Mixing Cement by Solids Fraction Instead of Density

Abstract

Abstract While mixing cement on the fly any density error made may induce large changes in critical slurry properties. Therefore controlling density during a cementing job is known to be one of the key factors to the success of the operation. This led service companies to develop process controlled mixing systems. These equipments work reasonably well when the density of the dry powder – the cement blend – differs significantly from that of the mix water, which is quite often the case. Blends with engineered particle size distribution have allowed designing cement systems with high performances nearly independently of their density. Recently this technology was upgraded to provide comparable physical properties at slurry density similar to that of water. These new cement blends now have a density that can be equal to that of the mix water. In this case, it is clear that the mixing process cannot be monitored or controlled by measuring the density of the mixed fluid since the mix water, the cement blend and therefore the mixed slurry all exhibit the same density. To overcome this problem, a new quality control principle based on solids fraction measurement was developed. The first part of this article presents the basic principles of the new device as well as their implementation on existing field equipments. The second part discusses the key advantages of controlling solids fraction and proposes to make it a universal quality control parameter for not only ultra-lightweight high performance slurries, but also for conventional systems be they lightweight or heavyweight. The benefits associated to this new technology are illustrated through the analysis of various cementing jobs while mixing slurries as light as water or at a much higher density.