3D TROMSO Survey Planning: Cost efficiency through seismic data quality.

Abstract

Abstract The approach described in this case history allows for the firs(hrclirrrr of a ‘full 3D’ dataset in order to solve the interpretation problems of [he area at reduced COSI. The structural definition of the main prospects in the area was unclear. mainly due to the poor quality of 2D seismic data, The committed 2D seismic survey would have probaby supplied a seismic-data set of slightly better quality, but on the other hand. there would not have been a suitable improvement in the imaging of the main prospects. In an attempt to overcome these problem, an ‘Explorative 3D’ survey was planned. In order m ensure a proper quality of the .3D dataset an integrated approach to the acquisition and processing planning was adopted. Acquisition was carried out utilizing ‘skipped configuration’ capable of acquiring 12 CMP lines for each sail line with a considerable reduction in cost. Introduction The area under investigation. located in the Barents Sea PL 20I on Blocks 701 8/3 - 7019/1, is characteristic by a complex lacating setting. Several 2D seismic surveys had shot in the Blocks in question in the past, Nevertheless. the quality of the previous data doesn't allow for a proper definition of the main plays to be made. The main geophysical problems are linked to the pattern of reflection and refraction multiples and the dipping noise that masks the primary events. The analysis of the area suggested that a new 2D seismic acquisition would not have supplied sufficient improvement in the imaging of the main prospects. A different approach was therefore considered. The approach, which we call ‘Explorative 3D’ allows for the production of a ‘full 3D’ dataset at reduced cost. The study started with the analysis of the previously acquired 2D data and with the reprocessing of part of it. By selecting an appropriate processing sequence, from the theoretical parameter study and the prospect geophysical constraints, an operaiorral proposal was presented 10 the partners, The final implementation takes into account the theoretical constraints for the main target, the experience already acquired in this kind of ‘Explorative 3D’ and the overall budget constraints. Acquisition was carried out utilising a quad streamer dual source configuration with a specific lay out capable of acquiring twelve CMP lines for each sail line. Such an approach requires proper handling of the data through special processing steps, such as the extensive use of flexibinning technique. Moreover, [he utilisation of special pre-stack deconvolution techniques in the TAU-P domain was also considered.