CN-122016619-A - Non-adhesive flexible pipe CO2Stress corrosion test system and method

CN122016619ACN 122016619 ACN122016619 ACN 122016619ACN-122016619-A

Abstract

The invention discloses a system and a method for testing stress corrosion of a non-bonded flexible pipe CO 2 , and relates to the technical field of marine engineering and oil and gas equipment tests. The system comprises a base and a support frame, wherein an axial loading device, an internal pressure and torsion loading device, a follow-up bending moment balancing device and an end follow-up sealing device are arranged on the base, and a movable lifting environmental cabin device is arranged on the support frame. The follow-up bending moment balancing device and the end follow-up sealing device form a flexible boundary constraint system, the movable lifting environment cabin device is used for locally forming a high-temperature high-pressure CO2 corrosion environment on the outer wall of the flexible pipe, and can axially move along the flexible pipe and synchronously lift along with bending displacement in the alternating bending loading process, so that the position of a corrosion area is maintained stable under a dynamic load condition, and the real simulation and quantitative evaluation of the CO2 stress corrosion behavior of the unbonded flexible pipe under the actual service working condition are realized through the collaborative design of multi-load coupling loading, local movable corrosion environment and multi-source online monitoring.

Inventors

FU GUANGMING
LIU YUAN
LIU SHUHAN
HE YIJIA
HU YIHAO
WANG ZHIYUAN
SUN BAOJIANG

Assignees

中国石油大学(华东)

Dates

Publication Date: 20260512
Application Date: 20260203

Claims (8)

