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北京和天津之间的廊坊—固安地区是一个地质构造复杂的地区。对于通过该区泉26井的一条地震剖面上的深部反射层(T_6)的岩性及时代的解释,尚有争议,故希望通过与此地震测线重合的重力剖面,进行联合解释。该剖面上的重力异常值由西北往东南单调降低,反映该区的区域场具有线性变化的特点,利用地震层速度、构造剖面和相剖面等资料进行重力异常的正、反演计算,其结果说明引起重力异常的因素不是单一的,也就是说,产生重力异常的主要密度界面不是一个统一的地质层位,它不能反映基底界面的起伏。但是,在泉26井附近,依据 T_6反射层换算的密度值为2.67g/cm~3,接近石灰岩的密度值,故推断 T_6反射波相当于石炭—二叠系石灰岩的顶面反射。
The Langfang-Gu’an area between Beijing and Tianjin is a geologically complex area. The interpretation of the lithology and epoch of the deep reflection layer (T_6) on a seismic section passing through this Ququan-26 well is still controversial. Therefore, it is hoped that joint interpretation will be made on the gravity section coinciding with this seismic line. The gravity anomalies in the profile decrease monotonically from northwest to southeast, reflecting the linear variation of the regional field in this area. Based on the data of seismic velocity, tectonic section and facies section, It shows that the cause of gravity anomalies is not single. That is to say, the main density interface that produces gravity anomalies is not a unified geological horizon, it can not reflect the ups and downs of the interface of the basement. However, in the vicinity of Well Quan-26, the density converted from T_6 reflector is 2.67 g / cm ~ 3, which is close to the density of limestone. Therefore, T_6 reflection wave is deduced to be equivalent to the top reflection of Carboniferous-Permian limestone.