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    12 June 2014, Volume 28 Issue 3
    Petrology and Study of Ore Deposits
    Lithogeochemistry and Sr-Nd-Pb Isotopic Characteristics of Mujicun Porphyry Cu-Mo Deposit in Taihang Mountains and Their Significances
    QU Kai,DONG Guo-chen, LI Sheng-rong, SHEN Jun-feng,WANG Yan-juan,WANG
    2014, 28(3):  449-460. 
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    Mujicun porphyry copper-molybdenum deposit, located in the northern section of Taihang Mountains, is an important ore deposit in the Taihang tectonic-magmatic-metallogenic belt. This article is based on the particular field works and systematic analysis of petrology, geochemical data and Sr-Nd-Pb isotopes. The result shows the ore-bearing diorite-porphyry of Mujicun belonging to the high-K calc-alkaline I-type intrusive rock. Geochemical analysis shows that the diorite-porphyry is rich in SiO2, Al2O3 and Sr, a high ratio of Sr/Y, (La/Yb)N, low in Yb and Y. All the ore-bearing porphyries in the study area have similar distribution of rare earths and trace elements, with right-oblique curve, and unclear postive Eu anomalies. It is characterized by enriched large-ion lithophile elements of Ba, K, U, Sr and depleted high field strength elements such as Nb, Ta, P and Ti with adakite affinity in geochemical characteristic. The diorite porphyry has ISr ratios of 0.705 386 to 0.706 838,εNd(t) values of -16.7 to -14.9. The averages of 208Pb/204Pb, 207Pb/204Pb and 206Pb/204Pb ratios are 36.614, 15.226 and 16.545, respectively, similar to those lead isotope ratios in ore of Mujicun deposit. Sr-Nd-Pb isotopes show that the formations of the magma were probably related to origin of partial melting of lower crust with mantle materials contribution. Combining with the geological background of the study area, the authors considered that the Mujicun ore-bearing diorite porphyry possibly resulted from partial melting in lower crust with the mantle mass exchange.

    Geochemical Characteristics and Its Significance of Biotite Monzogranite in the Keyinbulake Copper-Zinc Deposit at the Southern Margin of Altay, Xinjiang
    ZHANG Zhi-xin,CHAI Feng-mei,WANG Li-fen,LIU Feng,GENG Xin-xia
    2014, 28(3):  461-471. 
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    Granites at the southern margin of Altay, Xinjiang crop out widely in the Keyinbulake copper-zinc deposit, including monzogranite, moyite, biotite granite and tonalite, where ore bodies occur in the exocontact zones between Permian monzogranite and the Upper Silurian-Lower Devonian Kangbutiebao Formation. The monzogranite has two lithofacies of two-mica monzogranite and biotite monzogranite under the microscope. The biotite monzogranites are characterized by enrichment of silica, total alkali, low Na/K value, and metaluminous-prealuminous. Trace elements show characteristics of noticeable positive anomaly of Rb, Th, K, Ce, Nd, Tb and negative anomaly of Ba,Nb,Sr,Ti. The REE patterns show richness of LREE, moderate total REE contents and Eu negative anomaly. The characteristics indicate that the biotite monzogranites are high K-low Ca-metaluminous-peraluminous S-type granites. These rocks have near-zero or negative εNd(t) values and high Sr isotopic compositions, with corresponding to Nd model ages of 1.145 to 1.194 Ga. The granites were probably formed by melting of the middle Proterozoic biotitebearing metamorphic sandstone or orthometamorphite and limited mantle material, with residual of plagioclase in the melting source. Geochemical characteristics showed favorable mineralization potentiality of monzogranite. The deposit was formed in post-collision extension setting,  and metallogenesis is related to the hydrothermal from monzogranite magma.

    Discovery of Carboniferous Diorite from Moheertu in Dongwuqi Area, Inner Mongolia: Evidence from Zircon U-Pb Geochronology
    YANG Jun-quan, ZHANG Su-rong, LIU Yong-shun, CHENG Yin-hang, TENG Xue-jian
    2014, 28(3):  472-477. 
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    Dongwuqi area in Inner Mongolia, which lies in Uliastai active continental margin, is a part of Central Asian orogenic belt. Numerous magmatites are exposed in this area. The intrusive rocks mainly formed in Permian and Late Mesozoic, and seldom formed in the other period according to report. Diorite was discovered in Moheertu of this area during the 1∶50,000 regional geological surveys. By LA-MC-ICP-MS U-Pb isotopic dating for 24 zircons, weighted mean age of (337.1±1.9) Ma (MSWD=1.3) was obtained from the diorite. The characteristics of these zircons accord with magmatic zircon, and the results can represent the diagenetic age of diorite. Combined with regional geology, we concluded that a tectonothermal event occurred during 337-310 Ma in Dongwuqi area.

