THE STUDY OF GEOLOGY COURSE AND EXPERIMENT SIMULATION FOR FORMING ULTRA-LOW WATER SATURATION IN TIGHT SANDSTONES GAS RESERVOIRS
致密砂岩气藏超低含水饱和度形成地质过程及实验模拟研究

Recognizing the water saturation in tight gas reservoirs directly affects reserves evaluation and development measurement of the gas reservoirs. Sealed coring and log interpretation show there is an ultra-low water saturation in tight gas reservoirs in northern Ordos basin, the initial water saturation in tight gas reservoirs is between 20% and 30%, which is far below the irreducible water saturation. This article believe that the mechanism of forming ultra-low water saturation in tight gas reservoirs is the result of the process of removing water during hydrocarbon generating, then proving the conclusion by an experiment. The effects of isolation of mudstone, the variation of relative permeability between water and gas in gas and water transitional zone, the continual gas accumulation increasing the pressure in tight gas reservoirs are main issues for sustaining ultra-low water saturation.