Incremental improvements in 50:50 poz cementing yields enhanced properties and cost-effective application

O. A. Fasesan, L. R. Heinze, D. W. Walser

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

For nearly 50 years, admixtures of 50:50 Class H (or Class C): Pozzalon with 2% bentonite have functioned effectively worldwide as lightweight slurries for situations where heavier completion cements posed a risk of exceeding low fracture gradients in a particular wellbore. Pozzolanic materials are lightweight, and effectively combine with calcium hydroxide that is liberated during the hydration of Portland cement. Historically, the 2% bentonite has been utilized to assist in the specification of relatively high water-To cement ratios, and therefore lighter slurry density, without the generation of excessive free water as the cement progresses though the setting process. Though the bentonite has fulfilled the role quite well, it has two disadvantages: first, its presence in typical cement slurries reduces the effectiveness of a given concentration of most commercially available fluid loss additives. Second, while the 2% (by weight of cement) volume may seem of no consequence, the shipping costs associated with moving tons of the material over a long period of time can be significant. A project was undertaken to determine whether or not there were other commercially available materials that could substitute for bentonite and yield improved slurry qualities at the same or reduced cost. Extensive testing of 50:50 slurries revealed that small quantities of sodium metasilicate (on the order of 0.5% by weight of cement) could effectively replace bentonite. Free water was controlled to the same degree, and a synergy with a commonly available fluid loss additive was discovered, allowing either a) less total fluid loss additive for a given fluid loss control tolerance, or, b) better fluid loss control for a given concentration of fluid loss additive. The testing is summarized, and relative economics associated with the systems are discussed.

Original languageEnglish
Title of host publicationSociety of Petroleum Engineers - SPE Production Operations Symposium 2005, POS 2005
PublisherSociety of Petroleum Engineers
ISBN (Print)9781613990094
StatePublished - 2005
EventSPE Production Operations Symposium 2005, POS 2005 - Oklahoma City, United States
Duration: Apr 16 2005Apr 19 2005

Publication series

NameSociety of Petroleum Engineers - SPE Production Operations Symposium 2005, POS 2005

Conference

ConferenceSPE Production Operations Symposium 2005, POS 2005
CountryUnited States
CityOklahoma City
Period04/16/0504/19/05

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