准噶尔盆地滴北凸起天然气来源及成藏特征

Characteristics of Natural Gas Sources and Accumulation in Dibei Uplift of Junggar Basin

在准噶尔盆地腹部滴水泉凹陷南侧的滴南凸起上发现的大型气田,气藏层位多,储层主要为石炭系火山岩。滴北凸起南面紧邻滴水泉凹陷,北靠乌伦古坳陷,是南、北2个凹陷生成油气运移的有利富集区,但目前勘探尚未获得重大突破,仅在侏罗系和石炭系发现小型气藏。滴北地区天然气来自哪个凹陷目前尚不清楚。文章通过天然气碳同位素与气层抽提物的对比,指出滴北凸起天然气乙烷碳同位素比滴南凸起天然气重,与盆地东部地区典型石炭系来源的天然气相似,气层抽提物地球化学特征与北面乌伦古坳陷石炭系源岩一致,因此应来自北面的乌伦古坳陷。根据储层流体包裹体特征,指出气藏成藏时间在晚白垩世以后。

The large-scale gasfield,containing many gas reservoir layers mainly composed of Carboniferous volcanic rocks,is discovered in the Dinan uplift——the south of Dishuiquan depression in central Junggar basin.Dibei uplift,near the Dishuiquan depression in south and Wulungu depression in north,is considered as the favorable region of hydrocarbon accumulaion from two depressions.Recently,small-scale gas reservoirs have been found in Jurassic and Carboniferous strata,but no greater breakthrough has been made.It is still unclear about the origin of the natural gas of the Dibei uplift.By comparing with carbon isotope of natural gas and reservoir extraction of gas intervals,it is showed that the geochemical characteristics of natural gas in Dibei and Dinan uplift has significant differences,and natural gas of Dibei uplift is similar with that from typical Carboniferous sources in the eastern part of the basin.Consequently,the natural gas should be sourced from Wulungu depression whose geochemical characteristics of rocks in Carboniferous are similar with Dibei uplift.Based on the characteristics of fluid inclusions,it is concluded that the gas is accumulated at late stage of late Cretaceous.