Underbalanced (UB) drilling techniques are no longer being used simply to minimize reservoir impairment and improve access to remaining reserves in depleting fields. Traditionally archived and forgotten after the well was drilled, production data and reservoir information gathered while drilling underbalanced are increasingly gaining importance with oil and gas companies.

One Operator has been using UB technology in both clastic and carbonate reservoirs initially to maximize production through the minimization of reservoir impairment. Most of the operator's fields are supported by a weak aquifer or are under tertiary development through waterflood, and the task of water management is a growing concern. While minimizing reservoir damage is now a foregone conclusion when discussing UB operations, the ability to further maximize production through the ability to shut off water-producing zones is now a prime driver for drilling UB.

The comparison of ‘snapshot’ fluid production data during drilling offers a unique perspective on the well being drilled against geophysical LWD/MWD and post-drilling logging data. Temporal production data offers another piece to the reservoir makeup puzzle, and when placed alongside other available data allows reservoir engineers and geophysicists to forensically characterize their reservoir.

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