内蒙古自治区兴安盟突泉盆地TD-2井晚二叠世孢粉的发现及其油气地质意义

Discovery of Late Permian pollen and spores in TD-2 borehole in Tuquan Basin of Hinggan League of Inner Mongolia and their oil and gas geological implications

松辽盆地西缘的突泉盆地是在古生界之上形成的中生代盆地,近年因在侏罗系发现轻质原油而备受关注。然而,对于该盆地古生代下伏地层及其油气资源前景的研究,过去并未系统开展过。本次运用岩石地层、微体化石和烃源岩样品测试分析等方法对突泉盆地南部牤牛海凹陷TD-2井的岩心开展系统分析,TD-2井在中侏罗世万宝组砂砾岩之下发育一套以暗色泥岩、粉砂质泥岩为主的沉积,产孢粉化石19属26种,包括:Leiotriletes adnatus,Punctatisporites debilis, Cyclogranisporites sp., Alisporites auritus, Al. communis, Al. stenoholcus, Al. sp.?,Klausipollenites schaubergeri, Pityosporites evolutus, Sulcatisporites dalongkouensis, S. ovatus, S. sp.?, Hamiapollenites indistinctus, Lunatisporites tersus, Piceaepollenites opimus, P. sp., Voltziaceaesporites xinjiangensis, Crucisaccites variosulcatus, Divarisaccus cinctus, Plicatipollenites cf. densus, Parcisporites scabratus, Platysaccus sp., P. papilionis,Cycadopites caperatus, Samoilovitchisaccites chordens,孢粉指示的地质时代为晚二叠世;烃源岩分析结果显示,这套暗色泥岩、粉砂质泥岩的烃源岩指标较好,具良好的油气资源前景。岩石地层和生物地层综合对比研究表明,TD-2井下部发育的这套以暗色泥岩、粉砂质泥岩为主的细碎屑沉积为晚二叠世林西组,且其具有良好的生烃基础。该发现为研究松辽盆地西缘晚古生代地层序列奠定了基础,对探讨松辽及周边盆地上古生界油气资源具有重要意义。

Tuquan Basin near the west boundary of the Songliao Basin is a Mesozoic sedimentary basin formed above the Paleozoic strata,which has aroused much attention from geologists due to the discovery of light crude oil from the Jurassic strata in recent years.In the past,systematic research on the oil and gas resources from the Paleozoic was very insufficient.In this paper,the methods such as stratigraphic(lithostratic)and sporopollen analysis and source rock test were conducted so as to analyze synthetically the core samples collected from TD-2 well in the Mangniuhai depression of Tuquan Basin.A stratigraphic unit composed of grayish black mudstone and siltstone beneath the Middle Jurassic conglomerate was discovered in TD-2 well,and some spores and pollen were extracted from the unit,which consist of 26 species and 19 genera,including Leiotriletes adnatus,Punctatisporites debilis,Alisporites auritus,A.communis,A.stenoholcus,Klausipollenites schaubergeri,Pityosporites evolutus,Sulcatisporites dalongkouensis,Hamiapollenites indistinctus,Piceaepollenites opimus etc.indicating Late Permian.Combined with the research results such as the stratigraphy(lithostratic)and source rock test,it is reasonably assigned to Late Permian Linxi Formation,and some high-quality source rocks are discovered in this unit.This discovery is significant for confirming the existence of Permian strata in the Tuquan Basin and also for exploring the late Paleozoic oil and gas resources in the Songliao Basin and adjacent regions.