Characterizing Smart Cement Modified with Styrene Butadiene Polymer for Quality Control, Curing and to Control and Detect Fluid Loss and Gas Leaks Using Vipulanandan Models

Abstract

In this study, commercially available styrene butadiene rubber (SBR) polymer up to 3% was added to the highly sensing chemo-thermo-piezoresistive smart cement with a water-to-cement ratio of 0.38 to investigate the effects on the sensing properties. Series of quality control, curing and high pressure high temperature (HPHT) experiments were performed to evaluate the smart cement behavior with and without the SBR polymer. Addition of 1% and 3% SBR polymer increased the initial resistivity by 4% and 12% respectively and hence this parameter can be used for quality control in the field. Vipulanandan p-q curing model was used to predict the changes in resistivity with curing time. Addition of 1% and 3% SBR polymer also increased the compressive strength of the smart cement by 18% and 32% after 1 day of curing respectively, The piezoresistivity of smart cement with the addition of SBR polymer after 1 day of curing was over 500 times (50,000%) higher than the regular cement failure strain of 0.2%. The Vipulanandan p-q piezoresistivity model also predicted the experimental results very well. Addition of SBR polymer reduced the fluid losses 30 minutes and 24 hours after curing. The fluid loss was predicted using the Vipulanandan fluid loss model and compared it to the API model. The smart cement with and without SBR polymer detected the gas leak during initial slurry condition and after solidification. Addition of SBR polymer reduced the gas leak. During the gas leak in the piezoresisitive smart cement slurry the resistivity change was positive and for the solid smart cement the resistivity change was negative. During gas leak in the smart cement slurry the resistivity increase was about 45% and it reduced to 30% with the addition of 3% SBR polymer at pressure gradient of 2000 psi/ft. During gas leak in the solidified smart cement the resistivity reduced, opposite to the piezoresistive response to compressive stress, by about 30% and it reduced to 12% with the addition of 3% SBR polymer at a pressure gradient of 2000 psi/ft. Vipulanandan fluid flow model, generalized Dary's Law, predicted the non-linear responses of gas leak velocity (discharge per unit area) to the applied pressure gradient. Also electrical resistivity changes can be used to predict the gas leak velocity in the smart cement with and without SBR polymer.