During the production period of shale gas, proppant particles and rock debris are produced together,which will seriously erode the elbows of gathering pipelines. In response to this problem, this paper takes the elbow...During the production period of shale gas, proppant particles and rock debris are produced together,which will seriously erode the elbows of gathering pipelines. In response to this problem, this paper takes the elbow of the gathering pipeline in the Changning Shale Gas Field as an example to test the erosion rate and material removal mechanism of the test piece at different angles of the elbow through experiments and compares the four erosion models with the experimental results. Through analysis, it is found that the best prediction model for quartz sand-carbon steel erosion is the Oka model. Based on the Oka model, FLUENT software was used to simulate and analyze the law of erosion of the elbow of the gas gathering pipeline under different gas flow velocities, gas gathering pressure, particle size, length of L1,and bending directions of the elbow. And a spiral pipeline structure is proposed to reduce the erosion rate of the elbow under the same working conditions. The results show that this structure can reduce erosion by 34%.展开更多
Hydrogen embrittlement of pipelines depends on the hydrogen-induced cracking behavior of the pipeline steel microstructure.Based on molecular dynamics analysis,the ferrite–cementite(α-Fe/Fe3C)lamellar atomic structu...Hydrogen embrittlement of pipelines depends on the hydrogen-induced cracking behavior of the pipeline steel microstructure.Based on molecular dynamics analysis,the ferrite–cementite(α-Fe/Fe3C)lamellar atomic structure with the Bagaryatskii orientation relationship was established,and stepwise relaxation of the conjugate gradient energy minimization and constant-temperature and constant-pressure relaxation were performed under NPT(the isothermal–isobaric)conditions.The mechanical property curves of theα-Fe/Fe3C models were obtained under different cementite terminal plane structures,and the evolution of the atomic structure was analyzed in detail.In addition,the influence of different hydrogen concentrations,different temperatures,different strain rates,changes in voids,and different micro-degrees of freedom on the deformation and failure mechanism of the model was investigated,aiming to provide a reliable way to explore the micro-mechanism of macro-cracking behavior of pipeline steel.展开更多
The lack of research on flexible drilling tool leads to limited application of ultra-short radius horizontal wells.The flexible drilling tool is different from the conventional drilling tool.The flexible drilling pipe...The lack of research on flexible drilling tool leads to limited application of ultra-short radius horizontal wells.The flexible drilling tool is different from the conventional drilling tool.The flexible drilling pipe involves a mutual transition between the structure and the mechanism during the deformation process.At the same time,the flexible drilling pipe and the eccentric guide tube,the guide tube and the wellbore generate random contact.In this paper,3-D beam elements,universal joint elements,rigid beam elements and the beam-beam contact elements are combined to establish a two-layer contact nonlinear finite element model of the flexible drilling tool in the wellbore.The dynamic relaxation method is introduced for numerical solution.The feasibility of the model and the algorithm is verified by an example.The mechanical analysis of flexible drilling tool under the four hole inclinations in the oblique section is carried out.It is found that the flexible drilling pipe has a“folded line”deformation.The contact force between the flexible drilling pipe and the guide tube is randomly distributed.The contact force between the guide tube and the wellbore in the oblique section is greater than that in the vertical section.As the hole inclinations increase,the torque and axial force transmitted to the drill bit gradually decrease.展开更多
Electrochemical experiments,slow strain rate tensile testing(SSRT),and scanning electron microscopy were used to investigate the effect of various applied potentials on the stress corrosion cracking(SCC)of X80 pipelin...Electrochemical experiments,slow strain rate tensile testing(SSRT),and scanning electron microscopy were used to investigate the effect of various applied potentials on the stress corrosion cracking(SCC)of X80 pipeline steel in acidic soil containing sulfate-reducing bacteria(SRB).The results demonstrated that when the anodic potential was applied,X80 steel exhibited sensitivity to SCC,which was attributed to anodic dissolution.The SCC sensitivity initially decreased,but then increased with a negative shift in the applied potential.At-1200 mV,SCC was the most sensitive,which corresponded to the substantial cathodic polarisation and toxic impact of SRB,which increased the risk of hydrogen embrittlement.At-850 mV,the SCC sensitivity was the lowest because cathodic polarisation suppressed anodic dissolution.The experimental results can contribute to the prevention and management of SCC in operational pipelines.展开更多
基金supported by the Petrochina's “14th Five-Year plan” Project(2021DJ2804)Sichuan Natural Science Foundation(2023NSFSC0422)。
文摘During the production period of shale gas, proppant particles and rock debris are produced together,which will seriously erode the elbows of gathering pipelines. In response to this problem, this paper takes the elbow of the gathering pipeline in the Changning Shale Gas Field as an example to test the erosion rate and material removal mechanism of the test piece at different angles of the elbow through experiments and compares the four erosion models with the experimental results. Through analysis, it is found that the best prediction model for quartz sand-carbon steel erosion is the Oka model. Based on the Oka model, FLUENT software was used to simulate and analyze the law of erosion of the elbow of the gas gathering pipeline under different gas flow velocities, gas gathering pressure, particle size, length of L1,and bending directions of the elbow. And a spiral pipeline structure is proposed to reduce the erosion rate of the elbow under the same working conditions. The results show that this structure can reduce erosion by 34%.
