Deep Bed Filtration Modelling of Formation Damage Due to Particulate Invasion from Drilling Fluids

A Deep Bed Filtration model has been developed to quantify the effect of solids invasion from drilling fluids on the permeability of rock formations. The calculated particle-trapping profiles are compared directly with experimental profiles from scanning electron microscopy and synchrotron X-ray diffraction tomography mapping. The computed permeability reduction as a consequence of particle invasion is in broad agreement with experiment. Backflow was modelled by reversing the flow rate, starting off with a situation where all particles either remain trapped or are all released. It appears that the experimentally observed 30% release of particles upon backflow is reproducible within the limits of the two extreme cases. When erosion is included in the model, a peak in the backflow pressure time series can be observed. This peak may be correlated with the experimentally observed flow initiation pressure, which is the backflow pressure needed to initiate flow after initial inflow filtration. Finally, we conclude that internal reservoir damage, within the limits of our 1-D single phase DBF model, may contribute to the experimentally observed flow initiation pressure.