    Characteristics and Genetic Significances of Olivine from Xiangshan Complex in Eastern Tianshan,Xinjiang
    JIANG Chao,QIAN Zhuang-zhi,ZHANG Jiang-jiang,SUN Tao,XU Gang,MENG De-ming 1
    2014, 28(3):  478-488. 
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    The Xiangshan mafic-ultramafic complex was located in western part of Jing’erquan-Huangshan ma-fic-ultramafic rock belt, composed of the eastern part (Xiangshandong), the central part (Xiangshanzhong), and the western part (Xiangshanxi). Midium sized Cu-Ni sulfide deposits occur in the central part, and small sized Cu-Ni sulfide deposits and Fe-Ti-V oxide deposit occur in the western part. Electron microprobe analyses of olivine show that almost all the olivine crystals are chrysolite with the forsterite content (Fo) ranging from 81.90 to 85.66 and the Ni content ranging from 638×10-6 to 2,283×10-6. The content of MgO is about 10.70%, and the content of FeO is about 10.66% in the parent magma, which suggests that it belongs to high MgO basaltic magma.The Ni content with a maximum of 2,283×10-6 in olivine indicates that the Ni content of the primitive magma is 326×10-6; therefore, we can speculated that the primitive magma occured when 14% of the primitive mantle was melted. Sulfide separation and fractional crystallization happened simultaneously. The re-equilibration of olivine from silicate liquid or sulfide liquid should be taken as an important factor for olivine composition.

    Geochemical Characteristics and Tectonic Significance of Meta-sedimentaryRocks from Naij Tal Group, Eastern Section of East Kunlun
    CHEN You-xin,PEI Xian-zhi,LI Rui-bao,LI Zuo-chen,PEI Lei3,LIU Cheng-ju
    2014, 28(3):  489-500. 
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    Naij Tal Group mainly consists of metamorphic volcanic-sedimentary series, which is the important material records of Early Paleozoic tectonic evolution in East Kunlun. Petrologic and geochemical characteristics indicate that the meta-sedimentary rocks from Naij Tal Group are mainly composed of mica-quartz schist, chlorite sericite schist, feldspar quartz schist, sericite quartz schist. Additionally, marble, gneiss and quartzite were occasionally outcropped in some area. The geochemical characteristics are very similar to upper continental crust, with high SiO2 (average 69.82%), Sr (average 559.60×10-6) and Ba (average 194.68×10-6). The meta-sedimentary rocks have high quantity of LREE ((La/Yb)N=7.18) with obvious negative Eu anomalies (δEu=0.44-0.66), which is similar to active continental margin. The upper continental crust-normalized trace elements diagram shows that their protoliths are dominatly felsic rocks (e.g., sandstone, greywacke, and pelite) from upper continental crust. Tectonic discrimination based on geochemical data of meta-sedimentary rocks, as well as the CIA (49.70-75.95,Chemical Index of Alteration) and ICV (1.32-2.01, Index of Compositional Variation) reveal that the provenance of meta-sedimentary rocks are characterized by low degree weathering, and lied in the cold or semiarid zone. Based on the previous regional data, we conclude that the Naij Tal Group formed in the backarc basin relating to the Proto-Tethys northward subduction, and that the southern tectonic belt of East Kunlun was in the avtive continental margin in Early Paleozoic.

