东濮凹陷新生代构造-热历史研究

Cenozoic thermal history of the Dongpu sag,Bohai Bay Basin

东濮凹陷位于渤海湾盆地南缘,是中国典型的既富石油又富天然气的凹陷之一。文中通过镜质体反射率恢复了9个构造单元31口典型井的新生代热历史。研究结果表明:东濮凹陷各构造单元的新生代热历史总的趋势是一致的,并表现为"马鞍型"特征,分别在沙三段沉积时期和东营组沉积中晚期达到地温梯度高峰,其地温梯度分别为45~48℃/km和39~40℃/km,两期地温梯度高峰揭示了东濮凹陷经历了沙三段沉积时期和东营组沉积中晚期强烈的裂陷运动;新近纪开始,凹陷进入热沉降阶段,地温梯度逐渐下降至现今的31~34℃/km。此外,研究成果还揭示了东濮凹陷烃源岩热演化受东营组沉积时期的古地温场控制。文中的研究成果可以为东濮凹陷深层油气资源评价提供地热基础。

The Dongpu sag, located in the south of the Bohai Bay Basin, has abundant oil and gas reserves. In this paper, the Cenozoic thermal history was reconstructed using vitrinite reflectance data from 31 wells in 9 structural units. The results show that the Cenozoic thermal history exhibits a general trend of the ＂saddle type＂. The geothermal gradient reached high peaks twice during the 3ra stage of the Shahejie Formation ＆ the middle and late stages of the Dongying Formation depositional periods at 45 - 48 ℃/km and 39 - 40 ℃/kin, respectively, revealing that the Dongpu sag experienced two strong tectonic rifts during the geothermal gradient high peak periods. The geothermal gradient began to decrease from the Neogene period, and the geothermal gradient is 31 - 34 ℃/kin at the present day. In addition, the results show that the source rock thermal evolution was controlled by the paleo-geothermal fields of the depositional period of the Dongying Formation in the Dongpu sag. This work may provide a geothermal basis for the deep well oil and gas resource evaluation in the Dongpu sag.