Casing while drilling results in safer drilling, larger wellbores in Lake Maracaibo ///

Drilling in troublesome shallow gas areas represents one of the most risky activities in the oil industry. This is the case for Petróleos de Venezuela, S.A. (Pdvsa), in drilling Miocene and Eocene reservoirs in some areas in Lake Maracaibo in western Venezuela. For years, drilling activity in Lake Maracaibo has been performed with cantilever barges using conventional drilling equipment and standard procedures, with a contingency plan to mitigate the risk of influx and subsequent well control events. Part of this contingency plan is to drill a pilot hole through the gas zone. The pilot hole then is under-reamed and cased. The time to construct the well is long and the number of trips required is high. Statistics indicate that most of the well control events occur during tripping operations. Another area with shallow gas is Venezuela’s onshore La Vela and Cumarebo Fields, where drilling activity was deferred...

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