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A New Method for Determining Paleocurrent Direction Using Imaging Log

Abstract

The analysis of paleocurrent direction is one of the important methods for analyzing the sedimentary environment and sedimentary system in the study area. This paper presents an attempt to determine the paleocurrent direction by using microresistivity imaging logging data and rose diagram. The change of paleocurrent leads to the planar anisotropy and the directionality of permeability. Therefore, the flow direction can be determined by analyzing the direction of permeability, which can be determined by means of utilization of electrical imaging logging data. In general, the permeability direction of fluvial sand bodies and channel sand bodies is consistent with paleocurrent direction, which is the application scope of this proposed method.

After pre-processing such as azimuth correction, acceleration correction, and data equalization, the original data is generated into image data. Then draw a rose diagram by using the results of stratified statistics on imaging data after deducting mudstone layers. The direction of the maximum conductivity is the direction of the sector with the largest radius in the rose graph. In water-based mud electrical image logging, the greater the conductivity, the better the permeability of the formation. And the direction of permeability is consistent with the paleocurrent. So the direction of the maximum conductivity can be considered as the flow direction. Finally, one cake-like sample and several standard plugs are used to measure conductivity in different directions and permeability respectively. The experimental results are plotted in polar coordinates and the direction of maximum conductivity and the main direction of permeability can be determined. The proposed method can be verified by comparing the statistical results with petrophysical experiments.

The results of the new method are consistent with the petrophysical experiments. It improves the efficiency and accuracy of paleocurrent analysis and is free from many limitations of conventional approaches such as outcrop observation and manual identification. Provides an effective solution and credible results for paleocurrent analysis using logging data.