, Volume 36 Issue 2

    

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油气勘探
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  Practices and expectation of high-density seismic exploration technology in CNPC

  Liu Zhenwu; Sa Liming; Dong Shitai and Tang Donglei

  , 2009, 36(2): 1693-0.

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  China National Petroleum Corporation(CNPC) carried out 2D high-density seismic surveys in western and eastern China from 2003,and 3D high-density seismic surveys in Tazhong area of Tarim Basin, Northwest margin of Junggar Basin, Qiulin Oilfield of Tuha Basin, Songliao Basin, Huanxiling of Liaohe Oilfield and beach area of Jidong Oilfield from 2006. The total coverage area of 3D high-density seismic surveys was 654 km2 of which 100 km2 was 3D and 3C digital seismic. The surveys achieved preferable results under the high-coverage data acquisition and new data processing technologies. Technical advancement makes it possible to apply large-scale high-density seismic surveys. We can use the imaging trace density to scale whether the geometry is high-density seismic sampling, in order to meet the requirement of pre-stack data processing. In the principle of spatial sampling with “sufficiency, equality, symmetry and continuity”, and in combination with the geological targets and the problems to be solved, the integrated performance of acquisition, processing and interpretation shall be the orientation of high-density seismic technologies in CNPC in future.
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  Exploration theories and practices of buried-hill reservoirs: A case from Liaohe Depressions

  Meng Weigong; Chen Zhenyan; Li Pai; Guo Yanmin; Gao Xianzhi; Hui Xuefeng and Zhang Yali

  , 2009, 36(2): 1694-0.

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  In recent years, various breakthroughs have been made in buried hill reservoir exploration in Liaohe Depression. Exploration targets have shifted from the Shallow-medium buried hill reservoirs with clearer reservoir forming conditions to the low and inner buried hill reservoirs with deeper, hidden and more complex features. Reservoir-forming conditions of low and inner buried hills were studied in aspects of basement tectonic activity, type of buried hills, lithology and reservoir characteristics, hydrocarbon generating system and hydrocarbon conducting system. A practical classification method of inner buried hill reservoirs has been re-established in accordance with the relationship between buried hills and hydrocarbon accumulations, by studying reservoir characteristics of inner buried hill reservoirs with consideration of exploration practices. Such a classification method has widened the hydrocarbon searching scope in buried hills, and built up a reservoir forming pattern for the exploration targets inside buried hills with low amplitude, multiphase fractures and multisource charging. Based on the theoretical studies and exploration practices of low and inner buried hill reservoirs, the 3P reserves reported for low and inner buried hill reservoirs reached 2.54×108 t and 1.76×108 t respectively from 2001 to 2006. The buried hill reservoirs have made significant contribution to increasing reserves and stabilizing production in Liaohe Oilfield.
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  Cambrian dolomite origin and reservoir evolution in east Tarim Basin

  Ma Feng; Xu Huaixian; Gu Jiayu; Shao Longyi; Wu Guanghui; Liu Yongfu and Zhu Changjian

  , 2009, 36(2): 1695-0.

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  The petrologic and geochemical characteristics of the Cambrian dolomite are studied through core observation, thin section analysis and geochemical analysis. The evolution and development mechanism of the reservoir are revealed by comprehensive analysis of the origin and dolomitization models. The Cambrian dolomitization is developed in the Upper Cambrian Torsuqtagh Formation and distributed in the marginal zone of platform in the west and middle gentle slope in the east of eastern Tarim. The study on the carbon, oxygen and strontium isotopes, the testing of trace elements and the temperature measuring of fluid inclusions reveal that the micrite-crystal and cryptomere-macrocrystalline dolomites of the region of interest have different geochemical characteristics, were developed in three dolomitization environments including extra salinity, bury and hydrothermal fluid, and experienced the stacking of three dolomitization models including penetration reflux dolomitization, burial dolomitization and hydrothermal fluid dolomitization. The beneficial dolomitization models are penecontemporaneous penetration reflux dolomitization + burial dolomization, penetration reflux dolomitization + hydrothermal fluid dolomitization, and burial dolomitization + hydrothermal dolomitization. The adverse dolomitization models in the dolomite reservoir are simple dolomitization and penetration reflux dolomitization + burial dolomitization + hydrothermal fluid dolomitization.
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  Petroleum geological significance of Botryococcus in Triassic Yanchang Formation, Ordos Basin

  Ji Liming; Li Jianfeng and Song Zhiguang

  , 2009, 36(2): 1696-0.

