柴达木盆地北缘腹部侏罗系烃源岩热演化特征及其对油气成藏影响

侏罗系烃源岩为柴达木盆地北缘(下文简称柴北缘)腹部重要的烃源岩层系,但对其复杂的生烃演化尚未有系统的认识。在钻井、地震及分析测试等资料的基础上,应用PetroMod盆地模拟软件,根据EASY%RO模型,恢复了研究区内不同构造单元侏罗系烃源岩热演化史,分析不同生烃凹陷的差异热演化特征,为柴北缘腹部地区下一步油气勘探提供重要依据。研究表明:侏罗系烃源岩热演化程度自西向东逐渐降低,西南部昆特依凹陷、伊北凹陷的下侏罗统烃源岩在古近纪初期进入成熟阶段,古近纪末期达到生烃高峰;东北部赛什腾凹陷的中侏罗统烃源岩在上新世晚期进入生烃门限,现今仍处于生烃高峰末期。柴北缘腹部构造带总体经历了燕山运动末期和喜马拉雅运动末期2个关键成藏期,根据历史生烃时期与构造样式的匹配关系,认为冷湖七号地区为下一步勘探有利区带。

Thermal evolution of Jurassic source rocks and their impact on hydrocarbon accumulation in the northern margin of Qaidam Basin,NW China

Jurassic strata is the most important source rock in the center of north margin of Qaidam Basin,which was still lack of systematic research in their complex hydrocarbon evolution process. On the basis of drilling data,seismic data and testing data,the model of EASY% ROwas used to recover the thermal evolution history of Jurassic source rocks in different structural units of the study area and analyze the thermal evolution difference of source rock in different hydrocarbon sag,in order to provide important evidences for the next hydrocarbon exploration in the center of northern margin of Qaidam Basin. Research shows that the thermal evolution degree of Jurassic source rock decreased gradually from west to east. The Lower Jurassic source rock of Kunteyi and Yibei sags in the southwest entered the hydrocarbon generation threshold in the Early Paleogene and reached the peak in the Late Paleogene. The Middle Jurassic source rock of Saishiteng in northeast entered the hydrocarbon generation threshold in the Late Pliocene and is still at the peak now. The center of north margin of Qaidam Basin underwent the two key accumulation periods including Late Yanshanian and Late Himalayan. According to the matching relationship between the historical hydrocarbon generation time and tectonic style,it is clear that the Lenghu No.7 area is the next favorable exploration area.