济阳坳陷沾化东区块现今地温场及热历史

PRESENT-DAY GEOTHERMAL FIELD AND THERMAL HISTORY OF THE ZHANHUADONG BLOCK, JIYANG DEPRESSION

根据区内钻井测温和镜质体反射率RO 资料 ,在该区现今地温场分析的基础上 ,采用岩石圈和盆地尺度相结合的多期热演化模型对该区的热史进行了恢复 .结果表明 :( 1 )现今地温梯度为 35.8℃ /km .孤岛及垦东地区地温梯度较高 ,大于 37℃ /km .( 2 )古新世早期的大地热流值为 83.6mW /m2 ,相当于现代活动裂谷的热流值 .自古新世以来 ,盆地有逐步变冷的趋势 ,中间有二次回升 ,但回升的幅度逐渐变小 .现今大地热流值为 63mW/m2 ,接近全球大地热流的平均值 .( 3)该区主力烃源岩经历了持续的受热过程 ,现今仍处于“生油窗口”内 ,在深度上具有较大的油气赋存空间 ,热演化背景对油气生成有利 .上述模拟结果可以用渤海湾盆地的裂谷演化模式进行较好的解释 ,并对胜利油田沾化凹陷的油气勘探工作具有一定的实际意义 .

Present day geothermal field in the Zhanhuadong Block,Jiyang depression,is analyzed based on available borehole temperature data.The thermal history is reconstructed using tectonothermal modeling costrained by vitrinite reflectance( R O)data. The results indicate that (1) The average present geothermal gradient is 35.8℃/km, showing a decreasing trend with depth;higher geothermal gradient more than 37℃/km in Gudao and Kendong area is observed. (2) The heat flow evolution is associated with multi episodic rifting processes. The Palaeo heat flow reached the maximum of about 83.6 mW/m 2 in the early Paleocene corresponding to the major rifting stage,and then cooled down with pulsant variation corresponding to minor rifting to the present day regional average heat flow 63mW/m 2. (3) Since the main oil bearing layers experienced long term slowly heating process under a reasonable burial depth,they are still in the ‘oil generating window’with a wide depth range. The geothermal evolution in the Zhanhuadong Block is good for oil generation. The reconstructed thermal history results support the viewpoint that Bohai Bay is a rift basin and is of practical significance to the oil exploration in the studied area.