The present crude oil and natural gas reservoirs around the world have depleted conventional production levels. To continue enhancing productivity for the remaining mature reservoirs, drilling decision-makers could no longer rely on traditional balanced or overbalanced methods of drilling. Derived from conventional air drilling, underbalanced drilling is increasingly necessary to meet today's energy and drilling needs. While more costly and extreme, underbalanced drilling can minimize pressure within the formation, increase drilling rate of penetration, reduce formation damage and lost...