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AAPG GEO 2010 Middle East
Geoscience Conference & Exhibition
Innovative Geoscience Solutions – Meeting Hydrocarbon Demand in Changing Times
March 7-10, 2010 – Manama, Bahrain

“Just Listen”: Acquiring and Using Low Frequency Spectroscopy Data for Exploration in the South Rub' Al Khali Basin

Pieter van Mastrigt1; Abdulmohsin Al-Dulaijan1; Ashraf Khalil1; Geoff Pike1

(1) South Rub Al-Khali Company Limited, Al Khobar, Saudi Arabia.

The South Rub ‘al Khali Company Ltd is an Incorporated Joint Venture between Shell Saudi Ventures Limited (50%) and Saudi Arabian Oil Company (50%) and was set up in order to explore for non-associated gas in the South Rub ‘al Khali Basin as part of the Natural Gas Initiative in the Kingdom of Saudi Arabia.

In addition to the acquisition of conventional data (regional 2D seismic, (airborne) gravity, magnetics, uphole and well data), SRAK experimented with alternative, and more speculative methods, notably Magneto Telluric and Low Frequency Seismic Spectroscopy (“LF”). A total of three LF experiments were recorded in 2005/06, with promising results, after which SRAK decided to implement the method routinely alongside the acquisition of its seismic data. This provided a means to gather very large LF datasets at economical rates. The total acquisition now comprises well over 8,500 stations, along 5,600 km of 2D seismic lines, spread over an area of more than 30,000 sq. km. This is by far the largest LF dataset worldwide.

Whilst initial Industry publications and presentations concentrated on the experimental nature of the LF method and the speculative source of the observed anomalies, it is clear that large quantities of data would provide unprecedented insights into the robustness and repeatability of this technology. Together with its Contractors, SRAK climbed a steep learning curve, not only to streamline the reliability of the acquisition on this scale, but also in the processing and presentation of the data. Normalization between lines acquired at different times requires a hands-on approach as the sources of the LF signal appear to vary by at least one order of magnitude.

Initial results from the LF program, combined with robust geological models and conventional seismic interpretation, have helped to high-grade prospects in the SRAK portfolio.

We describe the implementation of the acquisition, processing, normalization and display of the data. Interpretation of the data is discussed in a companion paper at this conference.