ABSTRACT
Lightweight cement slurries with foam additions are used in multiple applications including onshore and offshore deep wells installed in varying geological formations with lower rock strengths. Also, foam cement has reduced thermal conductivity, making it a better insulator. It is also important to model the behavior of foam cement for real-time monitoring.
In this study, smart foam cement was tested for density, thermal conductivity, rheological, fluid loss, curing, and compressive piezoresistivity behavior. Smart foam cement piezoresistive behavior was studied up to 28 days of curing at room condition. The addition of foam reduced the density and thermal conductivity of the smart foam cement. The thermal conductivity was correlated to the density using the Vipulanandan correlation model. The addition of 20% foam increased the initial electrical resistivity of the smart cement. Smart foam cement slurry was piezoresistive, and with applied compressive pressure, the resistivity decreased due to very low shear effect. The change increased with the foam content and applied pressure. A rheological test showed that the smart foam cement had shear-thinning behavior, and the Vipulanandan rheological model predicted the test results very well compared to the Herschel–Bulkley model. The total fluid loss for the smart cement at 0.7 MPa (100 psi) pressure was reduced from 134 mL to 13 mL with the addition of 20% foam, about a 90% reduction.
The solidified smart cement foam was piezoresistive and verified THE piezoresistive cement theory, and with applied compressive stress, the resistivity increased. The piezoresistive behavior of the smart foam cement was modeled using the Vipulanandan p-q piezoresistive model.
