内蒙古海拉尔盆地乌尔逊凹陷现今地温场特征

摘要

乌尔逊凹陷作为内蒙古海拉尔盆地油气资源最丰富的凹陷之一,其地温场特征尚未进行系统研究.根据5口井系统测温数据和42口井油层测温数据以及实测热导率资料,分析了海拉尔盆地乌尔逊凹陷现今地温场特征.乌尔逊凹陷的现今地温梯度在2.8～3.7℃/hm之间,平均地温梯度为3.35℃/hm.现今大地热流密度值在42.2～59.4 mW/m2之间,平均大地热流密度值为56.0 mW/m2,表明乌尔逊凹陷是一个中温型地温场.现今地温梯度和大地热流密度值分布具有北高南低的特点,造成南北差异的原因主要为地下水活动、断裂及火山岩体.现今地温场对油气生成具有明显的控制作用;乌尔逊凹陷为持续埋藏性凹陷,现今地温为烃源岩经历的最高温度;西部地区现今温度最高,铜钵庙组、南屯组、大磨拐河组烃源岩仍处于较高的温度环境中,烃源岩现今仍处于生烃过程中,西部地区是乌尔逊凹陷主要的找油气区.%Wuerxun depression is one of the sags with the most abundant oil and gas resources in Hailer basin ,Inner MonGolia, but the characteristics of geothermal field of this depression have not been researched. the characteristics of present geothermal field in Wuerxun depression was analyzed according to the continuous temperature data of 5 wells and reservoir temperatures of 42 wells and heat conductivity data. The present geothermal gradient is 2. 8 - 3.7 ℃/hm with average value of 3. 35℃ /hm; the present heat flow is 42. 2 - 59.4mW/m2 with average value of 56. 0 mW/m2. This result shows that Wuerxun depression has middle-temperature field; the present geothermal gradient and heat flow in the north of the depression are higher than those in the south, which are mainly caused by the activity of the ground water and fault and volcanic rock. The present temperature is an important control factor on oil-gas generation of source rocks. The Wuerxun depression has undergone continuous burial with increasing temperature, and the present temperature is the maximum temperature that the source rock has experienced; the present temperature in the west is the maximum, which causes the source rocks in Tongbomiao, Nantun and Damoguaihe formations in a high temperature environment, thus the source rocks is still in the stage of oil-gas generation now, so the west area is the main oil-gas exploration region in the Wuerxun depression.