子北-子长地区长4+5、长6储层地层水特征研究

Formation Water Analysis of Chang 4+5 & Chang 6 Pay Zone in Zibei-Zichang Area

利用子北-子长地区90个长4+5、长6地层水分析实测资料,研究地层水类型、化学成分、酸碱度、密度、特征系数、矿化度及其平面规律,揭示了地层水特征与油气聚集成藏的关系。长4+5、长6地层水矿化度较高,以偏中性为主,纵向及平面上符合沉积盆地中地层水矿化度随深度增加而增大,距离盆地中心越近矿化度越高的一般特征。地层水密度与矿化度呈对数相关,主要阳离子和主要阴离子与矿化度呈线性相关,K^++Na^+和Ca^2+与矿化度之间存在"门限浓度",Ba^2++Sr^2+与SO4^2-受地层水溶液中盐效应的影响可共存。地层水特征系数反映研究区储层具有较好的油气聚集和保存条件。

Based on 90 measured analysis data of formation water in Chang 4+5 & Chang 6 pay zone of Zibei-Zichang area, the features about type, chemical composition, pH, density, ion characteristic coefficient, salinity and planar distribution rule of formation water were investigated, and the implications of such features and hydrocarbon accumulation were revealed. Salinity of formation water of Chang 4+5 & Chang 6 pay zone is overall higher in this area, which has a neutral value in pH. The features conform general characteristics of sedimentary basin which has an increasing value with depth in vertical, and has a higher salinity with a closer distance to the center of the basin in planar. The density of formation water is logarithmically related to the salinity,which increases with increasing salinity. The main cation and the main anion are linearly related to salinity. Threshold is existed between K^++Na^+& Ca^2+ and salinity. Beyond that, Ba^2++Sr^2+& SO4^2- can coexist in formation water which is caused by the salt effect in it. The characteristic coefficient reflected by the formation water can effectively represent the accumulation and preservation conditions.