鄂尔多斯盆地中部断裂带方解石脉天然气包裹体研究

喜马拉雅运动对鄂尔多斯盆地断裂构造演化和油气藏的形成与分布具有十分重要的影响。鄂尔多斯盆地中部断裂带穿过米脂气田南侧,在断裂带中三叠系野外露头发育有一组"X"型构造裂隙或节理,充填有含大量天然气包裹体的方解石脉。分析表明天然气包裹体形成温度在130~140℃之间,气态总烃含量为78.9%,其中CH₄为51.8%,并含21.1%的H₂S气体。天然气包裹体中有机质以中等碳数C₁₉—C₂₇正构烷烃和偶碳数优势为特征,其来源与鄂尔多斯盆地天然气藏源岩一致。研究认为方解石脉天然气包裹体是深部天然气藏受喜马拉雅运动影响沿构造裂隙发生运移的结果。 

RESEARCH TO THE NATURAL GAS INCLUSIONS CONTAINED IN CALCITE VEIN FILLED IN A BIG FAULT BELT ACROSS THE MIDDLE OF ORDOS BASIN

Himalayan tectonic movement has significant influence on the geology evolution and the oil-gas reservoir formation in the Ordos Basin.Large numbers of natural gas inclusions were found in the calcite vein filled in the structure joint and the fractures in the area of Triassic outcrop near the south margin of Mizi big natural gas field in the Eastern Ordos Basin.Analysis results shown that the organic inclusions formed at the temperature of 130～140℃ with H₂S of 21.1% and total gaseous hydrocarbon of 78.9% including C₄ of 51.8%.The organic matter of the natural gas inclusions is mainly saturated hydrocarbon of C₁₉-C₂₇ with the even carbon dominance.It is proposed that natural gas of the inclusions came from the carbonate source rock,which is also the main source rock of the Mizi big natural gas field.It is indicated that the natural gas inclusion was the marker of the natural gas migration from the Paleozoic gas reservoir through the structure joint and the fracture due to the Himalayan tectonic movement.