    Origin of Nodular Cherts in Limestones in Middle Permian Qixia Formation, Chaohu, Anhui Province
    YANG Rui, LI Hong, LIU Yi-qun, LEI Chuan, LEI Yun, FENG Shi-hai
    2014, 28(3):  501-511. 
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    The Middle Permian Qixia Formation in Chaohu area, Anhui Province, was mainly composed of fine-grained clastic rocks and limestones which were deposited in the coastal marsh and carbonate platform. Limestones were characterized by nodular and banded cherts. Most of cherts were axiolitic and moniliform in outcrops. Among some cherts and limestones developed transitional belts with 0.5 cm width around cherts. The limestones were composed of packstone and wackestone which consisted mainly of fragments of fossils and microcrystalline calcite through polarizing microscope observation. The transitional belts were mainly composed of micrites and the aragonite-shell fragments which were replaced or half replaced by quartz prior to the micrites. Meanwhile the amorphous silica was found to be precipitated into the pores due to the micrites’dissolution under SEM observation in the transition belts. The chert consists of microcrystalline or cryptocrystalline quartz together with the fossil fragments. The categories of the organic matter and fossil fragments in the cherts were similar to those found in limestones, however, most of them were replaced by quartz completely. The petrology analysis of the cherts and limstones indicates that the organic acid which was produced by degradation of organic matters, would greatly increase the saturation of CaCO3, promote the dissolution of aragonitic fossils and marls in the sediment. As a result, the calcium precipitation was inhibited yet gelatinous silica precipitated as well. The geochemistry of nodular cherts revealed that the average ratio of Al/(Al+Fe+Mn) was 0.63, which was higher than the maximum value (0.35) of hydrothermal deposition. The average ratio of Fe/Ti was 9.5 also lower than the minimum value (20) of hydrothermal deposition. The Al-Fe-Mn data of the cherts fell into in the non-hydrothermal field in the Al-Fe-Mn ternary diagram. The Al2O3 value (average 0.20%) was far beyond the other contents such as MgO,Na2O,K2O in the cherts and similar to the terrigenous silicon. Such geochemistry features indicated that the silica of the cherts in limestones was probably sourced from the continental materials in research area.

    Environmental Exploration
    Geochemical Characteristic and Fluxes of Heavy Metals in Water System of the Poyang Lake
    LI Wen-ming, YANG Zhong-fang, ZHOU Lei, TANG Man, YUAN Guo-li, LIU Chen
    2014, 28(3):  512-522. 
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    In this study, heavy metal pollution condition of Poyang Lake was investigated. During rainy and arid seasons, river water and suspended matters samples from the Poyang Lake area were collected and analyzed. In the studying rivers, the concentration of As, Pb, Cu, Zn and other elements were relatively high, whereas Cd was low. The levels of heavy metal showed significant difference between rainy and arid seasons. For the individual elements, Pb, Zn, Cu and Ni were transported mostly in the form of the suspended matters, while As was moved in the dissolved form mostly. Nevertheless, Cd was in both dissolved and suspended forms in all the samples. It is found that the distribution of heavy metal in solidliquid was affected by pH, temperature in water and concentration of suspended solids. However, the influence was different among elements. It is also found that the main input of heavy metal pollution in Poyang Lake was originated from Ganjiang and Xinjiang.

    Assessment of the Heavy Metal Pollution and the Potential Ecological Hazard in Soil of Plain Area of Baoding City of Hebei Province
    CUI Xing-tao, Qin Zhen-yu, LUAN Wen-lou, SONG Ze-feng
    2014, 28(3):  523-530. 
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    With the urban soil of plain area of Baoding city as a target, this essay evaluates the environmental quality of soil heavy metals and pollution characteristics by adopting the single factor index method and Nemerow comprehensive index method. Besides, the potential ecological hazard index suggested by Hakanson is used to assess the ecological hazard of heavy metal in urban soil. The results show that the elements, according to the pollution degree of heavy metal, are followed by the order of Cd>Zn>Hg>Cu>Pb>Cr>Ni>As. Most importantly, Cr,Pb,Ni,As and most of Hg and Cu are in a clean and safe condition, only to find 0.15% of Ni and 0.40% of Cu in an alert state. However, Cd, Zn are all in the pollution state, especially the pollution of Cd represents the largest polluted area, reaching 0.22%. On the whole, Integrated Pollution Assessment showed the soil environment is good, in which clean, safe, alert, contaminated soil area ratio is 94.39%,5.00%,0.50%,0.11% respectively; and alert and contaminated soil area accounts for 0.61%. Its formation may be related to industrial production and human activities. In the heavy metal elements, resulting in potential ecological hazard of heavy metals is mainly Hg, which have reached to moderate potential ecological hazard level, the remaining heavy metals are all mild potential ecological hazard. Considering synthetically the potential ecological hazard of heavy metals, we found that the percentage of small, medium, high and strong ecological hazard is respectively 93.71%,4.71%,1.29%,0.29%. Therefore, the general performance is the small potential ecological hazard.

