A Stochastic Approach for a Cosserat Rod Drill-string Model with Pseudo Stick-Slip Motion

RUBENS SAMPAIO; ROBERTA LIMA; FERNANDO S. BUEZAS; HÉCTOR E. GOICOECHEA; MARTA B. ROSALES

Rouen

Simposio; 5th. International Symposium on Uncertainty Quantification and Stochastic Modelling; 2020

INSA Rouen, France

Drill-strings employed in the oil extraction process present complex dynamics. Due to their slenderness (with length surpassing 1000m), geometrical aspects of oil-wells, and contact forces, drill-strings exhibit a strong non-linear response. Many unwanted phenomena, like stick-slip oscillations, may occur under certain conditions. Moreover, there are several intrinsic uncertainties, e.g. in modelling the soil, which may lead to unwanted operation regimes and affect performance, i.e. de- graded rate-of-penetration (ROP), and stick-slip. In this work, a stochas- tic approach to study drill-string dynamics is employed. The physical model is based on the Cosserat rod theory. Non-linearities of the drill- string problem may occur due to geometrical factors, such as finite dis- placements and rotations in deviated wells, as well as to contact and friction at the borehole wall and bit. In this particular paper, uncertain- ties are considered within the friction parameters. The random response is analysed through the trajectories of the drill-string axis and other quantities, such as the evolution of the angular velocities.