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  By microfossil analysis of the Middle and Upper Triassic in the Xifeng area of Ordos Basin, very abundant Botryococcus braunii have been found from the Yanchang Formation. The high-abundance strata of Botryococcus are members Chang 7-2 and Chang 7-3, which are the main source rock sections in the area. Botryococcus is an important component of the alginite and amorphogen in source rocks, and its abundance is in direct ratio to TOC content. The Botryococcus is an important biological source for the high quality terrestrial source rocks of the Triassic Yanchang Formation. C12-C16 bicyclic alkanes and C15-C34 monomethylalkanes were detected from both crude oil and source rocks in the Formation. These biomarkers from different samples have similar characteristics. The bicyclic alkanes are mainly homodrimane and drimane, and the methyl substituent positions of MMAs are 3 and 4. The studies show that these biomarkers in sediment are related to the parent material import of Botryococcus. Consequently, the hydrocarbon generation and source rock formation in the Triassic Yanchang Formation are closely related to the mass Botryococcus in the ancient lake of Ordos Basin area.
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  Oil generation threshold depth of Songliao Basin: Revision and its significance

  Lu Shuangfang; Li Jiaona; Liu Shaojun; Feng Zihui; Li Jingkun; Huo Qiuli; Wang Xue; Xue Haitao; Li Jijun and Shen Jianian

  , 2009, 36(2): 1697-0.

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  A systematic analysis was carried out on the relation curve of hydrocarbon transformation ratio vs. buried depth and that of vitrinite reflectance (Ro) vs. buried depth in Binbei area, major source rock area (Qijia-Gulong Sag and Sanzhao Sag), and major source rock layer (Cretaceous Qing-1 Member, Qing-2 - Qing-3 Members) in Songliao Basin, to re-determine the oil generation threshold depth of the basin. The oil generation threshold depth of the major source rocks is likely to range from 1 400 m to 1 700 m, rather than 1 200 m in the previous estimation. The change of oil generation threshold has different effects on the resources potential and exploration orientation of various areas: For the major source rock areas, increase of oil generation threshold depth will cause decrease of oil generation and expulsion quantity, with no evident effect on the resources potential of major source rock area, but with certain effect on the exploration orientation and favorable target evaluation. For the Binbei area with shallower buried depth of source rocks, it will have great effect on the exploration potential, exploration orientation and favorable target evaluation. For the southeastern uplift area with great denudation in the basin, the oil generation threshold depth is reduced to about 700 m, which will improve the exploration potential of Chaoyanggou terrace, Changchunling anticline and Binxian-Wangfu area.
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  Formation and pool-forming model of CO2 gas pool in eastern Changde area, Songliao Basin

  Wei Lichun; Lu Xuesong; Song Yan and Liu Shaobo

  , 2009, 36(2): 1698-0.

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  With the study on gas composition, gas genesis, reservoir characteristics, faults and volcanic lithofacies of CO2 gas pool in eastern Changde area in Songliao Basin, the pool-forming mechanism and model are established. The results show that CO2 gas in the pool is mantle origin, the hydrocarbon gas is mixture of oil-type gas and inorganic hydrocarbon gas; the CO2 gas pool in FS9-FS701 well field and the gas pool with high CO2 content in FS6-FS7 well field are two separate reservoirs unconnected. The forming mechanism of deep CO2 gas pool in Songliao Basin is as follows: the top of deep heat-flow diapris is full of CO2, and large basement fault converges downward to the detachment zone and communicates CO2 gas source, then CO2 migrates upward into proper traps through basement fault and ancient volcanic conduit. It is pointed out that different types of migration and accumulation pathways and the natural gas gravitational differentiation during the migration process are the fundamental reasons for the difference of CO2 content between the two gas pools.
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  Geochemical characteristics and distribution of CO2 gas fields in Bohai Bay Basin

  Hu Anping; Dai Jinxing; Yang Chun; Zhou Qinghua and Ni Yunyan

  , 2009, 36(2): 1699-0.

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  Eleven CO2 gas fields (pools) have been discovered in the Huanghua and Jiyang depressions of Bohai Bay Basin, Eastern China. The analyses of natural gas geochemical data in the CO2 gas fields (pools) reveal: First, there is a positive correlation between CO2 content, δ13CCO2 values and R/Ra values, but a negative correlation between CO2 content and CH4 content; Second, the elevated δ13CCO2, R/Ra and 40Ar/36Ar values show that CO2 is mantle-derived; Third, organic and inorganic alkane gases are both discovered in the CO2 gas fields of the Huanghua Depression, and the alkane gas in the Jiyang Depression is mainly oil-type. Taking the geological background of the region into consideration, the article concludes that the high geothermal field region, intersection part of faults, magmatic rock region and high R/Ra values region are favorable abundance zones for CO2 gas fields (pools).
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  Geochemical characteristics and source of oil seepages from Shiwandashan Basin

  He Xunyun; Zhong Ningning; Chen Jianping; Liang Digang and Chen Ziliao

  , 2009, 36(2): 1700-0.

