Effects of Dipping and Folded Structure on Gas Production from Hydrate-Bearing Sediments

Abstract

Summary Due to a dipping and folded structure, hydrate-bearing sediments (HBS) have obvious fluctuation characteristics, and the internal temperature and pressure of HBS are unevenly distributed. Subsequently, gas and water production of natural gas hydrate (NGH) is affected. When using a numerical simulation method to predict effectively the productivity of HBS, it is necessary to establish a conceptual model that considers the formation fluctuation. However, few reported studies accurately describe the fluctuation characteristics of HBS in numerical simulation models. Therefore, the spatial evolution of gas production, water production, and seepage parameters of each model was compared by establishing the initial temperature and pressure model of each representative model pair, using the TOUGH + HYDRATE (T + H) code for a long-time simulation; the production process of gas and water and spatial evolution of seepage parameters of each model were compared; and then the spatial evolution of gas production, water production, and seepage parameters of the different dipping/folded HBS was obtained. The spatial evolution of water production and seepage parameters for different dipping/folded HBS is obtained. (a) The dipping and folded structure had an obvious influence on the spatial distribution of the initial temperature and pressure of HBS. (b) The limits of heat supply and seepage capacity of the fluctuating HBS gave lower gas production than in horizontal HBS. There should be more emphasis on heat supply conditions and the formation of secondary hydrates. (c) The additional pore water in fluctuating HBS is not conducive to the discharge of methane. Consequently, the development of improved water blocking measures is significant for the future large-scale production of NGH.