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鄂尔多斯盆地上古生界的地层水主要分布在盆地边缘地区,地层水具有高矿化度特征(>40000mg/L)。盆地下倾方向的上古生界大面积含气,少量钻井钻遇的地层水具有很低的矿化度。地层水的矿化度与有机质的成熟度关系密切,在Ro大于2.0%的区域内,“酸点”水的矿化度降低至20000mg/L以下;向盆地北部边缘,随热演化程度的降低,“酸点”水的矿化度逐渐升高,至深盆气的北部边界,Ro为1.25%～1.4%时,地层水的矿化度上升至40000mg/L左右。地层水矿化度的这种分布趋势与常规盆地完全相反。地层水矿化度的降低源自于其相态的变化:深盆气形成过程中,逐渐升高的古地温不但使地层水溶解度降低,而且在汽化后完全失去盐离子。与此同时煤层大量生气,以及天然气稀释、溶解和扩散“汽化”的水分子,使深盆气只见气而不见水。晚白垩世—古新世,自东而西的构造挤压与抬升破坏了华北盆地深盆气原型,使深盆气仅在陕北斜坡构造部位保留,榆林—子洲气田东部出现气水过渡带。
The formation water in the Upper Paleozoic of the Ordos Basin is mainly distributed in the margin of the basin. The formation water has high salinity (> 40000mg / L). The Upper Paleozoic in the downwelling basin has a large area of gas and the formation water drilled by a small amount of drilling has very low salinity. The degree of mineralization of formation water is closely related to the maturity of organic matter. In the area where Ro is more than 2.0%, the salinity of the acid spot decreases to less than 20,000 mg / L. To the northern margin of the basin, The salinity of water gradually increases to reach the north border of deep basin. When the Ro is 1.25% ~ 1.4%, the salinity of formation water increases to about 40,000 mg / L. This trend of distribution of formation water salinity is completely opposite to conventional basins. The decrease of formation water salinity comes from the change of its phase state. During the formation of deep basin gas, the gradually increasing paleo-earth temperature not only decreases the solubility of formation water, but also completely loses salt ions after vaporization. At the same time a large number of coal seam angry, as well as natural gas dilution, dissolution and diffusion of “vaporized” water molecules, so that deep gas can only see the gas without water. During the Late Cretaceous to Paleocene, tectonic extrusion and uplift from the east to the west destroyed the prototype of deep basin gas in the North China Basin, leaving the deep basin gas to remain only in the structural parts of the northern Shaanxi Province, with the transition of gas and water in the east of Yulin-Zizhou Gas Field band.