四川盆地西南边缘的大兴场构造下二叠统气藏，产出水水型以氯化钙型为主，夹杂碳酸氢钠型。为找出水型变化的原因，在分析产出水化学特征的基础上，引入离子比例系数，结合气井生产史，找到影响水型的主要因素为，酸性环境下，CO2溶于水，形成了HCO3－，而非沟通地表淡水所致。同时，产出水矿化度远高于现代河水，水型以氯化钙为主，钙镁系数较大，处于封闭环境，保存条件较好，是易于油气聚集的还原坏境。%The gas reservoir in lower permian of daxinchang in the southwest edge of Sichuan basin ,water which type primarily is CaCl 2 ,oligarchically is NaHCO 3 was outputed.According to the chemical characteristics of outpu-ted water ,the ions ratio coefficients was introducted to find the reason of water type changed .with the production history of gas well.The reason was find that in the acid environment , CO2 dissolved in water and changed into HCO3-,it didn’t by the reason of communicating surface fresh water .Meanwhile,the salinity of outputed water was more higher than recent river water , water type primarily is CaCl 2 , rCa2-/rMg2+was high, all of these results ex-plained that the gas reservoir which preservation condition was very good , was in a closed reducted environment which was prone to oil and gas accumulating .
展开▼
