柴达木盆地西部新近系和古近系油田卤水水化学特征及其地质意义

Investigation of the chemical characteristics and its geological significance of the Tertiary oilfield brine in the western Qaidam basin

油田卤水的研究具有油气地质与矿产资源意义,柴达木盆地西部新近、古近系油田卤水的溶解性总固体最高可达316 g/L,平均为140 g/L,钾、硼、锂等离子有的可达工业开采品位,阴离子主要以Cl-为主,阳离子主要以Na++K+为主,其含量与溶解性总固体之间呈现极好的线性关系,具有高浓缩地层水特征。研究表明,油田卤水的溶解性总固体与油气成藏运聚有显著关系,值得进一步探讨。结合柴西区域地质构造特征,对比分析油田卤水各特征离子间关系、钠氯系数、脱硫系数、钙镁系数以及r Ca+Mg/r HCO3+SO4系数等基本可以推断柴西油田卤水的大气降水对岩盐层淋滤成因,并有深部地热水的补给,在油田卤水形成演化过程中伴有碳酸盐矿物的溶解作用,同时乌南—昆北油区可能存在柴西茫崖拗陷的补给区。

The research of oilfield brine has oil and gas geology and ore meanings,the TDS of the Tertiary oilfield brine in the western Qaidam basin can amount to 316 g / L,and the average is 140 g / L. Some element such as K、B and Li can reach industrial mining grade. The main anion is Cl-,the main cationic is Na++K+. The relation between there content and TDS shows good linear which shows that the oilfield brine has high concentrated formation features. It is worth further discussed the relationship between the TDS of the oilfield brine and the accumulation or migration of oil and gas. Combined with the features of the geological structure,r Na/ r Cl,r SO4/ r Cl,r Ca/ r Mg and r Ca + Mg/ r HCO3+ SO4can conclude the salt rock layers leaching factor of the oilfield brine orgin with the deep geothermal water supply. Also the carbonate minerals dissolved effect the evolution of the oilfield brine. The recharge area of the western Qaidam basin maybe is in Wunan—Kunbei oilfield.