塔东南民丰凹陷热演化史与油气关系

Relations Between Geothermal History and Hydrocarbon in Minfeng Depression,Southeast Tarim Basin

民丰凹陷位于塔里木盆地东南部,低程度的烃源岩热史研究制约着该区的油气资源评价和勘探。通过对研究区仅有的两口探井（民参1井、民参2井）进行热演化史模拟,探讨石炭系、侏罗系烃源岩热演化程度、过程及其与油气的关系。模拟结果表明：1受构造活动、火山活动等局部热事件影响,民丰凹陷C-P期古地温梯度为3.5℃/100m,中新生代古地温梯度为2.7~3.2℃/100m,高于盆地周缘其他地区;2民丰凹陷烃源岩在古近纪晚期—新近纪早期（41.3~21.7Ma）至中新世末期（7.0Ma）达到大量生烃条件,与新生代以来的快速沉降共同表明,民丰凹陷具有晚期成藏特征,钻井油气显示较差,可能与优质烃源岩规模小、生聚烃时间较短等因素有一定联系。

The low exploration degree of geothermal history of source rocks in Minfeng depression,located in the southeast of Tarim basin,restricted the assessment of petroleum resources and exploration in this area.Taking the only two exploration wells（Mincan Well 1and Mincan Well 2）in Minfeng depression as examples to simulate the geothermal history,this paper discussed the maturity level and process of Carboniferous and Jurassic source rocks evolution and probed their relationship with hydrocarbon accumulation.The results of simulation show that：1Influenced by partial thermal events such as tectonic and volcanic activities,the paleogeothermal gradients during the C-P and Meso-cenozoic period are 3.5 ℃/100 mand 2.7-3.2 ℃/100 mrespectively in Minfeng depression,higher than that in the other areas of the basin margin.2The hydrocarbon generation conditions of source rocks in Minfeng depression,which appeared in Late Paleogeneto Early Neogene（41.3-21.7Ma）and the end of Miocene（7.0Ma）,and the rapid subsidence during the Cenozoic show that Minfeng depression has the feature of late hydrocarbon accumulation and that the poor oil and gas shows are likely to have certain relations with the small scale and short hydrocarbon accumulating time of high quality source rocks.