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Xia L.,China University of Petroleum - Beijing | Luo D.,China University of Petroleum - Beijing | Luo D.,Chongqing Institute of Geology and Mineral Resources
Journal of Natural Gas Science and Engineering | Year: 2014

Target depth is a key measure of the commercial viability of a shale gas prospect. Although much research has been conducted in the shale gas techno-economic appraisal field, no reports are available on the economic critical depth (ECD) of shale gas resources. The present work aims at establishing a model for calculating the ECD using the break-even analysis-the reverse of calculating the net present value (NPV)-such that the break-even ECD occurs at zero NPV. The ECD is sensitive to production uncertainty, depending on the initial production (IP) rate and the production decline rate. Examples indicate that these have a marked effect on ECD based on current technology, gas price and exploitation policy, with the IP rate having the more pronounced effect. When the IP rate varies between 2.5 and 5.5 × 104 m3/day based on the fitted production decline trend from a pilot area in China, the corresponding ECD varies from 898 m to 3997 m. The ECD is thus able to rule out non-commercial shale gas prospects quickly. © 2014 Elsevier B.V.

Ma W.,Chengdu University of Technology | Liu S.,Chengdu University of Technology | Huang W.,China National Petroleum Corporation | Zhang C.,China National Petroleum Corporation | Zeng X.,Chongqing Institute of Geology and Mineral Resources
Xinan Shiyou Daxue Xuebao/Journal of Southwest Petroleum University | Year: 2012

The study area (western Hubei-eastern Chongqing) was a transitional zone between steep detachment fold belt in eastern Sichuan and block-basement fault-fold belt in western Hunan-Hubei. There the deformation is relatively weak, and oil & gas geological preservation condition was better than surrounding areas. Based on the well drilling and field data, employing the petrology, thin section, SEM and organic geochemical analysis, we studied the characteristics of the macro and micro Silurian reservoir rocks and their oil & gas prospection. The results show that: the main lithology of Longmaxi Formation was black carboniferous shale, deep gray (gray) shale and silty mudstone. The micro-reservoir spaces were highly developed including intergranular dissolution pores of clay minerals, dissolution pores in feldspar and quartz, microfratures and so on. Source rocks with high quality were developed east to the belt of Well Jianshen 1 and Lengshuixi. And the microporosity and microfractures were very rich in Silurian. The Silurian Hanjiadian Formation gas reservoir belonged to tight gas. Based on the Well Jianshen 1 gas reservoir characteristics and the existing drilling analysis data, we conclude that Shizhu composite anticline, Lichuan and Huaguoping composite syncline are fully equipped with tight gas and shale gas exploration potential.

Song X.-X.,China University of Mining and Technology | Song X.-X.,Taiyuan University of Technology | Tang Y.-G.,China University of Mining and Technology | Li W.,Taiyuan University of Technology | And 2 more authors.
Meitan Xuebao/Journal of the China Coal Society | Year: 2013

Nine standard coal samples from different coalbeds of Zhongliangshan southern coal mine in Huayingshan coalfield were tested using the low-temperature nitrogen adsorption method to study the fractal characteristics of adsorption pores (pore diameter <100 nanometers) and the relationship between fractal dimension and the gas adsorption capacity of tectonic coal. The results of both the low-temperature nitrogen adsorption and desorption show that different deformed coal has different adsorption characteristics under relative pressures between 0.5-1.0.Based on the results, the fractal dimension D of tectonic coal was studied using the fractal Frenkel-Halsey-Hill (FHH) method. The results demonstrate that the fractal dimension D can represent the variation characteristics of pore structure and pore surface area of tectonic coal. The higher fractal dimension D, the more micropores, the more irregular specific coal surface, and the higher heterogeneity of pore structure. The gas storage capacity of coal can be represented by the fractal dimension D, and the gas adsorption capacity of coal increases with the increasing of fractal dimension D. Therefore, the higher fractal dimension and the more homogeneous pore structure resulting from strong tectonic deformation, indicate that the coal has a higher gas adsorption capacity.

Yuan S.D.,Chinese Academy of Geological Sciences | Yuan S.D.,China University of Geosciences | Zhang D.L.,Central South University | Shuang Y.,Chongqing Institute of Geology and Mineral Resources
Acta Petrologica Sinica | Year: 2012

The Xintianling tungsten deposit is a large-sized skarn and vein-type tungsten-molybdenum polymetallic deposit located in southern Hunan Province, which is genetically associated with the early stage hornblende-biotite monzonitic granite of Qitianling pluton. Direct Re-Os dating on molybdenites collected from the skarn and quartz-vein type ore in the Xintianling deposit have been carried out, to better understand the age of mineralization. The results show that the Re-Os dating of one molybdenite sample collected from skarn- type ore yields a 187Re- 187 Os model age of 159.1 ± 1.9Ma, and six molybdenite samples collected from quartz-vein-type ore yield 187Re- 187Os model ages ranging from 159.1 ± 1.9Ma to 160.2 ±2.9Ma, with an average of 159.4 ± 1.3Ma, and give an isochron age of 161.7 ±9.3Ma (2σ) , with an initial 187Os of 0.6 ±2.3 ( MSWD =0.051). Comparison of the Re-Os ages with published Ar-Ar date ( 157.1 ± 0.3Ma) on iron mica and Rb-Sr date( 157.4 ± 3.2Ma) on quartz indicates that the timing of skarnization and tungsten- molybdenum mineralization are identical within error. Therefore, we can constrain the absolute age of tungsten-molybdenum mineralization in the Xintianling deposit at ca.161.7 ∼ 157.IMa. These ages are consistent with the SHRIMP zircon U-Pb ages (163 ∼ 160Ma) of the early stage hornblende-biotite monzonitic granite. Based on previous studies, it is suggested that the mineralization of the Xintianling W-Mo deposit is spatially and temporally related to the early stage hornblende-biotite monzonitic granite of Qitianling pluton.While the Furong tin deposit located in southern part of Qitianling pluton may be closely related to the late stage biotite monzonitic granite. The emplacement of the Qitianling A-type granite and associated tungsten-tin polymetallic mineralization is a continuous evolution process, which are the products of large-scale mineralization of the Nanling in Middle-Late Jurassic (150 ∼160Ma). Under the tectonic setting of Mesozoic lithospheric extension, asthenosphere upwelling along deep fault, intensive mantle-crust interaction processes probably provide not only the high heat flow, but also part mantle-derived material for large-scale W-Sn-polymetallic mineralization in this area.

Gao Y.,China University of Petroleum - Beijing | Xiao L.-Z.,China University of Petroleum - Beijing | Xie Q.-M.,Chongqing Institute of Geology and Mineral Resources
Zhongguo Shiyou Daxue Xuebao (Ziran Kexue Ban)/Journal of China University of Petroleum (Edition of Natural Science) | Year: 2014

In the Phillips-Twomey method, it is essential to find a suitable regular parameter r. The selection of the parameter r remains practically difficult, and is often biased by researcher's subjectivity. Finding a suitable regular parameter r in using Phillips-Twomey method to inverse nuclear magnetic resonance (NMR) logging transverse relaxation time was focused on. The way to finding the suitable r was based on the compromise criterion in BG theory and the r minimal criterion. The inversed transverse relaxation time was also assessed through the resolution matrix and the covariance matrix. Digital simulation and core analysis show that the approach in determining the regular parameter r of the Phillips-Twomey inverse method works very well for the inverse of NMR transverse relaxation time. Core analysis also shows that this method is better than the classical SVD method without subjective bias.

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