基于CO2与粘土的水岩反应研究致密砂岩油藏CO2气驱地层伤害机理

Currently, CO2 flooding is the first choice of extracting oil technology for exploiting the Bakken dense oil reservoir in the north American oil company. but if the technology directly applied to the high clay, dense sandstone reservoir, the weak acid of carbonate will cause the expansion of the clay minerals, wettability, surface tension, migration and other properties change of a series of physical and chemical reaction which can cause serious stratigraphic damage. and on the formation mechanism of the stratigraphic damage, there is no experiment which is conducted for the center with clay minerals of CO2 flooding oil water rock reaction by scholars at home and abroad. The topic aim at the advancement of the subject field, use a series of clay minerals, the real core, artificial core, carries out different concentration CO2 fluid injection static experiment and dynamic experiment, and then comparing the samples before and after CO2 corrosion of microscopic pore structure and physical parameters (porosity, permeability) of the change, establish a low permeability reservoir of clay type and content, formation water, CO2 injection temperature pressure reaction between the phase diagram, and conditions of reservoir damage. Topic from the perspective of geology, explain the formation mechanism of CO2 flooding formation damage and consequences, which can provide favorable geological basis for the next step exploiting the dense oil reservoir by CO2 flooding technology.

CO2气驱是目前北美各大石油公司开采巴肯致密油藏的首选采油技术，但该技术直接应用到高粘土的致密砂岩油藏，碳酸的弱酸性会引发与粘土矿物的膨胀、润湿、表面张力、运移等性质改变的一系列物化反应，而造成严重的地层伤害。而有关该地层伤害的形成机理，目前国内外还没有相关学者开展以粘土矿物为中心的CO2驱油水岩反应实验。本课题瞄准该学科的前沿领域，利用一系列粘土矿物、真实岩心、人造岩心，开展不同浓度CO2流体充注的静态实验和动态实验，对比CO2溶蚀前后样品的微观孔隙结构以及物性参数（孔隙度、渗透率）的变化，建立低渗油藏粘土种类与含量、地层水组成、CO2注入温压之间的反应相图，进而预测地层伤害发生的条件。课题是从地质角度出发，解释CO2驱地层伤害的形成机理以及造成的后果，可为下一步CO2驱油技术高效应用到致密油开采领域提供有利的地质依据。

CO2气驱是目前致密油气开发领域首选的采油技术，但该技术针对高粘土含量的致密砂岩油藏，碳酸的弱酸性会引发与粘土矿物的膨胀、润湿、表面张力、运移等 性质改变的一系列物化反应，而造成严重的地层伤害。本课题利用一系列粘土矿物、岩心等，开展不同浓度CO2流体充注的静态实验 和动态实验，对比CO2溶蚀前后样品的微观孔隙结构以及物性参数（孔隙度、渗透率）的变化，建立低渗油藏粘土种类与含量、地层水组成、CO2注入温压之间的反应相图，进而预测地层伤害发生的条件。研究表明：油藏条件下CO2饱和地层盐水与纯矿物或者岩芯的长期反应实验能检测水岩反应类型，致密岩芯因CO2水岩反应造成的渗透率变化存在复杂的机理；致密油藏物性可能变好或者变差，取决于矿物和盐水组成，以及CO2反应的热动力学条件，需要通过流动实验具体测定；数值模拟可以对低渗油藏CO2驱水岩反应进行长期预测，准确的岩石和地层水性质和精确的反应动力学常数对预测准确性至关重要；低渗油藏的物性变化对CO2的注入能力和原油在致密多孔介质中的流动产生重要的影响。CO2对低渗储层物性的影响存在两个相反的方面， 其反应性具有高度的油藏特异性和时间依赖性，需要具体油藏具体分析。课题的成果为下一步CO2驱油技术高效应用到致密油开采领域提供有利的地质依据。