用微观方法研究西峰油田长8油层特低渗透砂岩油藏的岩石应力敏感性

基于铸体薄片、岩心物性测试及压汞分析认为,西峰油田长8油层属于特低渗透砂岩油藏。通过试验研究孔隙型岩样和裂缝型岩样的应力敏感性,利用特殊设计的裂缝可视化测试系统、毛管流动孔隙结构仪等微观分析测试手段评价裂缝闭合规律及定量表征裂缝宽度变化;基于扫描电镜、X衍射分析等研究方法探讨孔隙和裂缝应力敏感性的损害机制。研究表明:研究区孔隙型岩样应力敏感性较弱,裂缝型岩样应力敏感性强;孔隙衬里绿泥石、局部分布的石英加大、自形程度高的石英雏晶是孔隙型岩石应力敏感损害率低、渗透率恢复率高的主要原因;裂缝表面的微凸起发生弹塑性形变是裂缝应力敏感性损害极强的主要原因。建立的孔隙和裂缝的应力敏感性损害模式可以为高效开发该类油藏提供依据。

Study on stress sensitivity in ultra-low permeability sandstone reservoir of Chang 8 oil formation in Xifeng Oilfield based on microscopic methods

Based on thin sections of casting,physical property analysis and mercury penetration analysis,the Chang 8 oil formation in Xifeng Oilfield belongs to the ultra-low permeability sandstone reservoir.The stress sensitivity of porosity and fractured rock samples was studied by experimental methods.The fracture closure laws were evaluated and fracture width change was characterized quantitatively by specially designed fracture visualization test system and capillary flow porometer.The damage mechanism of the stress sensitivity of pore and fracture was researched through research methods such as scanning electron microscope,X-ray diffraction analysis.The results show that in the research area,the stress sensitivity of porosity rock samples is weak and that of the fractured ones is strong.The chlorite in pore s liner,the quartz secondary distributed partly and the high automorphic quartz crystallite are main causes of the low stress sensitivity injury rate and the high permeability recovery for porosity rock.Elastic-plastic deformation of micro-salient on surface of fracture is the chief reason to severe damage of the fracture stress sensitivity.The established stress sensitivity damage modes of porous and fractured rock can provide the basis for efficient development of such reservoirs.