Conditions making high and unique gas water ratios of the natural gas dissolved in water of Mobara type

Abstract

The Mobara type, which is a main and unique production type of natural gas dissolved in water in Minamikanto area, has high gas water ratios. The gas water ratio of a standard type is from 1.8 to 2.0 and that of Mobara type is frequently from 10 to 20. The high value has been tried to explain for long time. This study shows the cause of high gas water ratios is prior production of dissolved gas due to decreased pressure and shows adsorbed gas in mudstone between sandstone layers keeps the gas water ratio in a later term using numerical production simulations.