莺歌海盆地高温高压气藏水溶气释放对气水界面的影响

莺歌海盆地X区属于高温高压气藏，水溶气含量大，水溶气释放对气水界面及水侵规律的影响不明.通过PVT物性分析仪，采用复配的天然气和地层水测试了X区不同区块水溶气溶解度变化规律.设计可视化填砂管实验，探索了水溶气释放对气水界面的影响规律.研究表明:水溶气溶解度受温度、压力、地层水矿化度和天然气组分的影响，随压力的增大逐渐增大，随温度的增大先减小后增大，拐点温度为80~90℃，地层温压条件下（145℃，54 MPa）X-1区块水溶气含量为22.5 m3/m3，X-2区块为8.7 m3/m3.可视化填砂管实验研究表明:衰竭开采过程中，水溶气不断释放且携带地层水运移，同时在地层水自身泄压及毛管力作用下，气水界面明显上升.在此基础上，数值模拟气藏衰竭开采表明:水溶气溶解度越大气水界面上升越快，气井见水越早.预测期10 a中，考虑水溶气时，X-1区要早800 d见水，平面上推进快800 m，纵向上推进快7.3 m；X-2要早300 d见水，平面上推进快近500 m，纵向上推进快7.0 m. 

Influence of Water-Soluble Gas Releasing on Gas-Water Interface for Yinggehai Basin High Temperature and Overpressured Gas Field

Yinggehai basin X area belongs to high-temperature and high-pressure gas reservoir, so that the content of dissolved gas in water is very large. However, the changing characteristics of gas-water interface and water invasion regularity is unknown because of the releasing of dissolved gas in water. In this paper, the variation of dissolved gas in water of different formations in X was tested through PVT facilities using natural gas and formation water. The sand packed model with visualization was designed to investigate the influence of water-soluble gas on gas-water interface. Results show that the solubility of water-soluble gas is affected by temperature, pressure, salinity and the components of natural gas, gradually increases with the increase of pressure, decreases with the increase of the temperature at first and then increases and the inflection point temperature is about 80-90℃. The solubility of water-soluble gas is 22.5 m3/m3, and 8.7 m3/m3 for X-1 and X-2 under condition of 145℃, 54 MPa respectively. Sand packed model with visualization experiment shows that the gas-water interface increases obviously in the process of natural depletion because of migration with gas releasing from the water, the pressure decreasing of formation water and capillary force. Numerical simulation of gas reservoir shows that gas-water interface of reservoir with high solubility of water-soluble gas increase faster and the water breakthrough time is earlier than those reservoirs with low solubility of water-soluble gas. During 10 years forecast period, water breakthrough in X-1 is about 800 days earlier, 800 m faster on the plane and 7.3 m faster on the vertical, considering water-soluble gas. And for X-2, those are 300 days, 500 m and 7.0 m respectively.