四川盆地东部石炭系黄龙组白云岩成因

Dolomite genesis of Carboniferous Huanglong Formation in eastern Sichuan Basin

四川盆地东部石炭系黄龙组是重要的天然气产层,白云石化作用是优质储层发育的必要条件,白云石化成因类型研究对该区油气勘探具有重要意义。根据岩心和野外剖面观察与描述,结合薄片资料,认为区内黄龙组主要发育以下几种类型的白云岩:泥—微晶白云岩、粉—细晶白云岩和残余颗粒粉—细晶白云岩等,以及充填于孔、洞或缝中的白云石胶结物。结合X射线衍射分析数据和稳定同位素δ13C与δ18Ο资料,发现该区不同类型的白云岩以及白云石胶结物的形成条件和物性特征各异,分别用不同的成因模式来解释更为合理,在此基础上总结了黄龙组具有如下4种白云岩成因模式:泥—微晶白云岩的蒸发泵白云石化成岩模式、(残余颗粒)粉—细晶白云岩的埋藏压实白云石化成岩模式、淡水白云岩的调整白云石化成岩模式和异形白云岩的构造热液白云石化成岩模式。

The Carboniferous Huanglong Formation in eastern Sichuan Basin is an important producing formation for natural gas. Dolomitization is a requirement for the development of high quality reservoir, and the research of genetic types for dolomite has important meaning for oil and gas exploration. Based on core observation and outcrop description, combined with thin section analysis data, it is considered that Huanglong Formation mainly developed the following types of dolomite： mud-microcrystalline dolomite, powder to fine-grained dolomite and residual particles powder to fine-grained dolomite as well as dolomite cement filling in pores, holes and cracks. On the basis of the data of X ray diffraction analysis and geochemical characteristics of stable isotope 813C and 8180, it is found that formation conditions and physical characteristics of different types of dolomite in the study area exhibit different characteristics, and it＇ s more reasonable to use different origin types for the explanation. Four kinds of genetic model of dolomite of Huanglong Formation were summarized, including： diagenetie dolomitization evaporation pump model for mud-microcrystalline dolomite, burial diagenetic dolomitization compaction model for （residual particles） powder to fine-grained dolomite, diagenetic adjustment dolomitization model for freshwater dolomite and construction hydrothermal dolomitization diagenetic model for abnormal morphology dolomite.