泌阳凹陷油田水化学特征及水——岩相互作用

Study on the chemical characteristics of oilfield water and the water-rock interaction in Biyang Depression.

根据测试资料,泌阳凹陷油田水主要为重碳酸钠型水,有少量硫酸钠型水、氯化镁型水和氯化钙型水。总体上,油田水分为2类:一类为经过水—岩相互作用改造过、矿化度较高的同生水;另一类为被大气降水稀释过、矿化度较低的同生水。泌阳凹陷在2 900m处存在一个化学分异面,即在深度小于2 900m的地层中,油田水中过剩的Na^+与HCO_3^-的物质的量呈近1:1的线性关系,水—岩相互作用以钠长石的高岭石化为主;在深度大于2 900m的地层中,Na^+与Cl^-呈现1:1快速同步增长的特点,表明水—岩相互作用以岩盐(NaCl)溶解为主。在油田水的演化过程中发生了不同的水—岩相互作用,导致了化学分异面上下不同的水化学特征,从油田水的化学特征入手研究水—岩相互作用对指导油气勘探实践有重要意义。

Based on the geochemical analytic data sampled from the Biyang Depression,the tested oilfield water mainly is NaHCO_3^- tpye with less NaSo_4,MgCl_2 and CaCl_2^- type.Generally,the oilfield water was divided into 2 groups:one is the connate water altered by water-rock interactions with higher salinity,the other is the one that diluted by leakage meteoric water with lower salinity.A chemical differentiation interface appears at the depth of 2 900m in the Biyang Depression.There exists a near 1:1 linear relationship between Na^+ and HCO_3^- in the oilfield water and albite kaolinized in the strata above 2 900m,while the above relationship is unclear,with Na^+ and Cl^- growing equally fast simultaneously and halite dissolves below this depth.Controlled by different water -rock interactions,oilfield water in different stratum separated by the chemical differentiation interface evolves respectively,and leads to different chemical characteristics.It is of great significance in guiding the practice of oil and gas exploration to research water-rock interaction according to the chemical characteristics of the oilfield water.