Dynamical mechanics behavior and safety analysis of deep water riser considering the normal drilling condition and hang-off condition

2020 ◽  
Vol 199 ◽  
pp. 106996 ◽  
Author(s):  
Liangjie Mao ◽  
Song Zeng ◽  
Qingyou Liu ◽  
Guorong Wang ◽  
Yufa He
Author(s):  
Zhu Yuan ◽  
Liu Kang ◽  
Chan Guoming

Abstract Deep-water natural gas hydrate has high environmental risk and high technical difficulty in drilling and production. In order to promote the development of gas hydrate, we develop the assessment methods and control technologies for the operation risk during hydrate drilling and production. The work completed includes: (1) Safety analysis of conductor and wellhead for the hydrate drilling and production Establish a pipe-wellhead stability model to determine the drilling and working conditions under different working conditions. (2) Risk assessment of wellbore blockage in hydrate drilling and production Construct a wellbore multiphase flow analysis model to determine the amount of drilling inhibitor injection; obtain the location and extent of the hydrate blockage. (3) Risk assessment of wellbore instability in hydrate production Combined with hydrate formation properties, ground stress distribution and casing mechanics model, the position of the formation instability, and the damage of casing crushing is determined. (4) Gas diffusion risk assessment due to hydrate decomposition in water Study the distribution of underwater gas diffusion formed by large-area decomposition of hydrate to get the overflow flow risk. (5) Safety model and process risk assessment of hydrate drilling operations Conduct hazard identification and operation safety analysis of hydrate drilling operations, determine the risk level of each operation stage, and support the drilling operation.


1988 ◽  
Vol 62 (01) ◽  
pp. 1-8 ◽  
Author(s):  
Ronald E. Martin

The utility of benthic foraminifera in bathymetric interpretation of clastic depositional environments is well established. In contrast, bathymetric distribution of benthic foraminifera in deep-water carbonate environments has been largely neglected. Approximately 260 species and morphotypes of benthic foraminifera were identified from 12 piston core tops and grab samples collected along two traverses 25 km apart across the northern windward margin of Little Bahama Bank at depths of 275-1,135 m. Certain species and operational taxonomic groups of benthic foraminifera correspond to major near-surface sedimentary facies of the windward margin of Little Bahama Bank and serve as reliable depth indicators. Globocassidulina subglobosa, Cibicides rugosus, and Cibicides wuellerstorfi are all reliable depth indicators, being most abundant at depths >1,000 m, and are found in lower slope periplatform aprons, which are primarily comprised of sediment gravity flows. Reef-dwelling peneroplids and soritids (suborder Miliolina) and rotaliines (suborder Rotaliina) are most abundant at depths <300 m, reflecting downslope bottom transport in proximity to bank-margin reefs. Small miliolines, rosalinids, and discorbids are abundant in periplatform ooze at depths <300 m and are winnowed from the carbonate platform. Increased variation in assemblage diversity below 900 m reflects mixing of shallow- and deep-water species by sediment gravity flows.


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