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  The group composition, chromatogram of oil and saturation hydrocarbon, carbon isotope and biomarkers of oil seepages in Lower Triassic limestone geode of Shiwandashan Basin were analyzed. The oil seepages are characterized by high content of saturation hydrocarbon and high ratio of saturation hydrocarbon to aromatic hydrocarbon; the value of main peak carbon is less than C21, Pr/ Ph ratio is 0.67 – 0.84, OEP is 0.84 – 0.97; δ13 C value of oil seepages is －31.6‰–－30.7‰; the content of sterane and terpane is very low, mainly consisting of pregnane and tricyclic terpane; there is nearly no aromatic sterane in oil seepages. All these demonstrate that the oil seepages come from lower aquatic organic matter and have high maturity. Comparing the geochemical characteristics of potential source rocks and oil seepages with the relevant previous research results shows that the oil seepages in Baxi paleo-oil reservoir have genetic relationship with the argillaceous source rock of Lower Triassic, and the oil seepages at southern area of Chongzuo City are mainly from the argillaceous source rock of Lower Triassic, but a small amount may come from the source rock of Upper Permian.
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  Acoustic detection of seabed hydrocarbon seepage in the north depression of South Yellow Sea Basin

  Zhao Tiehu; Zhang Xunhua; Wang Xiutian and Meng Xiangjun

  , 2009, 36(2): 1701-0.

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  The full-covered Side-Scan Sonar and high-resolution seismic survey method is initially adopted to research on the seabed hydrocarbon seepage in the survey area, for the purpose of the following: clarifying the shallow acoustic features related to seabed hydrocarbon seepage in the north depression area of South Yellow Sea Basin, analyzing the relations between the seepage and the structure, and providing evidence for selection of geochemistry sampling station and petroleum exploration. On the mosaic image of Side-Scan Sonar, the strong reflecting spots in strip-like distribution present the physiognomy of pockmark and dome. On the seismic profile, we can see the characteristics such as enhanced amplitude, columnar disturbance, gas chimney, and blank reflection, which result from gas accumulation. The analysis results indicate that the widely developed faults which approach or connect to seabed provide the channel and source of hydrocarbon seepage. The accumulation and seepage of subsea shallow-layer gas results from the upward migration of fluids from deep-layer pores, and the sub-sea survey area is still at tiny seepage stage.
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  Pyrolysis experiment and reservoir-forming potential of epimetamorphic rock

  Yang Chun; Dai Jinxing; Chen Hanlin; Luo Xia and Zheng Junwei

  , 2009, 36(2): 1702-0.

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  By taking pyrolysis experiments and analyzing composition and carbon isotopes of pyrolysis products,the hydrocarbon generation potential and products of very low-grade epimetamorphic rocks were studied. The carbon isotopes of alkane gases are relatively heavier, when the reactant was in an abundant gas generation stage (450–550 ℃), e.g. the δ13C1 were -31.4‰–-22.3‰, carbon isotope series showed δ13C1<δ13C2<δ13C3 or δ13C1<δ13C2， δ13C3<δ13C2, and the common feature being δ13C1<δ13C2 and δ13CCO2<-10.0‰, indicating the biogenic features. These less negative carbon isotope compositions inherit from heavy carbon isotope of organic matters in these rocks. High temperature may result in carbon isotopes of alkanes partly reversing and the mechanism has been discussed in this paper, but it isn't clear yet. The reservoir-forming potential of very low-grade epimetamorphic rocks is discussed from the aspect of hydrocarbon generation. Gas generation potential of muddy slate at a depth of 4 115.47 m in Well Zhaoshen 6 reached 86.4 m3/t. It is predicted that the hydrocarbon generation intensity can be 20×108m3/km2 in areas of eastern Daqing placanticline where very-low grade epimetamorphic rocks are distributed, capable of forming gas pools of certain scales.
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  Space-time relationship of seismic data structure and hydrocarbon prediction

  Lin Changrong; Wang Shangxu; Ma Zaitian; Chen Shuangquan and Fang Minhua

  , 2009, 36(2): 1703-0.

