雅布赖盆地侏罗系新河组致密油形成条件与有利区资源潜力

雅布赖盆地是我国西部一个侏罗纪湖相含油气盆地。为了评价其侏罗系新河组致密油的勘探前景，基于烃源岩、储集层条件及其配置关系的分析，采用地质要素叠合法优选出盆地的致密油有利区，并利用小面元容积法估算了资源潜力。研究表明，雅布赖盆地的优质烃源岩主要分布在中侏罗统新河组下段，累积厚度大、有机质丰度高、有机质类型好、处于生油的成熟热演化阶段，为致密油主要发育段；低孔、低渗的致密储集层主要以薄互层或夹层形式分布在烃源岩层内，原油具备典型的源内自生自储特征；成熟的富有机质烃源岩与储集层的大面积直接接触和巨厚的泥岩封盖是致密油发育的重要控制因素。首先，通过烃源岩成熟度确定了小湖次凹为致密油发育有利部位。然后，综合测井和录井油气显示成果，依据烃源岩TOC（有机碳含量）>1%、0.6%<R_o（镜质体反射率）<1.3%、储集层（孔隙度≥4%）累计厚度>10 m的标准，圈定了盆地致密油有利区主要分布在小湖次凹的中西部。最后，根据小面元容积法估算有利区石油地质资源量大致为0.92×10⁸t，资源丰度平均为34.5×10⁴t/km²。

Formation conditions of the Jurassic Xinhe Formation tight oil reservoirs and resource potential in the Yabrai Basin

The Yaburai Basin is a Jurassic lacustrine petroliferous basin in western China. In order to assess tight oil potential of the Xinhe Formation in the basin,we employed a geological factor superimposition method to select tight oil play fairway and a small cell volumetric method to calculate the resources based on analyses of source rocks and reservoiring conditions as well as their coupling relationship in the basin. The research shows that high-quality source rocks are mainly located in the lower Xinhe Formation in the Middle Jurassic. Tight oil reservoirs are mainly developed in this source rock interval featuring in large cumulative thickness,rich organic matter of favorable types,and being within oil window. Low-porosity and low-permeability tight reservoirs occur as thin interbeds and interlayers inside the source rocks. Crude found there shows clear signs of self-generation and self-preservation. The large area of contact between matured organic-rich source rocks and reservoirs and the effective sealing of massive mud rock cap are the most important controlling factors of tight oil reservoirs in the basin. The sub-sag Xiaohu was considered to be a play fairway based on analyses of maturity of source rocks. A comprehensive study of mud and wireline logging data as well as oil and gas shows were used to establish a standard (TOC>1%,0.6%<R_o<1.3%,reservoir porosity ≥ 4%,accumulative thickness>10m) to pinpoint the location of play fairway at the central and western part of the subsag. Calculation shows that the target holds an oil-in-place of 92 million tons and resource abundance of 345 thousand tons per square kilometers.