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Dr. P. V. (Suri) Suryanarayana has been selected to be a Distinguished Lecturer for the Society of Petroleum Engineers from September 2006 through May 2007. The purpose of the Distinguished Lecturers Program is to assist SPE sections in obtaining recognized, outstanding speakers for section meetings and recognize the professional contributions of the person selected as a Distinguished Lecturer. It is one of the most important programs through which the Society meets its principle objective-the dissemination of technical information. Through Suri’s lecture “Is Underbalanced Drilling the Right Answer for Your Reservoir?” he hopes to share his wealth of knowledge on this subject.
Is Underbalanced Drilling the Right Answer for Your Reservoir?
P.V. (Suri) Suryanarayana
Blade Energy Partners
Underbalanced drilling (UBD) has evolved from a drilling technique into a reservoir exploitation tool. The primary benefits of underbalanced drilling motivating its increasing consideration are enhanced productivity through mitigation of invasion damage, and reservoir characterization using UBD data. However, selection and valuation of underbalanced drilling candidates still remains a largely arbitrary and heuristic process. In this lecture, we present a rigorous, integrated approach that takes into consideration cost, value and risk to evaluate the underbalanced drilling candidature of a reservoir. The benefits and risks (particularly contra-indicators) of underbalanced drilling are first articulated through numerous examples. The emerging art of reservoir characterization using underbalanced drilling data is also presented with examples. Since the main premise of underbalanced drilling is that it mitigates damage from conventional overbalanced drilling, it is important to first characterize such damage, and evaluate the potential for underbalanced drilling to improve performance. We present an approach that combines results from special core tests with dynamic invasion modeling using fine-grid simulators to assess and quantify invasive damage and its impact on production. Results are illustrated using video clips. Finally, we present a rational valuation approach that uses probabilistic productivity estimation tools together with dynamic simulation methods to obtain expected production curves when underbalanced drilling is applied. Selection of appropriate candidates in the context of these methods is discussed. The lecture provides a broad coverage of recent developments and new challenges in reservoir application of underbalanced drilling.
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