Recently, more attention has been paid on the high gamma sandstone reservoirs of the Yanchang Formation in the Ordos Basin, China. These high gamma sandstones have logging characteristics different from conventional s...Recently, more attention has been paid on the high gamma sandstone reservoirs of the Yanchang Formation in the Ordos Basin, China. These high gamma sandstones have logging characteristics different from conventional sandstones, which influences the identification of sandstone reservoirs. Zhang et al （2010） proposed that the high gamma sandstones of the Yanchang Formation might be the result of re-deposition of homochronous sedimentary tufts or previous tufts as a part of the sandstone. However, we present a different viewpoint： 1） few tufts or tuff debris have been found in the high gamma sandstones of the Yanchang Formation; 2） high gamma （or high Th content） sandstones of Yanchang Formation are not related to either clay minerals or feldspar; 3） the heavy minerals in the sandstone reservoirs of the Yanchang Formation are dominated by zircon, which is characterized by abnormally high Th and U contents, up to 2,163 ppm and 1,362 ppm, respectively. This is sufficient to explain the high gamma anomaly. The conclusion is that the high gamma value of the Yanchang Formation sandstones might be caused by zircon with high Th and U contents in sandstones rather than from the tuff components.展开更多
The authors of ＇Genesis of the high gamma sandstone of the Yanchang Formation in the Ordos Basin, China＇ questioned the viewpoint that high-gamma-ray sandstone might be caused by homochronous sedimentary volcano tuf...The authors of ＇Genesis of the high gamma sandstone of the Yanchang Formation in the Ordos Basin, China＇ questioned the viewpoint that high-gamma-ray sandstone might be caused by homochronous sedimentary volcano tuff ash or previous tuff. The authors argued that the main reason for the high-gamma-ray sandstone should be from high Th and U contents in zircon. In reply, we discuss the problems with the authors from the category of high-gamma-ray sandstones, rock characteristics, and possible sources of radioactivity. The results still indicate that the high gamma ray characteristics might be caused by homochronous sedimentary volcano tuff ash or reworked previous turfs.展开更多
The large scale development of high natural gamma sandstones has been discovered in the Chang 73 Submember of the Triassic Yanchang Formation in the Ordos Basin, China. High natural gamma sandstones consist of terrige...The large scale development of high natural gamma sandstones has been discovered in the Chang 73 Submember of the Triassic Yanchang Formation in the Ordos Basin, China. High natural gamma sandstones consist of terrigenous detrital rocks with particle sizes ranging from silt to sand. They represent turbidite deposits characterized by high gamma ray values that are more than 180 American Petroleum Institute (API) units on a natural gamma ray log profile. For a long time, very high natural gamma sandstones had been identified as high-quality source rocks, such as oil shales, from conventional well log profiles, such as natural gamma ray well logs. Therefore, predicting the distribution of high natural gamma sandstones was studied. The sedimentary, lithological, and well log characteristics, as well as the genesis of the high radioactivity of high natural gamma sandstones were analyzed in the Chang 73 Submember. Thorium (Th), uranium (U) and other radioactive elements were found, carried by deep hydrothermal activity, and probably resulted in the formation of a relatively high radioactive zone in the cross-section, where high natural gamma sandstones usually develop in large quantities. This caused many turbidite sand bodies, which should have a continuous distribution in the cross-section, to appear to have a discontinuous distribution, when using conventional well log profiles, such as natural gamma ray well logs. From the above mentioned apparent discontinuous distribution of turbidite sand bodies in the cross-section, a continuous distribution can be predicted. It is obvious that the prediction of areas of continuous turbidite sand bodies in the cross-section usually corresponds with areas where high natural gamma sandstones are developed in large quantities. Exploration and development practice demonstrated that the developed method is fast and effective in predicting high natural gamma sandstones in the Chang 73 Submember.展开更多
