Shallow Play in The Netherlands - Derisked by Seismic Characterisation

Abstract

The Dutch North Sea area hosts more than 160 shallow gas leads in unconsolidated, Cenozoic reservoirs that are identified by amplitude anomalies on seismic data (bright spots). Several accumulations have been proven by wells and nowadays there are three successfully producing fields using innovative sand control measures in horizontal wells. An inventory of this play has pointed out significant potential volumes, raising a lot of interest from the industry. The present study highlights the advances in the shallow gas appraisal work in the Dutch offshore A-H blocks and includes an improved bright spot characterisation scheme in order to select those leads that have highest potential for development. Each individual bright spot is characterised based on ten parameters. The focus is on seismic expressions relating to the amplitude anomalies such as the presence of velocity pull-down, flat spots, gas chimneys and seismic attenuation. Several of the seismic features have been modelled to improve the understanding of their relation with gas saturation. The F12-Pliocene-Alpha prospect has well-expressed diagnostic features pointing towards the entrapment of shallow gas and is presented as a case study.