基金Financial support from the Scientific and Technological Innovation Team for the Safety of Petroleum Tubular Goods at the Southwest Petroleum University(Grant No.2018CXTD01)“The Young Scholars”Development Fund of the Southwest Petroleum University of China is appreciated.
文摘Hydrogen embrittlement of pipelines depends on the hydrogen-induced cracking behavior of the pipeline steel microstructure.Based on molecular dynamics analysis,the ferrite–cementite(α-Fe/Fe3C)lamellar atomic structure with the Bagaryatskii orientation relationship was established,and stepwise relaxation of the conjugate gradient energy minimization and constant-temperature and constant-pressure relaxation were performed under NPT(the isothermal–isobaric)conditions.The mechanical property curves of theα-Fe/Fe3C models were obtained under different cementite terminal plane structures,and the evolution of the atomic structure was analyzed in detail.In addition,the influence of different hydrogen concentrations,different temperatures,different strain rates,changes in voids,and different micro-degrees of freedom on the deformation and failure mechanism of the model was investigated,aiming to provide a reliable way to explore the micro-mechanism of macro-cracking behavior of pipeline steel.
基金support from the Natural Science Foundation of China(Grant numbers:51674088)supported by National Natural Science Foundation of China(Grant No.51674088).
文摘The lack of research on flexible drilling tool leads to limited application of ultra-short radius horizontal wells.The flexible drilling tool is different from the conventional drilling tool.The flexible drilling pipe involves a mutual transition between the structure and the mechanism during the deformation process.At the same time,the flexible drilling pipe and the eccentric guide tube,the guide tube and the wellbore generate random contact.In this paper,3-D beam elements,universal joint elements,rigid beam elements and the beam-beam contact elements are combined to establish a two-layer contact nonlinear finite element model of the flexible drilling tool in the wellbore.The dynamic relaxation method is introduced for numerical solution.The feasibility of the model and the algorithm is verified by an example.The mechanical analysis of flexible drilling tool under the four hole inclinations in the oblique section is carried out.It is found that the flexible drilling pipe has a“folded line”deformation.The contact force between the flexible drilling pipe and the guide tube is randomly distributed.The contact force between the guide tube and the wellbore in the oblique section is greater than that in the vertical section.As the hole inclinations increase,the torque and axial force transmitted to the drill bit gradually decrease.
基金the Joint Fund of Natural Science Foundation of Liaoning Province(Grant No.2020-HYLH-14)the Natural Science Foundation of Liaoning Province(2022-MS-362)。
文摘Electrochemical experiments,slow strain rate tensile testing(SSRT),and scanning electron microscopy were used to investigate the effect of various applied potentials on the stress corrosion cracking(SCC)of X80 pipeline steel in acidic soil containing sulfate-reducing bacteria(SRB).The results demonstrated that when the anodic potential was applied,X80 steel exhibited sensitivity to SCC,which was attributed to anodic dissolution.The SCC sensitivity initially decreased,but then increased with a negative shift in the applied potential.At-1200 mV,SCC was the most sensitive,which corresponded to the substantial cathodic polarisation and toxic impact of SRB,which increased the risk of hydrogen embrittlement.At-850 mV,the SCC sensitivity was the lowest because cathodic polarisation suppressed anodic dissolution.The experimental results can contribute to the prevention and management of SCC in operational pipelines.