    Energy Exploration
    Geochemical Evaluation on Land Quality in Bashang Plateau:Taking Shangyi County of Hebei Province as an Example
    WEI Jing, LI Hong-liang, LUO Jian-mei, LI Hai-gang, ZHANG Jing
    2014, 28(3):  531-536. 
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    The land quality in Bashang plateau of Shangyi County, Hebei Province is evaluated on geochemistry using land quality geochemical assessment model which is built using the analytic hierarchy process and membership functions.The results indicate that the land quality of assessment area is in good condition. The soil of the first quality grade is rich in nutrient elements and health indicators which accounts for 22.65% in the whole region,the proportion of second quality grade area is 40.65%,the proportion of third quality grade area with high of F- and Cl- is 6.80%, which has serious soda saline land. The irrigation water of the first and second quality grade accounts for 64.30% and 35.70%. The main influencing factors of irrigate water division are F- and Cl-, the over standard proportion of which are 5.70% and 34.30%. The 21 and 11 in geochemical assessment class and grade have a larger proportion, which accounts for 40.65% and 22.65%, relatively, the 32 and 31 with lower rate accounts for 1.60% and 6.80%.

    Environmental Exploration
    Mining of the Chaihe Pb-Zn Deposit in Liaoning Province and Reconstruction of Its Heavy Metal Pollution Record
    QIN Ai-hua ,YU Cheng-guang ,LI Kuo ,YANG Ke
    2014, 28(3):  537-542. 
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    The heavy metal pollution of soil resulting from Pb-Zn mining mainly appears within 3 to 5 km around the mine area of Chaihe Pb-Zn deposit, Liaoning Province, and the pH value clearly reveals soil acidification of the region, thanks on the results from soil geochemical survey over the mining area of Chaihe Pb-Zn deposit and its surrounding area. History of heavy metal pollution reconstructed from the profile of overbank sediment indicates that S concentration kept continueously increasing, and the pH dropped by 2 units since 1820 at the outlet of Chaihe reservoir. Whereas after 1900, Cd, Pb, and Zn in overbank sediment accumulated evidently, and the content of Pb and Hg in sediment profile declined after the cease of Pb-Zn mining. Soil acidification may remove Cd and Zn from accumulated in soil to water and sediment, and to result a potential risks to fish in Chaihe reservoir.

    Energy Geology
    Structural Features and Its Impacts on Hydrcarbon Accumulation of Neogene in Enping Sag, Pearl River Mouth Basin
    XU Xin-ming, CHEN Sheng-hong, WANG Fu-guo, HU Kun, YU Shui-ming,WANG Xu-cheng, G
    2014, 28(3):  543-550. 
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    There is close contact between fault features and faulted reservoir accumulation, because fault is the main channel of vertical hydrocarbon migration. Based on the analysis of fault features of Enping Sag, the fault is divided into 2 fault systems and 4 kinds of faults in different active stages, and then its structural styles, activities, sealing and its impacts on hydrcarbon accumulation in Neogene are studied. The results show that 7 structural styles were summarized from kinds of faulted belts, in which developing tilting half anticline and anticline are the most favorable traps in hydrocarbon accumulation; The long active faults and the late active faults are the main migration faults of Enping Sag, which play dual role with channel and sealing in hydrocarbon accumulation: its sealing abilities restricted the hydrocarbon column height, and its activities controlled the hydrocarbon enrichment of drilling traps; So the rules between drilling hydrocarbon enrichment and the migration faults activities of migration period is introduced, that is, 1.09 is the critical value of faults activities growing index in migration period; The higher of the growing index is, the stronger of fault’s vertical migration abilities is, so the better hydrocarbon accumulation probability in Neogene traps is.

    Petroleum Accumulation Significance of Polygonal Fault Systems in Sanzhao Depression, Songliao Basin
    DING Xiu-jian, LIU Guang-di, SUN Ming-liang, WANG Pan-gen, TANG Hui
    2014, 28(3):  551-558. 
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    There are abundant faults with different sizes in Sanzhao depression, Songliao basin. Predecessors who think that the large faults were main migration pathway for Fuyang and Putaohua oil layers, neglect the petroleum significance of small faults. There are a lot of small faults in the Cretaceous of Sanzhao depression, characterized by polygonal planform geometry and small distribution length, small fault throw and big angle of dip. So it is suggested that the small faults are Polygonal fault systems(PFS). In the plane, PFS distributed in the whole depression; while in the vertical, it distributed both in Fuyang and Putaohua oil layers. And PFS played a significant role during the accumulation of reservoirs. PFS, as the main migration pathway of Fuyang oil layer, have controlled the distribution of the oil layer, and widely-developed PFS are the main reason for continuous distribution of oil layer. Large faults and PFS are the main migration pathway of Putaohua oil layer, among which PFS played a bypass role in hydrocarbon migration of Putaohua oil layer and has some influence on the distributiion of Putaohua oil layer.

