鄂尔多斯盆地东部上古生界盒8段致密砂岩天然气成藏

为搞清鄂尔多斯盆地东部上古生界盒8段成藏与储层致密化关系,采用流体包裹体均一温度测试、激光拉曼光谱分析、伊利石测年分析对研究区盒8段的成藏时间进行了恢复,流体包裹体均一温度显示为双峰分布特征,主要分布在105~120℃之间和135~160℃之间,由捕获的包裹体内气体组分推算的R0介于0.6~1.0和大于1.2两个区间,伊利石测年分析显示峰值年龄分别为160和120 Ma,确定研究区主成藏时间为晚侏罗世和早白垩世。通过成岩作用及埋藏热演化史分析,三叠纪末时研究区盒8段储层孔隙度已小于12%,浮力无法克服毛管阻力,天然气将无法依靠浮力成藏,即储层已致密化。由此得出研究区气藏整体具有"先致密后成藏"的成藏特征,为在研究区寻找勘探有利区提供了理论基础。

Tight sand gas accumulation for the 8th layer in eastern Ordos Basin

In order to understand the relationship of densification and gas accumulation for the 8th Layer of Shihezi Formation in eastern Ordos Basin, using fluid inclusion homogenization temperature testing, la- ser Raman spectroscopy, and illite dating analysis of the study area, the 8th Layer of Shihezi Formation of the accumulation time were restored, homogenization temperature of fluid inclusions display a bimodal distribution,mainly in between 105 ~ 120 ℃ and 135 -160 ℃, the captured gas component body wrapped Ro projections ranged from 0.6 showed that the peak ages of 160 and 120 to 1.0 and two intervals greater than 1.2, illite dating analysis Ma, identified in the study area in the main accumulation time of the Late Jurassic and Early Cretaceous. Again by burial diagenesis and thermal evolution history analysis ,when the end of the Triassic, reservoir porosity is less than 12%, buoyancy less than capillary resistance, gas will not be able to rely on the buoyancy reservoir, the reservoir that has been densified. It follows the overall gas reservoirs in the study area has a reservoir characteristics of＂ dense earlier thanthe accumulation ＂. This accumulation characteristics provides a theoretical basis for exploration of favorable areas.