Basic Geological and Geochemical Analysis in Wenquanbingzhan Area
Zheng Xiang Guang,
Lu Lin,
Mao Yi Feng,
Wang Chen,
Meng Jun Feng
Issue:
Volume 8, Issue 4, August 2019
Pages:
217-227
Received:
13 May 2019
Accepted:
25 June 2019
Published:
18 July 2019
Abstract: According to the basic geology study, the feature of the element association and the analysis on characteristic element abnormal combination, we think that there are large scale intermediate-basic volcanic (subvolcanic) rocks with some medium acid intruded rocks or vein rocks groups by the work of 1 to 50000 scale geochemical exploration in the north Sanjiang-Wenquanbingzhan area. The fractures of Yanshiping and Wenquanbingzhan area etc. are the big fractures of guide rock and rock-controlled and the fracture zones in the northwest of Chuduo-Chaqiong play an ore conducting and controlling role in the process. The metallogenic condition of anticline structure is better than that of syncline structure. Based on the above consideration, the diagenesis and mineralization in this area are closely related to the intermediate-basic and acidic magmas activity. Copper and polymetallic ores can be classified to volcanics-type and sedimentary-reformed type.
Abstract: According to the basic geology study, the feature of the element association and the analysis on characteristic element abnormal combination, we think that there are large scale intermediate-basic volcanic (subvolcanic) rocks with some medium acid intruded rocks or vein rocks groups by the work of 1 to 50000 scale geochemical exploration in the nor...
Show More
Behaviors of Converted Wave in an Azimuthally Isotropic Medium - A Physical Model Study
Chih-Hsiung Chang,
Young-Fo Chang,
Hsiu-Chi Tsao
Issue:
Volume 8, Issue 4, August 2019
Pages:
228-234
Received:
7 August 2019
Accepted:
4 September 2019
Published:
20 September 2019
Abstract: The existence of subsurface fractures provides not only space for the residence of petroleum but also paths of migration. Therefore, subsurface fractures are of great interest to exploration geophysicists. In reflection seismology, a reservoir of vertically aligned fractures is often considered to possess azimuthal anisotropy, or Horizontal Transverse Isotropy (HTI), in terms of seismic anisotropy. The characteristics and information of this specific type of reservoir are widely obtained using seismic attributes, including the azimuthal variation in the P -wave amplitude and velocity, and the fractional difference of split S-waves. Essentially, a converted (C-) wave is initiated by a downward traveling P-wave, which is converted on reflection to upcoming S-waves. Hence, it combines the behaviors of P- and S-waves in theory. Using a forward model study, this study demonstrates the behaviors of a C-waves in a HTI medium, instead of the behaviors of P- or S-waves. Reflections are facilitated on the horizontal symmetry-axis plane of a scaled HTI model along seven different azimuths using end-on shooting arrangement. Using a P-type transducer as a source and an S-type transducer as a receiver, the behaviors of C-waves in a HTI medium are observed. In the acquired profiles, reflections of P-, PS1- (C1 -), and a mixture of PS2- ( C2-) and S1-waves were detected. The phenomenon of C-wave splitting is also observed because of the behavior of an S-wave in a Transversely Isotropic Medium (TIM), and it could be easily identified in the azimuths near the fracture plane. The reflectivity strengths obtained using a Hilbert transform show that the azimuthal variation in the Amplitude Versus Offset (AVO) for both P- and C1-waves are consistent, but the C1-wave amplitude variation depends more significantly on the azimuth than that of the P-wave. Furthermore, the percentage anisotropy of the C-wave computed from acquired data falls right between those of P- and S-waves. By incorporating C-wave splitting and azimuthal AVO variation into traditional signature analyses, our results show that the fracture orientation is more pronounced when the potential reservoir has vertically aligned fractures.
Abstract: The existence of subsurface fractures provides not only space for the residence of petroleum but also paths of migration. Therefore, subsurface fractures are of great interest to exploration geophysicists. In reflection seismology, a reservoir of vertically aligned fractures is often considered to possess azimuthal anisotropy, or Horizontal Transve...
Show More
