摘要
川中大安寨段致密灰岩储层是致密油发育的重要层位。大安寨段致密灰岩储层为特低孔、特低渗透储层,发育微米级和纳米级孔隙。对研究区30块岩心样品进行饱和水核磁共振T_2谱测量,结果表明,其核磁共振T_2谱特征表现为单峰、双峰(左峰占优和右峰占优)和近似三峰4种类型。综合分析孔隙分量与储层渗透率的关系以及岩石微观孔隙特征发现,研究区具有核磁共振T_2谱单峰特征的岩心样品主要发育纳米级孔隙,且渗透率较低。当核磁共振T_2谱峰值向短弛豫时间方向移动时,若发育连通性好的晶间孔、延伸较远的晶间缝和粘土矿物层间孔,则储层表现为较好的渗透性,且较大级别孔隙分量与渗透率的相关性变好;当核磁共振T_2谱峰值向长弛豫时间方向移动时,若壳间孔和晶间孔局部发育、晶间缝或介壳层间缝延伸长度较小,则储层的渗透率较低,且较大级别孔隙分量与渗透率的相关性变差。微米级构造缝、晶间缝对储层渗透性具有明显的改善作用。
The tight limestone in Jurassic Daanzhai Formation of Central Sichuan Basin is one of the most important tight oil reservoirs in China. The Daanzhai Formation is considered as ultra-low porosity and permeability reservoir with nanometer and micrometer pores and fractures. A total of thirty core plugs were saturated with saline water for days,and then nuclear magnetic resonance(NMR)T_2 measurement was conducted. The results obtained show that there are four types of peak distribution patterns for NMR T_2 spectrum,including unimodal distribution,bimodal distribution(dominated either by left peak or right peak)and pseudo triple-modal distribution. It is found that core samples with unimodal NMR T_2 spectrum are characterized by nanometer pores with low permeability through comprehensive analysis of the statistic relationship between pore components and reservoir permeability and the microscopic characteristic of pores. Although T_2 spectrum distribution shifts to short relaxation time,the permeability value can be high with a good relationship between components of larger pores and flowing capacity when connected intercrystal pores,extended intercrystal fractures and inter-layer pores within clay minerals develop well. When the T_2 spectrum distribution shifts to long relaxation time,the permeability valuecan be low with a weak relationship between components of larger pores and flowing capacity if inter-shell and intercrystal pores are locally developed and intercrystal fractures or inter-layer fractures within shells has limited length. The micronscale fractures such as structural fractures and intercrystal fractures contribute to the increase of reservoirs permeability obviously.
出处
《油气地质与采收率》
CAS
CSCD
北大核心
2017年第1期11-18,42,共9页
Petroleum Geology and Recovery Efficiency
基金
国家自然科学基金项目"深部碳酸盐岩油气储层原位溶蚀模拟实验研究"(41272137)
