Introduction to Underbalanced Drilling

Prepared by: Steve Nas, Asia Pacific Regional Engineering Manager Weatherford Underbalanced Systems/ Issue Date: January 2006/ 154 pages/This introduction is intended to provide an overview of current underbalanced drilling
technology and is therefore by no means exhaustive. It should serve as a guide to
the current UBD technology, explaining how, when and why underbalanced drilling is
carried out.