基于物性上、下限计算的致密砂岩储层分级评价——以苏北盆地高邮凹陷阜宁组一段致密砂岩为例

致密储层分级评价是致密油资源评价的核心内容之一，通过确定致密油储层的不同物性界限能准确有效的建立致密储层分级评价标准，为致密储层分级提供理论依据。以高邮凹陷阜宁组一段致密砂岩储层为例，运用含油产状法、核磁共振法确定了致密储层的含油物性下限，运用核磁共振法、最小流动孔喉半径法、试油法等确定了致密储层的可动物性下限，运用力平衡法确定了致密储层的物性上限；结合致密储层的渗流特征并辅以孔隙结构分类验证，建立了致密砂岩储层的分级评价标准，将高邮凹陷阜宁组一段致密砂岩储层划分为无效致密储层、致密含油储层、可动致密储层及易动致密储层4个级别，渗透率界限分别对应0.07×10^-3，0.12×10^-3，0.50×10^-3和1.13×10^-3μm²。致密储层的分级结果与储层试油试采结果相一致，印证了利用致密储层物性界限进行致密储层分级评价的准确性和适用性。

Classification assessment of tight sandstone reservoir based on calculation of lower and upper limits of physical properties-A case study of the tight sandstone reservoir in the 1st member of Funing Formation in Gaoyou Sag,North Jiangsu Basin

The classification assessment of tight sandstone reservoirs is one of the most important research focus of tight oil resource evaluation.Criteria of classification assessment for tight reservoirs can be effectively and accurately established by calculating the limits of various physical properties of tight oil reservoir,providing a theoretical basis for the classification of tight reservoirs.The tight sandstone reservoir in the 1st member of Funing Formation in the Gaoyou Sag,is taken as an example in the study.Its lower limit of oil-bearing property is calculated by methods of oil-bearing occurrence and nuclear magnetic resonance (NMR);its lower limits of physical properties for oil flowing are worked out by methods of NMR,minimum flowing pore throat radius and formation testing;and its upper limits of physical properties are figured out by balancing the buoyance and capillary resistance of oil in pores.Then following the characterization of tight reservoir permeability and verification of pore structure classification,we established the criteria for classification assessment of tight sandstone reservoirs.The tight reservoirs in the 1st member of Funing Formation,Gaoyou Sag,were accordingly classified into four classes,namely ineffective tight reservoir,oil-bearing tight reservoir,oil-movable tight reservoir and highly oil-movable tight reservoir,with the permeability boundaries of 0.07×10^-3 μm²,0.12×10^-3 μm²,0.50×10^-3 μm²,1.13×10^-3 μm² respectively.The consistency of the classification results and production tests serves to prove the accuracy and applicability of the method proposed in the study.