test and the hydrostatic test.

[0024] Furthermore, in S2, the three different test temperatures T1, T2, and T3 increase sequentially, with T2 being 15°C higher than T1 and T3 being 15°C higher than T2.

[0025] Furthermore, T1, T2, and T3 are 60°C, 75°C, and 90°C, respectively.

[0026] Furthermore, in S2, the test pressures P1, P2, P3, P4, P5, and P6 are selected based on the ultimate bearing strength P of the standard specimen at room temperature. yFor reference, P1, P2, P3, P4, P5, and P6 are greater than the ultimate bearing strength P of the standard specimen at room temperature. y One-third of the total, and there is a logarithmic relationship between P1, P2, P3, P4, P5, and P6.

[0027] Furthermore, the inner lining of the full-size non-metallic reinforced flexible composite pipe is high-density polyethylene or cross-linked polyethylene, and the reinforcing layer is polyester fiber.

[0028] Furthermore, in S4, the linear formula for failure time and test pressure at different test temperatures is:

[0029] Y = 10 [alog10(X)+b] ;

[0030] Where Y represents a test pressure, X represents the failure time of the standard sample under that test pressure, and a and b are constants.

[0031] Furthermore, in S5, the method based on three different test temperatures T1, T2, and T3, and the obtained t 501 t 502 t 503 The fitting method employed was an exponential function to obtain the ultimate compressive strength P of the full-size non-metallic reinforced flexible composite pipe at different temperatures. y Arrhenius formula for reducing failure time by 50%.

[0032] Furthermore, the full-size non-metallic reinforced flexible composite pipe was tested at different temperatures and its ultimate bearing strength P was measured. y The Arrhenius formula for reducing failure time by 50% is:

[0033]

[0034] Where T represents different test temperatures, and t represents the ultimate pressure bearing strength P of the full-size non-metallic pipe used in oil and gas field environments. y Failure time when reduced by 50%; y0, A1, and t1 are constants.

[0035] Furthermore, in S4, a logarithmic linear fit is performed based on the six test pressures P1, P2, P3, P4, P5, and P6, as well as the obtained pipe failure times t1, t2, t3, t4, t5, and t6, to establish linear formulas for different test temperatures and test pressures.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] This invention discloses a method for predicting the service life of full-size non-metallic reinforced flexible composite pipes. The method utilizes a hydrostatic testing machine and a constant-temperature water tank to place the full-size non-metallic reinforced flexible composite pipe in a simulated oil and gas transportation environment. By selecting six specific pressures at each of three temperature conditions, the pipe failure time at each pressure value is obtained. Based on the pressure-time correspondence, pipe failure time and pressure curves and corresponding linear equations are generated for the three different temperature conditions. Substituting 50% of the ultimate pressure-bearing strength of the full-size non-metallic pipe used in the oil and gas field environment into these three linear equations yields the corresponding time. Finally, a temperature-time Arrhenius relationship diagram for the non-metallic reinforced composite pipe is established, enabling accurate prediction of the pipe's service life at specific temperatures. This invention comprehensively considers the overall situation of full-size non-metallic pipes used in oil and gas field environments, innovatively establishing a full-size temperature-increasing testing method for service life prediction and evaluation, resulting in more accurate evaluation results. This method fully considers the actual operating conditions in the oil and gas environment and, for the long-term safe service application background of flexible composite pipes, innovatively establishes a temperature-increasing testing method based on the Arrhenius equation. A relatively stringent indoor accelerated testing method was established, and the influence of different temperatures on performance was obtained by analyzing the relationship between pressure and failure time at different temperatures. Secondly, this invention is the first to study and clarify the impact of temperature on the service life of full-size non-metallic pipes used in oil and gas field environments, elucidating the long-term service life of pipes at different temperatures, and providing fundamental support for standardizing the long-term safe application of full-size non-metallic pipes used in oil and gas field environments. Attached Figure Description

[0038] Figure 1 A linear relationship between test pressure and pipe failure time at 60℃;

[0039] Figure 2 The graph shows the linear relationship between test pressure and pipe failure time at 75℃.

