页岩层系致密储层物性下限--以鄂尔多斯盆地三叠系延长组长7段为例

鄂尔多斯盆地三叠系延长组长7段致密油是目前原油上产最重要的现实领域,其3个亚段的储层物性下限决定了长7段致密油勘探开发潜力的规模。运用经验统计法和压汞参数法对长7段物性及试油数据开展研究,发现长7段3个亚段储层物性下限存在差异,即长71亚段孔隙度和渗透率下限分别为7.0%和0.053×10^-3μm^2;长72亚段孔隙度和渗透率分别为6.5%和0.047×10^-3μm^2;长73亚段孔隙度和渗透率分别为5.5%和0.042×10^-3μm^2。利用鄂尔多斯盆地陇东地区长7段粒度分析、连续砂体厚度及含油饱和度等数据,开展储层物性下限差异的研究。结果表明,研究区长7段储层物性下限的控制因素主要为砂体连续厚度与含油饱和度,其中长73亚段成藏机理主要为"烃类聚集"与"致密化减孔聚集",供烃强度及含油饱和度对其致密储层物性下限起重要控制作用。

Study on the porosity and permeability cutoffs of tight sandstones in shale stratum:Case study of Chang7 Member of the Triassic Yanchang Formation,Ordos Basin

The tight oil of Chang 7 Member of Triassic Yanchang Formation in Ordos Basin is the most significant and actual domain for the oil production.The porosity and permeability cutoffs of the three sub-members of Chang 7 Member determine the scale of its exploration and development potential.Using the empirical statistics method and the mercury intrusion parameter method to study the physical properties and test oil data of Chang 7 Member,it is found that the porosity and permeability cutoffs of the three sub-members of the Chang 7 Member is different,that is,the lower limit of the porosity and permeability is 7.0%and 0.053×10^-3μm^2,respectively for the Chang 71 sub-member,6.5%and 0.047×10^-3μm^2,respectively for the Chang 72 sub-member,5.5%and 0.042×10^-3μm^2,respectively for the Chang 73 sub-member.Based on the grain size analysis,continuous thickness of sandstones and oil saturation of Chang 7 Member in the study area,the differences of porosity and permeability cutoffs were studied through the hydrocarbon accumulation mechanism.The results show that the porosity and permeability cutoffs of Chang 7 Member in the study area are mainly controlled by continuous thickness of sandstones and oil saturation.The formation mechanism of the Chang 73 sub-member is mainly"hydrocarbon accumulation"and"densification and reduction of pores".Hydrocarbon strength and oil saturation play an important role in controlling the porosity and permeability cutoffs of tight reservoirs.