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现代地质 ›› 2019, Vol. 33 ›› Issue (05): 1106-1117.DOI: 10.19657/j.geoscience.1000-8527.2019.005

• 环境地质学 • 上一篇    下一篇

鄂尔多斯盆地陇东地区长8致密砂岩油藏地层水化学特征成因及其油气指示意义

斯扬1,2(), 张文选3, 罗安湘3, 孙勃3, 朱玉双1,2()   

  1. 1.西北大学 大陆动力学国家重点实验室,陕西 西安 710069
    2.西北大学 地质学系,陕西 西安 710069
    3.中国石油长庆油田分公司 勘探开发研究院,陕西 西安 710018
  • 收稿日期:2018-10-25 修回日期:2019-06-27 出版日期:2019-10-26 发布日期:2019-10-28
  • 通讯作者: 朱玉双
  • 作者简介:朱玉双,女,教授,博士生导师,1968年出生,石油天然气地质专业,主要从事油藏早期评价与油气田开发地质、油层物理及提高采收率方面的教学与研究工作。Email: yshzhu@nwu.edu.cn
    斯 扬,男,博士研究生,1989年出生,油气田地质与开发专业,主要从事石油地质及油气田开发地质方面的研究工作。Email: 304085871@qq.com
  • 基金资助:
    “十三五”国家科技重大专项(2016ZX05046)

Hydrochemical Feature Genesis and Hydrocarbon Exploration Significance of Chang 8 Tight Sandstone Reservoir in Longdong Area,Ordos Basin

SI Yang1,2(), ZHANG Wenxuan3, LUO Anxiang3, SUN Bo3, ZHU Yushuang1,2()   

  1. 1. State Key Laboratory for Continental Dynamics, Northwest University, Xi’an, Shaanxi 710069, China
    2. Department of Geology, Northwest University, Xi’an, Shaanxi 710069, China
    3. Exploration and Development Research Institute of Changqing Oilfield Company, PetroChina, Xi’an, Shaanxi 710018, China
  • Received:2018-10-25 Revised:2019-06-27 Online:2019-10-26 Published:2019-10-28
  • Contact: ZHU Yushuang

摘要:

国内对地层水与油藏的关系研究多集中在断块坳陷内,在岩性油藏中此类研究相对较少。基于鄂尔多斯盆地陇东地区长8致密砂岩油藏大量的地层水化学分析及薄片和扫描电镜资料,对长8地层水化学特征及其成因进行了分析,并结合油藏地质条件,探讨其油气指示意义。长8致密砂岩岩性油藏地层水矿化度平均为33.6 g/L,地层水类型以CaCl2型为主,整体为封闭的水文地质环境,有利于油气保存。长8地层水中的离子特征与砂岩成岩具有良好的对应关系。Mg2+亏损、Na+轻微亏损及富集主要与绿泥石化、斜长石的钠长石化及溶解作用有关;Ca2+富集不仅与斜长石的钠长石化及溶解作用有关,还与泥岩中火山灰大量释放的Ca2+有关; SO 4 2 - HCO 3 - 含量则主要受脱硫酸作用和碳酸盐胶结作用控制。此外,由于长8砂岩成岩作用受烃类充注影响较大,研究区西部与中部及东部地层水化学特征存在差异,西部地层水中的钠氯系数整体小于中部及东部, SO 4 2 - 平均含量及脱硫系数平均值大于中部和东部等特征都与长8油藏在平面上充注条件差异有着很大联系。

关键词: 鄂尔多斯盆地, 致密砂岩油藏, 地层水, 水岩相互作用, 油气指示意义

Abstract:

Domestic studies on the relationship between formation water and reservoirs are mostly concentrated in fault block depressions, and such studies are relatively rare in lithologic reservoirs. Based on a large data set of the formation water chemical compositions,thin-section petrography and scanning electron microscopy of the Chang 8 tight sandstone reservoir in Longdong area of Ordos Basin, the chemical characteristics and genesis of the Chang 8 formation water were analyzed and their hydrocarbon exploration implications were discussed. The study shows that the average salinity of formation water in the reservoir is 33.6 g/L. The formation water is mainly of CaCl2 type, and the hydrogeological system is closed, conducive to oil preservation. Ionic characteristics of the formation water are closely linked with the Chang 8 sandstone diagenesis. The Mg2+ depletion and slight Na+ enrichment/depletion may have mainly related to chloritization, albitization and dissolution of plagioclase. The Ca2+ excess is unlikely only related to albitization and plagioclase dissolution, but also related to the Ca2+ release by volcanic ash in mudstone. The SO 4 2 - and HCO 3 - contents may have been controlled mainly by desulfurization and carbonate cementation. Since the diagenesis of the Chang 8 sandstone was much affected by hydrocarbon charging, the water chemistry characteristics of the western/central/eastern sequences of the study area are different. The Na/Cl coefficient of the formation water in the western part is lower than that of the central and eastern parts, whereas the SO 4 2 - content and desulfurization coefficient of the formation water are higher. We suggested that this is closely related to the different filling conditions of the reservoir.

Key words: Ordos Basin, tight sandstone reservoir, formation water, water-rock interaction, hydrocarbon exploration implication

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