Lucaogou formation in Jimsar sag is host to large quantities of bedding fractures which are known to play a critical role in the enrichment, accumulation, and efficient development of tight oil. In this paper, we examine and finely characterize the development of the bedding fractures found in the upper and lower sweet spots of Lucaogou formation of tight oil reservoir through field outcrop and core observation, cast thin section analysis, and imaging log recognition and investigate the factors affecting their differentiated oil-bearing by means of inclusion temperature measurement, TOC testing, physical property testing, high-pressure mercury injection, and physical simulation experiment. By comparison with the linear density, bedding fractures are more developed in the lower sweet spot. These fractures occur in parallel to the formation boundary and have small aperture. Most of bedding fractures are unfilled fractures. Among the few types of fractures found there, bedding fractures have the best oil-bearing property, but the oil-bearing can differ from one bedding fracture to another. The factors affecting the differentiated oil-bearing of bedding fractures include the temporal coupling of the formation of these fractures with the hydrocarbon generation of the source rocks and the spatial coupling of the bedding fractures with the source rocks. In terms of temporal coupling, mass hydrocarbon generation in Jimsar sag began in Late Jurassic. Inclusion temperature measurement indicates that the bedding fractures there formed in or after Early Cretaceous. Hence, by matching the mass hydrocarbon generation period of the source rocks with the formation period of the bedding fractures, we discovered that the bedding fractures formed within the mass hydrocarbon generation period, which favored the oil-bearing of these fractures. The spatial coupling is manifested in TOC, porosity, permeability, and pore throat, with TOC being the main controlling factor. For TOC, the higher the formation TOC, the better the oil-bearing property of the bedding fractures. For porosity, subject to the TOC level, if the TOC is adequate, the larger the porosity, the larger the chloroform asphalt “A,” accordingly the higher the oil content of the formation, and the better the oil-bearing property of the bedding fractures developed therein. In this sense, in terms of spatial coupling, TOC constitutes the main controlling factor of the oil-bearing property of bedding fractures.

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层理裂缝含油差异研究——以吉木萨尔凹陷芦草沟组为例

吉木萨尔凹陷芦草沟组发育大量层状裂缝，对致密油的富集、成藏和高效开发具有重要作用。本文通过野外露头和岩心观察、铸件薄片分析、成像测井识别等方法，对致密油藏芦草沟组上、下甜点区层理裂缝的发育情况进行了考察和精细刻画，并探讨了影响因素。通过夹杂物测温、TOC检测、物性检测、高压压汞、物理模拟实验等手段影响其差异化含油。与线密度相比，较低甜点区的层理裂缝更加发育。这些裂缝平行于地层边界发生并且具有小孔径。大多数层理裂缝是未充填的裂缝。在那里发现的少数几种裂缝中，层状裂缝的含油性最好，但含油性可能因一种层状裂缝而异。影响层理裂缝差异含油的因素包括这些裂缝的形成与烃源岩生烃的时间耦合和层理裂缝与烃源岩的空间耦合。从时间耦合上看，吉木萨尔凹陷大规模生烃始于晚侏罗世。包裹体温度测量表明，其中的层理裂缝形成于早白垩世或之后。因此，通过将烃源岩团块生烃期与层理裂缝形成期进行匹配，发现层理裂缝形成于团块生烃期，有利于这些裂缝的含油。空间耦合表现在 TOC、孔隙度、渗透率、孔喉等方面，其中 TOC 是主要控制因素。对于 TOC，地层 TOC 越高，层理裂缝的含油性越好。对于孔隙度，以TOC水平为准，如果TOC足够，孔隙度越大，氯仿沥青“A”越大，相应地层含油量越高，层理的含油性越好裂缝在其中发展。从这个意义上说，在空间耦合方面，