Study On 3-D Focusing Inversion Method Of Gravity Gradient Tensor Data

The second derivative of gravity potential is called gravity gradient tensor,which can be measured by gravity gradient measurement instrument.Compared to the vertical derivative of gravity potential which is measured by routine gravimetric prospecting instrument,gravity gradient tensor data not only has higher resolution,but also contain several components that can be used to joint interpretation.If gravity gradient data are used to inversion,the inversion result can describe the spatial structure and position of underground field source better.This paper analyzes the current development at home and abroad of three-dimensional focusing inversion of gravity gradient tensor data in detail,and on this basis the focusing inversion method of gravity gradient tensor data based on double weighting was proposed.In the classic Tikhonov regularization theory framework,a minimum support functional was introduced to constraint inversion model to avoid instability of inverse problem solution caused by underdetermined problems that observation points are far less than inversion parameters;and the double weighting functions were also added in the model objective function to overcome the accumulation of density occurring at shallow depths,including the depth weighting function and the weighted coefficient matrix;we also provided fast forward algorithm to solve problems of large calculated amount and storage capacity of geometric structure.Every single components and full tensor of gravity gradient tensor of theoretical models were inverted using regularized focusing inversion,which proves the validity of the regularized focusing inversion method with double weighting function,and at the same time,we proved inversion result of gravity gradient full tensor is better than inversion results of every single components.We also compared the results of smooth constraint inversion and focusing inversion,and it turned out that density distribution of focusing inversion results is more concentrated and density value is also in accordance with the theoretical model better.The proposed method was applied to the practical data of Sebei 1 gas field and the inversion result can reflect the position of the gas field well.