Evolution of a seismic acquisition methodology through integrated testing - onshore Abu Dhabi, United Arab Emirates, 1996-2000

Abstract

Summary For onshore seismic data the resolution at the exploration target level depends on the complex interaction of many factors. These include the survey environment, geology, acquisition configuration and data processing procedures. When designing seismic surveys we wish to achieve the required target level resolution while minimising both cost and risk. For Vibroseis surveys, the time expended recording each source point, called the sweep effort/VP, can be a key cost factor. Uncertainty about the impact of differing options for the acquisition geometry and source point sweep effort on the target level resolution represents a risk factor. A 3D seismic exploration methodology driven by the resolution at the target level has been implemented for onshore Abu Dhabi, United Arab Emirates, by the Abu Dhabi Company for Onshore Operations (ADCO), in co-operation with Western Geophysical. Techniques originally developed for the on-crew processing of 2D acquisition parameter tests have been extended to 3D. Integrated data acquisition and processing tests provide fully processed, 3D migrated data volumes. Test analysis is based on the interpreted resolution at the target level, allowing direct judgements on key parameters affecting data cost and quality. The spatial distribution of source energy, improving the trace offset distribution and increasing the CMP fold is seen as significantly more important than the sweep effort/VP. Close co-operation between ADCO and Western's Geophysical Abu Dhabi data acquisition and processing staff ensure that complex data manipulation issues are handled in a timely manner, allowing the results of the testing to influence an ongoing 3D project. Use of this methodology has so far provided both improvements in data quality to levels not seen before for Abu Dhabi onshore data while simultaneously reducing the cost and risk of data acquisition. This paper summarises results from some of the key events in the development of the acquisition testing methodology: (A) 1996 – 2D testing for 2D acquisition. (B) 1997 – 2D testing for 3D acquisition. (C) 1998 – Simultaneous downhole acquisition. (D) 1999 – 3D testing for 3D acquisition.