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Wang R.,China University of Geosciences | Gu Y.,China University of Geosciences | Ding W.,China University of Geosciences | Gong D.,China Energy Reserve Corporation | And 7 more authors.
Journal of Natural Gas Science and Engineering | Year: 2016

The Lower Cambrian organic-rich marine shale, which is a significant source of China's shale gas, is widely distributed in southern China. An integrated characterization of the Niutitang shale is provided in this study in terms of organic geochemistry, mineralogy, pore characterization, methane sorption capacity, rock mechanical properties, fractures and gas content based on samples from three wells. The results indicate that the Lower Cambrian Niutitang shale is thermally over-mature and has rich shale gas resources, with a total organic carbon content (TOC) between 0.51% and 10.49% and a high quartz content between 35.3% and 78.5%. Compared to the major gas-producing shales in the U.S. and China, most of the organic matter (OM)-hosted pores in the Niutitang shale are generally smaller than 5 nm, significantly affecting the methane sorption capacity. The inter-particle and intra-particle pores and fractures are the primary sources of storage space, especially for free gas. For samples with TOC values less than 6.5%, TOC is positively correlated with the total porosity, total pore volume, brittleness (Young's modulus), core fracture density, free gas content and Langmuir pressure; however, for samples with TOC values greater than 6.5%, the positive correlations become negative. These characteristics are due to the ductility and low hydrocarbon generation potential of organic matter in high thermal maturity shales that are vulnerable to compaction. Thus, TOC has a significant impact on the macroscopic (e.g., brittleness) and microscopic (e.g., pore structure and sorption capacity) properties of shale reservoirs, potentially controlling the enrichment and productivity of shale gas. These results can be used to optimize drilling and fracturing stimulation intervals during shale gas exploration and development. © 2016 Elsevier B.V. Source


Leng J.-G.,China Energy Reserve Corporation | Leng J.-G.,Tongren Sino Energy Natural Gas Corporation | Leng J.-G.,Beijing Sino Shale Gas Engineering Corporation | Han J.-H.,Chengdu University of Technology | And 3 more authors.
Natural Gas Geoscience | Year: 2014

The shale gas resources are rich in Upper Yangtze platform, especially in the Niutitang Formation. Huayuan shale gas block is located within the shale gas abundant play of Niutitang Formation in Upper Yangtze platform. Based on the stratigraphic correlation, reservoir analysis and geochemical analysis of source rock samples and in combination with previous study results, the structure, source rock and reservoirs characteristics of the Niutitang Formation in Huayuan block was systematically studied. The distribution range of the Niutitang Formation, reservoir physical property and thickness of source rocks were mapped. Furthermore, the resource volume of shale gas was calculated by using the gas content data obtained from testing in well Yuke 1 and well Cenye 1. The kerogen types of the Niutitang Formation in the Huayuan shale gas block wereIand II1. With average values of TOC and RO of 3.52% and 3.58%, respectively, reflecting the source rock has entered intoover-maturity stage. The reservoirs characteristics are low porosity-ultralow permeability and high specific surface area. The recoverable resource volume of shale gas is estimated up to 3.18 billion cubic meters. The area from Minle to Longzhai, in the middle-upper of the Huayuan block can be selected for the further exploration and evaluation. Source


Nie Y.,Chengdu University of Technology | Leng J.,China Energy Reserve Corporation | Han J.,Chengdu University of Technology | Sun L.,Chengdu University of Technology | Shen C.,Qinghai Institute of Environment Geological Survey
Oil and Gas Geology | Year: 2013

