Development and Characterization of Smart Cement for Real Time Monitoring of Ultra-Deepwater Oil Well Cementing Applications

Abstract

Abstract For a successful cementing operation, it is critical to determine the flowing of cement slurry between the casing and formation, depth of the circulation losses and fluid loss, setting of cement in place and performance of the cement after hardening. Recent case studies on cementing failures have clearly identified some of these issues that resulted in various types of delays in the cementing operations. At present there is no technology available to monitor cementing operations in real time from the time of placement through the borehole service life. Also, there is no reliable method to determine the length of the competent cement supporting the casing. In this study well cement was modified to have better sensing properties, smart cement, so that its behavior can be monitored at various stages of construction and during the service life of wells. A series of experiments evaluated well cement behavior with and without modifications in order to identify the most reliable sensing properties that can also be relatively easily monitored. During the initial setting the electrical resistivity changed with time based on the type and amount of additives used in the cement. During curing initial resistivity reduced by about 10 percent to reach a minimum resistance, and maximum change in resistance within the first 24 hours of curing varied from 50 to 300 percent depending on the additive. A new quantification concept has been developed to characterize cement curing based on electrical resistivity changes in the in the first 24 hours. When cement was modified with less than 0.1 percent of conductive additives, the piezoresistive behavior of the hardened smart cement was substantially improved without affecting the cement rheological and setting properties. For modified smart cement the resistivity change at peak stress was about 400 times higher than the change in the strain.