AB Gas Fields - From Drilling Hazard to Commercial Development

Shallow Gas in the AB blocks of the Netherlands offshore was first encountered in exploration wells, targeting deeper structures, in the 1970s. Targeted exploration wells for shallow gas in the 1980s proved significant static volumes of Hi-Cal gas in stacked shallow reservoirs. Appraisal and evaluation was completed in the 1990s. However, the shallow depth and low relief of the structures, the unconsolidated nature of the reservoir sands, together with difficulties modelling reservoir architecture and predicting water breakthrough, prevented successful commercial development of the discoveries.

Chevron acquired the AB shallow gas assets from NAM in 2005. Using lessons learned from shallow reservoir development in Asia, the A12 Field development, employing highly-deviated wells completed with expandable sand screens, delivered first gas in 2007. The B13 field came on line in 2011. Further understanding of sequence stratigraphic and glacial controls on sand quality and deposition was worked into the A18 field development static model with first gas scheduled for 2015. Possible future field developments are A15, B10 B16 and B17.

Chevron had to develop new ideas and understanding to overcome the technical challenges and successfully develop these fields showing that shallow gas is no longer a drilling hazard but an economic gas play.