Numerical Simulation on the Impact of Temperature Behavior for Cement Hydration for the World's First Offshore Methane Hydrate Production Test

Abstract The world's first offshore production test of the methane hydrate (MH) project was successfully carried out in the deepwater Nankai Troughin 2013. In February and March 2012, a production well and two monitoring wells were drilled and cemented to deploy temperature monitoring systems for which a combination of distributed temperature sensing (DTS) and array-type RTD (Resistance Temperature Detector) was employed. For cement hydration, the chemical reactions are exothermic in nature so that a measureable temperature increase will be observed once the heat is released. With a typical cement system in wellbore configuration, this temperature increase could result in MH dissociation prior to the production that may have some impacts on the extraction of actual methane gas. Additionally, potential problems of thermally induced cracking are another concern. To evaluate the thermal effect from the cement heat to MH, a 1D numerical model of cement hydration is developed based on the radial heterogeneity of thermal properties. The temperature data acquired during cementing stage is used as the input data for the model, and the parameters such as activation energies for the cement hydration heat correlation in the model are determined. It was shown that the variation of simulated temperature from different MH saturation within the upper MH zone is so small that a reliable estimation of MH saturation becomes difficult while the estimated MH saturations from temperature data inversion in the lower MH zone are relatively high. A sensitivity study is also performed to understand which parameters in the developed model most significantly influence the temperature during the different stages of the cement hydration, respectively.