鄂尔多斯盆地南部长7暗色泥岩与黑色页岩生烃动力学特征对比分析

Comparative Analysis of Hydrocarbon Generation Kinetics of Dark Shale and Black Shale of Chang 7 in Southern Ordos Basin

以往对鄂尔多斯盆地南部地区长7油层组(简称长7)中烃源岩生烃潜力的研究主要是采用静态地球化学指标进行的,目前尚无对生烃动态特征的系统评价,因而制约了对长7烃源岩生烃潜力和页岩油资源分布有利岩性的客观认识。为此,选取长7不同类型的烃源岩样品,通过开放和封闭热模拟实验,对比分析了不同类型烃源岩的动力学参数、生烃产物、产率特征及生烃演化规律。结果表明:(1)黑色页岩活化能分布范围比暗色泥岩更为集中,且主频活化能和频率因子均低于暗色泥岩,体现了快速生烃的特性;(2)在外推到地质条件下,黑色页岩主要生烃期对应的Ro值(0. 70%~0. 87%)低于暗色泥岩(1. 06%~1. 72%),且以生油为主;(3) Ro在0. 9%~1. 3%范围内,黑色页岩的总烃产率高于暗色泥岩,生油量高于暗色泥岩。结合研究区两类烃源岩的地球化学资料综合分析表明,黑色页岩是研究区页岩油资源形成与分布的有利烃源岩。

Previous studies on the hydrocarbon generation potential of Chang 7 hydrocarbon source rocks in the southern Ordos Basin were mainly focused on analyzing static geochemical parameters.No systematic evaluation of hydrocarbon generation potential has ever been carried out,which limited our understanding of the potential of Chang 7 hydrocarbon source rocks and the shale oil resource distribution.For this reason,rock samples were collected from two types of Chang 7 source rocks for thermal simulation experiments,and comparative analysis was performed on the hydrocarbon generation products,yield characteristics and hydrocarbon generation kinetics.We suggest that:(1)Distribution of activation energy of black shale is more concentrated than that of dark shale,and the peak frequency of activation energy and frequency factor of black shale are lower than those of the dark shale.This indicates that the black shale has the characteristics of short-term rapid hydrocarbon generation.(2)Under geological conditions,Rovalues of the black shale during the main hydrocarbon generation period(0.70%~0.87%)are lower than those of the dark shale(1.06%~1.72%).(3)In a closed system,Rois in the range of 0.9%~1.3%.The total hydrocarbon production rate and the amount of oil produced are both higher in the black shale than in the dark shale.Comprehensive analysis of geochemical data of the dark and black shales suggest that the former is more favorable source rock for shale oil resources in the study area.