Wells drilled overbalanced and underbalanced prove UBD value

This article briefly reviews the drilling and production history of the Gargdzai Region of Western Lithuania, and details the underbalanced drilling (UBD) program that evolved from close cooperation with the operator, UAB Minijos Nafta (MN), and Weatherford UBS, the lead UB contractor. The discussion overviews the first three-well UBD program starting in 2000 with Wells PS-2, 3 and 4. It then describes in detail drilling/completion of Well AS-1 and introduces the concept of Production Steering and use of MWD data, together with fluid influx data, to steer the well into higher-productivity layers. It also makes unique direct comparisons between overbalanced and underbalanced legs in the same well and reservoir - a direct result of the innovative relationships established during the drilling program. Finally, it discusses the ongoing drilling program that has evolved.