Genesis analysis of high-gamma ray sandstone reservoir and its log evaluation techniques: a case study from the Junggar basin, northwest China.
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.
State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China ; College of Geophysics and Information Engineering, China University of Petroleum, Beijing 102249, China.
Liang
L
Wang
Zhiqiang
Z
Mao
Zhongchun
Z
Sun
Xingping
X
Luo
Yong
Y
Song
Zhen
Z
Liu
D000538:Aluminum Silicates; D002681:China; D000077215:Clay; D005720:Gamma Rays; D005844:Geology; D009682:Magnetic Resonance Spectroscopy; D061329:Oil and Gas Fields / Q000737:chemistry; D017680:Potassium Compounds; D011834:Radiation Monitoring; D014501:Uranium / Q000737:chemistry
D000538:Aluminum Silicates; D017680:Potassium Compounds; C016447:feldspar; D014501:Uranium; D000077215:Clay