Improved Well Design with Risk and Uncertainty Analysis
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- PhD theses (TN-IPT) 
Original versionImproved Well Design with Risk and Uncertainty Analysis by John Emeka Udegbunam, Stavanger : University of Stavanger, 2015 (PhD thesis UiS, no. 242)
Uncertainty and associated risk assessment are frequently applied in many disciplines such as engineering, medicine and economics. Yet this study is limited to a quantitative uncertainty analysis with respect to well design, in view of modeling. Well planning is a complex process involving several physical parameters that are decisive for casing design. Some of the input variables that are subject to randomness are considered uncertain parameters. In addition, tools and mathematical models used for well design do not provide true interpretations of natural phenomena or geological processes. The models, also, are subject to the uncertainties, which may result from the approximate nature of the modeling processes. Therefore, it is important to show how these uncertainties affect the model outputs. This information is critical for decision-making during well planning. Traditionally, deterministic models are used for predicting critical fracturing and collapse pressures required for mud program and casing design. In underbalanced drilling, the operational envelope is predicted based on single-point estimates of pore and collapse pressures. The deterministic method usually neglects the modeling uncertainties. This thesis proposes an improved methodology for well design. The approach considers uncertainties in the input data and identifies the most critical parameters. The input uncertainties—expressed as probability distributions—are propagated by means of Monte Carlo simulation. The intent is to provide a systematic way of weighing the deterministic predictions against the results from the stochastic simulations. With the probabilistic approach, it may be easier for well planners to handle contingent well operations. The work also presents a one-dimensional, two-phase transient model termed the AUSMV scheme. The flow model has some potential that can be relevant to training and academic purposes. The capability of the scheme to simulate highly dynamic phenomena is presented for dual-gradient drilling and underbalanced operations.
PhD thesis in Petroleum engineering
Has partsJohn Emeka Udegbunam, Kjell Kåre Fjelde, Øystein Arild, Eric Ford, and Hans Petter Lohne. Uncertainty-Based Approach for Predicting the Operating Window in UBO Well Design. Paper SPE 164916, presented at the EAGE Annual Conference & Exhibition incorporating SPE Europec, London, UK, 10–13 June 2013.
John Emeka Udegbunam, Hans Petter Lohne Kjell Kåre Fjelde, Øystein Arild, and Eric Ford. Improved Underbalanced Operations with Uncertainty Analysis. Paper SPE 167954, presented at the 2014 IADC/SPE Drilling Conference and Exhibition, Fort Worth, Texas, USA, 4–6 March 2014.
John Emeka Udegbunam, Bernt Sigve Aadnøy, and Kjell Kåre Fjelde. Uncertainty Evaluation of Wellbore Stability Model Predictions. Paper SPE 166788, presented at the SPE/IADC Middle East Drilling Technology Conference and Exhibition, Dubai, 7–9 October 2013.
John Emeka Udegbunam, Kjell Kåre Fjelde, Steinar Evje. The Academic AUSMV Scheme — A Simple but Robust Model for Predicting Highly Dynamic Well Flow Phenomena. An extended abstract, presented at the Celle Drilling 2012, Celle, Germany, 17–18 September
John Emeka Udegbunam, Kjell Kåre Fjelde, Steinar Evje, Gerhard Nygaard. A Simple Transient Flow Model for MPD and UBD Applications. Paper SPE 168960, in the proceedings of the SPE/IADC Managed Pressure Drilling and Underbalanced Operations Conference and Exhibition, Madrid, Spain, 8–9 April 2014.
John Emeka Udegbunam. Mud Losses in Fractured Carbonate Formations. Presented at the 4th Annual Petroleum Research School of Norway (NFiP) PhD Seminar, Stavanger, Norway, 21 October 2013.