Phase Evolution of Oil Well Cements with Nano-Additive at Elevated Temperature/Pressure

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Title: Phase Evolution of Oil Well Cements with Nano-Additive at Elevated Temperature/Pressure

Author(s): Siwei Ma, Tony Yu, Yanbin Wang, Mohend Chaouche, and Shiho Kawashima

Publication: Materials Journal

Volume: 113

Issue: 5

Appears on pages(s): 571-578

Keywords: high pressure; high temperature; nanomaterials; oil well cement; synchrotron; X-ray diffraction

Date: 9/1/2016

Abstract:
Phase characterization of Class A oil well cement slurries was performed through synchrotron X-ray diffraction technique. This allowed for real-time, in-place measurements of X-ray diffraction patterns to be obtained and, subsequently, the continuous formation and decomposition of select phases over time (up to 8 hours). Phases of interest included alite, ferrite, portlandite, ettringite, monosulfate, and jaffeite (crystalline form of calcium silicate hydrate). The effects of elevated temperatures (140, 185, and 300°F [60, 85, and 149°C]) at elevated pressure (up to approximately 15 ksi [100 MPa]), as well as the effect of nanomaterial addition were investigated. Rate of conversion of ettringite to monosulfate increased with increasing temperature, and monosulfate became unstable when temperatures reached 185°F (85°C). The results of synchrotron X-ray diffraction provided evidence of a seeding effect introduced by nano-sized attapulgite clays at 0.5% addition by mass of cement, where acceleration in the rate of formation of portlandite and jaffeite was observed. This was supported by isothermal calorimetry results.