Dec 2007, Volume 1 Issue 4
    

  • Select all
  • On the geobiological evaluation of hydrocarbon source rocks
    XIE Shucheng, YIN Hongfu, XIE Xinong, QIN Jianzhong, HU Chaoyong, YAN Jiaxin, WANG Yongbiao, HUANG Junhua, ZHOU Lian, YANG Xianghua, XU Sihuang
    2007, 1(4): 389-398. https://doi.org/10.1007/s11707-007-0041-2
    Download PDF
    Hydrocarbon source rocks are characterized by the hydrocarbon discharge, and the alteration and variation in organic compositions and organic content due to the enhanced thermal maturation. These variations throw constraints on the application of the conventional inversion evaluation of hydrocarbon potential by assessing the residual organic matter left in source rocks. Geobiology, probing the interaction between the life system and the earth system, provides new principles in deciphering the whole dynamic processes related to the organic evolution history from living biomass to organic burial. Geobiological subdisciplines, including molecular geobiology, geomicrobiology, geoecology and biogeochemistry, offer new methodology and techniques to estimate the paleoproductivity, depositional organics and organic burial capacity and their components. Geobiofacies, newly proposed herein, is terminologized to define the geobiological dynamic processes through the combination of biofacies with organic facies and sedimentary facies, and expressed by the biohabitat types, paleoproductivity, depositional and preserved organics. Geobiofacies is identified as a useful means to create the geobiological evaluation system, which in turn rectifies the conventional evaluation system for the marine source rocks.
  • Chemical variation from biolipids to sedimentary organic matter in modern oceans and its implication to the geobiological evaluation of ancient hydrocarbon source rocks
    WANG Hongmei, MA Xiangru, LIU Deng, YANG Xiaofen, LI Jihong
    2007, 1(4): 399-404. https://doi.org/10.1007/s11707-007-0048-8
    Download PDF
    Understanding the dynamics of organic matter in modern marine water columns greatly favors the geobiologcal evaluation of hydrocarbon source rocks. Biolipids could make great contribution to petroleum hydrocarbons due to their comparable chemical components and the slightly refractory characteristics of biolipids during the microbial/thermal degradation. A variety of environmental factors such as temperature, CO2 and salinity could affect the biochemical contents in microorganisms. As a result, microorganisms living in a changing environmental condition might have a different contribution to the petroleum formation. Organic carbon flux is shown to bear a positive correlation with the primary productivity only within a certain range of biomass volumes in a specific biohabitat. Furthermore, organic matter is degraded much quickly in a water column with oxic conditions. Therefore, the anoxic condition, along with the enhanced biological productivity, would be one of the significant factors in the formation of high-quality hydrocarbon source rocks. The formation of biofilms and microbial mats favors the preservation of sedimentary organic matter by decreasing the degradation rate of organic matter. Identification of biofilms and microbial mats in sedimentary rocks will thus greatly help to understand the depositional processes of organic matter finally preserved in hydrocarbon source rocks.
  • Organic fraction of the total carbon burial flux deduced from carbon isotopes across the Permo-Triassic boundary at Meishan, Zhejiang Province, China
    HUANG Junhua, LUO Genming, BAI Xiao, TANG Xinyan
    2007, 1(4): 425-430. https://doi.org/10.1007/s11707-007-0052-z
    Download PDF
    By combining the carbon cycle model with the records of carbonate and organic (kerogen) carbon isotope, this paper presents the calculation of the fraction of organic carbon burial (forg) of beds 23–40 at the global boundary stratotype section and point (GSSP) of the Permian–Triassic boundary at Meishan, Zhejiang Province. The resulting calculation produces two episodes of forg maxima observed to occur at beds 23–24 and 27–29, which respectively corresponds to the two episodic anoxic events indicated by the flourish of green sulfur bacteria. Two episodic forg minima occurred at beds 25–26 and 32–34, generally coincident with the flourish of cyanobacteria (bed 26 and upper part of beds 29 to 34) as shown by the high value of 2-melthyhopnoanes. It appears that the forg is related to the redox conditions, with greater forg values observed under the reductive condition. The relationship between forg and the total organic carbon (TOC) content was complex. The forg value was low at some beds with a high TOC content (such as bed 26), while high observed at some beds with a low TOC content (e.g. bed 27). This association infers the important contribution of primary productivity to the TOC content. The original organic burial could be thus calculated through the configuration of the function of the primary productivity and forg, which can be used to correct the residual TOC measured today. This investigation indicates that compiling the organic-inorganic carbon isotopes with the carbon cycle model favors to understand the fraction of organic carbon burial, providing information for the reconstruction of the coupling among biota, environments and organic burial.
