• A distributed parameter systems view of control problems in drilling 

      Di Meglio, Florent; Aarsnes, Ulf Jakob Flø (Journal article; Peer reviewed, 2015)
      We give a detailed view of estimation and control problems raised by the drilling process where the distributed nature of the system cannot be ignored. In particular, we focus on the transport phenomena in Managed Pressure ...
    • A simplified two-phase flow model using a quasi-equilibrium momentum balance 

      Aarsnes, Ulf Jakob Flø; Ambrus, Adrian; Di Meglio, Florent; Vajargah, Ali Karimi; Aamo, Ole Morten; van Oort, Eric (Journal article; Peer reviewed, 2016)
      We propose a simple model of two-phase gas–liquid flow by imposing a quasi-equilibrium on the mixture momentum balance of the classical transient drift-flux model. This reduces the model to a single hyperbolic PDE, describing ...
    • An adaptive observer for hyperbolic systems with application to UnderBalanced Drilling 

      Di Meglio, Florent; Bresch-Pietri, Delphine; Aarsnes, Ulf Jakob Flø (Journal article; Peer reviewed, 2014)
      We present an adaptive observer design for a first-order hyperbolic system of Partial Differential Equations with uncertain boundary parameters. The design relies on boundary measurements only, and is based on a backstepping ...
    • Extremum seeking for real-time optimal drilling control 

      Aarsnes, Ulf Jakob Flø; Aamo, Ole Morten; Krstic, Miroslav (Peer reviewed; Journal article, 2019)
      This paper demonstrate the feasibility and illustrates some challenges of applying extremum seeking control to online optimization of the drilling process. Specifically, we consider the problem of finding the hook-load ...
    • Modeling of Two-Phase Flow for Estimation and Control of Drilling Operations 

      Aarsnes, Ulf Jakob Flø (Doctoral thesis at NTNU;2016:136, Doctoral thesis, 2016)
      Modern approaches to process monitoring, optimization and control promise enhanced robustness and performance through the merger of process knowledge encoded in mathematical models with real-time measurements from the ...
    • Real-time estimation of reservoir influx rate and pore pressure using a simplified transient two-phase flow model 

      Ambrus, Adrian; Aarsnes, Ulf Jakob Flø; Vajargah, Ali Karimi; Akbari, Babak; van Oort, Eric; Aamo, Ole Morten (Journal article; Peer reviewed, 2016)
      The ability to perform accurate pore pressure and reservoir inflow estimation during a kick incident is necessary, particularly when drilling in formations with narrow pressure margins. Currently available techniques for ...
    • Reduced Order Observer Design for Managed Pressure Drilling 

      Aarsnes, Ulf Jakob Flø (Master thesis, 2012)
      Reduced Order Observer Design for Managed Pressure Drilling
    • Review of two-phase flow models for control and estimation 

      Aarsnes, Ulf Jakob Flø; Flåtten, Tore; Aamo, Ole Morten (Journal article; Peer reviewed, 2016)
      Most model-based control and estimation techniques put limitations on the structure and complexity of the models to which they are applied. This has motivated the development of simplified models of gas-liquid two-phase ...
    • State and Parameter Estimation of a Drift-Flux Model for Underbalanced Drilling Operations 

      Nikoofard, Amirhossein; Aarsnes, Ulf Jakob Flø; Johansen, Tor Arne; Kaasa, Glenn-Ole (Journal article; Peer reviewed, 2017)
      We consider a drift-flux model (DFM) describing multiphase (gas-liquid) flow during drilling. The DFM uses a specific slip law, which allows for transition between single and two phase flows. With this model, we design ...