Depositional setting and diagenetic processes and their impact on the reservoir quality in the late Visean–Bashkirian Kashagan carbonate platform (Pre-Caspian Basin, Kazakhstan)
Depositional setting and diagenetic processes and their impact on the reservoir quality in the late Visean–Bashkirian Kashagan carbonate platform (Pre-Caspian Basin, Kazakhstan)
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DOI：
10.1306/01051009130
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发表时间：
2010-09
期刊：
影响因子：
3.5
通讯作者：
P. Ronchi;A. Ortenzi;O. Borromeo;M. Claps;W. Zempolich
中科院分区：
文献类型：
--
作者：
P. Ronchi;A. Ortenzi;O. Borromeo;M. Claps;W. Zempolich
卡沙干孤立碳酸盐岩台地发育于滨里海盆地维先期至巴什基尔期。沉积作用以向上变浅的旋回组织起来，在顶部以陆上暴露面为标志。本研究以12口取心威尔斯井的分析为基础，综合了沉积学、岩相学、流体包裹体、稳定同位素和微量元素等资料。重建了台地内部和边缘的孔隙系统演化。近地表成岩作用包括海相胶结物边缘，其次是大气溶解和胶结作用。陨石成岩作用在巴什基尔序列中较强，在维先统中逐渐下降。主要的岩溶表面证明了根的痕迹，尖锐的13 C亏损，和陨石中的水流体包裹体。由于淡水溶解作用、胶结作用和压实作用的相互作用破坏了旋回顶部和底部的孔隙度，台地内部的孔隙度遵循旋回模式。埋藏成岩作用，代表了一些方解石胶结作用，并没有显着改变在平台内部的循环孔隙度分布。在平台边缘，由于沉积旋回性更不明确以及与外来流体循环相关的更强的埋藏成岩叠加，孔隙度分布更加不均匀。盆地来源的流体造成溶解、胶结和局部石化。这些水泥显示明亮的发光，高锰含量，亏损18O，高均一温度，低盐度流体包裹体。复杂的成岩演化和成岩作用使台地内部基质孔隙度较好，台地边缘基质孔隙度较差，孔隙和裂缝较大，为非均质孔隙。
The Kashagan isolated carbonate platform developed from the Visean to the Bashkirian in the Pre-Caspian Basin. Sedimentation is organized in shallowing-upward cycles marked at the top by subaerial exposure surfaces. This study is based on analyses of 12 cored wells, integrated sedimentology, petrography, fluid inclusion, stable isotopes, and trace element data. We reconstructed the pore-system evolution in the platform interior and margin. Near-surface diagenesis includes marine cement fringes followed by meteoric dissolution and cementation. Meteoric diagenesis was stronger in the Bashkirian sequence and progressively decreased down section in the Visean. The main karst surfaces are evidenced by root traces, sharp 13C depletion, and meteoric water-fluid inclusions in calcites. Porosity in the platform interior follows a cyclic pattern due to the interaction of the freshwater dissolution and cementation and compaction that destroyed the porosity at the tops and bases of the cycles. Burial diagenesis, represented by some calcite cementation, did not significantly alter the cyclic porosity distribution in the platform interior. In the platform margin, porosity distribution is more heterogeneous due to more poorly defined sedimentary cyclicity and stronger burial diagenetic overprint linked to exotic fluid circulation. Basin-sourced fluids caused dissolution, cementation, and local dolomitization. These cements show bright luminescence, a high manganese content, depleted 18O, a high homogenization temperature, and low-salinity fluid inclusions. The complex diagenetic evolution diagenesis produced better matrix porosity in the platform interior and heterogeneous porosity with larger pores and fractures but with poor matrix porosity in the platform margin.