Sanding Process and Permeability Change

Abstract

This paper first presents a consistent mathematical framework to predict sand production volume, focusing on the coupling between hydro-mechanical factors, formation deformation and the resulting permeability change. Two types of sand production mechanisms are considered: production of coarse sands under mechanical failure and production of fine sands under hydro-dynamical erosion. The Drucker-Prager constitutive law with cap hardening is adopted to describe both dilative and collapsing deformation behaviour. The finite element method is used to solve the coupled governing equation system. After the model is validated with a field history case, it is used to compute two examples of wellbore pressure drawdown and the associated impact on the near-wellbore sanding process and permeability change. The calculation indicates that the permeability can be modified any time during the sanding. For example, under suitable reservoir depletion, the near-wellbore permeability can increase by 30%. However, more drastic pressure depletion under the otherwise identical in situ and operating conditions causes compaction near the wellbore and permeability decline by nearly 40%. Therefore, these simulated cases suggest that a balanced pressure depletion strategy should be used to manage the sand production.