Advanced Wellbore Transport Modelling

The project addresses knowledge needs identified by OG21 (TTA3) to be able to increase the number of drilled production wells on the Norwegian continental shelf, and specifically needs related to automation of drilling processes.

The project focus is on achieving a deeper understanding of the fluid and particle transport processes during drilling through use of advanced mathematical modelling,supported by experimental data. The choice of modelling methodology shall be guided by the need for improved models in drilling automation systems, with a hierarchy of models ranging from very detailed CFD-models to mechanistic models capable of faster than real-time execution.

The project is built around the three PhD candidates, two at NTNU and one at UoS, working in close cooperation with research teams in SINTEF and IRIS. Flow laboratories at the University of Stavanger and at NTNU will be used to generate experimental data sets for model development and verification.

Based on improved process understanding and improved modelling methodology, the project shall generate recommendations for new / improved real-time models for drilling process management.

Project goals:

  • Apply cutting edge mathematical tools and methods for detailed analysis of the process.
  • Further develop models using physical and physiochemical principles to achieve high accuracy process models with dynamic long term predictive capability.
  • Verify models with experimental data.
  • Generate detailed physical and physiochemical descriptions of mechanisms and processes.

Summary to date

A set of test-cases have been developed, covering the various elements of the drilling process. Studies have been performed with 3D models to assess to what extent it is possible to simulate stratified flows with particles collected in the lower layer (as for a cuttings bed). It has been shown that this is possible to representing the layers through mean layer viscosity and average density as a function of particle concentration. An analysis has been performed on the resulting mathematical equations, showing under which conditions solutions to the problem exist.

To study the interaction between cuttings bed and drillstring two experimental studies are to be performed at the Department of Petroleum Engineering at NTNU. The aim of this work is to develop a model based methodology using the dynamics behavior of the drillstring for indication of the amount and position of cuttings in the well. A horizontal test rig is to be used for measuring how cuttings in the well affect the friction forces that the drill string is subjected to. Another experimental study is to be performed to study vibrations of a drill string in a vertical well. A linear analytical mathematical model has been developed for modelling drillstring dynamics, where the drillstring response is modelled as elastic vibrations with frictional dampening. If the model is proven valid, it may be used in analysis of the results from tests in the horizontal rig.

At the flow laboratory of the Department of Petroleum Engineering at the University of Stavanger detailed experiments have been performed with high-speed laser and video equipment to study the more fundamental dynamics of cuttings particles in non-Newtonian flows. Experimental studies have been performed studying particle flow in a horizontal pipe with simulated rotating drill string. Further particle flow experiments have been performed in a vertical pipe with a blockage, allowing for study of the movement of cuttings bed and particle clouds in laminar and turbulent flow. Frequency analysis of the drillstring oscillatory behavior as a function of the string rotation, fluid flowrate, and fluid properties, have shown results which may be important for understanding of dynamics during drilling.

Flow simulations in 3D (Computational Fluid Dynamics-CFD) of the experiments with particle flow have been performed at UiS and NTNU, and simulations of cuttings transport in a pipe have been performed at IRIS with a simplified physics-based three-layer model, with good results. Similar models for annular geometry are being developed.

Finally, studies on 3D simulations of turbulent behavior have been performed at SINTEF, applying developed analytical wall models as boundary conditions. These simulations are performed with high resolution (so called Direct Numerical Simulations), and shall provide better knowledge of the effects of turbulence on particle transport.