The Road to Efficient Wide-Azimuth High-Density 3D Land Vibroseis Acquisition

Currently most 3D vibroseis crews use two fleets of vibrators in flip-flop mode. The productivity depends on the sweep length and the time it takes to move from one VP to the next. The slip sweep technique is an attractive way of optimizing productivity to a level that can keep the cost of increasing source density within reasonable limits. But nothing is free and the price to be paid is that the data can be severely contaminated by harmonic noise due to the use of long sweeps combined with a very short slip-time. To overcome this problem, a method of harmonic noise reduction known as HPVA (High-Productivity Vibroseis Acquisition) has been developed. This method consists in estimating the harmonic noise in the vibroseis signature so that it can be subtracted. Several crews are now routinely using this technique with three to four fleets of vibrators. Recent 3D tests with 12 fleets of single vibrators also show very promising results which will be presented. Combined with a densification of the source grid, single-vibrator acquisition can bring either an improvement in data quality or an increase in productivity and opens the road to affordable dense, wide-azimuth seismic acquisition in desert environments.