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AbstractAs the global demand for energy increases, operators are being forced to drill in increasingly challenging environments. Cementing across highly depleted zones and weaker formations requires a dedicated engineering focus and lowdensity cements that are stretching the limits of current technology. If cement cannot be successfully circulated, a large impact on the drilling cost can be experienced and delays in production delivery can occur due to the required remedial work.Historically, the industry has relied on two primary technologies for the creation of ultra-light cement slurrieseither foaming base cement with nitrogen or through the addition of microspheres to the slurry. While both of these technologies are considered premium solutions and have been used successfully for a number of years, they each have distinct advantages and also limitations when compared to one another. While ideal for certain situations, neither can be used to cover the entire spectrum of today's ever-increasing spectrum of challenges. This paper presents case histories from Mexico and Oman showing how both technologies, foam and microspheres, have been used in the same design to stretch current lower slurrydensity limits, allowing us to meet ever-challenging operational demands. Along with the case histories, guidelines are provided for how to best use these technologies. Details provided from the case histories illustrate how the advantages of both technologies were maximized, while their limitations were minimized.
Lightweight Cement SlurriesTypically, there are three ways to make lightweight cement:• Water extended • Microspheres • Foam 1,2