碳酸盐岩中缝洞方解石成岩环境的矿物地球化学判识——以塔河油田的沙79井和沙85井为例

摘要在塔里木盆地塔河油田4区沙79井、6区沙85井奥陶系鹰山组岩芯的详细观察基础上，对裂隙、溶洞及巨型洞穴中的方解石晶体的晶胞参数、化学成分、碳、氧同位素、流体包裹体中的氢同位素等分析与研究表明，至少存在两种成岩环境:一是以大气淡水表生环境，方解石中晶胞参数(c)=17.057~17.062，Fe2O3＝0.06%~0.07%，Sr=53.3×10-6~96.2×10-6、Ba=19×10-6~28×10-6，Mg/Ca(×103)＝1.94~5.14，Sr/Ba＝2.12~5.24，δ18OPDB较低（-15‰~-17‰）、较低δ13CPDB（-4‰~-2.0‰），不含或较少含烃类，流体包裹体中氢δDPDB＝-94.99‰~-109.54‰为特征；另一是地层混合水埋藏环境为主，方解石中晶胞参数(c)=17.064~17.065（个别达17.212）、Fe2O3＝0.06%~0.18%，Sr=111×10-6~208×10-6、Ba=215×10-6~479×10-6，Mg/Ca(×103)＝1.53~1.76，Sr/Ba＝0.49~0.58，方解石δ18OPDB低（-9.6‰~-13.7‰）、流体包裹体中氢δDPDB＝-77.5‰~-88.2‰为特征；另外，在巨型洞穴中方解石中组分的剧烈变化反映了洞穴充填发生于不同的水文地质—地球化学体系。

Mineralogical and Geochemical Identification for Diagenetic Settings of Paleo-caves and Fractures-Filling & Vugs Calcites in Carbonate:Taking Wells S79 and S85 for example

Based on observation of core of the Middle and Lower Ordovician carbonate in Wells S85 and S79,a wide range geochemical methods has been used to characterize the diagenetic settings of paleo-caves and fractures-filling & vugs calcites and to decipher their origin,which includes X-ray diffraction of crystal cell,carbon and oxygen isotope composition,fluid inclusion,hydrogen isotope of fluid inclusion and chemical elements analysis.Two diagenetic environments are defined and believed to be prevailing in the f...