准噶尔盆地阜康凹陷三工河组流体包裹体特征与成藏期压力恢复

Characteristics of Fluid Inclusions and Pressure Recovery during Hydrocarbon Accumulation Period in Jurassic Sangonghe Formation in Fukang Sag,Junggar Basin

油气成藏时间与地层压力恢复对于油气成藏过程分析具有重要意义.综合利用包裹体观测技术以及盐度-均一温度法和PVTx模拟法,恢复了阜康凹陷三工河组油气成藏时间与储层压力.研究表明,研究区侏罗系自4500 m开始发育超压,三工河组超压明显.三工河组发育两期烃类包裹体:第一期发育在石英颗粒内部,多呈黄色、黄绿色荧光,伴生盐水包裹体均一温度主区间为85~95℃,对应早白垩世中期成藏;第二期沿切穿石英次生加大或整个石英颗粒的愈合缝发育,多呈蓝白色荧光,气液两相明显增多,伴生盐水包裹体均一温度主区间为105~115℃,对应新近纪至今成藏.油气运聚成藏时,三工河组发育超压,第一期压力系数介于1.39~1.44,第二期高达2.11,呈现“增压-泄压-强增压”演化模式.强超压代表了油气运移动力较强,是侏罗系致密储层成藏的关键因素.

Formation pressure recovery is of great significance for the analysis of hydrocarbon accumulation process.This study restores the pressure of Jurassic Sangonghe Formation during hydrocarbon accumulation period in Fukang Sag with inclusion observation technology,the inclusion salinity homogenization temperature method and PVTx simulation method.The results show that the overpressure of Jurassic begins from 4500 m,and the overpressure amplitude increases with the increase in buried depth,in Fukang Sag.At the same depth,the overpressure of the main reservoir of Sangonghe Formation is obvious.There are two stages of hydrocarbon inclusions captured in the Sangonghe Formation.The fluorescence colors of hydrocarbon inclusions captured in the first stage which occur inside the quartz particles are mainly yellow and yellowish green,and the main temperature range of associated aqueous inclusions is 85-95℃,corresponding to the hydrocarbon accumulation in the middle of Early Cretaceous.Since Neogene,the fluorescence color of hydrocarbon inclusions captured in the second stage,which occur along the healing seams that cut through secondary enlargement of quartz or the whole the after the secondary,is mainly bluish white,and the number of the gas-liquid two-phase hydrocarbon inclusions significantly increases.The homogenization temperature of associated aqueous inclusions is 105-115℃,corresponding to hydrocarbon accumulation since the Neogene.During hydrocarbon migration and accumulation,overpressure developed in the Sangonghe Formation.The pressure coefficient in the first stage is 1.39-1.44 and that in the second stage is as high as 2.11.The pressure presents the evolution mode of“pressurizationdecompression-strong pressurization”.Strong overpressure represents strong hydrocarbon transportation and movement force.It is the key factor for hydrocarbon accumulation in Jurassic tight reservoirs.