In multistage horizontal wells, cemented completions provide zonal isolation during the hydraulic fracturing treatment. With the tendency to drill longer laterals and to shorten the distance between stages, cementing faces new technical challenges in cement slurry placement and zonal isolation. One of the challenges involves incomplete displacement of drilling fluid from the annulus, thus creating communication pathways behind the casing and potentially uncontrolled fluid flow during a hydraulic fracturing treatment. In addition, many horizontal sections are now being drilled with non-aqueous fluids (NAF’s), making the displacement process even more complex, due to the hydrophobic nature of those fluids.
This presentation will describe a new technology that addresses the incomplete mud removal challenge. This technology provides zonal isolation even for the sections with poor mud removal. The new cement system interacts with residual NAF and changes its properties without affecting the cement pumping operation. New laboratory techniques for studying residual drilling fluid properties and zonal isolation will also be discussed. Field cases demonstrating the efficiency and versatility of the cement system are also included.