The shale gas resources are rich in the Upper Yangtze platform, especially the Lower Cambrian Niutitang Formation. Cen'gong shale gas block is located within the Niutitang shale gas play on the Upper Yangtze platform. This paper systematically studied the structure, source rocks and reservoirs characteristics of the Niutitang Formation in Cen'gong block through stratigraphic correlation, laboratory test of reservoir rock sample and geochemical analysis of source rock samples and in combination with previous study results. The distribution of Niutitang Formation, reservoir physical property and thickness of source rocks were mapped. Further more, the resource volume of shale gas was calculated by using the gas content data obtained from testing in well Cenye 1 that the following results were obtained. The organic matters of the Niutitang Formation are mainly of type I and type II1. The average organic matter content of the source rock is as high as 3.38%. The average Ro is calculated to be 3.56%, which reflects the source rock has entered high maturation stage. The reservoirs are characterized by low porosity-ultralow permeability and large specific surface area. The recoverable resource volume of shale gas is estimated at 7.19 billion cubic meters. The Minhe, Yangqiao and Daping areas of the Cen'gong block can be selected as favorable shale gas play fairways for further exploration and evaluation. Source


Han J.,Chengdu University of Technology | Leng J.,China Energy Reserve Corporation | Wang Y.,Zhejiang University | Wang Y.,China University of Petroleum - Beijing
Marine and Petroleum Geology | Year: 2016

Based on 3D seismic data, the polygonal fault system (PFS) discovered in the southern slope of the Qiongdongnan (QDN) Basin was studied through fine seismic interpretation and coherent cube analysis. The results show that: circled digit one the PFS is mostly composed of small plate-type faults, with fault length of 1-3 km, maximum fault throw of 20-40 m and dip angle of 25°-45° circled digit one the PFS is mainly observed in the Huangliu Formation, deposited in the early stage of fast slope depression; circled digit three the PFS is layer-bound and can be separated into two tiers by T31' interface with obvious channel incision features; [U+2463] the PF of tier2 exhibit "y" structural style, including two parallel faults, master fault and associated fault, dipping in opposite directions. Their intersection relationship can be divided into three classes, and 14 sub-classes based on the fault intersection relationship of master fault and its associated fault; circled digit five the PFS is dominated by two strikes: NE60° and NW150°, indicating that it was controlled by tensile stress produced by differential settlement between the Xisha uplift and QDN basin; and [U+2465] its genesis was jointly controlled by the syneresis of clay minerals and overpressure cyclical dehydration. © 2015 Elsevier Ltd. Source


Wang R.-Y.,China University of Geosciences | Ding W.-L.,China University of Geosciences | Gong D.-J.,China Energy Reserve Corporation | Gong D.-J.,Tongren Sino Energy Natural Gas Corporation | And 4 more authors.
Meitan Xuebao/Journal of the China Coal Society | Year: 2015

Shale gas resources are abundant in China. Recently, China has achieved a breakthrough on the Lower Silurian Longmaxi shale in Sichuan basin and its surrounding areas. Compared with the Longmaxi shale, the Lower Cambrian Niutitang shale, which has a greater deposition thickness and wider distribution area, is a significant strata for China's shale gas. The feature of “source-storage integration” makes the evaluation of the total organic carbon (TOC) content as a significant research content in shale gas exploration and development. In this paper, the Δlg R, natural gamma ray spectrometry, density and multiple linear regression logging methods were used to calculate the TOC content of the Niutitang shale in the Cengong block on the basis of logging response and the geological features of overmatured marine organic-rich shale in the complex structural area in southern China. The calculation accuracy and applicability of each method were compared and analyzed. As a result, the calculation accuracies of the Δlg R, natural gamma ray spectrometry, density and multiple linear regression logging methods increase successively. The Δlg R method is not applicable for overmatured marine shales, which locate in the complex structural areas and have large differences of preservation. The natural gamma ray spectrometry and density logging methods have relatively high accuracy and applicability. Furthermore, the multiple linear regression logging method, which uses logging parameters that correlated with TOC content, can further improve the accuracy and applicability. Besides, some logging parameters such as resistivity and acoustic travel time (AC) are sensitive to gas content, fluid properties and preservation, which can be used as the indicators of shale gas content and preservation. © 2015, China Coal Society. All right reserved. Source

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