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Ichnofabrics and their roles in the modification of petrophysical properties: a case study of the Ordovician Majiagou Formation, Northwest Henan Province, China
Sedimentary Geology ( IF 2.8 ) Pub Date : 2020-11-01 , DOI: 10.1016/j.sedgeo.2020.105773
Yongbin Niu , Jim D. Marshall , Huibo Song , Bin Hu , Yazhou Hu , Yi Jin , Li-Jun Zhang , Jienan Pan , Wei Wu

Abstract The carbonate rocks of the Ordovician Majiagou Formation from the northwestern part of Henan Province and their diverse trace fossils provide an outcrop analogue for bioturbated, low porosity and low permeability carbonate reservoirs. Three ichnofabrics can be defined based on the ichnotaxonomy, ichnodiversities, individual abundances and overall bioturbation indices. The Balanoglossites ichnofabric represented medium to relatively high-energy sedimentary environments such as intertidal zone and subtidal shoals in the carbonate platform. The Planolites ichnofabric suggested relatively low-energy, protected sedimentary environments such as lagoons in a restricted carbonate platform, but also occurs in the deeper-water depressions in the open carbonate platform. The Chondrites ichnofabric characterized low-energy and reduced oxygen conditions, with burrows penetrating below a shallow redox interface in deeper-water settings that include the distal slope as well as local depressions in the open carbonate platform. Our analysis suggests that the modifications of petrophysical parameters are controlled or influenced by the ichnofabric characteristics (burrow architecture, burrow cross-cutting relationship, degree of bioturbation and burrow connectivity), the permeability contrast between burrow-fills and matrix, and the dolomitization of burrow-fills. The micritic host sediments have negligible porosity and permeability. The bioturbated sediments have significant differences in fabric, texture, porosity and permeability. The burrow-fills are very commonly dolomitised. Each of the burrow-types can enhance reservoir properties, but the greatest differences are associated with the Balanoglossites ichnofabric, in which porosity and permeability can reach over 2% and 70 mD. Preliminary stratigraphic studies indicate that reservoir potential in the subsurface will be linked to an understanding of the distribution of shoal and intertidal facies as well as their associated Balanoglossites ichnofabrics.

中文翻译:

异形织物及其在岩石物性改性中的作用——以河南西北部奥陶系马家沟组为例

摘要 河南省西北部奥陶系马家沟组碳酸盐岩及其多种微量化石为生物扰动低孔低渗透碳酸盐岩储层提供了一个露头类似物。可以根据鱼类分类学、鱼类多样性、个体丰度和整体生物扰动指数定义三种鱼类织物。Balanoglossites icnofabric 代表中等至较高能量的沉积环境,如碳酸盐台地中的潮间带和潮下带。Planolites ichnofabric 表明能量相对较低、受保护的沉积环境,例如受限碳酸盐平台中的泻湖,但也出现在开放碳酸盐平台的深水洼地中。球粒陨石 ichnofabric 具有低能量和低氧条件的特点,洞穴在深水环境中的浅氧化还原界面下方穿透,包括远端斜坡以及开放碳酸盐平台中的局部凹陷。我们的分析表明,岩石物理参数的变化受到土质结构特征(洞穴结构、洞穴横切关系、生物扰动程度和洞穴连通性)、洞穴填充物和基质之间的渗透率对比以及洞穴白云石化的控制或影响。 - 填充。泥晶基质沉积物的孔隙度和渗透率可以忽略不计。生物扰动沉积物在结构、质地、孔隙度和渗透率方面具有显着差异。洞穴填充物通常是白云石化的。每种洞穴类型都可以增强储层性质,但最大的差异与 Balanoglossites ichnofabric 相关,其中孔隙度和渗透率可以达到 2% 以上和 70 mD。初步地层研究表明,地下储层的潜力将与对浅滩和潮间带相的分布以及它们相关的 Balanoglossites ichnofabrics 的了解有关。
更新日期:2020-11-01
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