鄂尔多斯盆地中部气田奥陶系产层的油气源

OIL-GAS SOURCES OF ORDOVICIAN RESERVOIR IN GAS FIELD OF CENTRAL ORDOS BASIN

关德师 张文正 裴戈

Guan Deshi Zhang Wenzheng Pei Ge

利用天然气组分,碳同位素以及凝析油(原油)的在线碳同位素分析资料,结合区域地质条件、产层纵向分布特征,通过分析对比,确认鄂尔多斯盆地中部气田的天然气主要为上古生界煤系源岩的产物,可能有少量的下古生界源岩裂解气的混入。

The gas fields in Central Ordos Basin are in an unified and broad block.The gas in the fields is mainly from Upper Paleozoic coal measures.The principal evidences for this are:the δC values of the gas from Ordovician reservoirs are basically the same in wide areas and are well-matched or only have about 2‰ deviation with that of the gas from the Upper Paleozoic;the δC values of the gas-condensate light hydrocarbon monomeric molecule are consistent with that of condensate from Permo-Carboniferous;the δC val-ues are generally heavier than -25‰ and relatively enriched in heavier carbon isotope C;the carbon isotopes of the n-alkane,pristane and phytane all suggest that they are the products of high-matured coal measure source rocks and have a close parental rela-tionship with Upper Paleozoic coal measures.Besides,the compact rocks of Om -Om are overlained by gas productive rocks,whereas the compact rocks of Om -Om gas reservoir are poorly gas-bearing;bitumen are rarely present in the Lower Paleozoic rocks.

10.11743/ogg19930303