Abstract Folded, fractured, and karstified structures have been recognized in several carbonate reservoirs. However, they are rarely fully identified from seismic or well data and have been poorly described. The present study investigates the geological and structural controls that regional anticlines may exert on solution-enlarged fracture corridors and epigenic karst concentrations in folded-fractured carbonate units. We performed regional mapping based on 106 2D seismic lines, 51 well logs, unmanned aerial vehicle (UAV) imagery of four major outcrop sites (I, II, III and IV) and field investigations to parameterize fracture and karstic features (density, spacing, length, and aperture). The study area is Potiguar Basin, Brazil, where we identified the gentle NE-trending Apodi fold, ~10 km wide and ~20 km long. The fold formed along an inverted extensional fault during the latest Miocene-Quaternary stress field, and the envelope of the meandering trend of the Apodi River coincides with the NE-trending fold axis. The fracture pattern in the fold hinge zone consists of two orthogonal, syn-folding fracture sets: a NE-SW-striking hinge-parallel set and an orthogonal NW-SE-striking set. These fractures and superposed karstification are mostly concentrated in the hinge zone along fracture corridors in an area 1.5 km wide and 20 km long. We conclude that fracture corridors in anticline hinges are likely sites to have high fracture densities and wide apertures. These corridors provide reservoir spaces that are favorable for the formation of karst cavities, with significant increases in permeability and porosity along the fracture sets. These features act as important fluid pathways and storage areas where matrix porosity is low. The findings can be used for first-order prediction in karstified carbonate reservoirs.

中文翻译：

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巴西Jandaíra 组背斜铰链中沿裂缝走廊的岩溶溶蚀：对储层质量的影响

摘要 在几个碳酸盐岩储层中已发现褶皱、裂缝和岩溶构造。然而，它们很少从地震或井数据中完全识别出来，并且描述得很差。本研究调查了区域背斜可能对褶皱裂缝碳酸盐岩单元中溶解扩大的裂缝廊道和表生岩溶浓度产生的地质和结构控制。我们基于 106 条二维地震线、51 条测井记录、四个主要露头地点（I、II、III 和 IV）的无人机 (UAV) 图像和实地调查进行了区域测绘，以参数化裂缝和岩溶特征（密度、间距、长度和孔径）。研究区域是巴西的 Potiguar 盆地，在那里我们确定了平缓的 NE 向 Apodi 褶皱，宽约 10 公里，长约 20 公里。褶皱沿中新世-第四纪晚期应力场的倒张性断裂形成，阿波迪河蜿蜒走向的包络线与NE向褶皱轴重合。折叠铰链区的断裂模式由两个正交的同向折叠断裂组组成：NE-SW-strking 铰链平行组和正交 NW-SE-strking 组。这些裂缝和叠加岩溶作用主要集中在沿裂缝​​廊道的铰链带中，区域宽度为 1.5 公里，长度为 20 公里。我们得出结论，背斜铰链中的裂缝走廊可能是具有高裂缝密度和宽孔径的位置。这些廊道提供了有利于岩溶空洞形成的储层空间，沿裂缝组的渗透率和孔隙度显着增加。这些特征充当重要的流体通道和基质孔隙率低的存储区域。研究结果可用于岩溶碳酸盐岩储层的一级预测。