中国石油勘探 ›› 2017, Vol. 22 ›› Issue (3): 71-80.DOI: 10.3969/j.issn.1672-7703.2017.03.009

• 石油地质 • 上一篇    下一篇

二连盆地额仁淖尔凹陷下白垩统云质岩致密油储层特征与成因

魏巍1,2, 朱筱敏2, 朱世发1,2, 何明薇1,2, 吴健平3, 王名巍3, 吕思翰4   

  1. 1. 中国石油大学(北京)地球科学学院;
    2. 中国石油大学(北京)油气资源与探测国家重点实验室;
    3. 中国石油华北油田公司勘探开发研究院;
    4. 中国石油大庆油田公司第三采油厂电力大队
  • 收稿日期:2016-03-16 修回日期:2017-04-06 出版日期:2017-05-10 发布日期:2017-05-15

Characteristics and origin of the Lower Cretaceous dolomitic tight oil reservoir in Erenaor sag, Erlian Basin

Wei Wei1,2, Zhu Xiaomin2, Zhu Shifa1,2, He Mingwei1,2, Wu Jianping3, Wang Mingwei3, Lü Sihan4   

  1. 1. College of Geosciences, China University of Petroleum;
    2. State Key Laboratory of Petroleum Resource and Prospecting, China University of Petroleum;
    3. Research Institute of Petroleum Exploration and Development, CNPC Huabei Oilfield Company;
    4. Power Group, CNPC Daqing Oilfield No.
    3. Oil Production Company
  • Received:2016-03-16 Revised:2017-04-06 Online:2017-05-10 Published:2017-05-15

摘要: 为了研究二连盆地额仁淖尔凹陷下白垩统阿尔善组富含油气的湖相云质岩储层成因,在分析沉积构造及火山活动等地质背景基础上,通过岩心观察、薄片鉴定、物性压汞分析,以及碳、氧同位素等地球化学手段,系统研究云质岩致密油储层岩石学特征、成因、分布及储集空间特征,并初步讨论致密油储层勘探潜力。研究结果表明,云质岩包括云质沉凝灰岩、云质泥岩和云质粉砂岩,孔隙度主要为1%~15%,渗透率主要为0.008~2.8mD,属于低-超低孔、特低-超低渗储层,储集空间主要为晶间孔和微裂缝。云质岩中的白云石具有半自形-它形、泥-粉晶结构,高碳同位素值(-1.50‰~5.20‰)及高V/Ni 值(1.57~4.56)特征,沉积于陆相半咸水-咸水蒸发环境。云质泥岩和云质沉凝灰岩中白云石具有较高的碳、氧同位素,白云石晶体存在于凝灰质及泥质杂基中,其形成主要与产甲烷生成作用相关。云质粉砂岩中白云石具有较低的碳、氧同位素,受埋藏深度和有机质生烃作用影响。云质岩中Mg2+一方面来自于凹陷中深部大理岩和花岗岩,另一方面来自于火山物质及长石颗粒水解蚀变。此外,云质岩形成过程中,火山喷发导致湖中生物大量死亡,使有机质赋存,促使湖中甲烷菌生成,提供白云石形成的动力条件,促进早期白云石形成。后期盆内烃源岩的生排烃作用,使云质岩晶间孔及微裂缝中储集油气,为致密油储集提供有利场所。

关键词: 云质岩, 白云石成因, 致密油, 下白垩统, 额仁淖尔凹陷, 二连盆地

Abstract: In order to understand the origin of dolomitic tight oil reservoir of the Lower Cretaceous Arshan Formation in the Erenoar sag, the Erlian Basin, on the basis of sedimentary structure and volcanic activity analysis, the core observation, thin section identification and physical mercury analysis as well as geochemical analysis such as carbon and oxygen isotope were employed to systematically investigate the petrology, origin, distribution and reservoir space of dolomitic tight oil reservoir and to preliminarily discuss the exploration potential of this kind of reservoir. The research results show that the reservoir is mainly composed of dolomitic tuffite, dolomitic mudstone and dolomitic siltstone, with the porosity of 1%-5% and the permeability of 0.008-2.8 mD, suggesting as low-ultra low porosity and extra low-ultra low permeability type reservoir. The reservoir space comprises inter-crystalline pores and micro-fractures. The dolomite in the dolomitic rock is usually hypidiomorphic-allotriomorphic and micrite-powder crystal, with high carbon isotope (from -1.50‰ to 5.20‰) and high V/Ni (from 1.57 to 4.56), indicating terrestrial brackish-brine evaporating environment. The dolomite in the dolomitic mudstone and tuffite contains high carbon and oxygen isotopes, and the dolomite crystals exist in the tuffaceous and argillaceous matrix, mainly related to CH4 generation. The dolomite in the dolomitic siltstone contains low carbon and oxygen isotopes, which is influenced by burial depth and hydrocarbon generation. The Mg2+ in the dolomitic rock came from the deep marble and granite, and also from the volcanic matter and the hydrolytic alteration of feldspar grain. In addition, during the development of dolomitic rock, the volcano eruption triggered the mass mortality of the lake organism, making organic matters endowed to facilitate the cultivation of methanogens bacteria, which provided the dynamic conditions for the dolomite growth during the early stage. The hydrocarbon generation and expulsion of the source rocks during the late stage enabled the oil and gas to preserve in the inter-crystalline pores and micro-fractures, providing good storage space for tight oil.

Key words: dolomitic rock, origin of dolomite, tight oil, Lower Cretaceous, Erenoar sag, Erlian Basin

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