Abstract These effective reservoir rocks that can have sufficient porosity and permeability and hydrocarbon accumulations determine economic reserves and high yield of tight oil and gas. Understanding the origin and distribution of these effective reservoir rocks is important for sorting out “sweet spots” in tight reservoirs. Multiple-scale analyses from the microscopic, via drill core to single wellbore have been conducted to examine reservoir heterogeneity of the Upper Paleozoic Shanxi Formation in the southeastern Ordos Basin. Five sandstone petrofacies have been defined in terms of texture and framework composition, detrital matrix, diagenesis and pore types: quartz arenite, tuffaceous quartz arenite, ductile lithic-lean sub-litharenite, ductile lithic-rich sandstone and tightly carbonate-cemented sandstone. The various petrofacies show fundamentally different pathways of diagenetic and reservoir-quality evolutions, due to the complexity of texture and detrital composition in the Shanxi Formation, directly related to the provenance and depositional environment. Quartz arenites and ductile grain-lean sub-litharenites both form effective reservoir rocks. By translating petrofacies to well-log signatures corrected from petrographic and core analysis data, a model based on factor analysis has been built to predict petrofacies at the well scale. For investigating the distribution of each petrofacies at the field scale, sequential indicator simulation method has been used to construct a 3-D petrofacies model with facies conditioning. The isopach maps of quartz arenites and ductile lithic-lean sub-litharenites have been made from the 3-D petrofacies model to quantify their areal distributions, and to define the “sweet spots” by combining isopach maps of these effective reservoir rocks and gas production data from well tests. The concept of reservoir petrofacies is an important tool for the characterization of tight sandstone reservoirs.

中文翻译：

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通过测井和地质统计建模相结合的致密气砂岩储层岩相预测和 3-D 地质模型

摘要 这些有效的储集岩具有足够的孔隙度和渗透率以及油气聚集，决定了致密油气的经济储量和高产。了解这些有效储层岩石的成因和分布对于在致密储层中找出“甜点”很重要。鄂尔多斯盆地东南部上古生界山西组储层非均质性研究开展了从微观、钻芯到单井的多尺度分析。根据结构和格架组成、碎屑基质、成岩作用和孔隙类型定义了五种砂岩岩相：石英砂岩、凝灰质石英砂岩、韧性岩屑贫亚岩屑岩、韧性富岩屑砂岩和紧密碳酸盐胶结砂岩。由于山西组构造和碎屑组成的复杂性，与物源和沉积环境直接相关，各种岩相显示出根本不同的成岩和储层质量演化途径。石英砂岩和韧性晶粒贫化亚岩屑岩均形成有效的储集岩。通过将岩相转换为从岩相和岩心分析数据校正的测井特征，建立了一个基于因子分析的模型来预测井规模的岩相。为了在现场调查每个岩相的分布，已经使用序列指标模拟方法构建了具有相条件的 3-D 岩相模型。石英砂岩和延展性贫岩亚砂岩的等厚图是根据 3-D 岩相模型制作的，以量化它们的面积分布，并通过结合这些有效储层岩石和产气量的等厚图来定义“甜点”试井数据。储层岩相的概念是表征致密砂岩储层的重要工具。