In underbalanced drilling (UBD), the bottom hole pressure is kept below pore pressure, causing pressure-dependent influx of reservoir gas into wellbore that makes system unstable at low drawdowns. this article, we propose a feedback controller which stabilizes system, represented by “reduced drift flux model (DFM),” around an arbitrary setpoint, while using only topside measurement and assuming...

Uncertainty theory is a mathematical methodology for dealing withnon-determinate phenomena in nature. As we all know, uncertainprocess and uncertain integral are important contents of uncertaintytheory, so it is necessary to have deep research. This paperpresents the definition and discusses some properties of strongcomonotonic uncertain process. Besides, some useful formulas ofuncertain integr...

In this work, we present a novel approach for considering dependencies (often called correlations) in the uncertain parameters when performing (deterministic) flexibility analysis. Our proposed utilizes (linear) boundary functions to approximate observed or expected distribution of operating points (i.e. uncertainty space), and can easily be integrated index test problem. contrast hyperbox sets...

Uncertain input parameters may result from "fuzziness", "randomness" or "fuzzy randomness". With the use of fuzzy set theory, uncertain input parameters may be described mathematically as fuzzy variables or fuzzy random variables and may be integrated into safety assessment analysis. With the aid of -discretization involving the multiple solution of special optimization problems, fuzzy input pa...