Optimising 4D Repeatability

Use of Enhanced Acquisition Technologies
During the past thirty years subsurface seismic images have allowed Exploration and Production companies internationally to commercially develop thousands of hydrocarbon reservoirs. In response to increasing world demand some companies are employing more costly and complex seismic data-acquisition techniques to help them discover the next major field. A less costly alternative is to enhance the recovery rate of existing reservoirs by performing multiple surveys of the same reservoir over time. This technique, known as '4D seismic', gives companies the ability to dynamically track and monitor fluid movement and pressure change within reservoir compartments. Armed with this information asset man-agers can... (read more)
2008-01-01 01:00:00

Off-the-shelf Surveying Beyond 200 Miles

A contractor’s flexible approach to Art. 76-related surveys
The unique opportunity now open to Coastal States to extend their maritime boundaries seawards has led to great interest in the particular marine geophysical and hydrographic survey techniques required to collect additional data in support of continental shelf extension. Criteria laid down in the United Nations Convention on the Law of the Sea (Art. 76, UNCLOS) emphasise each nation being able to "…establish the outer limits of the continental margin wherever the margin extends beyond 200 nautical miles…" (www.un.org/Depts/los/index.htm). We describe Gardline’s experience with specific reference to surveying the continental margin of the Republic of Namibia. The objectives associated with... (read more)
2008-01-01 01:00:00

Sonar Propagation in Statified Waters

Effect of Estuarine Environment on Sound Speed Profile
Ports, harbours and naval bases are often located in estuaries, where river discharge and tidal stirring strongly affect the sound velocity profile. Scales of temporal and spatial variability are often particularly short, resulting in abrupt changes to the acoustic environment. Such small-scale estuarine sound velocity structures and temporal changes have significant impacts on sound propagation and therefore must be described and quantified in order to optimise sensor performance. The authors illustrate the impact of water column variability on high-frequency sonar propagation in the acoustically challenging estuarine littoral. Field data drawn from a temperate latitude estuary illustrate fluctuations in key oceanographic... (read more)
2010-03-02 01:52:01

The Prevention of Mutual Interference Within the Subsea Littoral

The Need for a Co-operative Approach with Non-military Users
The 2009 collision between two Royal Navy and French Navy submarines highlights the inherent risk of ‘flying blind’, and the ever-present danger that submerged activities present. Notwithstanding the diplomatic intricacies of operating nuclear deterrent submarine patrols, informed commentary suggests that the collision could be attributed to three factors: (1) France’s non-participation in the NATO waterspace management organisation (having ceased being a member of NATO in 1966); (2) the evolved silence of operational submarines and the relative effectiveness of sonars against silenced submarines and (3) bad luck. Specifically, the root of the problem was procedural. So what? The fact that the... (read more)
2010-11-02 12:19:06

Inshore Survey Vessels

The next size up
The May 2002 edition of Hydro international included two articles on small 7-10m outboard motor-driven inflatable and GRP road- towable planning boats adapted for near shore, sheltered water or estuarial hydrographic surveys. This article outlines the specifications and requirements of the larger 10m-14m LOA purpose-built inshore survey vessels which have evolved as the standard for most major or long duration open-sea inshore hydrographic and geophysical surveys. Inshore hydrographic and geophysical surveying is probably the most difficult and demanding of all survey work. Offshore deep-water operations from large and comfortable survey ships have become a day-to-day routine and make few demands... (read more)
2008-01-01 01:00:00

An Adaptable Survey ­Platform for Shallow Water

Bathymetric Charting of Nearshore, Harbour, Estuary and River Settings
High-resolution bathymetry and water quality surveys of shallow shelf and inland water bodies are an increasingly necessary part of environmental management with climate change pressures. This paper describes a new method for data acquisition using a small, stable, adaptable, single-operator survey platform. Development and natural (climate related) changes are placing an ever increasing pressure on our coasts, shallow marine shelves, estuaries, rivers, harbours and inland water bodies. In Europe these pressures have been recognised and attempts made to address the impacts under legislation such as the Water Framework Directive, which seeks to classify all water bodies by their health and... (read more)
2013-01-18 01:45:32

Submarine Erosion in North Spanish Atlantic Sea

Several surveys were carried out on board the R/V <i>Hespérides</i> in the north Spanish Atlantic Sea in order to obtain detailed hydrographical and geological information on the Prestige wreck area (the Galicia Bank) and the Bay of Biscay. The surveys show submarine erosion playing an important role in sculpting the morphology of these margins and deep-sea areas. The Research Vessel (R/V) Hespérides offers the facility of combining high and ultra-high resolution acoustic methods (multi-beam, parametric echo sounder, single-channel seismics) during oceanographic surveys. After the Prestige oil tanker sank on the Galicia Bank, a comprehensive hydrographic and geological study was carried... (read more)
2008-01-01 01:00:00

Robert Ballard: Exploring Human History Lost Beneath the Sea

Manned and unmanned underwater vehicles have been used for many years to explore the hidden features of the deep ocean. Dr Robert D. Ballard is an oceanographer most noted for his deep-ocean explorations for underwater archaeology. Ballard is best known for his discovery of the legendaryTitanicand underwater explorations of theBismarck,LusitaniaandBritannic. Hydrointernationalasks him about his experience and best practices when setting up explorations for human history lost beneath the sea.<P>     Please introduce yourself to our readers. I am an oceanographer who spent 30 years at the Woods Hole Oceanographic Institution (WHOI) where I studied ‘Plate tectonics and the volcanic,... (read more)
2008-07-04 12:00:00

Developments and Trends in Multibeam Echo Sounders

The multibeam echo sounders available on the market are constantly evolving as technology advances and as sonar producers seek new ways of refining and utilising the products. In this article we will provide a snapshot of current products and trends from the dominant (high-end) sonar producers focused on survey-grade products. Trend #1 – Resolution The neverending trend of getting higher resolution sonar systems is battling the physics of acoustics. Over the past several years, the battle for best-in-class multibeam for medium water depth has been between the Teledyne RESON SeaBat 7125, the Kongsberg EM 2040/2040C and the R2Sonic Sonic 2024.... (read more)
2016-02-01 03:59:24

Geophysical Surveys in West Africa

Detailed marine geophysical surveys are considered a key element in the process of development and construction of new offshore ports and load-out facilities. Specifically, seismic data constitute an essential part as they can reveal many unknown factors. Due to the challenging environment in West Africa and the often very shallow water depths, it requires a flexible and versatile approach from a survey company. This article gives an overview of how this type of project is approached and some of the lessons we have learnt when performing marine geophysical surveys in shallow water in West Africa.<P> West Africa is rich inmineral... (read more)
2009-01-05 12:00:00
Search Filter