MOORING FLOATING OIL RIGS - NORTHWEST AUSTRALIA

1970 ◽  
Vol 10 (1) ◽  
pp. 100
Author(s):  
S. Stroud
Keyword(s):  
Continental Shelf ◽  
Water Depth ◽  
Drill String ◽  
Weight System ◽  
Oil Exploration ◽  
Sea Floor ◽  
Sea Bottom ◽  
Sea Bed ◽  
Floating Type ◽  
Northwest Australia

B.O.C. of Australia Limited has drilled five wells on the continental shelf of Northwest Australia using floating type oil exploration vessels. To date three different methods of anchoring have been used in the Group's operations depending on the type of sea bottom encountered and the progress of technology.On coral and shoal areas south of Timor good anchoring ground has been located. Both drilling exploration vessels S.S. "Glomar Tasman" and the "Investigator," a drilling barge, have been anchored in this area using all chain anchor systems.Three wells have been drilled in an area approximately 100 miles northeast of Barrow Island where surveys revealed smooth limestone sea beds of such hardness that conventional ships anchors could not penetrate the surface to obtain a firm hold. Anchor pilings to hold the "Glomar Tasman" have been successfully installed on the sea floor at two drill sites using a small vessel, M.V. "Nyhavns Rose," of 400 tons. These piles were drilled into the sea bed using a drill string and a power swivel at the surface, and utilizing a counter weight system to allow for vessel heave. At the first locality, in 180 feet of water, divers were used to manually connect the heavy pendant wires to the anchor piles. At the second location a diverless method of installing drilled in anchor piles with chain mooring pendants attached was designed and successfully used in a water depth of 265 feet.

ELECTROMAGNETIC INVESTIGATION OF THE SEA FLOOR

Geophysics ◽  
1970 ◽  
Vol 35 (3) ◽  
pp. 476-489 ◽  
Author(s):  
J. H. Coggon ◽  
H. F. Morrison
Keyword(s):  
Mineral Exploration ◽  
Skin Depth ◽  
Electromagnetic Response ◽  
Horizontal Magnetic Field ◽  
Electromagnetic System ◽  
Sea Floor ◽  
Sea Bottom ◽  
Sea Bed ◽  
Receiver System ◽  
Field Strengths

Numerical evaluation of integral expressions for the fields about a vertical magnetic dipole in the sea allows analysis of the electromagnetic response over wide ranges of sea induction number and sea floor conductivity. Our analysis indicates that a marine electromagnetic system for measurement of bottom conductivity variations could readily be designed, with such applications as oceanographic and geologic studies, and mineral exploration. For a source‐receiver system on a homogeneous sea bottom, it is found that: (i) when the ratio k=(sea‐bed conductivity)/(seawater conductivity) is greater than about 0.03, both horizontal and vertical magnetic fields are useful for measurement of bottom conductivity at sea induction numbers less than 30 [induction number =√2 (horizontal transmitter‐receiver separation/skin depth)]. A separation of 30 m and frequencies in the range 300–3500 hz appear suitable for investigation of the upper few meters of unconsolidated bottom sediments. (ii) When the ratio k is less than 0.03, sea induction numbers from 10 to a few hundred are required for detection of seabed conductivity variations. In this case, the horizontal magnetic field, resulting from energy transmission mainly through the seafloor, is the suitable field to use. Electromagnetic sounding of indurated rocks may thus call for frequencies of 100 to 20,000 hz at a separation of 200 m. Field strengths vary strongly with relative sea depth D/R (D=sea depth, R=horizontal source‐receiver separation) when D/R is small; but sensitivity to bottom conductivity is little affected by D/R. Elevation of source and receiver above a seafloor less conductive than seawater reduces field strengths and sensitivity to seabed properties.

Estimation of sea‐floor wave velocities and density from pressure and particle velocity by AVO analysis

Geophysics ◽  
1995 ◽  
Vol 60 (5) ◽  
pp. 1575-1578 ◽  
Author(s):  
Lasse Amundsen ◽  
Arne Reitan
Keyword(s):  
Numerical Study ◽  
Offshore Structures ◽  
P Wave ◽  
Rock Properties ◽  
Sea Floor ◽  
S Waves ◽  
Interface Waves ◽  
Wave Velocities ◽  
Sea Bottom ◽  
Sea Bed

