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Ren C.,Southwest Petroleum University | Zhu M.,Southwest Petroleum University | Du L.,Southwest Branch of China Petroleum Engineering Co. | Chen J.,Southwest Petroleum University | And 3 more authors.
International Journal of Electrochemical Science | Year: 2014

An investigation on the galvanic corrosion of dissimilar metals in CO2/H2S environments to simulate annulus pressure between casing and tubing string in sour gas well was conducted by methods of electrochemical measurement technique, high-pressure and high-temperature corrosion test and corrosion scale analysis. When C110 steel is coupled with 17-4 stainless steel or 718 nickel-base alloy, the galvanic effect is obviously found due to looser scale. The galvanic corrosion strongly depends on coupled material, environmental temperature, medium phase and annulus protection fluid. To mitigate galvanic corrosion, the two-metal casing joint should be placed in vapor or immersed in annulus protection fluid. © 2015 The Authors.

Li P.,Southwest Branch of China Petroleum Engineering Co. | Tao Y.,Zhejiang University | Zhou J.,Zhejiang University
Natural Gas Industry | Year: 2013

The stress-based criteria have long been adopted as the major guideline in the design of line pipes, but for those under the displacement control, such as pipelines in seismic regions, landslide areas and subsea environment, the stress-based criteria tend to be relatively conservative, instead the strain-based criteria will be more economic and reasonable to use in the pipe design. Hence, the strain-based design methods in different international standards were summarized and compared, as well as their applicable conditions. In view of the different formulas of the ultimate compressive strain of local buckling in the standards of Norway, Canada, etc., calculations of the ultimate compressive strain were conducted under different radius-thickness ratios and design pressures. It is revealed that the Canadian standard expression and Japanese SUZUKI formula are more conservative. To meet the demand of real engineering application, it was suggested that 0.3 t/D (t refers to the pipe wall thickness; D refers to the external diameter of pipes) be adopted as a conservative estimation of the ultimate compressive strain in the absence of design pressure, and that the Canada standard expression be employed while the design pressure can not be ignored. Because the strain-based design process has not been proposed in the Chinese pipeline codes, the work of this paper can serve as a reference for the research in the relevant areas in present China.

Zhu Z.,Carnegie Mellon University | Zhao X.,Southwest Branch of China Petroleum Engineering Co.
Natural Gas Industry | Year: 2013

When a pure carbohydrate compound is developed as a novel combustion fuel, its physical properties of each component will be first necessarily predicted and screened. However, the experimental determination of these properties for a huge amount of molecules can be very time-consuming and costly. In view of this, the artificial neural network - quantitative structure-property relationships (ANN-QSPR) algorithm was applied to build the desired models. Molecular descriptors were calculated based on a large number of pure components with evaluated values in DIPPR 801 database and the software package DragonX. The models developed were combinations of QSPR and two-layer feed-forward ANN. Thus the relatively comprehensive and reliable models were developed for predicting physical properties, including normal boiling point, flash point, enthalpy of combustion, enthalpy of vaporization, liquid density, surface tension, liquid viscosity, melting point, etc. For improving the consistency, principal component analysis (PCA) was introduced to further eliminate the dimensions of molecular descriptor values. Finally, the idea of cross-validation for consensus modeling is further utilized to improve the predictive quality of obtained models.

Cen K.,Southwest Petroleum University | Jiang X.,Southwest Petroleum University | Yang J.,Southwest Branch of China Petroleum Engineering Co. | Zhu Y.,Southwest Petroleum University
Xinan Shiyou Daxue Xuebao/Journal of Southwest Petroleum University | Year: 2016

The hydrate freeze-plugging phenomenon is easy to occur in pipelines during the open period of natural gas wells especially for wells with high pressure. The dynamic characteristics and optimal hydrate control schemes during well opening period, however, have not been studied systematically. So the specific dynamic models have been established to analyze the dynamic characteristics during well opening period by Dynsim package. The influences of the fluid flowrate, installation modes of pipelines, thickness of thermal insulation layer as well as throttling regulation schemes on throttling temperature and pressure during well opening period have been discussed by using the dynamic models. The dynamic characteristics of heat transfer between fluid in pipelines and ambient environment during well opening period have also been analyzed. In addition, the optimal control schemes for hydrate inhibition during well opening period and optimization design for pipelines have also been put forward in the paper. The results demonstrate that the fluid flowrate during well opening period has dramatical influence on the risk of hydrate formation in pipelines. And no matter how to regulate the fluid flowrate during well opening period, hydrate formation risk in pipelines exists all the time, especially when the flowrate remains small. In order to avoid hydrate formation in pipelines, the fluid flowrate during well opening period should be increased as large as possible by regulating different throttle valves simultaneously or regulating the secondary and tertiary throttle valves mainly. Meanwhile, necessary measures like alcohol injection or heating should be done to mitigate the risk of hydrate formation. Furthermore, it is suggested that the pipelines between wellhead and heating furnace should be buried underground without thermal insulation layer, whereas other overhead pipelines should be covered by thermal insulation layer. © 2016, Science Press. All right reserved.

Zhang G.A.,Hubei Key Laboratory Of Materials Chemistry And Service Failure | Zeng Y.,Hubei Key Laboratory Of Materials Chemistry And Service Failure | Guo X.P.,Hubei Key Laboratory Of Materials Chemistry And Service Failure | Jiang F.,Southwest Branch of China Petroleum Engineering Co. | And 2 more authors.
Corrosion Science | Year: 2012

Through the design of experimental setup, the electrochemical corrosion behavior of carbon steel under dynamic high pressure of H 2S/CO 2 environment was studied by in situ electrochemical measurements and weight loss measurements. Computational fluid dynamics (CFD) was also performed to simulate the flow velocity and shear stress on specimen surface. The results show that both the anodic and cathodic processes are activation controlled. The impedance spectra are characterized by double capacitive semicircles. The in situ electrochemical measurements are in accordance with the CFD simulation of flow velocity and shear stress on the specimen surface. © 2012 Elsevier Ltd.

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