A stochastic approach for a Cosserat rod drill-string model with stick-slip phenomena

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

Rouen

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

INSA Rouen, France

Drill-strings employed in the oil extraction process presentcomplex dynamics. Due to their slenderness (with length surpassing1000m), geometrical aspects of oil-wells, and contact forces, drill-stringsexhibit a strong non-linear response. Many unwanted phenomena, likestick-slip oscillations, may occur under certain conditions. Moreover,there are several intrinsic uncertainties, e.g. in modelling the soil, whichmay lead to unwanted operation regimes and affect performance, i.e. degraded rate-of-penetration (ROP), and stick-slip. In this work, a stochastic approach to study drill-string dynamics is employed. The physicalmodel is based on the Cosserat rod theory. Non-linearities of the drillstring problem may occur due to geometrical factors, such as finite displacements and rotations in deviated wells, as well as to contact andfriction at the borehole wall and bit. In this particular paper, uncertainties are considered within the friction parameters. The random responseis analysed through the trajectories of the drill-string axis and otherquantities, such as the evolution of the angular velocities.