Increasing horizontals, narrowing annular gaps, more stringent cement regulations, fracturing with more stages and high pumping rates on top of more cost-efficient well completion are raising demand for lightweight cements, which are designed to prevent damage and lost circulation problems in weaker formations. However, many alternative lightweight materials that are more cost effective than glass beads, which are known to provide superior strength, are increasing waiting-on-cement time, thus delaying further drilling. They also struggle to deliver the required compressive strengths. This paper presents (1) recent case histories of successful field applications of new stronger non-beaded lightweight cement, (2) extensive laboratory data of various field designs with new lightweight cement versus premium commercial lightweight cements, and (3) detailed scientific study explaining how the innovative lightweight cement has provided superior fluid stability and set cement mechanical properties.
The successful field trials occurred in the Permian basin for all four wells on the same pad. About 400 bbl of the new lightweight cement at 10.5 lbm/gal density was delivered to complete each cementing job with 134°F BHST and 6,000-ft measured depth. The four wells were completed with the new lightweight cement, remarkably having no glass beads despite the extremely low density. Unlike the previous job designed with commercial lightweight cement, the new cement has provided far greater compressive strength and has shown faster (18 to 24 hr) strength development. During placement, the new lightweight cement slurry has demonstrated exceptional stability with fewer additives than the previous design, thus simplifying field operations. Multiple laboratory test data at different cement densities (10.5 to 14.5 lbm/gal) for other regions confirmed the enhanced performance of the new lightweight cement in both slurry form and set cement over conventional lightweight technologies. Detailed scientific study via X- ray Diffraction (XRD) explained how the new lightweight cement provided superior set cement performance.
The novelty of this work and invaluable contribution to the industry is the first successful field application of a newly developed micromaterial that provided a lighter, stronger, low-permeability, non-beaded cement that enhances wellbore integrity and provides better zonal isolation. New findings from XRD and Scanning Electron Microscopy (SEM) imaging techniques about the new micromaterial lightweight additive may provide insights for improving the performance of traditional materials.