The accelerator-generating 6.13 MeV pulsed Gamma by 19F（p, αγ）160 reaction usually synchronizes with an intense bremsstrahlung x-ray which has a maximum energy of 1 MeV. This paper proposes a new method, named the...The accelerator-generating 6.13 MeV pulsed Gamma by 19F（p, αγ）160 reaction usually synchronizes with an intense bremsstrahlung x-ray which has a maximum energy of 1 MeV. This paper proposes a new method, named the scattering and absorbing method, to diagnose the 6.13 MeV Gamma. This method includes two parts： the detector and a scatterer placed in front of the detector. The detector converts the Gamma to electrons and then collects the electrons by a scintillator. In order to restrain the interference of the low-energy background, the scintillator collects the electrons at a small angle. The scintillator is wrapped with electro-absorbing material to absorb the low-energy electrons generated by background x-rays. The theoretical sensitivity ratio of 6.13 MeV Gamma to 1 MeV x-rays is greater than 150. The scatterer is a pretreatment tool to scatter some background x-rays away from the radial beam before they enter the detector. By varying the length, the scatterer can reduce the background x-rays to an acceptable level for the detector.展开更多
A1GaN/GaN depletion-mode high-electron-mobility transistor （D-HEMT） and fluorine （F） plasma treated enhancement-mode high-electron-mobility transistor （E-HEMT） are exposed to 60Co gamma radiation with a dose of ...A1GaN/GaN depletion-mode high-electron-mobility transistor （D-HEMT） and fluorine （F） plasma treated enhancement-mode high-electron-mobility transistor （E-HEMT） are exposed to 60Co gamma radiation with a dose of 1.6 Mrad （Si）. No degradation is observed in the performance of D-HEMT. However, the maximum transeonductance of E-HEMT is increased after radiation. The 2DEG density and the mobility are calculated from the results of capacitance-voltage measurement. The electron mobility decreases after fluorine plasma treatment and recovers after radiation. Conductance measurements in a frequency range from 10 kHz to 1 MHz are used to characterize the trapping effects in the devices. A new type of trap is observed in the F plasma treated E-HEMT compared with the D-HEMT, but the density of the trap decreases by radiation. Fitting of Gp/w data yields the trap densities DT = （1-3）Х1012 cm^-2.eV^-1 and DT = （0,2-0.8）Х10^12 cm^2-eV^-1 before and after radiation, respectively. The time constant is 0.5 ms-6 ms. With F plasma treatment, the trap is introduced by etch damage and degrades the electronic mobility. After 60Co gamma radiation, the etch damage decreases and the electron mobility is improved. The gamma radiation can recover the etch damage caused by F plasma treatment.展开更多
基金supported by the National Science and Technology Major Subject(No.2008ZX05044 2-8-2)"Large scale oil and gas field and coal bed methane development"
文摘Recently, more attention has been paid on the high gamma sandstone reservoirs of the Yanchang Formation in the Ordos Basin, China. These high gamma sandstones have logging characteristics different from conventional sandstones, which influences the identification of sandstone reservoirs. Zhang et al （2010） proposed that the high gamma sandstones of the Yanchang Formation might be the result of re-deposition of homochronous sedimentary tufts or previous tufts as a part of the sandstone. However, we present a different viewpoint： 1） few tufts or tuff debris have been found in the high gamma sandstones of the Yanchang Formation; 2） high gamma （or high Th content） sandstones of Yanchang Formation are not related to either clay minerals or feldspar; 3） the heavy minerals in the sandstone reservoirs of the Yanchang Formation are dominated by zircon, which is characterized by abnormally high Th and U contents, up to 2,163 ppm and 1,362 ppm, respectively. This is sufficient to explain the high gamma anomaly. The conclusion is that the high gamma value of the Yanchang Formation sandstones might be caused by zircon with high Th and U contents in sandstones rather than from the tuff components.
文摘The authors of ＇Genesis of the high gamma sandstone of the Yanchang Formation in the Ordos Basin, China＇ questioned the viewpoint that high-gamma-ray sandstone might be caused by homochronous sedimentary volcano tuff ash or previous tuff. The authors argued that the main reason for the high-gamma-ray sandstone should be from high Th and U contents in zircon. In reply, we discuss the problems with the authors from the category of high-gamma-ray sandstones, rock characteristics, and possible sources of radioactivity. The results still indicate that the high gamma ray characteristics might be caused by homochronous sedimentary volcano tuff ash or reworked previous turfs.
