Field Test for Real Time Monitoring of Piezoresistive Smart Cement to Verify the Cementing Operations

摘要

In this study, a field well was installed and cemented using the smart cement mixture with enhancedrnpiezoresistive properties. The field well was designed, built, and used to demonstrate the concept of realrntime monitoring of the flow of drilling mud and smart cement and hardening of the cement in place. Thernwell was installed in soft swelling clay soils to investigate the sensitivity of the smart oil well cement. Arnnew method has been developed to measure the electrical resistivity of the materials using the two probernmethod. Using the new concept, it has been proven that the resistivity dominated the behavior of drillingrnfluid and smart cement. LCR meters (measures the inductance (L), capacitance (C) and resistance (R))rnwere used at 300 kHz frequency to measure the changes in resistance. The well instrumentation wasrnoutside the casing with 120 probes, 18 strain gages and 9 thermocouples. The strain gages andrnthermocouples were used to compare the sensitivity of these instruments to the two probe resistancernmeasure in-situ in the cement. The electric probes used to measure the resistance were placed verticallyrnat 15 levels and each level had eight horizontal probes.rnChange in the resistance of hardening cement was continuously monitored since the installation of thernfield well for over 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 and a piezoresistive model has been developed to predict the pressure in the casing from thernchange in resistivity in the smart cement.