  • Geobiological interpretation of the oxygen-deficient deposits of the Middle Permian marine source rocks in South China: A working hypothesis
    YAN Jiaxin, LIU Xinyu
    2007, 1(4): 431-437. https://doi.org/10.1007/s11707-007-0053-y
    Download PDF
    To decipher the origin of oxygen-deficient shelfal deposits is significant for tracing the distribution of marine source rocks and interpreting the evolution of depositional environment. The origin of the Middle Permian Chihsia Formation in South China remains a puzzle for long with its evident oxygen-deficient features but diverse benthos. This paper shows a typical Chihsian depositional rhythm composed of the massive and the laminated limestones with ecological and geochemical features. Massive bioclastic limestone from the rhythm was aerobic in paleoxygenation condition indicated by both the ecological and geochemical features. However, a contradictory oxygenation was inferred for the laminated  counterpart from the rhythm, with the ecological signal being aerobic and the geochemical one being anoxic. The difference in ecological and geochemical indications was interpreted as the instability of paleoxygenation condition in shelf environments, caused by an enhanced paleoproductivity. Rhythmic occurrence of the oxygen-deficient condition might have been stemmed from paleo-Tethyan paleocurrents flowing across South China.
  • Calci-microbialite as a potential source rock and its geomicrobiological processes
    YANG Hao, WANG Yongbiao, CHEN Lin, DONG Man
    2007, 1(4): 438-443. https://doi.org/10.1007/s11707-007-0054-x
    Download PDF
    The calci-mircobialite is a special carbonate buildup, which is formed due to the activities of different kinds of microbes. Abundant microfossils preserved in the microbialite show the high-level productivity during deposition, while characteristic sedimentary minerals and geochemical compositions suggest an anoxic marine environment for organic burial. The high-level productivity and anoxic sedimentary environment favor the efficient preservation of organic matter and thus the formation of source rocks. On these points, microbialites could be one of the potential hydrocarbon source rocks, awaiting further geobiological investigation and exploration. Precambrian and some of the great transitional stages in Phanerozoic are critical periods when mircobialites were well developed. Widespread microbialites have been found in North and South China. Bitumen observed in many outcrops of Precambrian and late Devonian mircobialites further raises the possibility of the calci-microbialite as a potential hydrocarbon source rock.
  • Potential contributions of extremophiles to hydrocarbon resources in marine extreme environments: A review
    WANG Jiasheng, WANG Yongbiao, LI Qing
    2007, 1(4): 444-451. https://doi.org/10.1007/s11707-007-0055-9
    Download PDF
    To understand the potential mechanism of marine extremophiles participating in the formation and the evo lution of hydrocarbon resources in marine extreme environments, some typical kinds of extremophiles and their distributions in marine hydrothermal and cold vents are discussed and evaluated respectively. The potential relationship between extremophile activities and hydrocarbon resources in marine extreme environments are then discussed in details. It could be now preliminary concluded that archaea and bacteria are the two main kinds of extremophiles in marine extreme environments. The dominating microbe com munities in hydrothermal vents are heterotrophic zymogens, sulfate reducers and methanogens, while the ANME-2 group (Methanosarcinales) surrounded by sulfate-reducing bacteria and ANME-1 group dominate in cold vents. Marine extremophiles would be able to use CH4 and H2S to synthesize energy for metabolism and to support food chains for other unique macrobiota nearby, which together present a high abundance but a low diversity with distinct characteristics of horizontal and vertical distributions. Marine extremophiles might play an important role either directly or indirectly in the processes of hydrocarbon formation and subsequent alteration, and could indicate the evolution of hydrocarbon resources in marine extreme environments. Our research thus has a great significance both in theoretical approach of potential hydrocarbon resources formed by marine extremophile activities and in practical exploration of the potential hydrocarbon-source sedimentary layers formed in the Earth history or the potential strata in southern China.
  • Depositional characteristics of Dalong Formation and its potential as hydrocarbon source rocks in Hubei, Hunan, Guizhou and Guangxi
    ZHANG Zhifeng, CAI Xiongfei, PENG Xingfang, FENG Qinglai
    2007, 1(4): 452-457. https://doi.org/10.1007/s11707-007-0056-8
    Download PDF
    The Late Permian Dalong Formation in Hubei, Hunan, Guizhou and Guangxi in South China could be subdivided into several sedimentary types according to the lithology, indicative of the great spatial variations of both the lithology and sedimentary facies. The Dalong Formation deposited during the highest transgression of Late Permian, in particular under the anaerobic and suboxic conditions, which shows a strong linkage with the hydrocarbon source rocks. The Dalong Formation has some favorable properties such as hydrocarbon source rocks, including the sediments deposited in highest transgression sea level, the deep slope sedimentary environments and the low sedimentary rate, which raises the importance of the investigations on the sedimentary features, the geochemical properties and their relationship with the oil potential.
