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Li B.,Chinese Academy of Geological Sciences | Ji J.,Peking University | Wang D.,Oil and Gas Survey | Gong J.,Peking University | Ma Z.,Peking University
International Geology Review | Year: 2014

The Ailao Shan-Red River (ASRR) shear zone, a long, narrow metamorphic belt that strikes NW-SE, is the continuation of the southeastern margin of the Tibetan Plateau. It mainly comprises amphibolite-facies mylonitic gneiss. In this study, we report zircon concordant U-Pb SHRIMP ages of 37.52 Ma ± 0.67 Ma [mean square weighted deviation (MSWD) = 1.4] and 30.8 Ma ± 0.3 Ma (MSWD = 3.2) from a granitic gneiss in the northern part of the Ailao Shan metamorphic belt, and from a leucogranitic dike in the middle of the zone, respectively. Zircon U-Pb ages between 35 Ma and 41 Ma were also obtained from a biotite gneissic granite in the southern part of the belt. Contrasting the internal structure of the zircon crystals with our new U-Pb dating suggests that their nucleation and growth initiated during a late Eocene tectonic uplift event between ca. 40 and 35 Ma. Detailed field observations and zircon U-Pb dating results suggest that the deformation time of mylonitic gneiss and granitic gneiss in the ASRR was 40-30 Ma, the formation age of the gneissic schistosity of the ASRR metamorphic belt was as early as ca. 40 Ma. © 2014 © Taylor & Francis.

Shi L.,China University of Petroleum - Beijing | Jin Z.,China University of Petroleum - Beijing | Yan W.,China University of Petroleum - Beijing | Li G.,China University of Petroleum - Beijing | And 2 more authors.
Zhongguo Kuangye Daxue Xuebao/Journal of China University of Mining and Technology | Year: 2015

Based on data from thin section analysis, core analysis, particle analysis, and SEM, this paper studies the influence mechanism of abnormal high pressure on dissolution and diagenetic stage in northwestern Bozhong sag. A new mechanism of reservoir dissolution was found. The particles dissolution was prior to occur in the specific grain size of sandstone under different reservoir pressures. The new mechanism reveals that reservoir dissolution will be promoted by abnormal high pressure. The dissolution strength changes very little and the envelope curve represents the gentle slope shape as depth decreases from abnormal pressure regions to the normal pressure regions. The new mechanism provides compelling evidence for inhibition of organic maturation and clay mineral transformation due to abnormal high pressure. The results show that particles dissolution is prior to develop in sandstone with coarser grain size in abnormal high pressure regions, where average added rate of secondary pore is about 32.0%, Ro is near 0.56% in the depth from 3 200 m to 3 300 m and the mass fraction of montmorillonite in mixed-layer is 20%. The sandstone with finer grain size has priority to form particle dissolution in normal pressure regions deeper than 2 950 m. The average added rate of secondary pore is approximate 34.2%, Ro is about 0.58% and the mass fraction of montmorillonite is about 14.6%. However, the particle dissolution has no obvious correlation with particle grain size in the normal pressure regions below 2 950 m. And the average added rate of secondary pore is about 26.5%. The developing depth of reservoir dissolution is over 430 m in normal pressure regions next to the abnormal high pressure regions. The influence model of abnormal high pressure on reservoir dissolution is summarized. Combined with the newly found dissolution mechanism, the hydrocarbon exploration in search of secondary pore zone can be guided. ©, 2015, China University of Mining and Technology. All right reserved.

Huang Y.,China University of Geosciences | Yang G.,Beijing University of Technology | Gu J.,China University of Geosciences | Wang P.,Oil and Gas Survey | And 3 more authors.
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2013

Songliao Basin in NE China developed the most productive oilfield in the world sourced from terrestrial rocks. The main source rock of the basin includes member 1 of the Qingshankou (K2qn1) and members 1 and 2 of the Nenjiang Formation (K2nj1-2). However the exact reasons for the formation of the source rock, especially the K2qn1 are still controversial. Former paleontological and organic geochemical research suggested that organic matter was deposited during marine incursion events of K2qn1 but further geochemical evidence is needed. This paper explores the distinct sulfate levels that distinguish marine from fresh waters of the Songliao paleo-lake. We undertook a systematic investigation the sulfur geochemistry of the sediments from top of member 4 of the Quantou Formation (K1q4) to top of member 1 of the Qingshankou (K2qn1). The ratio of organic carbon to the pyrite sulfur (TOC/PYS) proved the previously suggested saline conditions during the deposition of K2qn1; and the pyrite sulfur isotope indicated that marine incursion may not only have occurred for K2qn1, but also for top of K1q4. The exact time for the beginning of marine incursion is to be determined. The marine incursion within K2qn1 is not strong and partially controlled by the fluctuation of paleo-lake level. The present study will be helpful for understanding the contribution of marine incursion events to the burial of organic carbon in the Songliao paleo-lake, although further studies are still needed. © 2013 Elsevier B.V.

Lu Z.,Chinese Academy of Geological Sciences | Zhu Y.,Chinese Academy of Geological Sciences | Liu H.,Chinese Academy of Geological Sciences | Zhang Y.,Chinese Academy of Geological Sciences | And 3 more authors.
Marine and Petroleum Geology | Year: 2013

Gas source for gas hydrate is not clear yet in the Muli of Qilian Mountain permafrost. In this paper a case is illustrated in the hole of DK-2 during gas hydrate drilling; gas composition and isotopes of gas hydrate and its associated gases are analyzed; organic geochemistry on mudstone, oily shale, coal, oil & gas indications are correlated within the interval of gas hydrate occurrences; the aim is to discuss the source of gases from gas hydrate and its implication to gas hydrate exploration in the study area. Results from gas composition and isotopes of gas hydrate and its associated gases reveal that the origin of gases from gas hydrate is mainly concomitant with deep oil or crude oil in the study area. Parameters for the abundance, type and thermal evolution of organic matter in mudstone, oil shale, coal in the same interval of gas hydrate occurrence suggest that these strata, especially within gas hydrate stability zone, play little role in gas sources for gas hydrate. Reservoir pyrolysis results for oil & gas indication-bearing cores reveal that oil & gas indications are closely associated with gas hydrate within its interval, indicating that they may serve as a sign of gas hydrate in the study area. © 2013 Elsevier Ltd.

Cao J.,Oil and Gas Survey | Zhang Y.-S.,Chinese Academy of Geological Sciences | Song T.-R.,Chinese Academy of Geological Sciences
Acta Geoscientica Sinica | Year: 2013

The Cretaceous basins in east Heilongjiang Province constitute a very important oil-producing region. In Early Cretaceous, lacustrine facies was the dominant facies, while different scales of transgression occurred at the same time. According to further study and comprehensive analysis of texture, structure, clastic constituents, comprehensive textual coefficient, cement and mineral arrangement of the Cretaceous sandstones, the double layers were found in Early Cretaceous strata, which constituted the typical structure in the subtidal zone. The main types of Cretaceous sandstones are debris-feldspar sandstones and feldspar-debris sandstones (quartz content ca. 25%), whereas cements are carbonate. Influenced by the transgression, the average value of comprehensive textual coefficient was 20.16 in Chengzihe period and 46.65 in Muling period, indicating that transgression influence was more obvious in Muling period. Moreover, more than 20 kinds of heavy minerals were found in Cretaceous sandstones, assuming banded enrichment. The characteristic minerals such as glauconite, authigenic monazite, framboid pyrite and native gold all show transgression characteristics. All of these characteristics provide abundant evidence for the transgression in the Cretaceous basins of east Heilongjiang Province.

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