基金Project(18GK28)supported by the Doctoral Scientific Research Starting Foundation for the Yulin University,ChinaProject(20106101110020)supported by the University Research Fund of Science and Technology Development Center of Ministry of Education,ChinaProject(BJ08133-3)supported by the Key Fund Project of Continental Dynamics National Key Laboratory of Northwest University,China
文摘The large scale development of high natural gamma sandstones has been discovered in the Chang 73 Submember of the Triassic Yanchang Formation in the Ordos Basin, China. High natural gamma sandstones consist of terrigenous detrital rocks with particle sizes ranging from silt to sand. They represent turbidite deposits characterized by high gamma ray values that are more than 180 American Petroleum Institute (API) units on a natural gamma ray log profile. For a long time, very high natural gamma sandstones had been identified as high-quality source rocks, such as oil shales, from conventional well log profiles, such as natural gamma ray well logs. Therefore, predicting the distribution of high natural gamma sandstones was studied. The sedimentary, lithological, and well log characteristics, as well as the genesis of the high radioactivity of high natural gamma sandstones were analyzed in the Chang 73 Submember. Thorium (Th), uranium (U) and other radioactive elements were found, carried by deep hydrothermal activity, and probably resulted in the formation of a relatively high radioactive zone in the cross-section, where high natural gamma sandstones usually develop in large quantities. This caused many turbidite sand bodies, which should have a continuous distribution in the cross-section, to appear to have a discontinuous distribution, when using conventional well log profiles, such as natural gamma ray well logs. From the above mentioned apparent discontinuous distribution of turbidite sand bodies in the cross-section, a continuous distribution can be predicted. It is obvious that the prediction of areas of continuous turbidite sand bodies in the cross-section usually corresponds with areas where high natural gamma sandstones are developed in large quantities. Exploration and development practice demonstrated that the developed method is fast and effective in predicting high natural gamma sandstones in the Chang 73 Submember.
文摘The accelerator-generating 6.13 MeV pulsed Gamma by 19F（p, αγ）160 reaction usually synchronizes with an intense bremsstrahlung x-ray which has a maximum energy of 1 MeV. This paper proposes a new method, named the scattering and absorbing method, to diagnose the 6.13 MeV Gamma. This method includes two parts： the detector and a scatterer placed in front of the detector. The detector converts the Gamma to electrons and then collects the electrons by a scintillator. In order to restrain the interference of the low-energy background, the scintillator collects the electrons at a small angle. The scintillator is wrapped with electro-absorbing material to absorb the low-energy electrons generated by background x-rays. The theoretical sensitivity ratio of 6.13 MeV Gamma to 1 MeV x-rays is greater than 150. The scatterer is a pretreatment tool to scatter some background x-rays away from the radial beam before they enter the detector. By varying the length, the scatterer can reduce the background x-rays to an acceptable level for the detector.
基金Project supported by the National Natural Science Foundation of China (Grant No. 60736033)the Fundamental Research Funds for the Central Universities,China (Grant No. JY10000904009)
文摘A1GaN/GaN depletion-mode high-electron-mobility transistor （D-HEMT） and fluorine （F） plasma treated enhancement-mode high-electron-mobility transistor （E-HEMT） are exposed to 60Co gamma radiation with a dose of 1.6 Mrad （Si）. No degradation is observed in the performance of D-HEMT. However, the maximum transeonductance of E-HEMT is increased after radiation. The 2DEG density and the mobility are calculated from the results of capacitance-voltage measurement. The electron mobility decreases after fluorine plasma treatment and recovers after radiation. Conductance measurements in a frequency range from 10 kHz to 1 MHz are used to characterize the trapping effects in the devices. A new type of trap is observed in the F plasma treated E-HEMT compared with the D-HEMT, but the density of the trap decreases by radiation. Fitting of Gp/w data yields the trap densities DT = （1-3）Х1012 cm^-2.eV^-1 and DT = （0,2-0.8）Х10^12 cm^2-eV^-1 before and after radiation, respectively. The time constant is 0.5 ms-6 ms. With F plasma treatment, the trap is introduced by etch damage and degrades the electronic mobility. After 60Co gamma radiation, the etch damage decreases and the electron mobility is improved. The gamma radiation can recover the etch damage caused by F plasma treatment.
