Acoustic Zoom: The Future of Offshore Exploration

By Kira Coley

Since industrial oil extraction began in the mid-19th century, civilization has gradually turned to new offshore resources to meet global energy demands. As the industry ventures further into polar and deep-water regions, the complexity of today’s exploration projects continues to rise.  Given the falling oil prices and rising production costs, current market dynamics will become a catalyst for changes in conventional explorative and extraction practices. A new approach for seismic surveying developed by researchers at the University of Bath, offers a resolution and efficiency beyond the reach of existing seismic methods, reducing the need of unnecessary drilling and the associated impact to the marine environment.

According to the World Ocean Review, the total global energy consumption has risen by about 70% over the past three decades. In addition, the International Energy Agency (IEA) in Paris estimates that consumption will grow by a further 50% by 2030. While worldwide energy consumption appears to be on the rise, insipid economic growth combined with increased production activities in various countries has led to a drop in oil prices from $110 to less than $50 a barrel.
The UKs industry body, Oil & Gas UK, recently reported the worst annual performance for four decades. In 2014, the UK oil and gas sector invested $7.8 billion more than the total annual earnings. Due to surging costs, exploration in the offshore fields is also on a continuing downward trend.
Improvements in both cost and efficiency up to 40% per barrel may be required for the UK to maintain a sustainable future in the oil and gas sector. In an industry traditionally resistant to change, new approaches will need to be established in order to affordably meet the rising demands of the global energy market.
“The key is to be smart. We need to gather a more comprehensive, detailed knowledge of the environment and the geology before attempting to drill,” said Prof. Jacques Yves Guigné, inventor and developer of Acoustic Zoom. “For instance, brute strength drilling and hope for the best is not an option anymore. Higher definition and more reliable imaging is needed to delineate in advance and effectively assess potential in a deep water or polar site, especially in complex conditions.”
Given today’s prices and concerns for the environment, balancing industry overheads and marine impacts are paramount to both success and profitability. The changing market is set to drive the need for advanced remote sensing solutions which not only offer higher resolution and improved performance, but reduce the cost to both the industry and the ocean.
Oil and Gas Exploration
Seismic survey techniques are used to produce an image of the rock formations beneath the seabed and identify potential oil and gas deposits in sedimentary basins. Exploration and appraisal drilling can then determine the type and volume of any accumulations present.
Seismic surveys follow a similar general principle of echolocation or sonar. A ship-towed array of multiple airguns sends pulses of sound by a rapid release of compressed air through the water column, towards the seafloor. The sound waves will either refract (bend) or reflect off the seabed and the returning sound is detected by a receiver. The presence of possible deposits in rock formations can be revealed by analyzing the time the waves take to return. Properties of the substrate can be estimated by observing patterns in the returned sound. The problem is that the resolution of such imaging is poor and the sound used to create it can be disruptive to the marine community.
“The issue is that the industry as a whole is very conservative in adopting innovations until such new approaches have had a long history of proven use. This means changes to current geophysical practices have evolved slowly, often missing out on what could be a more effective seismic survey, better data and enhanced processing of features from such data,” said Guigné.
This conservative approach is now being challenged as the industry considers venturing into new targeted offshore fields previously thought too expensive and difficult to exploit. This includes areas such as the Arctic, where exciting geological formations are more subtle and complex, but hold great potential for revealing deposits.
These deposits can be missed or masked by the diffractive nature of the formations that surrounds the potentially rich fields. The necessity to capitalize on these untapped regions encourages acknowledgement that more rapid adoption of innovative imaging methods is necessary.

Acoustic Zoom
Developed by Prof. Jacques Guigné and Prof. Nicolas Pace at the University of Bath, Acoustic Zoom is a novel seismic exploration technique adapted from sonar applications. The principle differs from that of conventional seismic survey which analyzes the reflecting sound energy returned from the seafloor. Instead, Acoustic Zoom uses a 16-spoke array set on the ocean floor to measure how the energy is scattered.
The array transmissions transfer energy as small calculated bursts released slowly over time.  As the system is stationary, energy is directed in a localized manner at the seabed and not the water column, therefore marine mammals and their habitats are typically not disturbed.
The introduction of Acoustic Zoom addresses the need for producing high resolution images of the geology by fully exploiting the use of acoustics in a manner similar to a radio telescope. A principle first used to search galaxies in the mid 1950’s and still used today.
“Acoustic Zoom is an ‘earth telescope,’ a stationary lens from which propagating sounds can be manipulated and made to be directed to “zoom” into a field with unprecedented imaging qualities, capturing the way the sound energy gets redistributed - attenuated, reflected and scattered - all three forming the final but detailed image of the geology,” said Guigné. “It also allows a controlled low dose acoustic footprint, gentler on the surrounding environment, limiting the disturbances to fragile marine life. If anything, sea life of all forms has been seen to swim around the system out of curiosity, not out of alarm.”
The higher resolution found using this method offers the industry a way of reducing the need for unnecessary drilling in the future. Acoustic Zoom hails the beginning for innovative technologies in this industry, reducing both the associated operational costs as well as the environmental impacts of explorative activities.
 
Future of Offshore Exploration
Today’s regard for safety of personnel and environmental awareness is the central focus of industries’ designs. As organizations are reshaped in relation to the drop in oil prices, large ambitious offshore developments have had to be temporarily halted or reappraised. This has led to critical reviews on practices and expenditures.
The complexity of today’s exploration projects continues to rise, and the need for aggressive innovation in the seabed seismic segment has never been higher. Technologies which are both safe to operate and cost-effective, will become part of the resurgence in activities.
“There is no question that the oil and gas industry will persist, grow and remain very profitable. It is an industry that when pushed to the edge, responds through better cost effective management practices and adoption of more advanced technologies. Acoustic Zoom is part of this changing tableau and will over time be a recognized evolutionary force for changes to the way we execute exploratory surveying.” Guigné.
 

(As published in the APRIL 2015 edition of Marine Technology Reporter - http://www.marinetechnologynews.com/Magazine)

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