塔中地区晚奥陶世碳酸盐台地边缘沉积演化及其对古构造和海平面变化的响应

The platform-margin of Tazhong area with a length up to 200 km developed during the late Ordovician serves as the major oil and gas reservoir of the Tarim Basin. Thus the platform margin has long been scientific interests of sedimentology and petroleum geology. Previous studies have confirmed that the platform margin was composed of complex sequence architecture and facies constitution. However, due to the lack of systematic researches focusing on high-frequency sequence and microfacies features, and genetic mechanism of deposition evolution of the platform, the exploration is difficult to progress. This project focuses on the scientific issue that sequence architecture and deposition evolution of the carbonate platform margin and its response to tectonism and sea-level change, by using 3D seismic, well-logging and cores data. The aim of this study is to define the microfacies distribution in a high-frequency sequence framework, to reveal the deposition evolution process, to clarify how tectonics of No.1 fault belt, paleogeomorphy, and sea-level fluctuations impact on the deposition process through analysis of the No.1 fault belt, reconstruction of paleogeomophy, and geochemical results, and finally to forecast the reservoir. The result of this research will be of great significance on the better understanding of detailed deposition architecture and the genetic mechanism of depositional evolution, and the depositional model can be beneficial to reservoir prediction.

晚奥陶世塔里木盆地塔中地区发育超过200 km的碳酸盐台地边缘，其中礁滩相带构成了重要的油气储层而引起广泛关注。大量研究证实该台地边缘具有复杂的层序和沉积构成，然而台缘带的高频层序和微相的系统研究不足，沉积演化过程及主控因素认识不清，阻碍了储层预测和油气勘探的顺利进行。课题围绕“碳酸盐台地边缘的层序结构与沉积演化及其对古构造、海平面变化的响应”科学问题，利用三维地震、钻井、岩心等资料对塔中地区良里塔格组台缘沉积开展研究。拟在高精度层序格架内（四级到五级）查明微相和相组合的发育分布，揭示层序结构演化过程；重点结合Ⅰ号断裂带构造解析、地震-沉积古地貌重建、指示海平面变化的沉积地化分析等技术手段，阐明沉积演化对古构造和海平面变化的响应机制；最终预测有利储集相带分布。研究结果对于深化对碳酸盐台缘带沉积构成样式和沉积演化的影响机制的认识具有重要理论意义，在台缘带有利储层分布预测方面具有实际意义。

碳酸盐台地边缘具有复杂的沉积构成，精细解释台地边缘层序和沉积结构对于揭示台地边缘沉积演化的控制机制和预测有利储层至关重要。利用三维地震和大量钻井的测井、岩心和薄片的分析，对塔中地区晚奥陶世碳酸盐台地的高频层序结构和沉积微相构成开展研究，并揭示沉积演化对古构造和古海平面变化的控制，同时查明对储层发育的影响。提出了利用自然伽马能谱测井开展小波变换定量识别碳酸盐岩高频层序的技术方法，建立了台地范围的四级层序格架；精细刻画了台缘不同部位的高频层序格架内的沉积微相发育差异，阐明了台内滩和台缘滩的沉积差异；重建了良里塔格组沉积前古地貌，阐明了古地貌对不同区带台地结构和三级层序构成的控制；获得了高精度的碳氧同位素数据，结合四级和五级层序的划分，阐明了米兰科维奇天文旋回造成的海平面周期性振荡是台地边缘四级和五级层序的主控因素。提出奥陶系顶部不整合控制的岩溶作用发育模式、四级和五级层序控制的早期岩溶机制和礁滩相叠加后期构造和深部岩溶的储层发育机制。研究成果创新了碳酸盐岩微相分析方法，丰富了碳酸盐岩层序地层成因机制和超深层碳酸盐岩储层成因机制的理论，具有重要的科学意义。