[0040] Figure 3 A linear relationship between test pressure and pipe failure time at 90℃;

[0041] Figure 4 Arrhenius plot of temperature-time for full-scale oil and gas field environment non-metallic tube test. Detailed Implementation

[0042] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0043] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0044] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0045] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0046] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0047] This invention provides a method for improving the life prediction of full-size non-metallic reinforced flexible composite tubes at higher temperatures, comprising the following steps:

[0048] S1: Sample preparation

[0049] Test samples were cut from the flexible composite pipe section and processed into standard specimens that meet the requirements of water pressure burst and hydrostatic pressure tests. The specimens were then conditioned according to the standard requirements.

[0050] S2: Determination of test conditions

[0051] 1) Test temperature: This invention uses an enhanced temperature calculation method to determine three different temperatures (T1, T2, and T3), with a 15°C interval between the three temperature points. Based on the characteristics of the non-metallic reinforced flexible composite pipe (the inner lining is high-density polyethylene or cross-linked polyethylene, and the reinforcing layer is polyester fiber), it is recommended that the three temperature points be 60°C, 75°C, and 90°C respectively (the temperature is determined based on the highest long-term service temperature of the inner lining material. This patent assumes that the inner lining is the commonly used high-density polyethylene or cross-linked polyethylene material, whose long-term service temperature is no higher than 65°C and 75°C respectively. For other thermoplastic plastics as the inner lining, such as PVDF, higher three temperature points can be selected according to the actual situation).

[0052] 2) Test pressure:

[0053] ①: At three different test temperatures T1, T2, and T3, the standard specimen was subjected to a water immersion compression burst test, and the ultimate compressive strength P of the standard specimen at each of the three test temperatures was obtained. y1 P y2 P y3 ;

[0054] ②The ultimate bearing strength P of the standard specimen at three test temperatures y1 P y2 P y3 For reference, six test pressures (P1, P2, P3, P4, P5, and P6) were selected at each temperature.

[0055] S3: Performance Testing

[0056] Using three different test temperatures T1, T2, and T3, and six test pressures P1, P2, P3, P4, P5, and P6 corresponding to each temperature as immersion pressure burst test conditions, standard samples were subjected to immersion pressure burst tests to obtain the time (t1, t2, t3, t4, t5, and t6) for pipe failure under the corresponding pressure conditions.

[0057] S4: Establish linear equations

[0058] Linear fitting was performed using six test pressures P1, P2, P3, P4, P5, and P6, along with the pipe failure times t1, t2, t3, t4, t5, and t6, to establish linear formulas for different temperatures and test pressures. The ultimate bearing strength P of the standard specimen at room temperature was then calculated. y Substituting 50% of the value into the linear formulas for pipe failure time and test pressure at the corresponding temperatures, the ultimate bearing strength P of the full-size non-metallic reinforced flexible composite pipe at different temperatures is obtained. y Failure time t when reduced by 50% 501 t 502 t 503 Based on three different test temperatures T1, T2, and T3, and the obtained t 501 t 502 t 503 Fitting was performed to establish the ultimate bearing strength P of full-size non-metallic pipes used in oil and gas field environments under different temperatures and in different environments. y Arrhenius formula for failure time when reduced by 50%;

[0059] When the actual operating temperature of the full-size non-metallic pipe used in the oil and gas field environment is T, the actual operating temperature T is substituted into the Arrhenius formula in S5 to predict the service life of the full-size non-metallic reinforced flexible composite pipe.

[0060] (1) Logarithmic linear fit of pressure and failure time at temperature T1:

[0061] Table 2. Failure time corresponding to different test pressures under T1.

[0062]

[0063]

[0064] Logarithmic linear fitting was performed on the two sets of data (failure time (h) and test pressure (MPa) in Table 2 to obtain the mathematical equation (Equation 1) for the relationship between test pressure and failure time of non-metallic reinforced flexible composite pipe under condition T1:

[0065] Y = 10 [a1log10(X)+b1] (1)

[0066] In the formula: Y—the test pressure of the non-metallic reinforced flexible composite pipe

[0067] X — Failure time of the non-metallic reinforced flexible composite pipe under this pressure condition

[0068] Under temperature T1, when the pressure of the non-metallic reinforced flexible composite pipe reaches 50% of the threshold (i.e., the ultimate bearing strength P) y 50%, 1 / 2*P y When the pressure is MPa), substituting into equation (1) will give the corresponding exposure time X as t1 h (t1 / 24 days, t1 / 8760 years).

