重磁震联合解释在崖北凹陷地球物理解释中的应用

Gravity magnetic seismic joint interpretation of geophysics: Application in Yabei sag

在面对复杂地质条件下的勘探问题时,单一使用地震勘探方法存在局限性,经常难以得到满意的地质解释。这就需要使用多种物探方法进行辅助和补充。本研究综合利用海洋重力磁力测量数据,以Encom ModelVision解释软件为平台,结合琼东南盆地崖北凹陷区域地质背景资料,在两条地震剖面及邻近井资料的约束下建立地质地球物理模型,进行重磁反演,对两条测线中的地层及地质异常体的密度及磁化率进行计算。结果显示,崖北凹陷地层呈现四层密度结构,反演所得沉积基底密度为2.70 g/cm^3,沉积地层的密度为2.18-2.51 g/cm^3。地震剖面中向上侵入的地质异常体经判断为新近系末期喷出地表被后续沉积地层覆盖所形成的蘑菇状,低密度,中-强磁性的火成岩体。结合磁力异常可推断在测区西部还有更大规模的发育的火成岩侵入。这表明了同时新近系末期火成岩及相应火山活动的发现将会对崖北凹陷油气的成藏产生一定的影响。

The northern part of South China Sea is geologically complex; thus, the use of single seismic methods may not provide adequate geological interpretation. Based on a regional geological knowledge, this study uses the joint inversion of marine gravity and magnetic data. The logging of information and a seismic section are used to build a reasonable 2.5D initial model for conducting the inversion calculation. The result reveals that the stratum in Yabei sag have a typical four-layers model. Density of the deposited substrate is 2.70 g/cm^3, and density of sedi-mentary strata is between 2.18 g/cm^3 and 2.51 g/cm^3. Evidence shows that the geological anomaly piercing upwards is an igneous diapir of low density and medium susceptibility that was formed in the late Neogene era and that its presence and related volcanic activities may have a considerable impact on the formation and storage of oil and gas in Yabei sag.