Characterizing and Modeling of Silicate Modified Smart Cements, Smart Cement Grouts and Drilling Muds



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In this study, the effects of silicate based additives on the smart cements, smart cements grouts and drilling muds were investigated. Also the effects of clay soil contamination on the modified smart cement were investigated. Smart cement (Class A, Portland cement type I, Class H) was made using 0.1% conductive filler and was electrically characterized as a resistive material. In this study, a series of experiments were performed to evaluate the smart cement behavior with and without up to 0.3% of sodium meta-silicate (SMS) to determine the sensitivity in terms of electrical resistivity of the cement from curing to hardened state up to 12 months under different curing conditions. In the physical study small, large and field models were used and electrical resistance was monitored at various stages of construction and during the curing of cement in-situ. The test results showed that the SMS reduced the electrical resistivity of the smart cement slurries and hardened cement based on the amount of SMS. For long term curing under room temperature, under moisture control curing, under water curing or at high temperature curing under dry and saturated condition, the resistivity of the hardened cement was reduced with the addition of SMS. The moisture loss from the smart cement was also reduced with addition of SMS. The resistivity with curing time was modeled with curing model develop to characterize the curing of the cement. The smart cement showed piezoresistive behavior under compressive stress. Without any SMS piezoresistivity at peak stress varied from 315% to 545% which reduced up to 145% to 230% with the addition of 0.3% SMS. The nonlinear piezoresistive model predicated the compressive stress – change in resistivity relationship of the smart cement very well. The strength and piezoresistivity of the cement was correlated with the SMS content and curing time. The rheological properties of cement slurry with different SMS content and contamination, and the rheological properties of drilling mud with different silicates contents was modeled using Herschel–Bulkley model and Hyperbolic model. The smart cement grout showed piezoresistive behavior under compressive stress. Without any SMS, piezoresistivity at peak stress varied from 155-179% which is reduced up to 116-125% with 1% SMS. The repaired samples showed piezoresistivity varying from 48% to 62%. The strength regain of repaired damaged cement varied from 51% to 84% and the piezoresistivity regain varied from 21% to 42%.The fluid loss of the water based mud with different silicate content was modeled with API fluid loss model and the new Kinetic (Hyperbolic) Model. In the physical model study the rise of drilling mud and cement slurry in the simulated bore holes of various scales were effectively monitored using the changes in electrical resistance. The determination of resistance of the hardened cement and comparing with the predicted values were also found effective. The measured electrical resistance with curing time agreed very well with predicted resistance using the analytical models developed in this study.



Smart cement, Oil well cement, Smart sensing, Sodium silicate, Smart cement, Drilling mud, Oil wells, Piezoresistivity