    Inversion Structures in Tazhong-Bachu Area and Their Significance to Petroleum Geology
    YANG Yong,TANG Liang-jie,QI Li-xin,QIU Hai-jun,YAO Wen-qian
    2014, 28(3):  559-565. 
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    On the basis of the seismic interpretation, the deformation features and evolution periods of inversion structures and their significance on hydrocarbon in the Tazhong-Bachu aera are studied in this paper. The basement normal faults were inversted in the Early and Middle Caledonian and Later Hercynian to Later Yanshanian, respectively. Controlled by the basement normal faults, three styles of inversion structures were developed in Tazhong-Bachu area: (1) Inheritance inversion type. When the dip of the basement normal faults was small, inheritance inversion structures formed by the later inversion acted along the pre-existing normal faults; (2) Short cut type. When the dip of basement normal fault was big, the normal fault might not be favorable for its further inversion and forced the inversion to form in the adjacent faults, and the basement normal faults provided stress concentrations point for the thrust faults, and (3) Reverse cut type. The inversion structures formed by the later thrust faults cut the basement normal faults which have the opposite tendency. The periods of traps formation resulted from structural inversion were greatly match to the peak stages of hydrocarbon generation and expulsion, so inversion structures in the studied area are favorable to hydrocarbon accumulation.

    Interlayer Characteristics and Its Controlling Hydrocarbon Accumulation Model of Inner Buried Hill in Jizhong Depression
    GAO Chang-hai,ZHANG Xin-zheng,ZHA Ming,ZHAO Xian-zheng,JIN Feng-ming
    2014, 28(3):  566-572. 
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    The interlayers of inner buried hills are the main factors that control the hydrocarbon distribution. Starting from the exploration practice in Jizhong depression, this paper studies the characteristics of lithology, resistivity, seismic reflection and distribution of interlayers using the seismology, geology, logging and assay data. The result shows that the interlayers of inner buried hills in Jizhong depression have multiple types of rocks with preferable sealing ability. The distribution characteristics of interlayers in horizontal and vertical directions influence the hydrocarbon distribution of the inner buried hill reservoir. According to the relationship of interlayer and hydrocarbon, the patterns of hydrocarbon distribution can be classified into four main types,ie. top barriering,bottom barriering,lateral barriering and top-bottom sandwich. Explorations should be focused on the deep inner traps in the central uplift belt, and the inner traps of the slope belt and the fault step belt.

    Tectonic Evolution and Hydrocarbon Potential of Basins in Central Asia and Its Adjacent Regions
    Abitkazy Taskyn,LI Jiang-hai,LI Hong-lin, LI Wei-bo,MAO Xiang,WAN
    2014, 28(3):  573-584. 
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    In this paper based on the tectonics and basin evolution of central Asia and its adjacent region,combined with the previous studies,the paleoplate reconstruction and geographic information software were used to analysis the tectonic evolution and oil/gas system of basin group in central Asia. In Early Paleozoic,basins in central Asia and its adjacent region belong to different blocks. Since Early Carboniferous,these blocks began to converge and completely joined together in Early Permian.Before converging the study area was under the influence of Hercynian tectonics,and the basin group formed in Mesozoic stretching tectonic process and Cenozoic compressive tectonic process belong to superimposed basin. The hydrocarbons in the study area mainly accumulate in the Jurassic (41%) and Carboniferous (37%) strata, and the main exploration targets are carbonate rocks,reef limestones,gypsums and mudstones. As for foreland basins, such as Amu-darya,Fergana,Tarim,Turgay and Afghan-Tajik basins,oil and gas mainly accumulate in foreland fold-and-thrust belts and sagging step-fault zones. As for craton basins, such as Precaspian,North Ustyurt and Mangyshulak basins,oil and gas mainly accumulate in the edge,the uplift belts and stepfault zones of the basin,and the source and reservoir are in the same layer.

