Yu, Gang (BGP Inc.) | Hu, Wenbao (Yangtze University) | He, Zhenxiang (BGP Inc.) | Xiang, Kui (Yangtze University) | Hu, Hua (Yangtze University) | He, Lanfang (BGP Inc.) | Wang, Tianping (BGP Inc.) | Li, Pengfei (Yangtze University)
Total Organic Content (TOC) is one of the key and important parameters to effectively evaluate the shale gas formation production potential. According to geological deposition theory, the TOC is the basic key element that controls the form of pyrite in the marine sediment under deep water strong reducing deposition environment. There is a close relationship between the TOC and pyrite in such deep water reducing deposition environment. Through the laboratory measurement and analysis of the complex resistivity on marine shale formation core samples from South China, the high TOC shale reservoir core samples contain more pyrite, and they show clearly low resistivity and high polarization anomaly. In comparison with well log data, the laboratory measurements of TOC and pyrite are closely related to the results from the log data analysis. We concluded that high TOC marine shale formation has the characterization of low resistivity and high induced polarization (IP) anomaly. Based on the research results, the application of the induced polarization or complex resistivity method to measure the subsurface resistivity and polarization anomaly is a new approach to effectively evaluate the TOC content within the shale gas formation, and it has high potential value for future shale gas reservoir evaluation and characterization.
Yu, Gang (KMS Technologies) | Strack, Kurt (KMS Technologies) | Allegar, Norman (KMS Technologies) | Gunnarsson, A´rni (Landsvirkjun) | He, Zhanxiang (BGP) | He, Lanfang (BGP) | Tulinius, Helga (VGK-Ho¨nnun)
He, Lanfang (BGP) | He, Zhanxiang (BGP) | Strack, Kurt (KMS Technologies) | Allegar, Norman (KMS Technologies) | Yu, Gang (KMS Technologies) | Tulinius, Helga (VGK) | Ádám, László (VGK) | Halldórsdóttir, Heiða (VGK)
A successful case history of mapping the concealed structure using high-resolution EM in the investigation of B Tunnel route is presented in this paper. The high frequency electromagnetic system named STRATAGEM EH4, with the frequency ranging from 90 KHz to 1Hz, is used for the data acquisition. The orthogonal components of the electromagnetic field are measured, and the relevant electromagnetic attributes are extracted on the basis of the characteristics of the electromagnetic profiles. Hybrid sources, including the natural source and the full tensor controlled-source, are utilized to collect high quality field data. B Tunnel lies in the western part of Hubei province, the south of central China. The tunnel is only buried at the depth of less than 200 meters, but the geologic structure is very complex because of the regional geological action. During the first time of the B Tunnel route investigation, the investigators were deceived by the outcrop of the rock fall, considering that it is from the bed rocks and the roof of the tunnel fell when tunneling was in operation. High-resolution EM and seismic refraction were used in the second time investigation. The “real” bed rock and the geologic structure were mapped this time and a hidden fault was also detected. The tunneling result fits closely with what we have predicted.