基于零阶最小熵正则化的井地重力异常三维联合反演

3D joint inversion of surface and borehole gravity data using zeroth-order minimum entropy regularization

地面重力和井中重力数据含有相互补充的信息,联合反演地面重力和井中重力数据能够较好地反演异常体的真实空间分布。当地下地质体存在尖锐边界时,基于Tikhonov正则化的光滑反演得到的地质体的分界面不清晰,这给后续的地质解释带来一定的困难。为此,本文提出了一种基于零阶最小熵正则化的地面和井中重力数据三维联合反演方法,该方法通过利用这两种数据含有的相互补充的信息提高地下地质体的成像分辨率,而利用零阶最小熵正则化提高反演异常体的聚焦效果,且不需要事先选择合理的聚焦因子。将本文提出的井地联合聚焦反演方法应用于三个不同的理论模型,反演结果表明,相比光滑反演,基于零阶最小熵正则化的聚焦反演能够更加精细地刻画异常体的空间展布;当有钻井穿过异常体时,井地联合聚焦反演能够得到更加可靠和较高成像分辨率的反演密度模型。

Surface and borehole gravity data contain complementary information.Thus,the joint inversion of these two data types can help retrieve the real spatial distributions of density bodies.When a sharp boundary exists between an anomalous density body and its surrounding rock,the interface recovered by smooth inversion with Tikhonov regularization is not clear,leading to difficulties in the subsequent geological interpretation.In this work,we develop a joint inversion of surface and borehole gravity data using zeroth-order minimum entropy regularization.The method takes advantage of the complementary information from surface and borehole gravity data to enhance the imaging resolution of density bodies.It also produces a focused imaging of bodies through the zeroth-order minimum entropy regularization without requiring a preselection of a proper focusing parameter.We apply the developed joint inversion approach to three diff erent synthetic data sets.Inversion results show that the focusing inversion with the zeroth-order minimum entropy regularization provides a good description of the true spatial extent of anomalous density bodies.Meanwhile,the joint focusing inversion reconstructs a more reliable density model with a relatively high resolution when a density body is passed through by one or more boreholes.