1. The non-bonding flexible pipe CO 2 stress corrosion test system is characterized by comprising a base and a support frame, wherein an axial loading device, an internal pressure and torsion loading device, a follow-up bending moment balancing device and an end follow-up sealing device are arranged on the base; The base is provided with a bottom sliding rail along the axial direction of the base, the axial loading device is fixed on the base, the bottoms of the internal pressure and torsion loading device, the follow-up bending moment balancing device and the end follow-up sealing device are all connected with a bottom plate, the bottom plate is provided with a sliding block, and the sliding block is matched with the bottom sliding rail to realize movable connection with the base; The movable lifting environmental chamber device comprises a movable telescopic environmental chamber body and a movable telescopic environmental chamber base, wherein the movable telescopic environmental chamber base is matched with the top sliding rail to realize free sliding of the movable lifting environmental chamber device; Alternating bending loading devices are arranged on two sides of the movable lifting environmental chamber device and are movably connected with the bottom sliding rail; The bottom connecting bottom plate connected with the follow-up bending moment balancing device is provided with a longitudinal sliding rail, the bottom of the follow-up bending moment balancing device is provided with a sliding block, and the sliding block is embedded into the longitudinal sliding rail to realize the longitudinal movement of the follow-up bending moment balancing device.
2. The system for testing the stress corrosion of the non-bonded flexible pipe CO 2 according to claim 1, wherein limiting blocks are arranged on the bottom sliding rail between the axial loading device and the internal pressure and torsion loading device on the bottom sliding rail, between the follow-up bending moment balancing device and the alternating bending loading device and between the alternating bending loading device and the end follow-up sealing device, and the end limiting block is arranged at the right end of the bottom sliding rail.
3. The system of claim 1, wherein the axial loading device comprises an axial loading actuator and an axial force sensor, the axial loading actuator applies a tensile or compressive load through the axial force sensor, the flange joint and the thrust axial internal pressure and torsion loading device, the internal pressure and torsion loading device comprises an outer sleeve, the outer sleeve is internally provided with a torsion loading actuator, the torsion loading actuator is connected with a coaxial torsion shaft, the torsion loading actuator is connected with a rotary pressure-supply joint, and the rotary pressure-supply joint is matched with the air inlet/liquid outlet so as to maintain the connectivity and the tightness of a medium in the test piece during the application of the torsion load.
4. The stress corrosion test system for the non-bonded flexible pipe CO 2 , according to claim 1, wherein the follow-up bending moment balancing device and the end follow-up sealing device form a follow-up sealing and bending moment balancing structure for the non-bonded flexible pipe, the follow-up bending moment balancing device comprises an outer spherical surface structure formed by an upper outer spherical surface sealing element and a lower outer spherical surface sealing element, a sealing joint is arranged inside the outer spherical surface structure, an inner spherical surface structure is wrapped on the outer spherical surface structure, the inner spherical surface structure is formed by an upper fixed outer spherical surface groove and a lower fixed outer spherical surface groove, a spherical surface pair is formed by the inner spherical surface structure and the outer spherical surface structure, a spherical surface lateral limiting block and a spherical surface bottom limiting bolt are arranged on the groove of the inner spherical surface structure, and a follow-up bending moment balancing device base is connected on the lower fixed outer spherical surface groove.
5. The system of claim 1, wherein the alternating bending loading device comprises an upper limit roller press head, a lower limit roller press head, a servo hydraulic cylinder and an alternating bending device telescopic shaft, the upper limit roller press head and the lower limit roller press head form a constraint space allowing the flexible pipe to axially move and laterally limit, the press-in amount/roller displacement sensor is arranged in the upper limit roller press head, the force sensor is arranged in the lower limit roller press head, and the stroke displacement sensor is arranged in the telescopic shaft.
6. The non-bonded flexible pipe CO 2 stress corrosion test system as defined in claim 1, wherein two isolation seal rings are disposed in the enclosure of the movable telescopic environmental chamber, a cavity is formed in the enclosure, and a reaction chamber No. 1, a reaction chamber No. 2, a reaction chamber No. 3, a heating chamber and a cooling chamber are disposed in the cavity.
7. A non-bonded flexible pipe CO 2 stress corrosion test system as defined in claim 1, wherein the internal pressure and torsion loading means is provided with an in-pipe gas/liquid inlet pipe and an in-pipe gas/liquid outlet pipe.
8. A method of testing CO 2 stress corrosion in a non-bonded flexible pipe using a system as defined in any one of claims 1 to 7, comprising the steps of: S1, clamping a non-bonded flexible pipe test piece on a test system, enabling one end of the non-bonded flexible pipe test piece to be in sealing connection with a follow-up bending moment balancing device, and enabling the other end of the non-bonded flexible pipe test piece to sequentially pass through an alternating bending loading device and a movable lifting environmental chamber device and then be in sealing connection with an end follow-up sealing device; s2, removing an outer sheath layer of the non-bonded flexible pipe test piece in the target test section, and axially moving the non-bonded flexible pipe test piece to enable the movable lifting environment cabin device to form a local sealed high-temperature high-pressure corrosion environment space with the outer wall of the target test section; S3, introducing a CO 2 medium and an electrolyte medium into a corrosion environment space of the movable lifting environment cabin device, and regulating and controlling the temperature and the pressure of the corrosion environment space to a preset test working condition; S4, applying one or more of internal pressure, stretching, compressing, torsion and alternating bending load to the test piece through the load control subsystem, controlling the movable lifting environmental chamber device to lift and adjust the position along with the fluctuation of alternating bending displacement in the process of applying the alternating bending load, and realizing independent loading or combined loading of the load in a follow-up state of the end part of the test piece; S5, synchronously collecting strain, displacement, bending curvature, leakage, internal pressure and acoustic emission signals and/or crack expansion related monitoring signals along the axial direction of the test piece in the test process, and carrying out correlation processing on the collected signals, the load parameters and the environmental parameters to obtain a stress corrosion cracking process monitoring result of the test piece in the CO 2 corrosion environment. S6, after the set test time or failure criterion is reached, the alternating bending/torsion/axial load is unloaded in sequence, the internal pressure is released, then the environmental chamber is cooled and depressurized, CO 2 and corrosive medium are recovered, the sample is disassembled, and crack morphology, corrosive products and failure mode analysis are carried out on the target test section.

