Aspects of Seismic Prospecting in Tight Gas Reservoirs

Abstract

This paper describes some of the seismic aspects of BP's experiences developing and exploring tight gas in Algeria. BP are involved in two projects where seismic has played a key role. The first project is a known gas field in its development stage, which requires infill well locations. The second is in its early exploration stage and requires a more fundamental understanding of the reservoir architecture. Seismic AcquisitionBP seismic delivery teams have a commitment to deliver high quality seismic data to drive BP's exploration, appraisal and development programmes. This commitment has led to a move towards well sampled, high density, wide azimuth datasets. To record such surveys on land, over large concession areas, has been prohibitively expensive. One of the main aims of BP's land seismic technology programme has been to reduce the unit cost of seismic to an acceptable level. Vibroseis productivity rates are a significant limiting factor in achieving high fold well sampled data. Two techniques have been developed by BP and are in regular use in North Africa and the Middle East. The first of these, BP's proprietary ISS™ seismic acquisition technology, was tested in late 2006 in Algeria and fully deployed in late 2008 in Libya and in Algeria in 2009(Howe et al, 2008. During the last three years, BP has built up a unique level of skill and knowledge in the technique. In this method all vibrators work independently with no attempt to synchronize their activity. All interference between sources is treated as noise and removed in processing. To date, in excess of 15,000Km 2 has been acquired by BP using this technique. The second technique, DS3 (Bouska, 2010), has been employed to great effect in the Middle East by BP where the terrain is benign and no environmental considerations would slow down this very efficient technique. Approximately 14,000Km 2 of DS3 has been acquired to date with a large survey of approximately 5,000Km 2 to be acquired by BP early in 2011.