Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract： none
Subjects: Mechanics >> Applied Mechanics submitted time 2023-03-20 Cooperative journals: 《应用力学学报》
Abstract： H8b gas reservoir of well hy-A1 in the East China Sea has an abnormally high temperature andhigh pressure formation.The predicted fracture initiation pressure of fracturing design is inconsistent withthat of fracturing operation , resulting in high fracture initiation in operation. In this paper , the mathematicalmodel of high fracture initiation pressure of low permeability reservoir in the East China Sea is establishedby considering the factors of fluid pressure in fracture , including principal stress, wellbore permeability,and fracture dip angle.On-the-spot verification showed that the difference was 4.9% . With the help of di-chotomy , the model is solved , and the results show that with the increase of well deviation , the fracture ini-tiation angle decreases; with the increase of azimuth , the fracture initiation angle increases first and thendecreases until zero, and the fracture initiation pressure generally decreases first and then increases ; withthe increase of azimuth , the fracture initiation pressure has the lowest peak value , and the azimuth of thelowest peak value range is between 50� and 80�. When the azimuth angle is 71� in 0皏ertical well sec-tion , the peak value of minimum initiation pressure is 58.5 MPa;there is a maximum initiation angle in acertain azimuth angle , and the azimuth angle between the maximum initiation angle and the peak value isbetween 60� and 80�. Large stress difference ,small Poisson's ratio and abnormal high pressure are the keyfactors of high initiation pressure.In fracturing design , the azimuth angle and deviation angle should be asclose to the minimum force area of initiation pressure as possible.
Subjects: Mechanics >> Applied Mechanics submitted time 2023-03-20 Cooperative journals: 《应用力学学报》
Abstract： Tectonic fault is one of the main geohaards that occur to long-distance oil and gas pipelines.Large longitudinal strain induced by active fault will lead to pipeline rupture failure.The existing deterministic analysis methods based on strain design are relatively conservative and cannot take into accountthe multiple uncertainties of pipeline structure , circumferential soil or seismic fault displacement. There-fore , this paper proposes a reliability analysis method which takes into account the pipeline geometry , tube-soil interaction , and the uncertainty of fault displacement. Using the pipeline design strain database , theneural network prediction model between the pipeline design strain and the influencing parameters was es-tablished , and then the limit state equation based on the strain was obtained. Through Monte-Carlo simula-tion , the conditional failure probability of pipelines with uncertain parameters such as pipe size parameter ,pipe soil action parameter and intermal pressure under specific fault displacement was calculated. Basedon the probabilistic risk analysis process of fault displacement ( PFDHA ) , the uncertainty of fault displace-ment was considered , and the occurrence probability of each fault displacement during different service pe-riods was obtained. Combined with the obtained failure probability of pipeline conditions , the total failureprobability of pipeline in this service period can be obtained based on the calculation formula of total prob-ability. 'This paper takes the intersection site between XinYueZhe X80 pipeline and Bo -AF located inXinjiang an example to carry out the analysis , and the failure probability of the pipeline section in ten,twenty , thity years of service is obtained.'The results show that the pipeline will meet the target reliabilityrequirements laid down by CSA 7662 over next twenty years. However , if the service life is more thantwenty years,the failure probability of the pipeline will exceed the maximum allowable failure probability ,and the pipeline section at the crossing shall be eauipped with seismic fortification.
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