川北仪陇—平昌地区雷口坡组顶部古岩溶的识别及其与储层的关系

Recognition and Potential Zones of Paleokarst at the Top of Middle Triassic Leikoupo Reservoir in Yilong-Pingchang Area, Northern Sichuan Basin

研究区雷口坡组是一套中三叠统的海相碳酸盐岩．发育一至五段共五个地层段，雷五段已被全部剥蚀．顶部以雷四3亚段与上覆的须家河组接触。雷口坡组残厚800～950m．雷四3亚段顶部十几米至一百来米的范围内经历了广泛的溶蚀作用，主要受到表生期岩溶作用，形成了岩溶角砾岩、溶沟、硅化、膏模孔、溶孔、溶洞以及溶缝等，产生大量的溶蚀空间，但也有较多溶蚀空间被上覆须一段下落的泥质物充填或半充填。在成像测井上，岩溶角砾岩表现为明暗相间、大小混杂的棱角状斑块，未充填溶洞呈暗色高导特征，裂缝则呈连续的暗色条带。发育垂直渗流、水平潜流以及深部缓流这样三个岩溶带．垂直渗流带的储层发育总体好于水平潜流带，深部缓流带相对较差，古地貌地势较高之处溶蚀作用更强，储层更为发育。给出了研究区雷四^3亚段储能系数分布图，A21—A19井区、A22—A23井区以及A160井区的储能系数都大于0.6．是比较有利的储集区带。

The Middle Triassic Leikoupo carbonate rock is divided in five members （from T2l1 to T2l5） in Yilong-Pingchang Area, Northern Sichuan Basin. The Leikoupo 5th Member has been denudated up and at the top of Leikoupo 4th Member （T2/4） is directly unconformably overlied by Xujiahe Formation （T3x） . The residual thickness of leikoupo Fm. is from 800m to 950m. Extensive dissolution had been undergone in a range of over then to a hundred meters at the top of T2/4 Member, which resulted in epidiagentic karstification and formed karst breccia, silicification and dissolved ditches, holes, caves and fractures. Contributed to the karstification, a large amounts of dissolution space was produced, in which parts of dissolution space were filled all or locally with argillaceous material that had fallen from the overlying T3x. Acording to the analysis of imaging logging and well cores, it is shown that three karst zones develop, including vertical seepage flow, horizontal underflow and deep slow flowage zones. Overall, the development of the reservoir with the vertical seepage flow zone is better than that with the horizontal underflow zone and the development of the reservoir with slow flowage zone is poor. Besides, the karstification is more extensive and reservoir property is better in higher location. Based on the map of the drawing energy storage coefficient（ESC） distribution of T214, it is suggested that the areas of Well A21-We11 A19, Well A22-Well A23 and Well A160, in which the ESC are all great than 0.6, are the potential reservoir areas.