Pore pressure and fracture pressure analyses in non-consolidated rocks

摘要

Pore and fracture pressure trends were analyzed to provide recommendations and support drilling of deep wells in non-consolidated formations of the Gulf-of-Mexico fields (Matagorda Island and East Cameroon). The main objectives were to predict pore pressure and fracture gradient, analyze compartmentali-zation, aid to well design and control drilling in the overpressured sections. We were particularly interested in understanding the role of diagenetic changes and tectonic activities (faulting) that control (enhance/damage) the sealing properties of shales. Faulting is an important mechanism in forming of the overpressured zones, but on the other hand it can partially destroy shale sealing properties. These two different events were observed in the Gulf-of-Mexico area and thoroughly documented. Assessment of both examples allows defining an influence of particular fault and predicting formation pressure with more confidence.