Sea‐bottom properties play an important role in fields as diverse as underwater acoustics, earthquake and geotechnical engineering, and marine geophysics. Water‐column acousticians study shear and interface waves in the nearbottom sediments with the aim of inferring sea‐bed geoacoustic parameters for predicting reflection and absorption of waves at the sea floor. On the other hand, geotechnical engineers working on design and siting of offshore structures focus on these waves to characterize soil and rock properties. In the field of geophysics, sea‐bottom parameters are of interest for several reasons. In conventional marine acquisition, these parameters determine the partitioning of the incident P‐wave energy from the source into transmitted P‐waves and mode‐converted S‐waves (Tatham and Goolsbee, 1984; Kim and Seriff, 1992). The sea‐floor P‐ and S‐wave velocities and density are also necessary inputs for decomposing multicomponent sea‐floor data into P‐ and S‐waves (Amundsen and Reitan, 1995a and b), as well as in the numerical study of wave propagation phenomena.

scholarly journals Drilling cores on the sea floor with the remote-controlled sea floor drilling rig MeBo

2013 ◽  
Vol 2 (2) ◽  
pp. 329-337 ◽  
Author(s):  
T. Freudenthal ◽  
G. Wefer
Keyword(s):  
Complete System ◽  
Drill String ◽  
Drilling Process ◽  
Stability Studies ◽  
Sea Floor ◽  
Drilling Rig ◽  
Research Fields ◽  
Sea Bed ◽  
Recovery System ◽  
Marine Environmental

Abstract. The sea floor drill rig MeBo (acronym for Meeresboden-Bohrgerät, German for sea floor drill rig) is a robotic drill rig that is deployed on the sea floor and operated remotely from the research vessel to drill up to 80 m into the sea floor. It was developed at the MARUM Research Center for Marine Environmental Sciences at Bremen University. The complete system – comprising the drill rig, winch, control station, and the launch and recovery system – is transported in six containers and can be deployed worldwide from German and international research ships. It was the first remote-controlled deep sea drill rig to use a wireline coring technique. Compared to drilling vessels this technology has the advantage of operating from a stable platform at the sea bed, which allows for optimal control over the drilling process. Especially for shallow drillings in the range of tens to hundreds of metres, sea bed drill rigs are time-efficient since no drill string has to be assembled from the ship to the sea floor before the first core can be taken. The MeBo has been successfully operated, retrieving high-quality cores at the sea bed for a variety of research fields, including slope stability studies and palaeoclimate reconstructions. Based on experience with the MeBo, a rig is now being built that will be able to drill to a depth of 200 m.

Submarine Pipeline Installation JIP: Strength and Deformation Capacity of Pipes Passing Over the S-Lay Vessel Stinger

2006 ◽  
Author(s):  
Enrico Torselletti ◽  
Luigino Vitali ◽  
Erik Levold ◽  
Kim J. Mo̸rk
Keyword(s):  
Water Depth ◽  
Failure Modes ◽  
Bending Moment ◽  
External Pressure ◽  
Submarine Pipeline ◽  
Design Guideline ◽  
Moment Capacity ◽  
Sea Bottom ◽  
Major Vessel ◽  
Gas Fields

The development of deep water gas fields using trunklines to carry the gas to the markets is sometime limited by the feasibility/economics of the construction phase. In particular there is a market for using S-lay vessels in water depth larger than 1000m. The S-lay feasibility depends on the applicable tension at the tensioner which is a function of water depth, stinger length and stinger curvature (for given stinger length by its curvature). This means that, without major vessel up-grading and to avoid too long stingers that are prone to damages caused by environmental loads, the application of larger stinger curvatures than presently allowed by current regulations/state of the art is needed. The work presented in this paper is a result of the project “Development of a Design Guideline for Submarine Pipeline Installation” sponsored by STATOIL and HYDRO. The technical activities are performed in co-operation by DNV, STATOIL and SNAMPROGETTI. The scope of the project is to produce a LRFD (Load Resistant Factor Design) design guideline to be used in the definition and application of design criteria for the laying phase e.g. to S and J-lay methods/equipment. The guideline covers D/t from 15 to 45 and applied strains over the overbend in excess of 0.5%. This paper addresses the failure modes relevant for combined high curvatures/strains, axial, external pressure and local forces due to roller over the stinger of an S-lay vessel and to sea bottom contacts, particularly: • Residual pipe ovality after laying, • Maximum strain and bending moment capacity. Analytical equations are proposed in accordance with DNV OS F101 philosophy and design format.

