OUR GREAT MINDS

    by Tina Olivero

    The First True 3D Marine Seismic System

    Since their introduction in the 1980s, multi-streamer marine 3D ­seismic surveys have been widely recognized as a key ­enabler for increasing drilling success rates during the exploration and development of offshore oil and gas fields. Today, these surveys are ­typically acquired by a vessel equipped with between 8 and 16 ­streamers towed 50 to 100 m apart, each 3 to 8 km long. Each ­streamer contains hydrophone sensors, and spatial sampling of the data ­recorded along each streamer (inline) can be as fine as 3.125 m; ­however, the much greater distance between adjacent streamers means that sampling in the crossline direction can be 16–32 times sparser. Such coarsely sampled data cannot capture the whole 3D wavefield, which limits its ability to accurately image the ­subsurface. While ­developments in seismic sources and sensors have improved the frequency bandwidth that can be input to the subsurface and ­subsequently recorded back at the surface, achieving truly 3D ­high-resolution images of complex subsurface structures also requires adequate spatial sampling in both the inline and crossline directions.

    In 2012, WesternGeco announced the launch of its IsoMetrix* marine seismic technology, which for the first time enables true measurement of 3D seismic wavefields recorded using towed streamers. This capability is the result of an extensive ten-year research and engineering program that has been the largest single engineering project ever undertaken by Schlumberger, the world’s leading provider of oilfield services. The new technology delivers high-fidelity point-receiver seismic data while overcoming spatial wavenumber bandwidth compromises that have limited previous marine seismic acquisition methods. The result is a reliable, continuous measurement of the full upgoing and downgoing notchless seismic wavefield sampled at a 6.25 m x 6.25 m point-receiver surface grid. This fine isometric sampling in both crossline and inline directions makes the data suitable for use in a wide variety of interpretation and modeling applications, such as high-resolution near-surface imaging, deep reservoir characterization, and 4D reservoir monitoring.

    Isometric 3D sampling is enabled by the Nessie-6* point-receiver streamer system. This incorporates a new generation towed streamer design that combines measurements of wavefield pressure and gradient—vertically and crossline. It uses point-receiver technology that combines hydrophones with calibrated point-receiver microelectromechanical system (MEMS) accelerometers that measure the full particle acceleration of the upgoing and downgoing seismic wavefield. Direct measurement of the vertical and crossline gradient enables unaliased reconstruction of the pressure wavefield between the streamers.

    A new computer algorithm—which has been shown to be extremely robust in dealing with highly aliased data—performs simultaneous spatial reconstruction and receiver deghosting of the seismic pressure wavefield. The source ghost is addressed by the WesternGeco newly developed Delta calibrated marine broadband seismic source family of notchless seismic sources. The algorithm can compute the upgoing and downgoing separated wavefield at any desired position within a spread of streamers. This ability contributes to an unmatched level of repeatability in 4D (time-lase) projects, which map subtle changes in the seismic response of a reservoir related to changes in pressure or fluid content. The method can guide reservoir management decisions, identify flow barriers, and locate untapped compartments suitable for infill drilling. “We have developed a new category of seismic that not only includes the acquisition technology, but also the algorithms and workflows needed to manage such an unprecedented amount of data,” said Carel Hooykaas, president, WesternGeco, at the launch of the IsoMetrix system during the European Association of Geoscientists and Engineers (EAGE) 2012 annual conference and exhibition. “The step change in imaging is as profound as was the move from X-rays to full 3D scans in the world of medicine.”

    During August 2012, the 3D seismic vessel Western Pride, deploying eight full-length streamers in the North Sea, completed acquisition of its first commercial project on schedule. During September, commercial surveys were acquired for two other operators. The new technology has proved to be very robust during operations and is attracting considerable interest from oil and gas exploration and production companies of all sizes around the world.

    In February 2013, the seismic vessel WG Vespucci (pictured), equipped with 10 full length streamers, completed acquisition using IsoMetrix technology of a 3D survey for Thombo Petroleum Ltd. The survey covered a full fold area of 686 km2 extending over the A‐J1 graben of Block 2B located off the west coast of South Africa. This graben contains the A‐J1 oil discovery drilled and tested by Soekor in 1988. The new data will allow Thombo and its partner Afren plc to evaluate in detail not only the extent of the A‐J1 oil discovery but also the many other prospects and leads in the graben that have been identified from existing 2D seismic data. WG Vespucci is embarked on a busy schedule of IsoMetrix projects around the world and other vessels will soon be fitted with the new equipment.

    Stuart Papworth is IsoMetrix Business Manager for WesternGeco
    *Mark of Schlumberger

    Top:  WG Vespucci is one of the first vessels in the WesternGeco seismic fleet acquiring commercial 3D surveys using IsoMetrix technology. (Image courtesy of WesternGeco)

    Tina Olivero

    30 years ago, Tina Olivero looked into the future and saw an opportunity to make a difference for her province and people. That difference came in the form of the oil and gas sector. Six years before there was even a drop of oil brought to the shores of Newfoundland, she founded The Oil and Gas Magazine (THE OGM) from a back room in her home on Signal Hill Road, in St. John’s, Newfoundland. A single mother, no financing, no previous journalism or oil and gas experience, she forged ahead, with a creative vision and one heck of a heaping dose of sheer determination. With her pioneering spirit, Ms. Olivero developed a magazine that would educate, inspire, motivate and entertain oil and gas readers around the world — She prides herself in marketing and promoting our province and resources in unprecedented ways. The OGM is a magazine that focuses on our projects, our people, our opportunities and ultimately becomes the bridge to new energy outcomes and a sustainable new energy world. Now diversifying into the communications realms, a natural progression from the Magazine, The OGM now offers an entirely new division - Oil & Gas Media. Today, The Oil and Gas Magazine is a global phenomenon that operates not only in Newfoundland, but also in Calgary and is read by oil and gas enthusiasts in Norway, Aberdeen, across the US and as far reaching as Abu Dhabi, in the Middle East. Believing that Energy is everyone’s business, Ms. Olivero has combined energy + culture to embrace the worlds commitment to a balance of work and home life as well as fostering a foundation for health and well being. In this era of growth and development business and lifestyle are an eloquent mix, there is no beginning or end. Partnering with over 90 oil and gas exhibitions and conferences around the world, Ms. Olivero's role as a Global Visionary is to embrace communication in a way that fosters oil and gas business and industry growth in new and creative ways.

      Would you like to know more about this story?

      Let us know who you are and how we can assist you.

      First Name *required

      Last Name

      Company

      Website

      Email *required

      Mobile required

      What are you interested In?

      Learning more about this story?Contacting the company in this story?Marketing for your company?Business Development for your company?

      I am interested in...


      Did you enjoy this article?

      Get Media Kit


      OGM - Our Great Minds