Describing and understanding the basement relief of sedimentary basins is vital for oil and gas exploration. The traditional method to map an interface in each spatial direction is based on 3D modeling of gravity Bouguer anomalies with variable lateral and vertical density contrasts using a priori information derived from other types of geoscience data sets as constraints (e.g., well and/or seismic data). However, in the preexploration stage, vertical gravity $g_z$, which is sometimes the only available geophysical data, is typically used to recover smooth density contrast distributions under a generic set of constraints. Apparently, the use of the $g_z$ component is not sufficient to produce geologically reasonable interpretations with high resolution. To address this, we have developed a novel process of hybrid inversion, combining gravity migration and inversion using the same $g_z$ data set, to distinguish the complicated interface between basement and sedimentary basin rocks from a full-space inverted density distribution volume. First, a 3D-migrated model delineating the basic sedimentary basin structure is derived using a focusing gravity iterative migration method, where a priori information is not necessary. Subsequently, under the framework of the regularized focusing conjugate inversion algorithm, a high-resolution density contrast model is inverted for delineation of the basement boundary by integrating the 3D-migrated density model as a priori information. We examine the method using one synthetic example and a field data case, of which a transformed resolution density matrix is developed from logarithmic space to qualitatively evaluate the practical resolutions. The high resolution of the density distribution of the Cretaceous basement with a clear interface is achieved and verified by limited seismic data and strata markers in limited wells.

中文翻译：

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基于重力偏移和正则化聚焦反演的3D混合成像预测鄱阳盆地界面

描述和理解沉积盆地的基底起伏对于油气勘探至关重要。在每个空间方向绘制界面的传统方法是基于重力布格异常的 3D 建模，使用从其他类型的地球科学数据集导出的先验信息作为约束（例如，井和/或地震数据），具有可变的横向和垂直密度对比）。然而，在勘探前阶段，垂直重力$G_z$有时是唯一可用的地球物理数据，通常用于在一组通用约束下恢复平滑的密度对比度分布。显然，使用$G_z$成分不足以产生具有高分辨率的地质合理解释。为了解决这个问题，我们开发了一种新的混合反演过程，使用相同的方法将重力迁移和反演相结合。$G_z$数据集，从全空间倒置的密度分布体积中区分基底和沉积盆地岩石之间的复杂界面。首先，使用聚焦重力迭代迁移方法推导出描述基本沉积盆地结构的 3D 迁移模型，其中不需要先验信息。随后，在正则化聚焦共轭反演算法的框架下，通过将3D迁移的密度模型作为先验信息进行积分，反演高分辨率密度对比度模型以圈定基底边界。我们使用一个合成示例和一个现场数据案例来检查该方法，其中从对数空间开发了转换分辨率密度矩阵，以定性评估实际分辨率。