Designing drill in fluids which can guarantee minimum invasion into the reservoir rock is a must for open hole completion wells. The industry has proposed several ideas to deal with the problem, most of them based on adding bridging agents to the fluid formulation. Such agents would block the pores near the well bore and, consequently, prevent additional fluid invasion into the rock, but often require acid treatment for their removal.

A different concept is proposed for controlling invasion in this article: designing a polymer based fluid which would generate extremely high friction losses when flowing through a porous media without generating extra losses while flowing in the well. In this case the fluid would present proper flow and solids transport properties in the well and would not invade the rock formation.

Previous studies by the authors showed that the viscoelastic behavior of fluids can be a major restriction to fluid invasion. This article deals with the optimization of viscoelastic parameters, such as the first normal stress difference and the extensional viscosity, for minimizing fluid invasion through oil reservoirs. The invasion analysis is based on a two phase (viscoelastic fluid + Newtonian oil) radial flow through porous media and supported by a commercial CFD package. Static and dynamic filtration phenomena are represented.

The arrival of this rheology controlled invasion concept brings to the polymer manufacturers a new challenge: the development of a highly viscoelastic polymer with non damaging behavior and adequate wellbore properties.

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