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成藏物性下限研究可为致密砂岩储层的含油有效性评价提供重要参数,可为资源潜力较大的鄂尔多斯盆地致密油勘探发现提供重要指导。运用录井、测井、试油试采、物性、压汞、流体包裹体、铸体薄片、扫描电镜等资料,综合确认了鄂尔多斯盆地陕北斜坡东南部长7段有效储层物性下限和油气的关键成藏时期,进一步对现今有效储层物性下限进行关键成藏时期以来成岩作用对物性的改变量校正,得到了研究区长7段致密砂岩油气成藏物性下限。结果表明,研究区长7段有效储层孔隙度下限为5.0%,渗透率下限为0.038×10~(-3)μm~2;关键成藏时期主要为早白垩世中晚期,关键成藏时期与现今时期储层物性存在较大差异,研究区Ⅳ_a型、Ⅳ_n型、Ⅴ型3种储层类型在2个时期的物性差异大小平均值分别为5.15%、3.46%、2.32%;研究区Ⅳ_b型、Ⅴ型储层的物性大小多分布在现今有效储层物性下限值附近,这2种储层类型的关键成藏与现今时期孔隙度相差平均为2.79%,进而得到研究区长7段致密砂岩油气成藏孔隙度下限约为7.79%、成藏渗透率下限约为0.10×10~(-3)μm~2。
The research on the lower limit of reservoir forming property can provide important parameters for the evaluation of oil-bearing effectiveness of tight sandstone reservoirs and provide important guidance for the discovery of tight oil in the Ordos Basin with great resource potential. Using logging data, well logging, test-oil production, physical properties, mercury intrusion, fluid inclusions, cast thin films and scanning electron microscopy data, the lower limit of effective reservoir physical properties and hydrocarbon in the southeast segment of Shaanbei slope in Ordos Basin are comprehensively confirmed During the key accumulation period, diagenesis was further corrected for the change of physical properties since the lower limit of physical property of the effective reservoirs during the key reservoir-forming period. The lower limit of the physical properties of tight sandstone reservoirs in Chang 7 section of the study area was obtained. The results show that the lower limit of effective reservoir porosity in the Chang 7 Member of the study area is 5.0% and the lower limit of permeability is 0.038 × 10 ~ (-3) μm ~ 2. The key accumulation periods are mainly mid-late Early Cretaceous, Compared with the present reservoir physical properties, there are large differences in the physical properties of the three types of reservoirs Ⅳ_a, Ⅳ_n and Ⅴ in the study area. The mean values of physical properties in the two periods are 5.15%, 3.46% and 2.32% respectively. The physical properties of type Ⅴ and Ⅴ reservoirs are distributed in the vicinity of the lower limit of physical properties of today’s effective reservoirs. The key reservoirs of these two types of reservoirs differ from the present porosity by an average of 2.79% The lower limit of the porosity of tight sandstone reservoirs is about 7.79%, and the lower limit of reservoir permeability is about 0.10 × 10 ~ (-3) μm ~ 2.