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The Scientific World Journal
Volume 2013 (2013), Article ID 848201, 6 pages
http://dx.doi.org/10.1155/2013/848201
Research Article

Genesis Analysis of High-Gamma Ray Sandstone Reservoir and Its Log Evaluation Techniques: A Case Study from the Junggar Basin, Northwest China

1State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China
2College of Geophysics and Information Engineering, China University of Petroleum, Beijing 102249, China
3Research Institute of Exploration and Development, Xinjiang Oilfield Company, PetroChina, Karamay 834000, China
4No. 203 Research Institute of Nuclear Industry, Shanxi 712000, China

Received 9 May 2013; Accepted 29 June 2013

Academic Editors: A. Billi, A. Gudmundsson, A. Koustov, and G. Zhao

Copyright © 2013 Liang Wang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

In the Junggar basin, northwest China, many high gamma-ray (GR) sandstone reservoirs are found and routinely interpreted as mudstone non-reservoirs, with negative implications for the exploration and exploitation of oil and gas. Then, the high GR sandstone reservoirs’ recognition principles, genesis, and log evaluation techniques are systematically studied. Studies show that the sandstone reservoirs with apparent shale content greater than 50% and GR value higher than 110API can be regarded as high GR sandstone reservoir. The high GR sandstone reservoir is mainly and directly caused by abnormally high uranium enrichment, but not the tuff, feldspar or clay mineral. Affected by formation’s high water sensitivity and poor borehole quality, the conventional logs can not recognize reservoir and evaluate the physical property of reservoirs. Then, the nuclear magnetic resonance (NMR) logs is proposed and proved to be useful in reservoir recognition and physical property evaluation.