[0069] (2) Logarithmic linear fit of pressure and failure time at temperature T2:

[0070] Table 3. Failure time corresponding to different test pressures under T2.

[0071] Test pressure (MPa) Failure time (h) <![CDATA[P 21 ]]> <![CDATA[t 21 ]]> <![CDATA[P 22 ]]> <![CDATA[t 22 ]]> <![CDATA[P 23 ]]> <![CDATA[t 23 ]]> <![CDATA[P 24 ]]> <![CDATA[t 24 ]]> <![CDATA[P 25 ]]> <![CDATA[t 25 ]]> <![CDATA[P 26 ]]> <![CDATA[t 26 ]]>

[0072] Logarithmic linear fitting was performed on the two sets of data (failure time (h) and test pressure (MPa) in Table 3 to obtain the mathematical equation (Equation 2) for the relationship between test pressure and failure time of non-metallic reinforced flexible composite pipe under T2 conditions:

[0073] Y = 10 [a2log10(X)+b2] (2)

[0074] In the formula:

[0075] Y—Non-metallic reinforced flexible composite pipe test pressure

[0076] X — Failure time under this pressure condition

[0077] Under temperature T2, when the pressure of the non-metallic reinforced flexible composite pipe reaches 50% of the threshold (i.e., the ultimate bearing strength P)y 50%, 1 / 2*P y When the pressure is MPa), substituting into equation (2) will give the corresponding exposure time X as t2 h (t2 / 24 days, t2 / 8760 years).

[0078] (3) Logarithmic linear fit of pressure and failure time at temperature T3:

[0079] Table 4. Failure time corresponding to different test pressures under T3.

[0080] Test pressure (MPa) Failure time (h) <![CDATA[P 31 ]]> <![CDATA[t 31 ]]> <![CDATA[P 32 ]]> <![CDATA[t 32 ]]> <![CDATA[P 33 ]]> <![CDATA[t 33 ]]> <![CDATA[P 34 ]]> <![CDATA[t 34 ]]> <![CDATA[P 35 ]]> <![CDATA[t 35 ]]> <![CDATA[P 36 ]]> <![CDATA[t 36 ]]>

[0081] Logarithmic linear fitting was performed on the two sets of data (failure time (h) and test pressure (MPa) in Table 4 to obtain the mathematical equation (Equation 1) for the relationship between test pressure and failure time of the non-metallic reinforced flexible composite pipe under condition T1:

[0082] Y = 10 [a3log10(X)+b3] (3)

[0083] In the formula:

[0084] Y—Non-metallic reinforced flexible composite pipe test pressure

[0085] X — Failure time under this pressure condition

[0086] Under temperature T3, when the pressure of the non-metallic reinforced flexible composite pipe reaches 50% of the threshold (i.e., the sample test pressure is 50% of the room temperature ultimate pressure, 1 / 2*P), y When the pressure is MPa), substituting into equation (3) will give the corresponding exposure time X as t3 h (t3 / 24 days, t3 / 8760 years).

[0087] (4) Establish the Arrhenius equation

[0088] The ultimate bearing strength P of the standard specimen at three test temperatures. y Substituting 50% of the value into the linear formulas for pipe failure time and test pressure at the corresponding temperatures, the ultimate bearing strength P of the non-full-size non-metallic reinforced flexible composite pipe at different temperatures is obtained. y Failure time t when reduced by 50% 501 t 502 t 503 The corresponding parameters are shown in Table 5.

[0089] Table 5 Time-temperature parameters at different simulation temperatures

[0090] type Simulated temperature 1 Simulated temperature 2 Simulated temperature 3 T(℃) <![CDATA[T1]]> <![CDATA[T2]]> <![CDATA[T3]]> T(K) <![CDATA[T1+273]]> <![CDATA[T2+273]]> <![CDATA[T3+273]]> 1 / T(K) <![CDATA[1 / (T1+273)]]> <![CDATA[1 / (T2+273)]]> <![CDATA[1 / (T3+273)]]> <![CDATA[t 50 (h)]]> <![CDATA[t 501 ]]> <![CDATA[t 502 ]]> <![CDATA[t 503 ]]> ln(1 / t) <![CDATA[ln(1 / t 501 )]]> <![CDATA[ln(1 / t 502 )]]> <![CDATA[ln(1 / t 503 )]]>