Seasonal deposition of phytodetritus to the deep-sea floor

1986 ◽  
Vol 88 ◽  
pp. 265-279 ◽  
Author(s):  
A. L. Rice ◽  
D. S. M. Billett ◽  
J. Fry ◽  
A. W. G. John ◽  
R. S. Lampitt ◽  
...  
Keyword(s):  
Deep Sea ◽  
Benthic Communities ◽  
Time Lapse ◽  
Sediment Traps ◽  
Temporal Variations ◽  
Sea Floor ◽  
Porcupine Seabight ◽  
The Past ◽  
Sea Bed ◽  
Seasonal Deposition

SynopsisEvidence has accumulated over the past twenty years to suggest that the deep-sea environment is not as constant as was at one time thought, but exhibits temporal variations related to the seasonally in the overlying surface waters. Recent results from deep-moored sediment traps suggest that this coupling is mediated through the sedimentation of organic material, while observations in the Porcupine Seabight indicate that in this region, at least, there is a major and rapid seasonal deposition of aggregated phytodetritus to the sea-floor at slope and abyssal depths.This paper summarises the results of the Porcupine Seabight studies over the past five years or so, using time-lapse sea-bed photography and microscopic, microbiological and chemical analyses of samples of phytodetritus and of the underlying sediment. The data are to some extent equivocal, but they suggest that the seasonal deposition is a regular and dramatic phenomenon and that the material undergoes relatively little degradation during its passage through the water column. The mechanisms leading to the aggregation of the phytodetritus have not been identified, and it is not yet known whether the phenomenon is geographically widespread nor whether it is of significance to the deep-living mid-water and benthic communities.

scholarly journals SEA-BED CONFIGURATION IN RELATION TO BREAKWATER STABILITY

1972 ◽  
Vol 1 (13) ◽  
pp. 81 ◽  
Author(s):  
J.H. Van Oarschat ◽  
A. Wevers
Keyword(s):  
The Netherlands ◽  
Present Article ◽  
Water Depth ◽  
Systematic Study ◽  
Public Works ◽  
Irregular Waves ◽  
Sea Bed ◽  
Hydraulic Conditions ◽  
Overall Stability ◽  
The Stability

Stability tests on the Europoort breakwaters, situated on a shallow foreshore, clearly demonstrated the effect of the foreshore configuration on the overall stability. The present article gives a descriptionof the stability experiments and the interpretation leading to general conclusions regarding foreshore effects in combination with hydraulic conditions such as wave period, water depth and wave height. Both regular and irregular waves have been used. The experiments, carried out in commission of the Netherlands Government Department of Public Works (Rijkswaterstaat) were of an applied nature and were not directed primarily to the systematic study of foreshore effects.

Diving behaviour of two Ross seals off east Antarctica

2005 ◽  
Vol 32 (1) ◽  
pp. 63 ◽  
Author(s):  
Colin Southwell
Keyword(s):  
Continental Shelf ◽  
Additional Data ◽  
Prey Species ◽  
Current Knowledge ◽  
East Antarctica ◽  
Maximum Depth ◽  
Diving Behaviour ◽  
Sea Floor ◽  
Transmission Period ◽  
The Antarctic

The Ross seal (Ommatophoca rossii) is the least frequently sighted and least known of the Antarctic pinnipeds. Current knowledge of foraging and diving behaviour is based on observations of a single seal over <2 days. The current study provides some additional data on the diving behaviour of two Ross seals off east Antarctica over periods of 31 and 12 days during December–January 1999–2000 using satellite-linked dive recorders. Both seals remained over the continental shelf for these times, the female remaining some distance from the coast and the male moving close to the coast approximately half-way through his transmission period. Most dives by the female reached depths >150 m (maximum depth 372 m) and the modal duration was 10–11 min. The male’s dives were slightly shallower (most >100 m) and shorter (mode 6–7 min) when distant from the continental coast, and were truncated to a depth of 180 m when close to the coast, presumably by the sea floor. These dive patterns suggest that their prey species, thought to comprise mostly fish and squid, were relatively unavailable at depths <100 m.

Deep-Ocean Exploitation Technology

1971 ◽  
Vol 8 (02) ◽  
pp. 145-158
Author(s):  
Raymond Kaufman
Keyword(s):  
Continental Shelf ◽  
Large Scale ◽  
Deep Ocean ◽  
Abandoned Mine ◽  
Economic Potential ◽  
Mining Method ◽  
Mine Shaft ◽  
Sea Floor ◽  
Ocean Mining ◽  
Air Lift

The paper discusses the latest techniques proposed for mining minerals from the deep ocean. Deep ocean is defined as the sea beyond the continental shelf, particularly areas of the sea floor exceeding 1200 ft in depth. The three principal deep-ocean minerals having economic potential in the immediate future are identified. Four recently proposed advanced deep-ocean mining concepts are presented. Use of the air-lift pump as a viable mining method is discussed and a large-scale air-lift pump experiment conducted in an abandoned mine shaft at Galax, Virginia is described. The principal features of the conversion of a small C1-M-AV1 type cargo ship to a deep-ocean mining prototype vessel, RV Deepsea Miner, is outlined.

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