The Delineation of Pre-Salt License Blocks in the Deep Offshore Campeche-Yucatan Basin

Abstract

The emergence of pre-salt exploration in the past 30 years has resulted in a significant addition to world oil reserves since the first pre-salt discovery offshore Angola in 1983. Among the most successful deep water pre-salt exploration plays is the Campos Basin offshore Brazil, where a milestone achievement of 800,000 bpd production level was achieved just 8 years after the first pre-salt well was drilled in 2006. The Yucatan Basin offshore Mexico represents one of the last significant pre-salt exploration provinces yet to see any significant exploration activity. In this paper we illustrate evidence of an extensive pre-salt layer using newly acquired long-offset 2D seismic data. We distinguish between sub-salt and pre-salt prospects in the Yucatan Basin by illustrating images of pre-salt horst and graben rift structures and pre- and syn-rift deposits, which have been proven as potential source and reservoir rocks elsewhere. Sub-salt plays are also in evidence in the northeastern Campeche Basin, and are well documented in the northern Gulf of Mexico as an exploration analog. The success of pre-stack depth migration for the purpose of improving sub- and pre-salt imaging has been well documented, and the prolific discoveries offshore the US Gulf of Mexico, Brazil and Angola speak to the importance of this imaging tool. However a more fundamental tool necessary for improved imaging is and has always been fold of coverage. The pre-salt section in the Yucatan Basin is in water depths exceeding 3,500 m with a thick sedimentary section, consequently a 15 second record length is necessary to image the sediments and structures beneath the salt. Normally this would require a low fold acquisition geometry to accommodate the extra time between shots, which we resolve using continuous recording acquisition technology and source de-blending to achieve a high fold geometry with a record length sufficient to image the deep pre-salt section. Foremost among the requirements for successful pre-salt exploration is an accurate delineation of block definitions prior to a commercial license round. We demonstrate that clear images of the pre-salt section can be obtained using a high-fold, long record length acquisition geometry with detailed pre-stack depth migration. A dense grid of properly imaged 2D seismic is shown to be necessary and sufficient to provide a basis for block definition and bid round evaluation in the early stages of pre-salt exploration in the Yucatan Basin.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016