Online Journal for E&P Geoscientists

Musser, James A.^*1; Al-Amri, Mohammed ¹; Al-Omar, Waleed ¹; Lafon, Stephen K.¹; Arifin, Mustajar ²
(1) Exploration Operations, Saudi Aramco, Dhahran, Saudi Arabia. (2) Coastline Geophysical Saudi Arabia Ltd, Al-Khobar, Saudi Arabia.

Saudi Aramco has embarked on a challenging 3D seismic campaign to image below salt bodies in the geologically complex Red Sea region. Based on existing 2D seismic data, limited well information, and 3D seismic modeling, independent seismic evaluation and design (SED) studies were conducted both internally and by two contractors to recommend the best 3D acquisition design to illuminate and image below the complex salt overburden. All three of these studies concluded that 3D seismic data acquired with extremely long offsets and wide azimuths were critical for illumination, and that pre-stack depth migration was needed for accurate imaging of the pre-salt target objectives.

Numerous strategies for acquiring wide azimuth (WAZ) 3D marine seismic data have been developed in the seismic industry. Some involve a single marine 3D streamer vessel making multiple passes over the same area from different shooting directions (multi-azimuth or circular shooting), while others involve using multiple seismic vessels, often with multiple passes over the same area. To meet the requirements of Saudi Aramco’s Red Sea exploration program, it was important to acquire the best possible WAZ data in the minimum amount of time. The three SED studies concluded that the most efficient and effective WAZ survey design would be achieved using four seismic vessels, two towing multiple long streamers and large air gun array sources, and the other two vessels towing sources only.

Three very large four-vessel WAZ marine 3D surveys were completed in the Red Sea in late 2010 and early 2011, with very high efficiency and high data quality results. Thanks largely to the broad swath of coverage acquired using the four vessel shooting design and the inherent redundancy of the in-line data recorded by each of the streamer vessels with its own source, the need for infill shooting was held to a minimum.

These three multi-vessel WAZ surveys are the first of their kind in the Middle East region. They demonstrate the efficiency and value of this type of acquisition and its importance to an exploration strategy over complex geologic objectives. They will also provide crucial information for drilling in this deep water, pre-salt frontier area.