Abstract:

By studying the relation between response characters and the lengths of Gamma ray detector, we choose 0.1 m length of NaI scintillation detectors to develop a new high resolution Gamma ray tool which measures the total Gamma ray flux emanating from the formation. To overcome the increase of statistical fluctuation errors arising from the reduction of Gamma ray count rates due to the short detector, we assemble four detectors of the same type to achieve the four logs of Gamma ray fluxes with high vertical resolution simultaneously. And we sum up the four different curves from the detectors and then execute low-pass filter to reduce statistical fluctuation error in the Gamma ray logs. After that, we apply regularized deconvolution to enhance the vertical resolution of Gamma ray logs. The theoretical modeling and field results prove that the new Gamma ray tool has the vertical resolution up to 0.15 m, whose vertical resolution is about 4 times higher than that of other conventional Gamma ray tools.

Key words: nature Gamma-ray, well logging, high vertical resolution, low-pass filter, regularized deconvolution