鄂尔多斯盆地西南部上古生界烃源岩特征及其对天然气藏形成与分布的控制作用  

Characteristics of Source Rocks and Its Controls on the Formation and Distribution of Gas from Upper Paleozoic in Southwest Ordos Basin

作　　者：胡维强[1] 赵靖舟[1,2] 李军 李磊[3] 郑杰[3] 井向辉[3] 

机构地区：[1]西安石油大学地球科学与工程学院,陕西西安710065 [2]陕西省油气成藏地质学重点实验室,陕西西安710065 [3]中国石油长庆油田分公司勘探开发研究院,陕西西安710018

出　　处：《天然气地球科学》2015年第6期1068-1075,共8页Natural Gas Geoscience

基　　金：国家科技重大专项项目(编号:2011ZX05007-004)资助

摘　　要：利用有机质丰度、类型、成熟度及生气强度指标对鄂尔多斯盆地西南部上古生界烃源岩进行综合分析,确定主力气源岩及平面分布特征,并与苏里格地区气源条件进行对比,分析气源条件对天然气藏形成与分布的控制作用。研究表明,研究区上古生界烃源岩包括山西组、太原组的煤层和暗色泥岩,其中煤层是主力烃源岩,平均厚度为4.7m,苏里格地区煤层平均厚度为14m。烃源岩有机质丰度较高,山西组和太原组煤层残余有机碳均值分别为54.94%和66.96%,泥岩残余有机碳均值分别为2.88%和1.75%;干酪根碳同位素值介于-24.56‰^-22.05‰之间,属于Ⅲ型干酪根;镜质体反射率介于1.6%~3.2%之间,均值为2.3%,整体处于高成熟—过成熟阶段;研究区生气强度介于(8~20)×108 m3/km2之间,而苏里格地区的介于(11~29)×108 m3/km2之间。与苏里格地区相比,研究区气源条件略显较差。研究区的气源条件对气藏的形成与分布起着明显的控制作用。平面上研究区的产气井主要分布在煤层厚度大于4m,生气强度大于10×108 m3/km2的区域,且存在随着烃源岩条件的变好含气性也变好的趋势;纵向上天然气垂向运移距离与煤层厚度和生气强度存在良好的正相关关系,煤层厚度越大、生气强度越高,天然气垂向运移距离越远。By using abundance,type,maturity and gas generation intensity of organic matter,the comprehensive analysis of Upper Paleozoic source rocks in southwest Ordos Basin has been made to determine the plane distribution characteristics of main gas reservoirs,and the controlling effects of gas source rock on the formation are analyzed,which has been compared with that in the Sulige area.The Upper Paleozoic source rocks are composed of coal and dark mudstone of Shanxi Formation,Taiyuan Formation,of which coal seams are main source rocks.The average thickness of coal seams is 4.7min the study area,while 14 min Sulige.Source rocks are abundant in organic matters.That is,the mean residual TOCin coal seam of the second member of Shanxi Formation and Taiyuan Formation are 54.94%and 66.96%,respectively and in mudstone are 2.88% and 1.75%,respectively;The carbon isotope of kerogen varies from-24.56‰to-22.05‰,indicating that the kerogen belongs to typeⅢ;Vitrinite reflectance of organic matter is 1.6%-3.2%,with an average of 2.3%,which is at high to over-mature stage.Gas generation intensity is mainly between（8-20）×10^8 m^3/km^2,while between（11-29）×10^8 m^3/km^2 in Sulige region.Compared with the condition of gas source rocks of Sulige region,condition in the study area is slightly bad.Condition of source rocks controls the formation and distribution of gas reservoir in the study area.Horizontally,gas-producing wells are mainly distributed in coal seams with thickness more than 4mand gas generation intensity greater than 10×10^8 m^3/km^2,showing a trend that the better the source rocks,the more the hydrocarbon content.Vertically,it has a good positive correlation among the vertical migration distance of gas migration,the thickness of coal seam and gas generation intensity.That is,the vertical migration distance of gas becomes farther along with greater thickness of coal seam and higher gas generation intensity.

关 键 词：上古生界 烃源岩 气源条件 控制作用 运移 

分 类 号：TE122.3[石油与天然气工程—油气勘探]