台内生物礁储层非均质性形成机制研究

Reefs deposits are widely developed in the Permian in southern China. With the discovery of a great quantity of reefs gas reservoirs, reefs reservoir have been becoming the major exploration targets in the marine carbonate formations. Relative to higher degree of research and attention of platform edge reef reservoir, the research degree of internal platform organic reef widely distributed in eastern Sichuan hinterland is lower. The oil&gas exploration of internal platform organic reef is restricted by complex topographic situation and internal composition, strong reservoir heterogeneity, unclear distribution regulars and difficult prediction This project selects internal platform organic reef of the Permian Changxing Formation in eastern Sichuan as main study target, based on finely geologic description of typical outcrop profiles, describing in detail the organic reef lithofacies, microfacies types, vertical superimposed types and dimensional distribution of high-frequency units. Combining with rock-mineral, reservoir characteristics and diagenesis analysis, heterogeneity distribution model of internal platform organic reef is established. Through main control and formation process analysis of organic reef reservoir, heterogeneity formation mechanism is further studied. According to the above study, in association with subsurface drilling comparison analysis and logging-seismic interpretation results, we try to establish a set of approaches to identify and forecast internal platform organic reef reservoir. The implement of this project will make contribution to expand research depth of internal platform organic reef reservoir, and also be significant for the exploration of marine carbonate rocks reef reservoirs in China.

生物礁在我国南方地区二叠系广泛发育，随着大量礁型气藏的发现，生物礁储层已经成为南方海相油气勘探的重点。相对于台缘礁储层较高的研究和重视程度，广泛分布于川东腹地的台内礁研究程度还较低，其发育地形及内部构成复杂，储层非均质性强，分布规律不清和预测难等现实问题成为制约台内礁油气勘探的瓶颈。本项目选择川东地区上二叠统长兴组台内生物礁为主要研究对象，以典型露头剖面精细地质描述为基础，对生物礁体岩相、沉积微相类型、高频层序单元的垂向叠加样式及空间展布规律进行精细刻画，结合岩矿、储层和成岩作用分析，研究台内礁储层非均质性分布规律；通过储层主控因素和形成过程解析，对生物礁储层非均质性形成机制进行深入研究；在宏观和微观储层非均质性研究基础上，结合钻井对比解析、测井-地震资料解释成果，建立台内生物礁储层非均质性模型。该项目的实施将有助于拓展台内生物礁储层研究深度，对我国海相碳酸盐岩礁型油气藏勘探具有现实意义。

近年来，随着勘探开发不断加强，生物礁非均质性强的特征已严重制约礁滩油气勘探开发。相较于台缘礁滩，台内礁滩研究程度低，其发育背景及内部构成复杂，储层非均质性更强，分布规律不清和预测难等现实问题成为台内礁油气勘探的瓶颈。. 基于此，本项目以川东地区长兴组台内生物礁为主要研究对象，以典型露头剖面精细地质描述为基础，对岩相、沉积微相类型、高频层序单元的垂向叠加样式及空间展布规律进行了精细刻画，结合岩矿、储层和成岩作用分析，建立了台内礁储层非均质性分布模式；通过储层主控因素和形成过程解析，对生物礁储层非均质性形成机制进行了深入研究；在此基础上，结合地下钻井对比解析、测井-地震资料解释成果，探析了台内生物礁储层综合识别模式及预测方法。. 通过典型剖面和关键井刻画，确定了长兴组早期发育碳酸盐缓坡沉积体系，中-晚期发育碳酸盐台地沉积体系，建立了长兴组三-四级层序地层格架，明确了层序格架内台内礁分布规律。研究结果表明，长兴组划分为两个三级层序和五个四级层序，台内礁总体上发育于高位体系域中。典型台内生物礁剖面可识别出三期生物礁生长旋回，均由粒屑滩沉积的礁基和障积礁或骨架礁组成的礁核构成，分别对应于三个向上变浅的准层序组。各期生物礁生长旋回顶部的礁滩复合体白云石化作用相对强烈，有利于储层形成。. 探讨了川东地区长兴组生物礁储层宏观和微观非均质性特征，研究表明：垂向上存在很强的旋回性，其储层沉积厚度、白云石化程度、溶蚀现象受海平面周期性的升降变化影响而呈现周期性变化。通过分析储层非均质性的控制因素，认为高能相是形成储层原生非均质性的主要控制因素，是储层发育的物质基础，大气淡水淋滤是后期储层形成非均质性关键控制因素。应用地震沉积学的思想，选择三维地震探区，结合地质、测井和地震解释成果，建立了台内生物礁储层综合识别模式及预测方法。项目成果有助于拓展台内生物礁储层研究深度，对于台内生物礁储层勘探可提供地质依据。