Geophysical Vessel Research Articles

The Technology of Geophysical Vessel Control for the Study of the World Ocean

The article performs the issues of positioning and ensuring the movement of a geophysical vessel along a routing line, applied aspects of marine geophysical technologies according to the technical characteristics of a vessel, allowing to carry out the operation complex on the shelf zone of the World Ocean. The points of balancing modes and stability region of the controlled object without stalling vessel in the circulation of the vertical plane relative to center-line plane are calculated for the realization of the parameters of the vessel motion. We determine a linearized model of a controlled device and a table of the numerical values of the coefficients determined in the vicinity of various balancing modes. In addition, the roots of a characteristic equation for the pair of towed objects directly from an underground garage and a vehicle have been established.

The ice and ocean coupling effect on towing cables

With the growth of global warming, the scope and the thickness of sea ice decrease drastically. In order to monitor this trend, polar geophysical vessels travel to the polar region frequently. The resistance of the geophysical exploration ships in polar areas will increase due to the change of the environments, and the towing operation of those ships will also be affected. Thus, it is of great significance to carry out ice load analysis and parameter sensitivity research on the geophysical exploration ship in ice floe environments. In the present paper, the numerical curve of the ice load over time has been obtained via FEM simulation. The influence of sensitivity parameters (speeds and ice sizes) on the towing cables has been analyzed. On the basis of the calculation results, an empirical formula suitable for the collision between towing cables and ice has been summarized and verified.

The Concept Of Marine Seismic Research Quality Coefficient Of To Improve Its Accuracy And Efficiency

Abstract The paper presents the stages of quantitative coefficient of marine seismic researches creation for the geophysical vessels towing the geophysical seismic equipment understood as system of seismic streamers where set of geophones are installed. The quality coefficient of geophysical research works is based on the mathematical model of the deviation of the position of the arrangement of streamers geophone points with relation to their idealized position. The proposed coefficient can be used during realization of seismic researches and for short-term prediction of their quality.

From dog sledge to satellite: Knud Ellitsgaard‐Rasmussen (1923–2009), geologist

Knud Ellitsgaard‐Rasmussen's career spanned an astounding period of change in the science. He was not a geologist whose name was widely known and it is probably true to say that few students today, even in his native Denmark, have heard of him. He was nevertheless a figure of huge importance to geological research in his role as someone who directed geology along very productive lines, creating an environment which was highly conducive to the successful careers of many talented researchers. He saw and presided over geology as it evolved from the heroic days of an individual with a dog‐sledge and a microscope to later days with armies of personnel, aircraft, marine geophysical vessels, the GPS and the ICP‐MS. He led the mapping of a subcontinent.

Acoustic propagation effects on airgun pulses and whale calls in the Beaufort Sea.

In 2008, vocalizing bowhead whales (Balaena mysticetus) conducted their fall migration in the Beaufort Sea amidst short‐ and long‐range seismic exploration activities. Whale calls and airgun pulses were recorded on five arrays of Directional Autonomous Seafloor Acoustic Recorders (DASARs) deployed along 280 km of Alaska’s North Slope. One particular sequence of pulses was recorded from the Louis S. St. Laurent, a Canadian geophysical vessel conducting surveys in deep offshore waters in collaboration with the United States Geological Survey (USGS), thus providing a fix on the location of some distant airgun activity. The distant airgun signals display an interesting selection of long‐range propagation effects, which will be discussed and analyzed in the context of range‐dependent propagation modeling in a combined deep‐water upward‐refracting and shallow‐water bottom‐interacting environment. [Work supported by the U.S. Geological Survey.]

Observations on the Behavioral Responses of Bowhead Whales (<i>Balaena mysticetus</i>) to Active Geophysical Vessels in the Alaskan Beaufort Sea

The responses of bowhead whales to controlled approaches by geophysical vessels producing airgun blasts were observed during the course of four field experiments conducted in the Alaskan Beaufort Sea in September 1984. Behavioral responses included shorter surfacing and dive times, fewer blows per surfacing, longer blow intervals and subtle to overt changes in surface behaviors. Subtle behavioral responses occurred at 3.5 and 8.2 km with received airgun noise levels of 142 and 157 dB respectively (all levels in dB re 1 micro Pa). Partial avoidance (i.e., some whales leaving the observation area while others remained) occurred at ranges of 3.5 and 7.6 km, with sound levels of 142 and 158 dB respectively. Total avoidance (i.e., all whales leaving the observation area) occurred at 1.3, 7.2, 3.5 and 2.9 km, with corresponding sound levels of 152, 165, 178 and 165 dB. The similarities among experiments reported here support the conclusion that short-term behavioral changes occur when bowhead whales are exposed to airgum blasts from approaching geophysical vessels at ranges <10 km. These disturbance efforts wane within one hour after a disturbance; long-term effects on social, behavioral or physiologic parameters are not known at this time. Key words: bowhead whale, Balaena mysticerus , geophysical vessel, bioacoustics, airguns

Oil and Gas Developments in Central and Southern Africa in 1981

Exploratory activity in central and southern Africa continued to grow during 1981. Geophysical operations reached nearly record levels and the number of wells increased markedly. Oil production suffered from the adverse conditions that existed throughout the world and dropped by a significant amount. New concession acquisitions occurred in several of the countries in northeast Africa. Elsewhere, the operating companies negotiated new concessions and renewed those that were expiring. In several countries where production has been proven, the operators were assigned exploitation concessions. Seismic crews and marine geophysical vessels were active throughout the countries in this area. A total of 365 party-months of work was done to yield 98,035 km of new lines. A moderate amount of 3-D recording was carried out in connection with field development. Some aeromagnetic work was done, principally in northeast Africa and in Mozambique. Forty-four new fields or pools were discovered by drilling 115 new-field wildcat and exploratory wells. These wells accounted for 1,060,254 ft (323,248 m) of hole. Appraisal and development drilling resulted in 321 wells with a total of 2,533,305 ft (772,349 m) of hole drilled. At year end, 25 exploratory wells were under way or testing, and 49 rigs were active in development drilling. Oil production for the year was 691,995,939 bbl, a decrease of nearly 25% from 1980. Nigeria suffered the greatest drop in production; however, increases were achieved in Cameroon, Congo, and Zaire. The cumulative production from this part of Africa passed the 10 billion bbl mark.

Distribution and seasonality of cetaceans in tropical waters between Angola and the Gulf of Guinea

The species richness, spatial distribution, seasonality and interspecific associations of cetaceans in tropical oceanic waters between the Gulf of Guinea and Angola were examined using 5 905.3 h of dedicated survey effort collected from 13 platforms of opportunity (geophysical vessels) between 2004 and 2009, and from incidental records. Most effort (87.8%) was recorded in waters >1 000 m deep. A total of 1 814 on-effort and 1 496 incidental sightings were recorded, comprising 22 species. Physeter macrocephalus and Megaptera novaeangliae were the most frequently sighted cetacean species, with Globicephala macrorhynchus and Stenella frontalis the most frequently sighted delphinids. Five species occurred in both neritic and oceanic waters, while the remainder had exclusively oceanic distributions. The occurrence of P. macrocephalus and M. novaeangliae differed significantly according to depth category. Most species occurred year-round; however, M. novaeangliae exhibited a strong, significant winter and spring occurrence. There were 65 interspecific groups recorded, involving at least 12 species. Mixed schools of G. macrorhynchus and Tursiops truncatus accounted for 55.4% of recorded associations. This extensive year-round dataset adds considerably to the understanding of cetacean distribution in the eastern tropical Atlantic and provides baseline information on which to base cetacean conservation and management in this poorly studied region.