岩心尺度下储层基础参数对CO2-原油MMP的影响规律与机理

For low permeability sandstone reservoirs, water injection is difficult, and carbon dioxide miscible flooding is the most promising EOR technology. The minimum miscibility pressure (MMP) is the key parameter to determine miscible phase. However, the known experiment test methods have been questioned because they can not simulate the actual reservoir pore scale very well. At present, there is a lack of study on the influence of the basic MMP parameters between carbon dioxide and oil under the reservoir pore scale, including the influence law of macro porosity and permeability, micro structure and the formation water saturation. As for above issues, this project will test the minimum miscible pressure by using displacement experiment method during the whole course, for the first time, study the influence law of macro porosity and permeability on MMP by using the self-developed long tube cementation model; by the constant-rate mercury injection and CT, test microscopic pore parameters of Berea sandstone cores, classify cores and carry out displacement experiments, reveal the influence law of microscopic parameters on the minimum miscible pressure. And for the first time, based on above two kinds of models, we will study the influence of formation water saturation on MMP under the condition of the existence of microscopic pores or not. To reveal the influence and mechanism of calcium and magnesium ions on the minimum miscible pressure, we will proceed the experiment further about the effect of content change of calcium and magnesium ions on the MMP.. This project will focus on the basic research, which results will provide a strong technical support for carbon dioxide miscible flooding in low permeability reservoirs. So the research is of great significance.

低渗砂岩储层注水困难，二氧化碳混相驱是最有发展前途的EOR技术，最小混相压力（MMP）是决定是否混相的最关键参数。已有测试方法使用的多孔介质被质疑与实际储层孔喉尺度差异大，目前缺少岩心尺度下的储层基础参数对MMP的影响研究。本项目将针对上述问题，全程选用驱替实验法确定MMP，首次采用自行研制的长细管胶结模型进行宏观上孔隙度与渗透率变化对MMP的影响规律研究；借助恒速压汞和CT将贝雷砂岩岩心依据微观参数分类后采用驱替实验法确定MMP，进而揭示微观参数对MMP的影响规律；首次采用上述两种岩心模型开展不同地层水含量对MMP的影响研究，获得有无微小孔隙存在的前提下地层水含量对MMP的影响规律；并首次增加钙镁离子含量的变化对MMP的影响测试实验，揭示钙镁离子对MMP的影响规律及机理。. 本项目立足基础研究，为低渗油藏实现混相驱提供强大技术支持，意义重大。

低渗砂岩储层注水困难，二氧化碳混相驱是有发展前途的EOR技术，最小混相压力（MMP）是决定是否混相的最关键参数。已有测试方法使用的多孔介质被质疑与实际储层孔喉尺度差异大，目前缺少岩心尺度下的储层基础参数对MMP的影响研究。. 项目研制了长细管（12m）胶结岩心模型，采用岩心驱替法研究了渗透率、孔隙度对最小混相压力（MMP）影响规律及机理以及CO2混相驱与近混相驱开采规律。筛选贝雷岩心研究了储层微观参数对MMP的影响规律研究。包括孔隙尺寸、孔喉比及微小孔隙的存在对最小混相压力的影响规律及机理，揭示了真实储层情况下CO2混相驱与近混相驱开采规律。研究了不同地层水饱和度对CO2-原油最小混相压力的影响规律及机理以及不同钙镁离子含量对CO2-原油最小混相压力的影响规律及机理；.通过对比细管实验标准和岩心驱替实验结果发现：岩心驱替法测定的MMP为19.85MPa，低于细管实验测定的MMP (21.72MPa)。岩心驱替法测试表明：随渗透率增大，孔隙度增大， CO2-原油MMP增大。孔隙结构对最小混相压力影响实验中发现：贝雷岩心孔道尺寸、喉道尺寸越小，越利于CO2-原油多级接触混相，最小混相压力越小。岩心喉道尺寸范围在0.16-25μm之间时，岩心孔喉比越小，CO2-原油的最小混相压力越小。贝雷岩心与人造岩心的对比实验表明微小孔隙的存在使得CO2-原油更容易达到混相。地层水的存在增加了混相难度，含水饱和度越大，混相压力越大。钙镁离子的存在生成部分沉淀，但是又被后续注入生成的碳酸溶解，间接的提高了采收率，对最小混相压力存在积极影响。钙镁离子含量越高，最小混相压力越小。. 本项目揭示了孔隙度与渗透率变化对MMP的影响规律研究；揭示了储层微观参数对MMP的影响规律；钙镁离子含量的变化对MMP的影响测试实验，揭示钙镁离子对MMP的影响规律及机理。对矿场实践具有指导意义。