| Water-dissolved gas is an important unconventional natural gas resources, its reserve is very rich in the world. The solubility of gas in formation water is mainly affected by temperature, pressure and formation water salinity. Water volume of L gas reservoir is relatively large, and salinity is low, thus water-dissolved gas reserves are relatively large. In the mining process, these gases can become gas supplies. These gases can also affect the total reserves of gas reservoirs and recovery, so the research on the effects of water-dissolved gas has practical significance to develop water-dissolved gas reservoir.Based on the systematic investigation of the domestic and foreign literature, this paper analyzed the mechanism of the gas dissolved in water; On this basis, the experimental study of gas solubility in the formation water at different pressures was accomplished; model of considered and not considered water-dissolved gas were established use numerical simulation software Eclipse, which could study the impact of water-dissolved gas to reserves and recovery; applied material balance equation of considered water-dissolved gas to calculate the gas cumulative production change with pressure, and compared with the results of numerical simulation software. Through these studies, achieved major results are as follows:(1) Gas dissolved in water mainly has two ways, gas gap filling and hydration. The solubility of natural gas is mainly affected by temperature, pressure and formation water salinity.(2) Experimental study obtained the water-dissolved gas reserve under different pressures. And gas-water ratio increases with increasing pressure, the corresponding volume factor also increases with increasing pressure.(3) The water-dissolved gas reserves of L gas reservoir are relatively large, accounting for9.88%of natural gas reserves. Water volume of SAND3layer is the largest and water-dissolved gas reserve accounted for28.07%of this layer’s reserve, thus the impact of water-dissolved gas is relatively large; water-dissolved gas would influence gas reservoir recovery to a certain extent, when considering water-dissolved gas, recovery rose from72.8%to78.3%, which SAND3layer recovery rose from67.4%to80.5%.(4) Based on the investigation of the domestic and foreign material balance equation literature, refer to previous material balance equation, and modify, to deduced material balance equation of considering water-dissolved gas. And use this equation to calculate the gas reservoir cumulative production under different pressure points, the calculation results is very close to the results calculated by the software. |