[0091] For the test temperature 1 / T (K) and time ln(1 / t) (h) in Table 5, the two sets of data are fitted with an exponential function to obtain the temperature-time (Equation 4) of the non-metallic reinforced flexible composite pipe:

[0092] ln(1 / t)=y0+A1*exp(-1 / T / t1) (4)

[0093] In the formula:

[0094] T — Temperature (K)

[0095] t—Time (h) when the failure pressure reaches 50% of the threshold.

[0096] Where y0, A1, and t1 are constants.

[0097] S5: Lifespan Estimation:

[0098] When the service temperature of the pipe is known to be T, it is substituted into the above formula (4) to calculate the service life t corresponding to that temperature.

[0099] Since the test medium is pure water, the service life needs to be reduced depending on the medium being transported: t'=t*f f

[0100] a) When transporting gas f f The value is no greater than 0.67;

[0101] b) When transporting liquid hydrocarbons and multiphase fluids f f The value is no greater than 0.8;

[0102] c) When transporting water f f The value is no greater than 1.0.

[0103] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0104] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0105] Example 1

[0106] The method for predicting the lifespan of a DN100mm PN8 MPa non-metallic reinforced flexible composite pipe includes the following steps:

[0107] 1) The ultimate pressure bearing capacity P = 32 MPa under normal temperature conditions was obtained using a hydraulic pressure testing machine;

[0108] 2) Conduct logarithmic linear fitting of pressure and failure time at a temperature of 60℃:

[0109] Table 6. Failure time at different test pressures at 60℃

[0110] Test pressure (MPa) Failure time (h) 26 10 24 80 22 500 20 3000 19 8000 18.5 10000

[0111] Logarithmic linear fitting was performed on the two sets of data (failure time (h) and test pressure (MPa) in Table 6, as shown in the appendix. Figure 1 As shown, the mathematical equation (Equation 5) for the test pressure and failure time of the non-metallic reinforced flexible composite pipe under 60℃ conditions is obtained:

[0112] Y = 10 [-0.04898log10(X)+1.4694] (5)

[0113] In the formula:

[0114] Y-Non-metallic reinforced flexible composite pipe test pressure

[0115] X — Failure time of the non-metallic reinforced flexible composite pipe under this pressure condition

[0116] At a temperature of 60℃, when the pressure of the non-metallic reinforced flexible composite pipe reaches the threshold of 50% (the sample test pressure is 50% of the room temperature limit pressure, i.e., 16MPa), the corresponding exposure time X can be obtained by substituting into equation (5), which is 260615h (10859 days, 29.75 years).

[0117] 3) Conduct logarithmic linear fitting of pressure and failure time at a temperature of 75℃:

[0118] Table 7. Failure time at different test pressures at 75℃

[0119] Test pressure (MPa) Failure time (h) 27 10 22 500 20.5 1000 19.5 3000 19 6000 18.5 10000

[0120] Logarithmic linear fitting was performed on the two sets of data (failure time (h) and test pressure (MPa) in Table 7, as shown in the appendix. Figure 2 As shown, the mathematical equation (Equation 6) for the test pressure and failure time of the non-metallic reinforced flexible composite pipe under 75℃ conditions is obtained:

[0121] Y = 10 [-0.05245log10(X)+1.46461] (6)

[0122] In the formula:

[0123] Y—Non-metallic reinforced flexible composite pipe test pressure

[0124] X — Failure time under this pressure condition

[0125] At a temperature of 75℃, when the pressure of the non-metallic reinforced flexible composite pipe reaches 50% of the threshold (the sample test pressure is 50% of the room temperature limit pressure, i.e., 16MPa), the corresponding exposure time X can be obtained by substituting into equation (6), which is 92564.6h (3856.8 days, 10.56 years).

