陇东地区某井延10段砂岩中黄铁矿结核成因分析

Cause Analysis of Pyrite Nodule in Y10 Sandstone of Certain Oil Well in Longdong Region

陇东地区某井延10段是河流相沉积的一套砂体,岩性包括细砂岩、中砂岩、中—粗砂岩、粗—中砂岩和粗砂岩。在这些砂岩中,大量发育黄铁矿结核,通过岩心观察和沉积相分析,并结合前人分析,认为该处黄铁矿结核的成因主要为生物降解作用和细菌硫酸盐还原作用两种类型。

Y10 of certain oil well in Longdong region is a set of ore mass of fluvial facies deposits.Its lithologic characters include packsand,medium sandstone,medium-grit sandstone,grit-medium sandstone and grit stone.Pyrite nodule is very popular among all sandstones.Generally,the formation of iron pyrites is the outcome of combination between Fe2+ and S2-.According to the analysis,Fe2+ may come from the shale(such as shale folium or shale stripe) in sandstone or ferruginous detrital minerals.And S2-may come from certain types of water solution or H2S made by certain mechanism of action.In addition,the possible source of S2-includes desulfurization,bacterial sulfate reduction or thermochemical sulfate reduction of organic matter.