缝合线
地质学
成岩作用
岩石物理学
喀斯特
碳酸盐
钻孔
露头
磁导率
碳酸盐岩
溶解
岩石学
地貌学
白云岩
矿物学
地球化学
沉积岩
多孔性
古生物学
岩土工程
物理化学
生物
遗传学
化学
冶金
材料科学
膜
作者
Juliana A.G. Lopes,Walter E. Medeiros,Juliana Paula Felipe de Oliveira,Flávio L. Santana,Raphael Ferreira de Souza Bezerra Araújo,Vincenzo La Bruna,Milton M. Xavier,Francisco H.R. Bezerra
标识
DOI:10.1016/j.marpetgeo.2023.106126
摘要
Fractures and karstic dissolution features have been recognized to significantly affect subsurface fluid flow on a range of scales in carbonate rocks. However, due to the information gap between seismic and borehole scales, characterizing these features is a real challenge. We present a three-dimensional multidisciplinary approach to identify the main factors controlling the formation of connected rock volumes composed by permeable karstic dissolution zones. We investigate two outcrops in the Jandaíra Formation, which is an intensely fractured and karstified carbonate platform in the Potiguar Basin, Brazil. Two GPR cubes are jointly interpreted with cored boreholes, borehole images, petrophysical profiles, and thin sections. We verified that attenuated zones of GPR signal are related to secondary carbonate changes caused by fracturing and/or diagenetic alterations, leading to the development of relatively high secondary permeability. At least three types of attenuation/karstic zones might occur: fractured or broken zones affected by fracture enlargement due to dissolution, zones submitted to intense diagenetic alterations, and void spaces as a final end-member of these two processes. Fractures are preferential routes to fluid flow, thus contributing to increase dissolution processes, particularly in layers having relatively high values of primary matrix porosity and permeability. On the other hand, relevant diagenetic alterations might occur in layers that contain high concentration of stylolites. As a result of interconnecting dissolved stylolites, zones of relatively high secondary permeability can be created regardless of the primary values of matrix porosity and permeability. Geobodies of connected volumes of karstic zones often present tabular shapes and are delimited by subvertical fractures and subhorizontal lithostratigraphic interfaces. In the reservoir scale, these tabular geobodies might compose highly connected permeable volumes of altered carbonate rocks that constitute thief zones or super-K layers.
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