[0126] 4) Conduct logarithmic linear fitting of pressure and failure time at a temperature of 90℃:

[0127] Table 8. Failure time at different test pressures at 90℃

[0128]

[0129]

[0130] Logarithmic linear fitting was performed on the two sets of data (failure time (h) and test pressure (MPa) in Table 8, as shown in the appendix. Figure 3 As shown, the mathematical equation (Equation 7) for the test pressure and failure time of the non-metallic reinforced flexible composite pipe under 90℃ conditions is obtained:

[0131] Y = 10 [-0.0658log10(X)+1.47414] (7)

[0132] In the formula:

[0133] Y—Non-metallic reinforced flexible composite pipe test pressure

[0134] X — Failure time under this pressure condition

[0135] When the pressure of the non-metallic reinforced flexible composite pipe reaches 50% of the threshold (the sample test pressure is 50% of the room temperature limit pressure, i.e., 16MPa) at a temperature of 90℃, the corresponding exposure time X can be obtained by substituting into equation (7), which is 12695.45h (529 days, 1.45 years).

[0136] 5) Establish the Arrhenius equation

[0137] The test time t when the failure pressure P of the non-metallic reinforced flexible composite pipe is reduced by 50% under conditions T1, T2, and T3. 50 The corresponding parameters are shown in Table 9.

[0138] Table 9 Time-temperature parameters at different simulation temperatures

[0139] type Simulated temperature 1 Simulated temperature 2 Simulated temperature 3 T(℃) 60 75 90 T(K) 333 348 363 1 / T(K) 0.003003 0.002874 0.002755 <![CDATA[t 50 (h)]]> 260615 92564.6 12695.45 ln(1 / t) -12.47 -11.44 -9.45

[0140] The experimental temperature 1 / T (K) and time ln(1 / t) (h) data in Table 9 were fitted using an exponential function, as shown in the attached figure. Figure 4 As shown, the temperature-time Arrhenius equation (Equation 8) for non-metallic reinforced flexible composite tubes is obtained:

[0141] ln(1 / t)=-13.36178+53158300*exp(-1 / T / 0.000167734) (8)

[0142] In the formula:

[0143] T — Temperature (K)

[0144] t—Time (h) when the failure pressure reaches 50% of the threshold.

[0145] 6) Lifespan estimation:

[0146] Substituting the different service temperatures of the pipe into formula (8), we can obtain the service life of the pipe under the clear water environment conditions in the oilfield at different temperatures, as shown in Table 10.

[0147] Table 10 Service life under different temperature and medium conditions

[0148]

[0149] Since the test medium is pure water, the service life needs to be reduced depending on the transport medium. Depending on the transport medium, a medium correction factor can be introduced to further obtain the service life under different media environments, as shown in Table 11.

[0150] a) The transported oilfield wastewater is 0.9;

[0151] b) The reduction factor is 0.8 when transporting liquid hydrocarbons and multiphase fluids;

[0152] c) The reduction factor is 0.67 when transporting gas;

[0153] The reduction factor is 0.81 when transporting high-pressure sulfur-containing gaseous media.

[0154] d) In cases where multiple operating conditions overlap, a reduction factor can be considered for superposition processing to ensure long-term safe service.

[0155] Table 11 Service life under different temperature and medium conditions

[0156]

[0157] By replacing the non-metallic reinforced flexible composite pipe in the above embodiments with a full-size non-metallic pipe for oil and gas field environments, including metal-reinforced flexible composite pipes, fiberglass pipes, PE pipes, and plastic alloy pipes, the life prediction method disclosed in this invention can also be used.