    Structural Geology and Hydrocarbon Accumulation in Para-Maranhao Basin, Northeast Brazil
    CUI Min,KANG Hong-quan,LI Shao-peng
    2014, 28(3):  585-591. 
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    Based on the seismic interpretation and reservoir characteristics, combined with previous studies on the formation and evolution of the Atlantic, we analyzed the structural characteristics, tectonic evolution and petroleum geology of Para-Maranhao Basin in northeast Brazil, then summed up its accumulation mode. The Para-Maranhao Basin can be divided into four units, which are Marajo Block, Para-Maranhao platform, Ilha de Santana platform and deep sub-basin. The basin is a typical passive continental margin basin, which experienced three tectonic evolutions, i.e. rift stage, transform stage and drift stage, forming different sedimentary styles and lithologies. The accumulation combination is proven that the Albian Caju Group is source rock, which is good for hydrocarbon generation, and the Late Cretaceous Ilha de Santana Group is good reservoir, which is fractured sandy platform carbonate. The traps associated with thrust are well developed in the deepwater fold and thrust belt. The Paleogene Travosas Group is proven to be source rock in the peripheral basin, so it is a potential source rock in this basin. Besides this, the Travosas Group turbidite sandstone is a good reservoir. In summary, this area is thought to have potential for hydrocarbon accumulation.

    Conditions of Giant Volcanic Gas Field in the Deep Fault Depressions of Songliao Basin and Its Exploration Practice
    ZHAO Ze-hui, SUN Ping, LUO Xia, XU Shu-juan, JIANG Xiao-hua, CHENG
    2014, 28(3):  592-603. 
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    The deep zone of Songliao basin is made up of more than 30 separated fault depressions where volcanic gas reservoir is the main exploration target. Starting from the analysis of the formation characteristics of deep fault depression and analyzing the factors of controlled source and controlled gas reservoir, the conditions of giant volcanic gas field in fault depressions are summarized for guiding the exploration. The comprehensive research suggested that the deep fault depressions are controlled by two faults system that are NNE-NE and NNW-NW strikes, along the strike direction of faults controlled fault depressions. The typical asymmetrical model of volcanic eruption pattern controlled by faults is characterized by one smallscale side on the higher part of faults and by the other large-scale side in the lower part of faults, as molten magma flowed from the top down, with zonal distribution along the strike direction of faults controlled fault depression. Generally, each fault depression is composed by one or more fault troughs which control the distribution of source rock, so each fault depression has its own independent petroleum system and the key factor of gas accumulation is favorable spatial configuration between fault troughs and volcanic rocks. The deep volcanic gas reservoirs are characterized by nearby distribution surrounding source rocks and main troughs. The faults controlled the formation and distribution of fault depressions, fault troughs and volcanic rocks, and improved the channel conditions for oil-gas migration and accumulation, which indicates fault structural zone close to hydrocarbon bearing troughs is gas enrichment region. In short, deep faults controlled regional distribution of giant volcanic gas field. Further exploration practice prove that: for oil and gas exploration of fault basins, main fault troughs which controlled hydrocarbon generation is the key unit for the evaluation and exploration. As long as the high quality hydrocarbon source rock are developed in the fault troughs, with good space configuration with volcanic rocks, small and medium sized fault depressions with area smaller than 3,000 km2 also can form giant volcanic gas field (proven geological reserves of more than 300×108 m3), which have presented as exploration strategy changed from searching for big lake basins or fault depressions to main hydrocarbon bearing troughs which need to be proved.

    Contrastive Study on Geological Characteristics of Cretaceous Bashijiqike Formation in Keshen2 and Kela2 Gas Fields in Kuqa Depression
    CHU Guang-zhen, SHI Shi, SHAO Long-yi,WANG Hai-ying, GUO Zhen-hua
    2014, 28(3):  604-610. 
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    The geological features of sand reservoirs in Bashijiqike Formation in Keshen2 gas field in Kuqa depression were contrastively studied with those in Kela2 gas fieldthrough analysis of sequences, sedimentary facies,petrophysics,reservoir property and reservoir connectivity. The results reveal that the sequences and sedimentary facies in the two gas fields have good relationship, but their reservoir characteristics are much different, especially in the content of feldspar, petrophysics, and development of interlayers, fractures and faults. Combined with Kela2 gas field, the reservoir propertyand connectivity in Keshen2 gas field are not well, and the gas field is in the initial process of exploration and development, therefore it is essential to use for reference from the abundance geological data and perfect development technology in Kela2 gas field.

