Behavior of Piezoresistive Smart Cement Contaminated with Oil Based Drilling Mud

摘要

As deep-water exploration and production of oil and gas expands around the world, there are uniquechallenges in well construction beginning at the seafloor. There are several benefits in using oil baseddrilling mud (OBM) in drilling operations but there are concerns about the potential contamination of thecement and have severe impact on cement performance in the wellbores. Recent case studies on cementingfailures have clearly identified some of these issues that resulted in various types of delays in thecementing operations. For a successful cementing operation, it is critical to determine the contaminationof cement during the installation so that necessary remediation can be made to minimize the effect. Atpresent there is no technology available to monitor cementing operations and also to determine thepotential of contamination in real time during the installation of the oil and gas wells.In this study well cement was modified to have better sensing properties, smart cement, so that itsbehavior can be monitored at various stages of construction and during the service life of wells. A seriesof experiments evaluated the smart well cement behavior with and without OBM to determine thesensitivity the electrical resistivity of cement to determine the level of contamination. Electrical resistivitywas used as a monitoring tool to capture the contamination of cement with up to 3 percent OBM. The testresults showed that mud contamination increased the electrical resistivity of the slurries based on the levelof contamination. The OBM contamination also affected the rheological properties, setting characteristicsand also reduced the compressive strength and the piezoresistive properties of the smart cement. Thechanges in the rheological properties were correlated to the level of contamination. A linear correlationwas obtained between the 24-hour change in electrical resistivity and the compressive strength of thecontaminated and uncontaminated cement based on the curing time.