石油学报 ›› 2010, Vol. 31 ›› Issue (5): 748-753.DOI: 10.7623/syxb201005008

• 地质勘探 • 上一篇    下一篇

鄂尔多斯盆地上古生界地层水分布与矿化度特征

王运所 1,2  许化政 3  王传刚 3  贾斌峰 2   

  1. 1中国地质大学能源学院  北京  100083; 2中国石化中原油田分公司勘探开发科学研究院  河南濮阳  457001; 3中国石化石油勘探开发研究院  北京  100083
  • 收稿日期:2010-01-04 修回日期:2010-02-20 出版日期:2010-09-25 发布日期:2010-11-30
  • 通讯作者: 王运所
  • 作者简介:王运所,男,1974年10月生,1997年毕业于大庆石油学院,现为中国地质大学(北京)在读博士研究生,中国石化中原油田分公司勘探开发科学研究院高级工程师,主要从事油气地质勘探及综合研究。
  • 基金资助:

    中国石化科技研发项目(P09014)“鄂南地区油气富集规律与勘探潜力评价”与国家科技重大专项(2008ZX05002)“碎屑岩层系大中型油气田富集规律和勘探关键技术”联合资助。

Characteristics of the salinity and distribution of the Neopaleozoic formation water in Ordos Basin

WANG Yunsuo 1,2  XU Huazheng 3  WANG Chuangang 3  JIA Binfeng 2   

  • Received:2010-01-04 Revised:2010-02-20 Online:2010-09-25 Published:2010-11-30

摘要:

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(>40000 mg/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20000 mg/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40000 mg/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。

关键词: 鄂尔多斯盆地, 上古生界, 地层水, 矿化度, 深盆气, 汽化作用

Abstract:

The Neopaleozoic formation water in the Ordos Basin is mainly distributed in updip reservoir beds on the margin of the basin and characterized by high salinity (>40000 mg/L), while the downdip beds are largely full of gas associated with a little formation water that has low salinity and was encountered in several drills. There seems to be a close relationship between the salinity of formation water and the maturity of Neopaleozoic source rocks, namely, the salinity of “acid point” water is always lower than 20000 mg/L in the region where the Ro of source rocks is above 2.0%; the salinity of “acid point” water increases gradually along the northern edge of the basin with increasing the maturity of source rocks until the value reaches to about 40000 mg/L in the northern boundary of deep-basin gas pools where source rocks show maturities ranging from 1.25% to 1.4%.In a word,the distributional trend of formation water salinity in deep-basin gas pools is entirely different from that of common gas reservoirs. The present study suggested that it was the phase state transform that caused the decrease of formation water salinity. During the formation of the deep-basin gas,the gradually elevated paleotemperature resulted in not only the decrease of formation water solubility but also a complete depletion in cationic ions for the formation water as it vapored into a gas.At the same time, vast amounts of gas were generated from coal beds and all the natural gases together further diluted,dissolved and diffused the “vapored” water,leading to the accumulation of deep-basin gas without water. From late Cretaceous to Paleocene, tectonic compression and destructive uplifting from the east to west were destroying the primary framework of deep-basin gas pools in basins of North China,giving rise to the deep-basin gas remaining only in the Shaanbei structural slope and the occurrence of a gas-water transitional zone in the eastern Yulin-Zizhou gas field.

Key words: Ordos Basin, Neopaleozoic, formation water, salinity, deep-basin gas, vaporization