The PARTRACK model for calculation of the spreading and deposition of drilling mud, chemicals and drill cuttings

A model has been developed for the calculation of the spreading and deposition on the bottom of drilling mud and cuttings as well as the spreading of chemicals in the free water masses. The calculations are based on the ‘particleʹ approach, combined with a near field plume model and with the possibility of applying external current fields for the horizontal advection of the particles. The model consists of a plume mode and a far-field mode. The plume mode takes into account effects from water stratification on the near-field mixing, ambient currents and geometrical configuration of the outlet. Once the plume has been trapped in the water masses, particles are free to fall out of the plume and deposit on the bottom. Downwards (or rise) velocity of the particles is dependent on size and particle density. Up to 36 different particle classes can be used. Chemicals may be represented in the model as ‘particlesʹ which are either very small or with neutral buoyancy. The far-field mode includes the downstream transport and spreading of particles and dissolved matter, once the plume mode is terminated. The model has been applied to calculate concentration fields for releases of matter into the free water masses, as well as the accumulated deposition on the bottom from an exploration drilling and a regional study of expected depositions from more than 15 years of drilling activity at 10 locations outside the western coast of Norway.