Abstract

By using thin section identification, cathodoluminescence, major and trace elements and fluid inclusion tests and authigenic illite dating, based on observation of core cracks, combined with the microscopic characteristics and imaging logging characteristics of fractures, the stages of the fractures in the Huagang Formation of the central reversal tectonic belt of the Xihu Sag in the East China Sea, and the matching relationship between the fracture development stages and the oil and gas charging stages are clarified. There are diagenetic fractures and tectonic fractures in the reservoirs of the Huagang Formation in the study area. The diagenetic fractures developed during the diagenetic stage of the reservoirs and have less effect on oil and gas migration and transport. The tectonic fractures are divided into three stages based on tectonic movements controlling the fractures and their relationships with hydrocarbon charging: The first stage of fractures was generated in the early stage of the Himalayan Movement–Longjing Movement (12–13 Ma ago), when the tectonic stress caused the sutures and shale strips to twist, deform, and break. Tectonic microfractures generated in this period had short extension, narrow width, and poor effectiveness, and had little effect on oil and gas migration and transport. The second stage of fractures came up during the middle-late period of Himalayan Movement–Longjing Movement (9–12 Ma ago), when tectonic movements caused the development of tectonic fractures in the central reversal tectonic belt, these fractures are of large scale, long extension, and good effectiveness, and matched with the first stage of large scale oil and gas charging (9–12 Ma ago), so they play an important role in oil and gas migration, transportation, and accumulation. The third stage of fractures were created from Himalayan Movement–Okinawa Trough movement to the present day (0–3 Ma ago), the fractures are tectonic ones developing successively; matching with the second stage (0–3 Ma ago) of large-scale oil and gas charging, they created conditions for continuous natural gas migration and transportation. All these prove that the development of reservoir fractures in the Huagang Formation of Xihu Sag can provide seepage space and continuous and effective channels for efficient migration and accumulation of oil and gas.

中文翻译：

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东海西湖凹陷逆转构造带古近系花岗组致密砂岩储层裂缝发育与油气成藏

摘要

通过薄层识别，阴极发光，主要元素和微量元素以及流体包裹体测试和自生伊利石定年，在观察岩心裂缝的基础上，结合裂缝的微观特征和成像测井特征，确定了花岗组的裂缝阶段。明确了东海西湖凹陷的中部逆转构造带，明确了裂缝发育阶段与油气充注阶段的匹配关系。研究区花岗组储层有成岩裂缝和构造裂缝。成岩裂缝是在储层成岩阶段发育的，对油气的运移影响较小。根据控制裂缝的构造运动及其与烃类充注的关系，将构造裂缝分为三个阶段：裂缝的第一阶段是在喜马拉雅运动—龙井运动的早期（12-13 Ma以前），构造应力导致缝线和页岩带扭曲，变形和断裂。这一时期产生的构造微裂缝延伸时间短，宽度窄，有效性差，对油气运移影响不大。断裂的第二阶段出现在喜马拉雅运动—龙井运动（9-12 Ma以前）的中晚期，当构造运动引起中央逆转构造带的构造裂缝发展时，这些裂缝是大规模的，扩展时间长，效果好，并且与大规模油气充注的第一阶段（9-12 Ma以前）相匹配，因此它们在油气运移，运输和聚集中起着重要作用。裂缝的第三阶段是从喜马拉雅运动到冲绳海槽运动形成的，直到今天（0-3 Ma以前），这些裂缝是构造性的，并逐渐发展。与第二阶段（0-3 Ma以前）的大规模油气充注相匹配，他们为持续的天然气运移和运输创造了条件。所有这些证明，西湖凹陷花港组储层裂缝的发育可以提供渗流空间，为油气有效运聚提供连续有效的渠道。因此它们在油气的迁移，运输和积累中起着重要作用。裂缝的第三阶段是从喜马拉雅运动到冲绳海槽运动形成的，直到今天（0-3 Ma以前），这些裂缝是构造性的，并逐渐发展。与第二阶段（0-3 Ma以前）的大规模油气充注相匹配，他们为持续的天然气运移和运输创造了条件。所有这些证明，西湖凹陷花港组储层裂缝的发育可以提供渗流空间，为油气有效运聚提供连续有效的渠道。因此它们在油气的迁移，运输和积累中起着重要作用。裂缝的第三阶段是从喜马拉雅运动到冲绳海槽运动形成的，直到今天（0-3 Ma以前），这些裂缝是构造性的，并逐渐发展。与第二阶段（0-3 Ma以前）的大规模油气充注相匹配，他们为持续的天然气运移和运输创造了条件。所有这些证明，西湖凹陷花港组储层裂缝的发育可以提供渗流空间，为油气有效运聚提供连续有效的渠道。裂缝为构造性裂缝，相继发育。与第二阶段（0-3 Ma以前）的大规模油气充注相匹配，他们为持续的天然气运移和运输创造了条件。所有这些证明，西湖凹陷花港组储层裂缝的发育可以提供渗流空间，为油气有效运聚提供连续有效的渠道。裂缝为构造性裂缝，相继发育。与第二阶段（0-3 Ma以前）的大规模油气充注相匹配，他们为持续的天然气运移和运输创造了条件。所有这些证明，西湖凹陷花港组储层裂缝的发育可以提供渗流空间，为油气有效运聚提供连续有效的渠道。