Operational Implementation of Full Azimuth, High Density land Acquisition – 3D Irharen (Algeria)

摘要

Using a square spread of dense receiver stations (25 m), a full azimuth dense 3D survey (730 km2 full fold 225) was recorded in 2005-06 over the Irharen gas discovery in Algeria. This land acquisition is representative of the coming trends aimed at improving reservoir illumination and anisotropy detection. If the basic square spread (7,200 channels) was defined from geophysical considerations, its practical implementation (a super-spread of 11,880 channels) resulted from a compromise between the daily source production and the receiver stations available. A range of VibroSeis methodologies was implemented to increase productivity: three sets of 3 vibrators were used in flip-flop mode to keep the recording as continuous a possible; they were functioning in source driven mode; on the recorder side, the super-spread avoided delays for line forming and prevented vibrators from changing of shot line too often. The huge quantity of data and quality controls produced every day by the crew led client representatives to use a Geographical Information System (GIS) to compile and analyze all of them. This approach enabled all kinds of immediate control over the different steps of the survey. It also helped to highlight geographic and temporal trends.