渭河盆地固市凹陷烃源岩及生物气资源评价

EVALUATION OF HYDROCARBON SOURCE ROCK AND BIOGENIC GAS RESOURCE OF GUSHI SAG OF WEIHE BASIN

以沉积及有机地化资料为基础,分析了渭河盆地固市凹陷新近系上新统张家坡组生物气烃源岩的地质及地化特征,借鉴柴达木盆地技术经验评价了生物气烃源岩有机质丰度指标及烃源岩标准,其结果是:①张家坡组烃源岩以浅湖-较深湖相的暗色泥质岩为主,分布广厚度大,是渭河盆地最好的烃源岩;②烃源岩有机碳(不可溶)平均质量分数0.49%,总有机碳(不可溶和可溶)质量分数1.76%,有机质丰度高,属于好烃源岩标准;③有机质类型以Ⅱ_1腐殖腐泥型和Ⅰ腐泥型为主,为较好-好的类型。镜质体反射率平均0.54%,热演化处于未成熟-低成熟阶段,以生成生物气为主,且具有水溶生物气特征。利用生气率法和生聚系数法计算固市凹陷张家坡组生物气总生气量为23.61×10^(12)m^3,总资源量为5460×10~8m^3,评价表明固市凹陷具有较大的生物气资源潜力和勘探前景。

With the sedimentary and organic geochemical data as the foundation,analyze the characteristics of geological and Geochemical of biogenic gas source rocks of Miocene Zhangjiapo formation of Gushi sag of Weihe basin,referring to Qaidam Basin technology experience evaluation of biogenic gas source rock organic matter abundance index and source rock standard,and the results are;① Zhangjiapo formation hydrocarbon source rocks in shallow lake-Semi deep lake facie are dark mudstones,with wide distribution,big thickness,which are the best hydrocarbon source rocks in Weihe basin;② organic carbon source rock Ⅱ(insoluble) the average mass fraction is 0.49%,the total organic carbon(mass fraction of insoluble and soluble) 1.76%,with high abundance of organic matter,which belongs to the better-good hydrocarbon source rock standards;③ the organic matter type Ⅱ_1 humic sapropel type and Ⅰ sapropel type based,which is good type with 0.54%vitrinite reflectance,thermal evolution in immature-low mature stage,in order to generate biogas,which is of water soluble biological gas characteristic.Use gas generation rate method and raw poly coefficient mefhod to calculate the solid city sag Zhang Jia Po group biological gas and total gas-generated quantity is 23.61×10^(12)m^3,and total resource quantity is 5460 × 10~8m^3.The evaluation indicates that Gushi sag has larger biogenic gas resource potential and exploration prospects.