The cost of drilling fluid loss often represents one of the single peak capital expenditure during drilling. Fluid loss as well as many other drilling related problems can be mitigated by strengthening wellbores. Many reagents have been employed by industry to strengthen wellbores. There are two widely accepted mechanisms for wellbore strengthening; namely fracture tip isolation and stress caging. The two mechanisms, however, require fluid loss to formation in order to disconnect the fracture pressure from the wellbore pressure. Designing fluids to achieve the required loss lends itself to higher drilling cost and significant large environmental footprint. Moreover, loss of drilling fluids might not be readily abundant in tight formation.
This talk addresses the strengthening of sandstone, an example of permeable formation, and shale, an example of tight formation, by means of nanoparticle-containing drilling fluid and explores the dominant wellbore strengthening mechanism. Furthermore, the talk will attempt to relate trends in wellbore strengthening to fluid loss prevention capability of the nanoparticle-based fluid. Employing in-house prepared nanoparticles resulted in as high as 100% increase in fracture pressure and more than 50% reduction in fluid loss. In our laboratory at the University of Calgary we have developed methods for in-house preparation of dispersed nanoparticles in wide variety of virgin and recycled drilling fluids; including WBM and OBM.
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