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高校地质学报 ›› 2021, Vol. 27 ›› Issue (2): 218-228.DOI: 10.16108/j.issn1006-7493.2020017

• 其他学科 • 上一篇    下一篇

方解石与含硅流体的水-岩反应实验及其对“硅化碳酸盐岩”储层成因的启示

杨源显1,陈强路2,丘 靥1,尤东华2,王小林1*   

  1. 1. 南京大学 地球科学与工程学院,南京 210023;
    2. 中国石化 石油勘探开发研究院无锡石油地质研究所,无锡 214126
  • 出版日期:2021-04-20 发布日期:2021-04-20

Experimental Investigation on the Interaction Between Calcite and Silica-bearing Fluid: Implications for the Formation of Silicified Carbonate Reservoir

YANG Yuanxian1,CHEN Qianglu2,QIU Ye1,YOU Donghua2,WANG Xiaolin1*   

  1. 1. School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China;
    2. Petroleum Exploration and Production Research Institute of SINOPEC, Wuxi 214126, China
  • Online:2021-04-20 Published:2021-04-20

摘要: 近年来的油气勘探表明, 含硅热液是碳酸盐岩层系中一种重要的溶蚀性流体, 查明其与碳酸盐岩的水-岩反应机理是揭示“硅化碳酸盐岩”储层发育机制并实现储层分布预测的基础和关键问题之一。文章采用熔融毛细硅管和水热反应釜为反应腔,开展了200~375℃范围内方解石和含硅流体的水岩反应实验。利用原位拉曼光谱技术在线描述反应过程中体系组成的变化,对于淬火后的固相样品,则采用扫描电镜—能谱分析进行形貌观测和成分鉴定。首先,查明了含硅流体与方解石脱碳反应发生的温度条件。方解石和含硅流体在275℃以上反应形成CO2,固相为非硅灰石的钙硅酸盐,其结构有待进一步揭示。该结果表明单纯的硅质组分难以在储层温度条件下与灰岩发生反应;其次,提出高盐度、富CO2流体作用是造成灰岩溶蚀的重要因素;最后, CO2的存在能够促进硅质(含石英)沉淀。在上述实验认识的基础上,结合前人研究结果探讨了塔里木盆地顺托果勒地区“硅化碳酸盐岩”储层的发育机制。含硅热液沿深大断裂上移,途径震旦系—下奥陶统白云岩层系,其中的硅质组分将与白云石反应形成富镁硅酸盐和CO2。CO2是重要的酸性组分,有利于鹰山组碳酸盐的溶蚀和孔隙的保存。流体温度和压力的降低以及CO2的存在促进了石英沉淀,并形成了大量的石英晶间孔隙。

关键词: 方解石, 含硅热液, 水岩反应, 脱碳反应, 碳酸盐岩储层

Abstract: Recent oil and gas exploration shows that silica-bearing hydrothermal fluid is an important acidic fluid in carbonate sequences. Knowledge on the interactions between silica-bearing fluid and carbonate rock is critical to understand the origin of the silicified carbonate reservoir and the prediction of reservoir distribution. In this study, experimental investigation was carried out on the interaction between calcite and silica-bearing fluid at temperatures ranging from 200 to 375℃ by using fused silica capillaries and
hydrothermal reactor as the reaction chambers. In situ Raman spectroscopy was used to describe the process of the reaction. Besides, Scanning electron microscopy equipped with energy dispersive spectroscopy (SEM-EDS) was used to observe the morphology and to identify the composition of the quenched solids. Firstly, the temperature condition of the decarbonization reaction between silica-bearing fluid and calcite is revealed. Calcite reacts with silica-bearing fluids at temperatures above 275℃ to form CO2, and the solid phase is non-wollastonite calcium silicate. The detailed structure of this calcium silicate needs further investigation. This result indicates that the dissolved silica itself cannot react with limestone at the reservoir temperatures. Secondly, the high salinity and the CO2-bearing nature of the silica-bearing fluid are the important factors causing limestone dissolution. Finally, the presence of CO2 can promote the precipitation of siliceous component, including quartz. Based on the above experiments, the formation of the silicified carbonate reservoir in the Shuntuoguole area of the Tarim basin is proposed, integrated with the previous studies. The silica-bearing hydrothermal fluid migrates upward along the deep and large faults, passing through the Sinian-Lower Ordovician dolomite layer, where the siliceous components will react with the dolomite to form magnesium-rich silicate and CO2. CO2 is an important acidic component, which is conducive to the dissolution of the shallow carbonate and the preservation of pores. Decrease in fluid temperature and pressure, and the presence of CO2 result in the precipitation of quartz, forming large amounts of intercrystalline pores.

Key words: calcite, silica-bearing fluid, water-rock interaction, decarbonization, carbonate reservoir

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