  • Study on the restitution coefficient of original total organic carbon for high mature marine source rocks
    QIN Jianzhong, ZHENG Longju, Tenger
    2007, 1(4): 482-490. https://doi.org/10.1007/s11707-007-0059-5
    Download PDF
    On the basis of the results of hydropyrolysis simulations for about 90 different types of immature to mature source rocks selected from about 5 000 marine source rocks in China, along with the natural thermal evolution profiles, the following conclusions were obtained. (1) Total organic carbon (TOC) content of excellent marine source rocks does not change obviously when Ro<0.8% or Ro>1.3%, and the residual TOC content is decreasing gradually with the maturity increase at 0.8%<Ro<1.3%. (2) At the high-post mature stage (Ro>1.3%), the decreased maximums of residual TOC content for the kerogen of sapropel (I), II1, and II are usually 40%, 32% and 24%, respectively, and their TOC restitution coefficient is, respectively, 1.68, 1.48 and 1.32. (3) Both the TOC decreasing amplitude and the restitution coefficient decrease gradually with the decrease of TOC content for the source rocks with low organic matter abundance (usually 0.3%res. of solid bitumen and shale with high organic matter abundance (TOC>30%) also require no restitution at the high mature stage. Such kind of TOC restitution is further supported by the coincidence of the decrease of residual TOC with the decreasing of S1+S2 and the increasing of hydrocarbon quantity during the experimental simulation of hydrocarbon generation and expulsion for marine source rocks (0.3%<<30%) in natural thermal evolution profiles.
  • Application of quantitative grain fluorescence techniques to study subtle oil migration pathway of lithological reservoir
    CHEN Dongxia, ZHANG Jun, LI Minggang, PANG Xiongqi
    2007, 1(4): 498-504. https://doi.org/10.1007/s11707-007-0061-y
    Download PDF
    This paper analyzes the quantitative grain fluorescence (QGF) and quantitative grain fluorescence on extract (QGF-E) properties of 101 rock samples by using quantitative grain fluorescence techniques. The samples are collected from five wells in tight sandstone and thin siltstone in the third sector of the Shahejie Formation in the Niuzhuang sag of the Dongying depression. It was observed that both the tight sandstone and thin siltstone show relatively high fluorescence intensity of hydrocarbon, which suggests that they are possibly good subtle oil-migration pathways in the present or geological time. These thin subtle oil-migration pathways afford important clues for the researches on hydrocarbon accumulation in lithological reservoirs in the middle and lower of Es3 in deep sag zone, which has the hydrocarbon source from the upper of Es4 when there is no apparent fault playing oil migration conduits to connect lithologic traps and deep source rocks. This study shows good prospect of QGF techniques in discriminating oil migration pathways and paleo-oil zones. The results of this study may be of great significance to the researches on hydrocarbon accumulation mechanism of subtle reservoirs in the Dongying depression and other areas.
  • Characteristics and significance of seismite of Silurian in member III at Shahejie Formation
    WEI Chuigao, ZHANG Shiqi, JIANG Zaixing, LIU Jinhua
    2007, 1(4): 505-513. https://doi.org/10.1007/s11707-007-0062-x
    Download PDF
    Based on studies of regional tectonic setting and the observation of drilling cores, the seismite is recognized in member III at Shahejie Formation in the Xianhe area of the Dongying sag. The principal mark of the seismite is the develop ment of all kinds of soft sedimentary deformation structures, such as micro-step fault, intraformational minor fold, deformation, vibrational liquefied sandstone dike and seismic breccias. By observing the drilling cores of He 152, Wang 59, Niu 38, Niu 22 and so on, we found that the vertical sequences of the seismite are different because of the differences in structure and seismic intensity. We also found that different seismite structures are formed by different seismic intensities and that the relationships between seismite structures and paleoearthquakes were further confirmed by studying the relationship between all kinks of seismite structures and seismic intensity. Researches on reservoirs show that seismite can be an effective reservoir. These researches provide an important geological theoretical foundation for the study of the tectonic evolution of the Dongying sag and for seismite identification and description, and also supplies evidence for the researches of paleoearthquakes.