磨溪地区灯影组顶部石灰岩归属探讨及其地质意义  

Classification of limestone at the top Dengying Formation, Moxi area, Sichuan Basin: Implications for geology

作　　者：罗文军[1] 刘曦翔 徐伟[1] 罗冰[1] 王丽英[1] 舒婷[2] 张淼 Luo Wenjun;Liu Xixiang;Xu Wei;Luo Bing;Wang Liying;Shu Ting;Zhang Miao(Exploration and Development Research Institute, PetroChina Southwest Oil and Gasfield Company, Chengdu, Sichuan 610041, China;PetroChina Southwest Oil and Gasfield Company, Chengdu, Sichuan 610051, China;Geological Exploration ＆ Development Research Institute, CNPC Chuanqing Drilling En- gineering Company Limited, Chengdu, Siehuan 610051, China)

机构地区：[1]中国石油西南油气田公司勘探开发研究院 [2]中国石油西南油气田公司 [3]中国石油川庆钻探工程公司地质开发研究院

出　　处：《天然气勘探与开发》2018年第2期1-6,共6页Natural Gas Exploration and Development

基　　金：中国石油天然气股份有限公司重大科技专项"西南油气田天然气上产300亿立方米关键技术研究与应用"(编号:2016E-0606)

摘　　要：钻井显示在磨溪地区上震旦统灯影组顶部的局部区域发育了一套最厚达30 m的石灰岩地层,该套石灰岩地层的时代划分存在争议。但对于磨溪地区灯四段而言,其顶部地层界线的准确识别是对其内部岩溶发育带预测的基础。通过对磨溪地区灯影组顶部石灰岩的薄片及岩心观察分析,发现:(1)薄片上可见大量具有寒武系代表性的"小壳类"化石;(2)此套石灰岩与下伏的白云岩地层间存在风化面。由此认为:(1)此套石灰岩属于寒武系底部的麦地坪组;(2)在此套石灰岩残留厚度较大的区域,地震上曾认为是筇竹寺组与灯影组界线的波阻抗界面,实际上是筇竹寺组与残留的麦地坪组所形成的反射界面,在进行储层预测时应对震旦系顶界深度进行相应校正;(3)磨溪地区灯四段尤其是无麦地坪组石灰岩残留的区域可能受到了桐湾运动Ⅱ幕与Ⅲ幕2次抬升剥蚀。It is shown from drilling that a set of limestones with the maximum thickness of 30 m is locally developed at the top Dengying Formation, Moxi area, Sichuan Basin. But, its geological age is in controversy. For the Dengying 4 Member, to accurately identify its top formation boundary is fundamental for predicting the karst zones in this stratum. So, thin section analysis and core observation were conducted on the limestones. Results show not only large amounts of small shelly animal fossils representing the Cambrian being found on the thin section, but also an erosion surface existing between this stratum and its underlying dolomites. It is deemed that,（1） this limestone stratum should be classified into the Lower Cambrian Maidiping Formation;（2） the area where the residual thickness of this stratum is greater, which was seismically deemed as the wave impedance interface of the boundary between Qiongzhusi Formation and Dengying Formation, is actually the reflecting boundary between Qiongzhusi Formation and residual Maidiping Formation, so it＇s necessary to correspondingly correct the depth of top Sinian in the process of reservoir prediction; and（3） the Dengying 4 Member, especially in some regions without Maidiping limestones, might experience twice uplifting and denudation, i.e., Episodes II and III of Tongwanian tectonic movements.

关 键 词：四川盆地 磨溪地区 晚震旦世 灯影组 麦地坪组 石灰岩 小壳化石 

分 类 号：P618.13[天文地球—矿床学]