[0158] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for predicting the lifespan of a full-size non-metallic reinforced flexible composite pipe, characterized in that, Includes the following steps: S1: Cut test samples from a section of full-size non-metallic reinforced flexible composite pipe and process the test samples into standard specimens. S2: Under room temperature conditions, a water immersion compression burst test is performed on a standard specimen to obtain the ultimate compressive strength P of the standard specimen at room temperature. y ; Then, three different test temperatures T1, T2, and T3 were selected, and six test pressures P1, P2, P3, P4, P5, and P6 were selected for each test temperature. S3: Using three different test temperatures T1, T2 and T3, and six test pressures P1, P2, P3, P4, P5 and P6 corresponding to each test temperature as the conditions for immersion pressure burst test, the standard sample is subjected to immersion pressure burst test to obtain the failure time t1, t2, t3, t4, t5 and t6 of the standard sample under the corresponding test pressure at the three different test temperatures; S4: Based on the six test pressures P1, P2, P3, P4, P5, P6 and the failure times t1, t2, t3, t4, t5, and t6, a linear fit is performed to establish a linear formula for failure time and test pressure at different test temperatures; the ultimate bearing strength P of the standard specimen at room temperature is then used as the basis for this formula. y Substituting 50% of the value into the linear formula for failure time and test pressure at different test temperatures, the ultimate bearing strength P of the full-size non-metallic reinforced flexible composite pipe at different test temperatures is obtained. y Failure time t when reduced by 50% 501 t 502 t 503 ; S5: Based on three different test temperatures T1, T2, and T3, and the obtained t 501 t 502 t 503 By performing fitting, the ultimate bearing strength P of the full-size non-metallic reinforced flexible composite pipe under different test temperatures was established. y Arrhenius formula for reducing failure time by 50%; S6: When the actual working temperature of the full-size non-metallic reinforced flexible composite pipe is T, substitute the actual working temperature T into the Arrhenius formula obtained in S5 to predict the life of the full-size non-metallic reinforced flexible composite pipe.

2. The method for predicting the lifespan of a full-size non-metallic reinforced flexible composite pipe according to claim 1, characterized in that, In S1, the standard sample meets the requirements of the water pressure burst test and the hydrostatic pressure test.

3. The method for predicting the lifespan of a full-size non-metallic reinforced flexible composite pipe according to claim 1, characterized in that, In S2, the three different test temperatures T1, T2 and T3 increase sequentially, with T2 being 15°C higher than T1 and T3 being 15°C higher than T2.

4. The method for predicting the lifespan of a full-size non-metallic reinforced flexible composite pipe according to claim 3, characterized in that, The temperatures T1, T2, and T3 are 60℃, 75℃, and 90℃, respectively.

5. The method for predicting the lifespan of a full-size non-metallic reinforced flexible composite pipe according to claim 1, characterized in that, In S2, the test pressures P1, P2, P3, P4, P5, and P6 are selected based on the ultimate bearing strength P of the standard specimen at room temperature. y For reference, P1, P2, P3, P4, P5, and P6 are greater than the ultimate bearing strength P of the standard specimen at room temperature. y One-third of the total, and there is a logarithmic relationship between P1, P2, P3, P4, P5, and P6.

6. The method for predicting the lifespan of a full-size non-metallic reinforced flexible composite tube according to claim 1, characterized in that, The inner lining of the full-size non-metallic reinforced flexible composite pipe is high-density polyethylene or cross-linked polyethylene, and the reinforcing layer is polyester fiber.

7. The method for predicting the lifespan of a full-size non-metallic reinforced flexible composite pipe according to claim 1, characterized in that, In S4, the linear formula for failure time and test pressure under different test temperatures is: Y＝10 [alog10(X)+b] ； Where Y represents a test pressure, X represents the failure time of the standard sample under that test pressure, and a and b are constants.

8. The method for predicting the lifespan of a full-size non-metallic reinforced flexible composite pipe according to claim 1, characterized in that, In S5, the method is based on three different test temperatures T1, T2, and T3, and the obtained t 501 t 502 t 503 The fitting method employed was an exponential function to obtain the ultimate compressive strength P of the full-size non-metallic reinforced flexible composite pipe at different temperatures. y Arrhenius formula for reducing failure time by 50%.

9. The method for predicting the lifespan of a full-size non-metallic reinforced flexible composite pipe according to claim 8, characterized in that, The full-size non-metallic reinforced flexible composite pipe was tested at different temperatures and its ultimate bearing capacity P. y The Arrhenius formula for reducing failure time by 50% is: Where T represents different test temperatures, and t represents the ultimate pressure bearing strength P of the full-size non-metallic pipe used in oil and gas field environments. y Failure time when reduced by 50%; y0, A1, and t1 are constants.

10. The method for predicting the lifespan of a full-size non-metallic reinforced flexible composite tube according to claim 1, characterized in that, In S4, logarithmic linear fitting is performed based on the six test pressures P1, P2, P3, P4, P5, and P6, as well as the obtained pipe failure times t1, t2, t3, t4, t5, and t6, to establish linear formulas for different test temperatures and test pressures.

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