Ordovician glacial paleogeography: Integration of seismic spectral decomposition, well sedimentological data, and glacial modern analogs in the Murzuq Basin, Libya
Ordovician glacial paleogeography: Integration of seismic spectral decomposition, well sedimentological data, and glacial modern analogs in the Murzuq Basin, Libya
复制标题
奥陶纪冰川古地理：利比亚穆尔祖克盆地地震谱分解、井沉积学数据和冰川现代模拟的整合
作者：
F. Bataller;N. McDougall;A. Moscariello
在世界上的几个地区，古冰川沉积物形成了主要的烃储层；最显著的是北非、拉丁美洲和中东。我们描述了一种在这样一个沉积体系中重建大尺度古地理的方法，使用了利比亚西南部穆尔祖克盆地最上层奥陶系冰川沉积物的大量地下数据集。我们的工作流程首先是分析大量高质量的3D地震数据集，以了解频率内容。随后，提取最佳频带，进行频谱分解，重组为R（红）G（绿）B（蓝）混合立方体。然后将该卷作为图像处理，其中可以区分古形态特征，并与现代冰川类似物进行比较。在不同深度（时间片）对这些特征进行绘图，然后结合岩心和图像测井沉积学，在使用井数据和已发表的露头研究开发的相方案框架内定义特定的沉积环境。利用光谱分解作为框架，将这些沉积环境外推到很少或没有井资料的地区，并始终考虑到地震数据集和岩心尺度描述之间在垂直分辨率上的显著差异。该方法的结果是一组经过校准的地图，在三个不同的时间深度（双向时间旅行），显示了研究区冰川沉积环境的古地理重建以及这些冰川环境随时间（在不同深度/时间片2D + 1）的演变。
Ancient glacial sediments form major hydrocarbon plays in several parts of the world; most notably, North Africa, Latin America, and the Middle East. We have described a methodology for reconstructing broad-scale paleogeographies in just such a depositional system, using an extensive subsurface data set from the uppermost Ordovician glacial sediments of the Murzuq Basin of southwest Libya. Our workflow begins with the analysis of a large, high-quality 3D seismic data set, to understand the frequency content. Subsequently, optimum frequency bands are extracted, after applying spectral decomposition, and then recombined into an R (red) G (green) B (blue) blended cube. This volume is then treated as an image within which paleomorphological features can be distinguished and compared with modern glacial analogs. Mapping at different depths (time slices) of these features is then tied, by integration with core and image-log sedimentology, to specific depositional environments defined within the framework of a facies scheme developed using the well data and published outcrop studies. These depositional environments are extrapolated into areas with little or no well data using the spectral decomposition as a framework, always taking into account the significant difference in vertical resolution between the seismic data set and core-scale descriptions. The result of this methodology is a set of calibrated maps, at three different time depths (two-way time travel), indicating paleogeographic reconstructions of the glacial depositional environments in the study area and the evolution through time (at different depths/time slices 2D + 1) of these glacial settings.