Formation damage in horizontal wells, often open hole completed, is a critical point for oil fields developed in deep off-shore, where acceptable development costs are based upon a limited number of highly productive wells. This paper describes a simplified numerical approach to model filter cake removal by natural cleanup when the well is put under a drawdown pressure difference. A flow simulator taking into account the near well permeability variation has been developed using a cylindrical grid with very small gridblocks around the well. Laboratory data obtained on sandstones damaged with an oil-based mud have been used as input data to model filter cake removal by natural cleanup. The purpose of this modelling is to optimize the applied drawdown pressure, to study the variation of well productivities as a function of the pressure drawdown, and to get the best possible well performance preventing sand production problems in poorly consolidated formations.