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22. Sensitivity analysis of reservoir risk in marine gas hydrate drilling

Author

Sun, Wantong, primary, Pei, Jun, additional, Wei, Na, additional, Zhao, Jinzhou, additional, Xue, Jin, additional, Zhou, Shouwei, additional, Zhang, Liehui, additional, Kvamme, Bjørn, additional, Li, Qingping, additional, Li, Haitao, additional, Jiang, Lin, additional, Zhang, Chao, additional, and Li, Cong, additional

Published
2021
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26. Wellbore Temperature and Pressure Field in Deep-water Drilling and the Applications in Prediction of Hydrate Formation Region

Author

Sun, Wantong, primary, Wei, Na, additional, Zhao, Jinzhou, additional, Zhou, Shouwei, additional, Zhang, Liehui, additional, Li, Qingping, additional, Jiang, Lin, additional, Zhang, Yao, additional, Li, Haitao, additional, Xu, Hanming, additional, Li, Cong, additional, Shen, Xuncheng, additional, and Xiong, Chenyang, additional

Published
2021
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36. Routes to hydrate formation from water dissolved in gas and impact of mineral surfaces

Author

Kvamme, Bjørn, Wei, Na, Zhao, Jinzhou, Zhou, Shouwei, Zhang, Liehui, Sun, Wantong, and Saeidi, Navid

Abstract

Mineral surfaces adsorb water to extreme densities and corresponding low chemical potentials. This results in a dual effect in terms of hydrate. Water and slightly polar components adsorb directly on mineral surfaces and generate efficient conditions for hydrate nucleation. But due to the extremely low chemical potential of adsorbed water the hydrate nuclei formed towards mineral surfaces have to either detach from the vicinity of mineral surfaces, or be bridged by structured water in a dynamic attachment of hydrate cores some few nm outside mineral surfaces. During transport of gas (CH4, gas mixtures, CO2) the conventional water dew-point analysis will typically result in a substantially higher acceptable water concentration as compared to the concentration for adsorption of water from gas to rust surface. Direct formation of hydrate from water dissolved in gas is thermodynamically feasible, as discussed in open literature. In this work we demonstrate that it is also feasible in terms of mass transport. A new theory for enthalpy of hydrate dissociation has been extended to also direct hydrate formation from water dissolved in gas. The remaining question is whether direct hydrate formation from gas is also feasible in terms of transporting the hydrate formation heat away through a heat insulating medium. We propose further research strategies to enlighten this issue. Addition of glycols to critical points in processing of gas or transport is already in use by companies like for instance EQUINOR. There is, however, a need for more work on how efficient it is and if it can also be used for multiphase transport of hydrocarbons with significant water cut. Some research activities are in progress and briefly outlined here.

Published
2021
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39. Research on intelligent judgment method of natural gas hydrate drilling risk

Author

Li, Haitao, Ge, Zhaolong, Wei, Na, Sun, Wantong, Zhang, Yao, Xue, Jin, Jiang, Lin, Pei, Jun, Liao, Bing, Cao, Hongliang, Zhang, Ruixu, Li, Shuangli, Lu, Qixia, and Luo, Jinyan

Abstract

There are many emergency risks in the process of natural gas hydrate (NGH) drilling. In order to ensure the safe and efficient exploitation of NGH, it is urgent to establish an intelligent judgment method for the risks in the process of NGH drilling. In this paper, the response relationship between monitoring parameters and risk categories of NGH while drilling is established. Based on fuzzy analytic hierarchy process (FAHP), the comprehensive weights of 10 risk monitoring parameters are obtained, including gas production, wellbore instability, hydrate ice barrier, drill string fracture, sticking, bit balling, drilling tool piercement, gas seepage, seabed subsidence and seabed landslide. Besides, the comprehensive judgment weight matrix is constructed, and the reasonable fluctuation range of monitoring parameters is formed. Thus, the intelligent judgment method of NGH drilling risk is established. The intelligent judgment and alarm of NGH drilling risks can be realized quickly and accurately by this method, namely, it can monitor the risks in the process of operation and guarantee the construction safety of NGH drilling.

Published
2021
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40. Weekly variation in quality of care for acute ST-segment elevation myocardial infarction by day and time of admission: a retrospective observational study.

Author

Wang C, Li X, Sun W, Li J, Wang Y, Bao X, Liu M, and Zhang Q

Subjects
Hospitalization, Humans, Quality of Health Care, Retrospective Studies, Treatment Outcome, Percutaneous Coronary Intervention, ST Elevation Myocardial Infarction therapy
Abstract

Background: The admission time of patients with ST-segment elevation myocardial infarction (STEMI) may affect the quality of care they receive. This study aimed to explore the pattern and magnitude of variation in quality of care for patients with STEMI in both the process and outcome domains., Methods: We performed a retrospective study based on STEMI data from China. We estimated the adjusted ORs of six process indicators and one outcome indicator of STEMI care quality by fitting multilevel multivariable regression models across 42 4hour time periods per week., Results: The study cohort comprised 98 628 patients with STEMI. Care quality varied by time of arrival to the emergency department. We identified three main patterns of variation, which were consistent across days of the week. In the first pattern, which applied to electrocardiographic examination within 10 min of arrival and to aspirin or clopidogrel use within 10 min of arrival, quality was lowest for arrivals between 08:00 and 12:00, rose through the day and peaked for arrivals between 24:00 and 04:00. Percutaneous transluminal coronary intervention treatment within 90 min showed the same pattern but with maximal performance for those arriving 20:00-24:00. In the third pattern, applying to lipid function evaluation within 24 hours and beta blocker use within 24 hours, quality was best for arrivals between 04:00-08:00 and 16:00-19:00 and worst for arrivals between 24:00-04:00 and 12:00-16:00., Conclusions: The quality of care for STEMI shows three patterns of diurnal variation. Detecting the times at which quality is relatively low may lead to quality improvement in healthcare. Quality improvement should focus on reducing the weekend effect and off-hour effect and the diurnal temporal variation., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2021. No commercial re-use. See rights and permissions. Published by BMJ.)

Published
2021
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