Depicting the basement relief of a sedimentary basin with gravity data is vital to predicting the hydrocarbon potential of a sedimentary basin and guiding exploration work. We have developed a gravity inversion method to estimate the depth to a blocky basement of a sedimentary basin. The basement rocks are assumed to be homogeneous and have uniform density, while the density of the sediment over the basement increases exponentially with depth. The density contrast between the sediment and the basement at the surface varies horizontally. The decay factor of density contrast is also nonuniform. The sediment above the basement is divided into vertically juxtaposed prisms, and the depth of the bottom of each prism represents the depth to the basement and is the parameter to be estimated. The L0 norm is introduced to limit the gradient of the parameter vector to obtain the model constraint function. We then establish the objective function for inversion by combining the gravity data misfit function, the known depth constraint function, and the model constraint function. The inversion is performed by minimizing the objective function using the nonlinear conjugate gradient algorithm. The inversion method is evaluated using a 2D and a 3D sedimentary basin model. The results show that our proposed method is capable of delineating the blocky basement relief of a sedimentary basin, and the result is sharper than that obtained using the L1 norm constraint. The method is applied to real data from the western part of the Zhu 1 depression in the Pearl River Mouth Basin, northern South China Sea. The solution reveals a strongly faulted basement, which is in accordance with the known tectonic information indicating the basin is a fully developed graben.

中文翻译：

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使用具有指数密度对比度变化的 L0 范数约束的块状基底浮雕重力反演

用重力数据描绘沉积盆地的基底起伏对于预测沉积盆地的油气潜力和指导勘探工作至关重要。我们开发了一种重力反演方法来估计沉积盆地块状基底的深度。假定基底岩石是均质的并且具有均匀的密度，而基底上的沉积物的密度随着深度呈指数增加。地表沉积物与基底之间的密度对比水平变化。密度对比度的衰减因子也是不均匀的。基底上方的沉积物被分成垂直并列的棱柱，每个棱柱底部的深度代表到基底的深度，是待估计的参数。引入L0范数来限制参数向量的梯度以获得模型约束函数。然后结合重力数据失配函数、已知深度约束函数和模型约束函数建立反演目标函数。通过使用非线性共轭梯度算法最小化目标函数来执行反演。反演方法使用 2D 和 3D 沉积盆地模型进行评估。结果表明，我们提出的方法能够描绘沉积盆地的块状基底起伏，并且结果比使用 L1 范数约束获得的结果更清晰。该方法应用于南海北部珠江口盆地朱1凹陷西部的真实数据。