Analysis of Deep Water Single Point Moorings

Author(s):  
John H. Nath
Keyword(s):  
Author(s):  
Marcelo Torres Piza Paes ◽  
Antonio Marcos Rego Motta ◽  
Lauro Lemos Lontra Filho ◽  
Juliano Ose´ias de Morais ◽  
Sine´sio Domingues Franco

Scratching abrasion due to rubbing against the sediment layer is an important degradation mechanism of flexible cable in deep water oil and natural gas exploitation. The present study was initiated to gain relevant data on the wear behaviour of some commercial materials used to externally protect these cables. So, Comparison tests were carried out using the single-point scratching technique, which consists of a sharp point mounted at the extremity of a pendulum. The energy dissipated during the scratching is used to evaluate the relative scratch resistance. The results showed, that the contact geometry strongly affects the specific scratching energy. Using SEM imaging, it was found, that these changes were related to the operating wear mechanisms. The observed wear mechanisms are also compared with those observed on some cables in deep water operations.


2006 ◽  
Vol 46 (1) ◽  
pp. 405
Author(s):  
B. Beinart

The Kuito field lies in the offshore Cabinda Province, Angola. Kuito was Angola’s first deep-water oil and came on stream in December 1999. Kuito oil is produced via an FPSO. Kuito oil ranges 18–22 API. The FPSO has threephase, horizontal, gravity separation vessels that are used to separate oil and gas from unwanted produced water and solids prior to transportation. The production separators were designed with traditional, single point transmitters for measurement of the fluid interface and overall fluid levels. These were capacitance type instruments mounted inside the vessels in stilling wells.Following production start-up, separation problems began to emerge; these were manifested in numerous process upsets and shutdowns. Kuito oil can form emulsions quickly, and calcium naphthenate is produced at higher temperatures. If allowed to cool, it solidifies. The point instrumentation was unable to detect these emulsion and naphthenate layers resulting in the instrumentation becoming fouled and ceasing to function. The separators were operated ‘blind’, using tri-cocks located on the side of the vessel, and as the instrumentation was installed in stilling wells inside the vessel, it was impossible to maintain them without shutting down and depressurising the vessels. This paper describes how nucleonic profiling instruments were retrofitted to the vessels and shows how their operation was able to identify the different layers within the separators. This enabled the time of oil production to be increased and allowed the pro-active use of effect chemicals such as emulsion breakers and defoamers to be applied before the plant became unstable.


Author(s):  
Ning He ◽  
Cheng Zhang ◽  
Zhuang Kang ◽  
Youwei Kang ◽  
Changhong Wang

Abstract In order to ensure the safety of the single point moored shuttle tanker in waves, the numerical model of a shuttle tanker moored with a fixed point was established on the basis of radiation / diffraction theory and pressure integral method in this paper, which was further checked by a series of model tests. Then the plane motion characteristics of the tanker like fishtailing oscillation were analyzed by applying the combined approach of numerical simulation and model test. On this basis, the effects of wave and ballast conditions as well as mooring line length and stiffness on the plane motion of the single point moored tanker were investigated by means of model test. Overall, the research can provide a reference for the design and safety assessment of deep-water offloading system, and give the technical support for the engineering development of deep-water oil and gas projects.


1970 ◽  
Vol 96 (4) ◽  
pp. 815-833
Author(s):  
John H. Nath ◽  
Michael P. Felix
Keyword(s):  

2015 ◽  
Author(s):  
Simanta Hazarika ◽  
Niladri Sinha ◽  
Rajeev Bansal ◽  
Rajan Jayaram
Keyword(s):  

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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