Application of gelled polymer solution containing one or more reactive component of a polymer and a crosslinker has been widely used as water shut off fluid. They were used with the ability to reduce water production by two main performance criteria. First by reducing water relative permeability more than oil permeability using disproportionate relative permeability reduction (DPR) or relative permeability modifier (RPM), and secondly by totally block the fluid flow/total shut off using strong gels.

The current invention is related to polymerization process for total water shut off. In this study blocked isocyanate was identified and chooses as an active component in the fluid system. The polymerization process was initiated when the temperature of the injected zone reached the deblocked temperature (~90°C and above). The blocking agent (contain in the fluid) starts to unblocked and allow the isocyanate to react with other component in the system to form hard solid polyurethane. This polyurethane will form a barrier to totally block the flow of formation fluid during production.

This paper presents the performance of a blocked isocyanate water shut-off fluid designed for PETRONAS field. The newly designed fluid is one component system which works in the temperature range between 80 – 120°C. The effects of temperature at 80, 95 and 120°C and aging of core flooding experiments in water saturated condition, the treated sandstone Berea cores showed high extrusion pressure of 100psi/inch. This system is applicable for total water shut off where at residual oil saturation and irreducible water, high extrusion pressure was achieved.

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