    Fine Research and Application of Internal Architecture in Point Bar of Meandering River
    ZOU Tuo, LIU Ying-zhong, NIE Guo-zhen
    2014, 28(3):  611-616. 
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    Point bar is the most important reservoir sand of sedimentary units in meandering river, whose internal side of lateral accretion bedding is the main factors of controlling the remaining oil distribution. This paper took the pilot test Five of Area II in Gangdong oilfield as an example, dissected the architecture of point bar by comprehensive use of logging, core, dense well, horizontal wells, etc. Quantitative understanding of lateral accretion thickness is about 0.2 to 0.3 m, inclination 3.5°, and lateral accretion body scale sizes are different in the test area. After that, the 3D super-fine model of inner point bar is established, through secondary infilling and embedding technology of grading times, and fine simulation studies is carried out. At the same time, logging, core, laboratory analysis, etc. are combined to find out the residual oil distribution law qualitatively, which are mainly in the top of sand and side of lateral accretion bedding. Applying geology-modeling-simulation integrated studies to setting up plan of reservoir and site implementation, good results is achieved. It provides an innovative idea and method for point bar configuration.

    Characteristics and Controlling Factors of Effective Reservoirs in Es3 Formation of Wen’an Slope, Baxian Sag, Jizhong Depression
    LI YU-zhi,JIN Jie-hua, CAO Ying-chang, XI Ke-lai, ZHOU Lie, CUI Zhou-qi, H
    2014, 28(3):  617-625. 
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    The petrologic features, diagenesis characteristics and reservoir characteristics of the Es3 reservoirs in Wen’an slope were systematically studied by core observation, thin section observation and physical property analysis. It can be seen that the study area mainly developed lithic arkose, which contains a few matrixes and its component maturity and structure maturity are in the middle. The reservoir spaces of the lithic arkose are primary pores, which occupy 72.81% of the total pores. The reservoirs possess comparatively bad reservoir characteristics, and belong to middle-low porosity, low to ultra-low permeability reservoirs. The reservoirs sequently underwent a series of diagenetic stages as follows: consolidation and early carbonate cementation→feldspars and rock debris dissolution, quartz enlargement, kaolinite fillings →quartz dissolution and carbonate cementation→pyrite cementation. On basis of analyzing the lower limits of effective reservoir properties, this study systemically analyzed the controlling factors of effective reservoirs, which include sedimentary microfacies, particle size, sorting, diagenesis and formation pressure. Better reservoirs developed in coarser grains in underwater distributary channels and estuary dams, which have better sorting and fewer matrixes. Cementation has distinct control effect on reservoir characteristics, and is the major controlling factor of characteristics of mid-deep reservoirs. Dissolution is mainly shown as the corrosion of silicate minerals such as feldspars, in which the average increasing of pore volume is 3.42%. The overpressure of early phase restrained compaction, protecting the pores, and became the favorable factor of the development of effective reservoirs.

    Characteristic of Dense Dual Pore Medium Reservoir and Optimization of the Favorable Block in the Second Member of  Xujiahe Formation in Xinchang Area of  Western Sichuan
    FENG Dong-jun, ZHOU Hong-rui,XIAO Kai-hua, LI Xiu-peng, WANG Dan-dan
    2014, 28(3):  626-634. 
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    In the study of dense sandstone reservoir in the Second Member of Xujiahe Formation in Xinchang area, the reservoir characteristics were analyzed using approved slice and properties data acquired with test methods. Fractures and fluid were identified and predicted using core, logging and seismic methods, to guide the synthetic evaluation of reservoir and the favorable block optimization. It is indicated that secondary pore and micro-fracture develop mostly in target formation, and fractures are mainly low-angle fractures, spreading along fault and fold-belt in structural limbs. The effective reservoir are mainly controlled by sedimentary facies, diagenesis, structure and petroleum accumulation, however, corrosion and crack are the main control factors. The blocks of reservoirⅠ locate in high structural place or nearby faults inTx22and Tx42. It is concluded that the areas of two sides of F3 fault in middle and up sub-segments are the most favorable blocks, while two sides of southern edge of F1 fault in up sub-segment and Xin10-Chuanke1 well area in middle sub-segment are the secondary. The study results are significant in effective development of the Second Member of Xujiahe Formation in Xinchang area.

    Diagenesis and Its Control Factors of Donghe Sandstone in Hanilcatam Depression of Tabei Uplift
    LIU Yong-fu, ZHAO Jian-hua, FAN Qiu-hai, LIN Chang-song, SUN Qi, HUANG Li
    2014, 28(3):  635-644. 
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    Donghe sandstone diagenesis were studied through core and rock slice observations and data analysises of scanning electron microscope and cathodoluminescence in the Hanilcatam depression. The reservoir rocks mainly is lithic quartz sandstone. The types of the diagenesis are the compaction, cementation, replacement and dissolution. The diagenetic stage belongs to the A middle diagenesis. The control of sedimentary facies, burial and sequence stratigraphy on diagenesis are discussed. Donghe sandstone in the study area was long-term shallow buried and shortterm quick deep buried in later period in the low-temperature background, so the degree of compaction is moderate in general. Shore and wave-dominated deltaic depositional systems are developed. Near the high-resolution sequence boundaries where relative sea-level rises, accommodate space increases, sediment deposition rate is relatively low, and residence time is long, develop laterally persistent carbonate cemented horizons in syndiagenesis and early diagenesis stages.

