Simulating the gas hydrate behavior at equilibrium dissociation: A study from Mahanadi basin of eastern offshore, India

DibakarGhosal, ShibSankarGanguli, Rishi N.Singh,andKalachandSain

Globally, gas hydrates have been explored either by geophysical, geochemical and geological surveys, however, the full-scale commercial production of gas hydrates is itself a huge challenge for the scientific community until today. Understanding the feasibility of field scale gas hydrate production is the need of the hour to meet the ever-increasingenergy demand. Simulating gas hydrate production through the analyses of the effects of external stimuli such as changes in pressure and temperature on the gas production behavior,can be a useful input to decide gas production from real field cases. In general, there are three major methods such as thermal stimulation, depressurization and inhibitor injections, which have been considered as promising methodologies for gas production from gas hydrates.
The present analysis reports the development of a proper model that helps to understand the feasibility of gas production from the Mahanadi basin, India. This involves analyzing the spatial distributions of several key parameters including hydrate saturation, gas and aqueous phase velocities, heat flux, enthalpy changes, within the system. The simulation results recommend that the studied field has a great prospect for commercial gas production. It has been identified that the speed of dissociation front varies with the boundary pressure, and depressurization is the suitable dissociation method to produce more gas from the studied field when compared to the thermal stimulation. The developed model can be used as an opportunity for further detailed study of natural gas production from the hydrate reservoir of this region.
For further reading, the readers are referred to the web version of this paper published inMarine & Petroleum Geology (https://doi.org/10.1016/j.marpetgeo.2018.09.007 external link).
 

Fig. 1. Simulation responses at different temperatures (50 °C, 100 °C and 150 °C) and constant permeability (2.00 × 10−14 m2) at 60 days in hydrate accumulation undergoing thermal stimulation: (a) pressure, (b) temperature, (c) gas velocity (Vg), (d) hydrate saturation (Sh), (e) aqueous saturation (Sa), and (f) gas saturation (Sg).

Fig. 2. Spatial distributions of (a) pressure, (b) temperature, (c) saturation of hydrate (Sh), (d) gas saturation (Sg), and (e) aqueous saturation (Sa) in the X-Z (depth) plane. Solid black circle and arrows indicate the production well location and direction of decreasing values, respectively. Here, depressurization is the driving force for the dissociation.