Influence of the ratio of drill bit size and conductor casing diameter on jetting with Lattice Boltzmann method

Resumo

Conductor casing is the first stage of the wellbore. It is responsible for supporting the installation of the
following strings by resisting the stresses involved in the entire process. The conductor seals unconsolidated
formation and guarantees the ideal pressure balance between internal and external environments. Installation by
jetting is a widely adopted solution in deep water due to its reduced execution time. Furthermore, the process
requires attention to control the size of the cavity. This work presents a numerical simulation of the jetting in a
clayey offshore soil during conductor casing placement, aiming to quantify the influence of the ratio between the
drill bit and conductor diameters on soil disturbance and operation time and other operational parameters. A Lattice
Boltzmann (LBM) model is adopted to deal with the soil-fluid interaction. A drill bit with three inclined nozzles
rotates while jetting drilling fluid and descends alongside the jetting system toward the soil domain. The soil
domain is governed by a viscoplastic model based on a Herschel–Bulkley fluid. The size of drill bit influences the
soil area reached, allowing better control over the advance. The presented results help to properly understand the
operational jetting parameters and can be employed to set optimal installation procedures.