近地表温压条件下白云岩溶解过程的实验研究

黄思静; 成欣怡; 赵杰; 张文正

doi:10.3969/j.issn.1001-4810.2012.04.002

近地表温压条件下白云岩溶解过程的实验研究

doi: 10.3969/j.issn.1001-4810.2012.04.002

1.
油气藏地质及开发工程国家重点实验室(成都理工大学)
2.
中国石油长庆油田公司勘探开发研究院

基金项目: 国家自然科学基金(40839908,41172099)

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出版历程
- 收稿日期: 2012-08-17
- 发布日期: 2012-12-25

Test on the dolomite dissolution under subaerial temperature and pressure

1.
State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology
2.
Research Institute of Exploration & Development, Petro China Changqing Oilfield Company

摘要

摘要: 与溶解作用有关的次生孔隙是碳酸盐岩最主要的油气储集空间,从实验模拟角度研究碳酸盐溶解机制具有重要的理论与应用价值。本文在近地表的温度和压力条件下,进行了具相同成分和结构的白云岩在CO2和乙酸介质中的对照溶解实验,两种类型的具相同成分和不同结构的白云岩在CO2介质中添加和不添加硬石膏的对照溶解实验,以及方解石含量50%的岩石在CO2介质中添加和不添加硬石膏的对照溶解实验。实验结果表明:(1)近地表温压条件的酸性环境中,乙酸对碳酸盐矿物的溶解能力显著大于CO2流体,乙酸对白云石的溶解是接近化学计量的,而CO2流体则是非化学计量的,白云石中Ca优先溶出而Mg滞留;(2)溶解CaSO4的加入会显著改善近地表温压条件下CO2流体对白云石的溶解效果,使得白云石溶解接近化学计量组成,该过程是通过抑制Ca的溶出和加速Mg的溶出来实现的;(3)对于白云石含量大于90%的较纯的白云岩来说,溶解CaSO4的加入会使得白云岩溶出离子的Ca、Mg合量增加,因而总体上有利于白云岩溶解,与之相反,溶液中CaSO4的沉淀可能导致白云石的沉淀。实验结果可以帮助我们更深刻理解近地表环境白云岩的溶解过程,尤其是与膏盐伴生的白云岩的溶解及相应岩溶过程和次生孔隙的形成机制。
- 白云岩溶解 /
- 实验模拟 /
- 近地表温压条件 /
- 石膏
Abstract: Secondary porosity resulting from the dissolution serves as the main oil reservoir spaces in carbonate rock. The dissolution mechanism of carbonate rock needs to be researched from the point of view of simulation test. In this paper, several groups of dissolution contrast tests have been made for three types of the dolomites with or without adding anhydrite in both acetic acid and CO2 solutions under subaerial temperature and pressure. Several findings from the tests are as follows:(1)Under subaerial temperature and pressure, acetic acid has more solubility than CO2 for carbonate minerals; Besides, the products of the dissolution in acetic acid approach the chemical measurement of the solute, while Ca2+ is released and Mg2+ is detained in CO2 solution; (2)Adding anhydrite in CO2 solution remarkably improves the dissolution effectiveness of the dolomite under subaerial temperature and pressure, which makes the products of the dolomite dissolution approaching the chemical measurement by inhibiting the release of Ca2+ and speeding up the release of Mg2+ ; (3)For pure dolomite with over90% dolomite component, adding anhydrite will lead to the dissolution of the dolomite and increase in total amount of the released Mg2+ and Ca2+. On the contrary, if the anhydrite in the solution deposits, the dolomite will deposit, too. The findings of the test in the paper can help us make out the process of the dolomite dissolution under subaerial temperature and pressure, especially the dissolution of dolomite associated with gypsum as well as the corresponding process of karst and the forming mechanism of secondary porosity.
- dissolution of dolomite /
- simulation test /
- subaerial temperature and pressure /
- gypsum

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