南川地区南页1井五峰组-龙马溪组页岩特征与生物地层

CHARACTERISTICS AND BIOSTRATIGRAPHY OF WUFENG―LONGMAXI FORMATION SHALE IN NANYE WELL 1 OF NANCHUAN AREA

南川区块为国内首个页岩气招拍挂区块,生产实践表明该区具有较大的页岩气勘探开发潜力。为了进一步分析南川地区五峰组一龙马溪组页岩气成藏条件,对该区岩芯资料较全的南页1井开展了系统的笔石鉴定和笔石带划分对比,建立了从凯迪阶的Dicellograptus complexus带(WF2带)至埃隆阶上部的Lituigraptus convolutus带(LM7带)连续的生物地层序列。同时利用薄片、有机地化、全岩X衍射、氮离子抛光扫描电镜等分析测试资料和测井资料,对五峰组一龙马溪组下部优质页岩段进行了精细岩石地层划分,发现①一③小层为深水陆棚亚相细粒沉积,富有机质纹层和含有机质纹层发育,海水富营养,古生物繁盛,有机质富集程度高,有机成因硅质含量高,储层物性好,页岩气成藏物质基础和富集条件优于④一⑤小层,是页岩气勘探开发甜点段。与威202井和宁211井生物地层对比表明,宁211井WF2-LM4带页岩气最富集层段沉积速率最快、厚度最大、页岩气成藏物质基础最好,南页1井、威202井沉积速率较慢、厚度较薄、页岩气成藏物质基础略差。

The Nanchuan block is the first bidding block of shale gas in China.The production practice shows that the area has a large potential for shale gas exploration and development.For further analysis of the shale gas accumulation conditions of Wufeng Formation and Longmaxi Formation in Nanchuan area,the systematic graptolite identification and graptolite zonation were carried out in Nanye Well 1 with complete core data.And the biostratigraphic succession was established from Dicellograptus complexus Zone(WF2 Zone)of the Katian stage to Lituigraptus convolutus Zone(LM7 Zone)of the upper Aeronian stage.At the same time,using thin slices,organic geochemical,full-rock X-ray diffraction,argon ion-polishing scanning electron microscopy and other analytical test data and logging data,the high-quality shale section of Wufeng Formation and Longmaxi Formation were divided in high resolution.The①一③layers are fine-grained sediment of deep-water continental shelf.Rich-organic laminae are developed.The seawater was eutrophic and enriched in organic matter.The biogenetic silicon content was high.The reservoir properties are good.The material foundation and enrichment conditions of shale gas accumulation in①一③layers are better than that in④一⑤layers.So®~®layers are sweet spot sections for shale gas exploration and development.The biostratigraphic correlation with Wei Well 202 and Ning Well 211 shows that the most enriched layer of shale gas in WF2—LM4 zone in Ning Well 211 has the quicker sedimentary rate,larger thickness,and the better material foundation for shale gas accumulation,while Nanye Well 1 and Wei Well 202 have a slower deposition rate,a thinner thickness,and a slightly poor material foundation for shale gas accumulation.