Study of a novel density well-logging tool using A position-sensitive detector
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| Authors: | Niu, FF; Liu, ZY; O'Neil, D; Dashtgard, S; Liu, JT |
| Year: | 2019 |
| Journal: | Appl. Radiat. Isot. 154 Article Link (DOI) PubMed |
| Title: | Study of a novel density well-logging tool using A position-sensitive detector |
| Abstract: | Density well-logging tool is an essential instrument used in the petroleum industry for determining formation density, porosity, and lithology of subsurface strata. To improve the vertical resolution and accuracy of density measurements in thin-bedded sedimentary rocks, we proposed an innovative density well-logging tool in which the traditional short- and long-spacing detectors are replaced with a position-sensitive detector (PSD). This replacement enables the measurement of the continuous gamma-ray flux in the area near the PSD. To demonstrate the feasibility of this new tool, we first simulated the performance of a PSD with NaI(Tl) crystal by using the Monte Carlo simulation method (GEANT4). The outcome shows that both gamma-ray deposited energy and interaction position can be determined by the photoelectron yield at each end of the detector, and the resolutions for energy and position are 19.0% and 1.3 cm, respectively, when the gamma-ray energy is 100 keV. Next, we created a Monte Carlo model of a density well-logging tool using such a PSD and simulated its response in a geologic model of thin-bedded strata. The result proves that the proposed tool can yield a good density evaluation when the thickness of the layer is 5 cm, which is significantly better than that obtained with the 16 cm-thick layer of traditional density tools. This study confirms the feasibility of using a PSD in density well-logging tool in theory and indicates that the proposed tool has a promising application in measuring the density of thin-bedded strata. |
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