Numerical Analysis of the Behavior of Gas Hydrate Layers After Cementing Operations

Abstract

Since the 2000s, the number of gas hydrate wells (i.e., exploration wells, production test wells) has increased. Moreover, in the marine environment, gas hydrate zones are drilled in conventional hydrocarbon wells. Different than conventional hydrocarbon wells, the heat released with cement hydration cannot be ignored because gas hydrates are heat sensitive. In this study, by analyzing different cement compositions (conventional cement compositions and novel low-heat of hydration cement), it is aimed to investigate the effect of the heat of cement hydration on gas hydrate zones near the wellbore. For this purpose, numerical simulations with TOUGH+HYDRATE simulator were conducted in the conditions of the Nankai Trough gas hydrates. According to the numerical simulations in this study, if the increase in temperature in the cemented layer is above 30°C, significant gas hydrate dissociation occurs, and free gas evolved in the porous media. This might cause gas channeling and poor cement bond. The heat released with cement hydration generally affects the interval between the cemented layer and 0.25 m away from the cemented layer. Within a few days after cementing, pressure, temperature, gas hydrate saturation, and gas saturation returned to almost their original values.

Hydration kinetics of oil well cement in the temperature range between 5 and 30°C

“…Offshore natural gas hydrates are usually buried at depths of 762-4,572 m (Reddy, 2008), where the formation temperature can range from 0 to 30 °C (Wang et al, 2009;Wang et al, 2017). Once the temperature rises above 30 °C, the gas hydrate will decompose into gas and liquid phases (Merey et al, 2021). In recent years, significant effort has been devoted to studying the potential of extracting natural gas hydrates as an energy resource.…”