石油与天然气地质 ›› 2024, Vol. 45 ›› Issue (4): 1155-1167.doi: 10.11743/ogg20240418

• 油气地质 • 上一篇    下一篇

琼东南盆地松南低凸起YA区花岗岩潜山风化壳储层特征及发育控制因素

郭原草1,2(), 郭建华2,3(), 劳海港4, 李智宇3, 余烨2, 陈广3, 吴诗情3, 黄俨然2   

  1. 1.湖南科技大学 土木工程学院, 湖南 湘潭 411201
    2.湖南科技大学 地球科学与空间信息工程学院, 湖南 湘潭 411201
    3.中南大学 地球科学与信息物理学院, 湖南 长沙 410083
    4.华北理工大学 矿业工程学院, 河北 唐山 063210
  • 收稿日期:2023-10-11 修回日期:2024-05-10 出版日期:2024-09-05 发布日期:2024-09-05
  • 通讯作者: 郭建华 E-mail:xctmac@sina.cn;gjh796@csu.edu.cn
  • 第一作者简介:郭原草(1984—),男,博士、讲师,沉积学与石油地质学,E-mail:xctmac@sina.cn
  • 基金项目:
    国家科技重大专项(2016ZX05026-002);中海油湛江分公司外部协作项目(CCL2018ZJFN1603)

Characteristics and factors controlling the development of weathered crust reservoirs in buried granite hills, YA area, Songnan swell, Qiongdongnan Basin

Yuancao GUO1,2(), Jianhua GUO2,3(), Haigang LAO4, Zhiyu LI3, Ye YU2, Guang Chen3, Shiqing WU3, Yanran HUANG2   

  1. 1.School of Civil Engineering,Hunan University of Science and Technology,Xiangtan,Hunan 411201,China
    2.School of Earth Sciences and Spatial Information Engineering,Hunan University of Science and Technology,Xiangtan,Hunan 411201,China
    3.School of Geosciences and Info-physics,Central South University,Changsha,Hunan 410083,China
    4.College of Mining Engineering,North China University of Science and Technology,Tangshan,Hebei 063210,China
  • Received:2023-10-11 Revised:2024-05-10 Online:2024-09-05 Published:2024-09-05
  • Contact: Jianhua GUO E-mail:xctmac@sina.cn;gjh796@csu.edu.cn

摘要:

为揭示琼东南盆地松南低凸起YA区花岗岩潜山型油气藏发育机理与成藏规模,运用岩心、物性、元素、磷灰石裂变径迹分析测试资料及测井-地震解释,研究了区内花岗岩潜山风化壳储层特征及发育控制因素、风化壳发育史及残余厚度分布。研究表明:YA区花岗岩系形成于印支期早三叠世,盆地基底在古新世—中新世经历多次构造抬升及沉降,风化壳分两期形成并得以保存,区内热带季风型古气候促进了花岗岩系化学风化作用。区域构造演化、古气候及岩石类型是控制区内古潜山风化壳发育的主要因素。风化壳发育程度存在显著差异性,区内古构造高点处的花岗岩风化壳残余厚度大。YA区花岗岩具有显著的钙碱性-碱性、准铝质-过铝质特征,属于易风化岩石类型。区内风化壳垂向上可分为残积-坡积层、砂化层、风化裂缝层、水平潜流层和基岩层。风化裂缝层是最有利储层,平均孔隙度为11.46 %,平均渗透率为5.98×10-3 μm2,物性随深度增加逐渐变差。花岗岩风化壳在测井曲线上呈现高自然伽马值、高电阻率、低密度和高声波时差等特征,测井指标变化趋势与物性变化趋势基本吻合。地震波反射属性高异常程度与风化壳裂缝发育程度基本呈正相关规律。

关键词: 风化裂缝层, 储层特征, 储层发育, 风化壳, 花岗岩潜山, 松南低凸起, 琼东南盆地

Abstract:

This study aims to reveal the developmental mechanisms and scale of hydrocarbon reservoirs in buried granite hills in the YA area, Songnan swell, Qiongdongnan Basin. Using the analytical and test data of cores, physical properties, elements, and apatite fission tracks, as well as log and seismic interpretations, we investigate the characteristics and factors controlling the development of weathered crust reservoirs in the buried granite hills, as well as the developmental history and residual thickness of the weathered crust. The results indicate that the granite series in the YA area are formed during the Early Triassic of the Indo-Chinese Epoch. The granite basinal basement underwent multiple tectonic uplifts and subsidence from the Paleocene to the Miocene, during which the weathered crust is formed and preserved in two distinct phases. The tropical monsoon paleoclimate promoted the chemical weathering of the granite series in the area. Key factors governing the development of the weathered crust of ancient buried hills in the area include regional tectonic evolution, paleoclimate, and rock types. The weathered crust exhibits significantly different developmental degrees across the area, with the weathered granite crust at paleo-structural crests exhibiting substantial residual thicknesses. Granites in the YA area possess distinct calc-alkaline to alkaline and meta-aluminous to peraluminous characteristics, which make them prone to weathering. Vertically, the weathered crust in the YA area can be categorized into five layers, namely eluvial-deluvial, sandy, weathered fractured, horizontal phreatic, and bedrock layers from top to bottom. The weathered fractured layer, among others, emerges as the most favorable reservoir, demonstrating an average porosity of 11.46 % and an average permeability of 5.98 ×10-3 μm2, and its physical properties deteriorate with increasing burial depth. The weathered granite crust exhibits high natural gamma-ray (GR), high resistivity, low density, and high interval transit time values, as indicated on logging curves, which are consistent with its physical property evolution. Furthermore, there exists a positive correlation between the degree of high-amplitude anomalies in seismic wave reflections and the developmental degree of fractures within the weathered crust.

Key words: weathered fractured layer, reservoir characteristics, reservoir development, weathered crust, buried granite hill, Songnan swell, Qiongdongnan Basin

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