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Non-linear Stiff String Torque and Drag Modelling Made Easy

Since the development of the first torque and drag models used to predict rig hook loads in the early 1980s, drilling and completion engineers have relied on various forms of proprietary and commercial software to:

  • optimize well trajectory and tubular designs;
  • prevent buckling and lockup; and
  • understand the installation load profiles for critical string components.

Longer laterals, advanced completion tools, and complex well trajectories demand a more flexible and rigorous torque and drag solution built for the modern equipment and well designers.

The Industry Challenge:

The majority of the current torque and drag software estimates hook loads and downhole forces using either soft string or simplified stiff string approaches, which include simplifications designed to speed up simulations, such as:

  • Zero bending stiffness –  which can lead to inaccurate estimation of contact loads, especially for large and stiff assemblies and high curvature wells
  • Tubular string matches the wellbore trajectory – ignores the effect of tubular-to-wellbore radial clearance on the deflected tubular shape and can also lead inaccruate estimation of local contact loads
  • Linear geometrical and material behavior – prevents predictions of buckling and assessment of post buckling response

As a result, the effectiveness of the majority of the current torque and drag software is limited to wells with low curvature, tubulars and completion equipment with low stiffness and simple geometries, and in scenarios where buckling and localized curvature of the string are not a concern.

How We Help:

C-FER has developed an advanced non-linear stiff string torque and drag model that is customizable to any string design and is able to be combined with detailed structural analyses.

Advantages include:

  • Apply any design – sand control systems, non-API connections, centralization and complex completion tools can be accommodated
  • Conduct accurate contact assessments – both contact locations and magnitudes can be accurately predicted
  • Consider non-linear effects – non-linear material response, geometric variations, composite structures, and predictions of buckling onset and post-buckling response including lock-up
  • Use any well geometry – complex well trajectories including local tortuosity are accommodated

These factors and others can strongly impact the installation loads in your string and the success of installing complex bottomhole assemblies in modern well trajectories.  C-FER will work with you to complete your simulation and provide results specific to your needs.

Further Information

For more details and to learn more through an example analysis case, download C-FER’s paper, "Evaluation of Horizontal Liner Installation Loads Using Advanced Numerical Simulation Technique."

Contact Gang Tao, Senior Research Engineer to learn more.


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