Real Time Monitoring of Oil Based Mud, Spacer Fluid and Piezoresistive Smart Cement to Verify the Oil Well Drilling and Cementing Operation Using Model Tests

摘要

Well control operations are critical to ensure successful cementing of the oil wells with any losses. Withrnincreased drilling depths for production of oil and gas there are greater challenges due changes in thernnatural geological formations with in situ pressure and temperature conditions. Recent case studies on oilrnwell failures have clearly identified cementing and drilling mud contamination as some of the issues thatrnresulted in various types of delays in the cementing operations. For a successful cementing operation, itrnis critical to monitor the drilling and cementing operation during the installation so that necessaryrnremediation can be made to minimize the delays and losses of cement. At present there is no technologyrnavailable to monitor cementing operations without using buried sensors within the cement sheath and alsornmonitor the movement of the drilling mud and spacer fluid to determine the changes real time during therninstallation of oil or gas wells.rnIn this study, small well models were designed, built, and used to demonstrate the concept of real timernmonitoring of the flow of smart drilling mud, space fluid and smart cement and hardening of the cementrnin place. Also, a new method has been developed to measure the electrical resistivity of the materials usingrnthe two probe method. Using the new concept, it has been proven that resistivity dominates the behaviorrnof drilling mud and smart cement. LCR meters (measures the inductance (L), capacitance (C) andrnresistance (R)) were used at 300 kHz frequency to measure the changes in resistance. Several laboratoryrnscale model tests have been performed using instrumented casing with wires and thermocouples. Whenrnthe drilling mud was in the model borehole the measured resistance was the highest based on the highrnresistivity of the drilling mud. Notable reduction in electrical resistance was observed with the flow ofrnspacer fluid and cement. Change in the resistance of hardened cement has been continuously monitoredrnup to about 100 days. Also, a method to predict the changes in electrical resistance of the hardeningrncement outside the casing (Electrical Resistance Model – ERM) with time has been developed. The ERMrnpredicted the changes in the electrical resistances of the hardening cement outside the cemented casingrnvery well. In addition, the pressure testing showed the piezoresistive response of the hardened smartrncement.