Characterizing the Behavior of Smart Oil Well Cement after Contamination and Repairs

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Effect of drilling mud contamination on the smart cement behavior was investigated. Also, materials for repairing damaged smart cement was investigated. API class H oil well cement and ultrafine cement were used in this study. Firstly, comparative study between piezoresistivity and fiber optic sensor under small compressive stresses was performed and it was determined that piezoresitivity was over 20 times more sensing to stress change. Hence, electrical resistivity was used to monitor behavior and changes due to mud contamination up to 10%. Maximum reported pirzoresistivity was more than 300% and it was observed for uncontaminated smart cement. With the drilling mud contamination of smart cement, the compressive strength was reported in the range of 800 psi to 1400 psi for 24 hours of curing depending on the level of contamination. While the strength reduction was in the range of 14% to 45%, the piezoresistivity reduction was in the range of 37% to 78%. Due to repairs, regaining of piezoresistivity and mechanical strength was studied. Up to 87% of strength gain was achieved with 82% of piezoresistivity regained.

Piezoresistivity, Repairs, Drilling mud, Contamination, Smart cement, Oil well cement, Oil wells