鄂西渝东地区晚燕山—喜马拉雅期剥蚀量

鄂西渝东地区是中国南方海相油气勘探的重要区块，又是目前页岩气勘探的热门地区，该地区晚燕山—喜马拉雅期以来长期遭受隆升剥蚀.剥蚀量是烃源岩热演化、油气藏形成与演化、资源量计算和盆地模拟中不可缺少的基础参数.考虑到剥蚀量恢复方法固有的局限性和适用条件，本文在分析了古温标镜质体反射率Ro剖面特征之后，采用古地温梯度反演法进行钻井剥蚀量恢复，然后分析钻井剥蚀量与钻井开孔层位之间的相关性，再与地质图相结合编制剥蚀量平面分布图.结果表明：鄂西渝东地区古温标Ro剖面不存在明显的“错断”、“跳跃”现象，记录的古地温为达到最大埋深时的古地温；钻井剥蚀量与钻井开孔层位之间具有明显的相关性，开孔层位越老，剥蚀量越大，反之亦然；晚燕山—喜马拉雅期剥蚀量总体上从东往西逐渐变小.东部的利川复向斜剥蚀量为2000~4000 m，中部的石柱复向斜为1500~2500 m，方斗山以西为1000~1500 m.

Yanshan-Himalayan denudation in Western Hubei Eastern Chongqing area

Western Hubei Eastern Chongqing area is a major exploration block of marine oil and gas and is currently the popular area of shale gas exploration. It has been suffered long term uplift and erosion since the Late Yanshan-Himalayan period. Erosion thickness is an indispensable basic parameter for study of thermal evolution of source rocks, reservoir formation and evolution, and basin modeling to calculate the amount of resources. Considering the inherent limitations and applicable conditions of the existing erosion thickness reconstruction methods, firstly we used the paleogeothermal gradient inversion method to reconstruct erosion thickness of boreholes after analyzing the vitrinite reflectance Ro profile characteristics. Then, we concerned the relationship between the erosion thickness of boreholes and the upmost sequences of the boreholes drilled. After that, a contour map was compiled based on the geological map. The results show that the vitrinite reflectance Ro profiles of boreholes in the western Hubei Eastern Chongqing area do not show obvious "dislocations" or "jumps", recorded maximum palaeotemperatures of sequences in the maximum burial depth. There exists a clear correlation between the erosion thickness and the upmost sequence drilled by the wells: the greater age of the upmost sequence, the greater erosion thickness of the wells, and vice versa. Generally, the late Yanshan-Himalayan erosion amounts gradually decrease from east to west in the Western Hubei Eastern Chongqing area. From the Lichuan area to the Shizhu and to the west of the Fangdou Mountain, the erosion thickness decreases from 2000~4000 m to 1500~2500 m and to 1000~1500 m.