Technological advances in well cementing have made possible the use of ultra-lightweight (ULW) cement slurries with densities as low as 7.5 ppg, without foaming. These ULW slurries often achieve significant compressive strengths, even at moderate or low curing temperatures, such as in deep water environments. However, there are plenty of opportunities for disaster to occur when conventional cement slurry design criteria, laboratory testing procedures, and field practices are inappropriately applied to ULW cementing applications. This paper will discuss the relevant issues that must be taken into account when planning a successful ULW cement operation, including materials selection, liquid volume fraction, surface and downhole densities and rheologies, compressive strength testing procedures, quality control measures, blending and bulk handling, operating error margins and on-the-fly mixing control systems. As drilling activity continues to grow into depleted and low fracture gradient areas, especially in the offshore developments, adherence to the guidelines proposed in this paper will serve to improve the likelihood of successful ULW cementing operations.
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