Abstract
Wellbore strengthening is a technique for increasing formation fracture pressure and widening the mud window. In this study, smart wellbore strengthening materials (WSMs) built on shape memory polyurethane (SMPU) are introduced. SMPU WSMs are programmed to release pre-determined recovery stress once unfold at predetermined temperature. The molecular structure of the SMPU WSM synthesized here is characterized and its shape memory, recovery stress and mechanical properties are determined. Compatibility of SMPU with xanthan gum-based drilling fluid is confirmed through mud rheology and filtration tests. SMPU WSMs mixed with SMPU lost circulation materials (LCMs) smoothly flow through the bit, pack against and seal fractures and release recovery stress once activated. Wellbore strengthening and fracture sealing of the SMPU WSM and LCM mixture show a recovery stress of 3.52 MPa in a constrained environment. The seal showed high plugging pressure of 110 bar with only 150 cm3 total fluid loss.
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