Influence of cement slurry heat release on physical properties of marine hydrate reservoirs during well cementing

Abstract

Natural gas hydrates gradually become the focus of new energy resources, and the study of hydrate exploitation is growing vigorously during recent years. Well cementing is an important process during energy exploitation, especially when encounters hydrate bearing sediments in deep-water oil and gas drilling, showing great research significance and becoming a research hotspot. In this study, the exploratory well of SH2 of GMGS-1 project is chosen as the object of study, a cementing model of two dimensions based on this exploratory well is build, the invasion process of cement slurry is reappeared by TOUGH+HYDRATE, and the physical properties response of hydrate reservoirs during the cementing process is analyzed based on the numerical simulation data. In which, a view of “continuous stage simulation” to solve the problem of dynamic heat release of cement slurry is created and used for the first time. Result illustrated that the invasion behavior of cement slurry almost only occurred during the stage of holding pressure, the temperature has significantly increased in the area of reservoir which is invaded by cement slurry. At the same time, a large amount of decomposed hydrate have generated gas and water, which form high pressure region and transfer toward the deeper of reservoir. However, the variation in the temperature is not significant and the hydrate barely no longer decomposed in those area which outside or even though close to this area. There also have generated secondary hydrate closed to the area of decomposition and formed high saturation zone of hydrate. The results also proved the feasibility of “continuous stage simulation”, and played a guiding significance for the field well cementing.