Underbalanced Drilling (UBD) technology has been widely used in the last decades all over the world. The main application for it was the depleted "well developed" reservoirs. Using UBD technology in the HPHT Exploration wells is considered to be a huge turn in UBD Applications. It is a continuous challenge to get it done safely with the high uncertainties of the available information about the formations and the reservoir in this area.
As the easy hydrocarbon resources are depleting and the industry has to search for oil and gas in deep environment, PDO has taken the route that not too many companies did in using the UBD technology to speed up the identification of the existence of the flowing gas in deep tight gas exploration wells.