Description

Non-bonded flexible pipe CO 2 stress corrosion test system and method Technical Field The invention relates to the technical field of marine engineering and oil and gas equipment tests, in particular to a system and a method for testing stress corrosion of a non-bonded flexible pipe CO 2. Background With the development of ocean oil and gas resources to deep water/ultra-deep water, the non-bonded flexible pipe is widely applied to wellhead connection and conveying systems due to the characteristics of excellent mechanical properties, convenience in transportation and installation and the like. The non-bonded flexible pipe is generally composed of a multi-layer structure such as a framework layer, an inner sheath layer, a compression-resistant armor layer, a tension-resistant armor layer, an outer sheath layer and the like. In the actual service process, the flexible pipe is influenced by the motion of the platform and the sea state load besides bearing the internal pressure caused by the conveying medium, and generates complex working conditions such as alternating bending, torsion, axial pulling/pressing and the like, and the flexible pipe presents a stressed state of multi-load and multi-field coupling. When the outer sheath layer is broken or partially failed, external seawater may enter the flexible pipe annulus and form a high-temperature high-pressure corrosion environment rich in CO 2 together with the permeated CO 2. In the environment, the metal armor layer of the flexible pipe is easy to generate corrosion damage, and stress corrosion cracking (CO 2 -SCC) is induced or accelerated under the action of alternating load and stress concentration, so that interlayer damage, bearing capacity degradation, medium leakage and even structural failure are caused, the service life of the flexible pipe is obviously shortened, and the safety and reliability of an ocean oil and gas conveying system are further threatened. The existing research on CO 2 -SCC is concentrated on small-size material samples, the test equipment usually adopts a fixed corrosion cavity and applies a single or few load forms, and service behaviors of the full-size structure of the non-bonded flexible pipe under the conditions of multi-load coupling and dynamic load are difficult to truly reflect. Especially when the internal pressure and alternating bending co-act, the end clamping and sealing sites often introduce additional bending moments or restraining effects, leading to the following problems: (1) The risk of sealing failure is increased, and the test is difficult to stably run for a long time; (2) The boundary condition deviates from the actual service boundary of the flexible pipe, the true stress state of the test sample is distorted, and the effectiveness and comparability of the test result are affected; (3) Additional bending moments may be transmitted to the axial/torsional load actuators, causing loading deviations or equipment anomalies. In addition, the fixed corrosion cavity is generally difficult to carry out local comparison evaluation on different axial pipe sections on the same sample, and is also difficult to flexibly change the contact area/contact mode of the sample under the condition that the volume of the corrosion medium is kept consistent so as to carry out variable control test, thereby leading to insufficient test repeatability and poor result comparability. The system is required to realize long-term stable operation under a high-temperature high-pressure CO 2 -rich corrosion environment, can still apply dynamic loads such as alternating bending and torsion under an internal pressure condition, keeps sealing reliable and a stress boundary real, and is also required to be flexibly arranged along the axial direction of a flexible pipe on the premise of not damaging sealing and loading stability so as to meet the requirements of local corrosion comparison and variable control tests of different pipe sections and simultaneously ensure the continuity and reliability of temperature and pressure regulation and multisource monitoring signal acquisition and transmission processes. Disclosure of Invention Aiming at the defects, the invention provides a test system and a test method capable of effectively simulating the behavior of CO 2 -SCC of a non-bonded flexible pipe under the actual service working condition, and the controllable test of multi-field coupling loading conditions under the high-temperature high-pressure and CO-rich 2 environment is realized. The invention adopts the following technical scheme: The non-adhesive flexible pipe CO 2 stress corrosion test system comprises a base and a support frame, wherein an axial loading device, an internal pressure and torsion loading device, a follow-up bending moment balancing device and an end follow-up sealing device are arranged on the base; The base is provided with a bottom sliding rail along the axial direction of the base, the axial loading device is fixed