Isogeometric analysis : applications for torque and drag models, drillstring and bottom-hole assembly design

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Date

2018-05

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Hanson, Katy Lynn

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Abstract

The drilling industry today relies on torque and drag models to analyze and ensure success during all phases of well construction and operations, including planning, drilling, and completion. Analytical models are based on equations that are undergoing constant development and improvement. The finite element method is an alternative to complex analytical calculations that is used often to determine torque and drag forces that are present when a drillstring is lowered, raised, and rotated in a wellbore. Traditional finite element analysis (FEA), however, is not time efficient or computationally able to simulate the complexities of a real wellbore. Thus, we introduce an alternative to the traditional finite element approach: isogeometric analysis. Isogeometric analysis is similar to finite element analysis except that it uses NURBS (Non-Uniform Rational B-Splines), as opposed to interpolatory polynomials used in traditional FEA, as the basis functions. NURBS functions are the same as those used in CAD programs, and they are able to construct exact conic shapes, such as circles and ellipses. Adopting NURBS basis functions allows finite element analysis to be performed directly on the exact geometrical surface - not on an approximate geometric surface mesh, as in traditional FEA. IGA yields a significantly faster and more accurate simulation. This thesis presents a real-world application of IGA to a drag force model to determine the resultant surface hook load during run-in-hole (RIH) operations. Real well data is used, and IGA results are compared to a similar FEA analysis. The outcome shows that IGA is indeed a superior finite element method that has immense potential for further application in the industry

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