Grover, Tarun (Petroleum Engineering Department, Texas A&M University College Station, Texas, USA) | Holditch, Stephen A. (Petroleum Engineering Department, Texas A&M University College Station, Texas, USA) | Moridis, George (Earth Sciences Department, Lawrence Berkeley National Laboraotry 1 Cyclotron Road, Berkeley, CA)
The Messoyakha Gas Field is located in Siberian permafrost. The field has been described as a free gas zone, overlaid by hydrate layer and underlain by an aquifer of unknown strength. The field was put on production in 1970 and has produced intermittently since then. Some characteristic observations were increase in average reservoir pressure during shut-in, perforation blocking due hydrate formation and no change in gas-water contact. It is believed the increase in reservoir pressure was caused by the hydrate layer dissociation, rather than aquifer influx. The objective of this study was to use numerical model to analyze the observed production data from the Messoyakha field. In this study, a range of single-well 2D cross-sectional models representative of Messoyakha have been developed using the TOUGH+Hydrate reservoir simulator. The simulation results were then analyzed and compared with various field observations. Further, we have done a parametric study of reservoir properties of hydrate capped gas reservoir.
Gas hydrate is a crystalline substance in which the gas molecules are trapped in the voids created by arrangement of water molecules. The water molecules are held together by the hydrogen bonds. Natural gas consists mainly of methane. It also consists of heavier hydrocarbon gases like ethane, propane, butane and non-hydrocarbon gases like CO2, N2 and H2S, etc. Only methane hydrate is considered in this study. One m3 of methane hydrate (formed at 26 atm and 0°C) on dissociation yields 164 m3 of methane at standard temperature and pressure (Makogon et al., 2007). Naturally occurring gas hydrates are found in two distinct settings; in marine sediments and in permafrost. The volume of gas resource in the form of natural gas hydrate is huge as compared to the conventional gas reservoirs. Current estimates of hydrated gas worldwide are in therange of 105to 106 Trillion cubic feet (TCF).