Offshore Coring are time consuming and expensive operations which, if well conducted, provide extremely important information concerning rock and fluid properties. Drilling fluid invasion may be a relevant issue to affect fluid and rock reservoir original properties. Different hypothesis for pressure dissipation in the core are formulated and their impact on invasion are quantified.

This article deals with the derivation of an analytical formulation for drilling fluid invasion in cores, based on filter cake permeability results obtained in lab testing. The formulation represents the radial flow from the external lateral walls of a cylinder and considers plug flow in the porous medium and external filter cake formation. A comparison of the prediction and the observed invasion in real cores obtained in exploratory wells is presented.

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