    Occurrence Characteristics of Minerals and Their Influences on Physical Properties of Coal Reservoirs in Southern Qinshui Basin
    LIU Bei, HUANG Wen-hui, AO Wei-hua, ZHANG Shou-ren, WU Jian, XU
    2014, 28(3):  645-652. 
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    Minerals in coal can influence coal reservoir physical properties and the development of coalbed methane. Mineral species, content and occurrence characteristics in coal of southern Qinshui Basin were studied by using optical microscope and scanning electron microscope (SEM). Based on the test of isothermal adsorption experiment and mercury-injection method, the effects of minerals on adsorption capacity, porosity and permeability of coal reservoir were analyzed. The results show that the mineral content of No.3 and No.15 coal seams of Shizhuang block are 10.68% and 12.81%, respectively, and the content of sulfide minerals in No.15 coal seam is higher than that in No.3 coal seam. Calcite, pyrite, kaolinite and quartz filling in cell pores, intergranular pores and microfractures can be identified under SEM. The values of langmuir volume, proportion of macropores and mesopores, porosity and permeability decrease with the increasing of ash content, indicating that minerals in coal can decrease the adsorption capacity, porosity and permeability of coal reservoirs. Minerals in coal mainly fill in macropores, mesopores and microfractures of coal and they can influence the diffusion of coalbed methane in cleats and fractures, causing the decrease of porosity and permeability. However, a small part of clay minerals which fill in micropores of coal reservoir can lead to the decrease of adsorption capacity.

    A Method for Targeting Favorable Coalbed Methane Development Area Based on Primary Geological Parameters and Its Application
    LI Jun-qian, LIU Da-meng, YAO Yan-bin, CAI Yi-dong, GUO Xiao-qian
    2014, 28(3):  653-658. 
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    Favorable coalbed methane (CBM) development area is characterized by high CBM content, high coal reservoir permeability and high gas productivity. Finding out the primary geological parameter representative of the three high properties is a key to comprehensively evaluate CBM-bearing reservoirs. In this paper, a quantitative method was proposed to target favorable CBM area for a CBM development block. Coalbed gas content, reservoir pressure, critical desorption pressure and coal permeability obtained by injection/falloff well test were selected to be as primary geological parameters used for comprehensively evaluating favorable CBM area. Their weight coefficients and evaluation value functions were obtained by analyzing correlation degree of the geological parameters with the mean gas production rate at stable production period. Based on the soft of MapInfo professional, comprehensive evaluation values for the arbitrary locations of the study area were calculated, and then were calibrated by the mean gas production rate so as to divide different CBM development areas. This method was successfully applied to Zhengzhuang block in southern Qinshui Basin, and favorable CBM areas with the gas-production value larger than 2,000 m3/d were predicated; the result is significant to guide the CBM well drilling in the next stage.

    Experimental Study on Thermal Front Movement of Natural Gas Hydrate by Injecting Hot Water
    LI Shu-xia,CAO Wen,LI Jie,GAO Yong-hai
    2014, 28(3):  659-662. 
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    Injecting hot water is one of the effective ways to dissociate natural gas hydrate (NGH), and the movement of thermal front determines the dissociation rate of hydrate, which is a key parameter for thermal stimulation. A one-dimensional experimental system is designed to form NGH with different initial conditions in sand-packed tube, and then hot water with different thermal parameters was injected to analyze the movement of thermal front. Results show that the higher the NGH saturation is, the less the thermal front movement rate is; the thermal front movement rate increases slightly with the initial temperature increasing;the thermal front movement rate is larger with higher hot-water temperature and larger hot-water injection rate. Among the four parameters, i.e.NGH saturation,initial temperature,hot-water temperature and hot-water injection rate,the most sensitive parameters are the NGH saturation and hot-water injection rate, followed by the hot-water temperature, and the least sensitive parameter is initial temperature. In order to increase dissociation rate of hydrate, it is reasonable to increase the hot-water injection rate within the technical feasibility. Lowering the hot-water temperature can slightly decrease the dissociation rate of hydrate, while the economic feasibility will increase.