Computational modeling of the nonlinear stochastic dynamics of horizontal drillstrings

TL;DR

This paper models the complex nonlinear stochastic dynamics of horizontal drillstrings, incorporating effects like impacts and uncertainties, and proposes optimization strategies to enhance drilling efficiency.

Contribution

It introduces a comprehensive nonlinear stochastic model of drillstrings considering impacts and uncertainties, and develops optimization methods for improved drilling performance.

Findings

Rich nonlinear stochastic behaviors observed, including bit-bounce and stick-slip.

Numerical simulations demonstrate the model's ability to replicate real drilling phenomena.

Optimization strategies effectively increase penetration rate while respecting structural limits.

Abstract

This work intends to analyze the nonlinear stochastic dynamics of drillstrings in horizontal configuration. For this purpose, it considers a beam theory, with effects of rotatory inertia and shear deformation, which is capable of reproducing the large displacements that the beam undergoes. The friction and shock effects, due to beam/borehole wall transversal impacts, as well as the force and torque induced by bit-rock interaction, are also considered in the model. Uncertainties of bit-rock interaction model are taken into account using a parametric probabilistic approach. Numerical simulations have shown that the mechanical system of interest has a very rich nonlinear stochastic dynamics, which generate phenomena such as bit-bounce, stick-slip, and transverse impacts. A study aiming to maximize the drilling process efficiency, varying drillstring velocities of translation and rotation is presented. Also, the work presents the definition and solution of two optimizations problems, one deterministic and one robust, where the objective is to maximize drillstring rate of penetration into the soil respecting its structural limits.