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  There has been a new hydrocarbon prediction technology to use the space-time relationship of seismic data structure characteristics for reservoir prediction. The seismic data structure characteristics refer to the wave characteristics shown in the discrete amplitude data points of each seismic trace arranged by the order of time. Based on the space-time relationship of seismic data structure characteristics, we can interpret the oil and gas layers quantitatively and find the oil-gas distribution rules on the seismic profile, so as to further improve the precision of reservoir prediction. Through the study on the space-time relationship of seismic amplitude for the main gas layers found in Well Kela-2 in Kela-2 Gasfield and Well Puguang-5 in Puguang Gasfield, the gas-layer boundary can be identified clearly, providing a strong basis for reserves estimation. This research method applies well to the target layers with depth of 200-7 000 m and thickness of over 5 m, in the oil-gas provinces of various lithologies and sedimentary facies (marine, paralic and continental facies). The prediction accuracy can reach over 80% on average.
油气田开发
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  Methodology for estimation of CO2 storage capacity in reservoirs

  Shen Pingping; Liao Xinwei and Liu Qingjie

  , 2009, 36(2): 1704-0.

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  The CO2 storage in reservoirs is one of the most effective ways of reducing the greenhouse gas emission, which is based on the mechanisms of structural and stratigraphic trapping, residual gas trapping, dissolution trapping and mineral trapping. The CO2 storage capacity in oil reservoirs includes theoretical, effective, practical and matched storage capacities. In the estimation of the CO2 storage capacity in both waterflooding and CO2 flooding oil reservoirs, theoretical and effective storage capacities can be obtained by the material balance and analogy methods. The theoretical storage capacity represents the physical limit of what the reservoir system can accept. The effective storage capacity represents a subset of the theoretical capacity and is obtained by applying a range of technical cut-off limits to a storage capacity assessment which incorporate the cumulative effects of reservoir and fluid parameter. When the material balance method is used, the amount of CO2 dissolution is not negligible. In using the analogy method, the key is to determine CO2 utilization factor. Examples show that the method is simple and convenient for the estimation of the CO2 storage capacity in China.
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  Automatic demarcation of sequence stratigraphy using the method of well logging multiscale data fusion

  Li Xia; Fan Yiren; Deng Shaogui and Wang Tongshan

  , 2009, 36(2): 1705-0.

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  Strata division with well logging utilizes the abrupt changing points or regions of signals, while the changing law of the wavelet modulus maxima under different scales can exactly describe the position and modality of the changing points. Based on the idea of reconstruction of wavelet modulus maxima, the well logging data fusion method built on the multiscale edge detection principle is put forward and is applied to the quantitative demarcation of sequence stratigraphy. For case study, single logging curve and multiscale fusion curve in well A in Shengtuo Oilfield are processed by quadric spline wavelet and thereby sequence boundaries on different scales can be detected. The result shows: by demarcating sequence stratigraphic units with the multiscale fusion curve analysis, better effect could be obtained. The energy accumulation and distribution on the wavelet time-frequency graph could clearly reflect the boundaries and cycle types of parasequences and parasequence sets. All these researches provide a completely new method for the quantitative demarcation of sequence and its inner depositional features.
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  A new prediction model on production performance for polymer flooding

  Huang Xue; Liu Zhaoxia; Han Dong and Wang Qiang

  , 2009, 36(2): 1706-0.

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  To establish an effective production prediction model for polymer flooding, the characteristics and applicability of four typical prediction models in polymer flooding were analyzed, including Weibull model, generalized Weng’s model, Rayleigh model and HCZ model. On the basis of analyzing influential factors on polymer flooding production, several parameters were put into a new prediction model, such as polymer injection volume, development time and polymer concentration. The new model was used to predict the oil production of four polymer-flooding blocks in Daqing Oilfield successfully. The results show: All the coefficients of correlation between the actual production curves and the predicted curves were higher than 0.985; and the errors of predicted production peaks and corresponding polymer injection volumes were less than 3%. The prediction is reliable and the model is applicable to analyze the effect of polymer injection volume, polymer concentration and injection speed, etc. on the production in polymer flooding. Only a few parameters are required, and it is easy to calculate and use.
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  Pseudo threshold pressure gradient to flow for low permeability reservoirs

  Xiong Wei; Lei Qun; Liu Xiangui; Gao Shusheng; Hu Zhiming and Xue Hui

  , 2009, 36(2): 1707-0.

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  Rate-controlled Hg injection experiments, NMR core tests and core flooding experiments are carried out to study the low permeability cores from the Daqing and Changqing oilfields. The forming and affecting factors are studied to demonstrate why the pseudo threshold pressure gradient to flow should be overcome. Because of the boundary layer caused by interaction between solid and fluid and the micro throats of low permeability reservoirs, the pseudo threshold pressure should be overcome for fluid to flow in low permeability reservoirs. Few throats are involved in the flow and the seepage cross section area is also less at lower pressures. The throats number and the seepage cross section area increase with the increasing of flooding pressure. The pore structure and movable fluid saturation of low permeability reservoirs have remarkable influence on the pseudo threshold pressure to flow, the bigger the mainstream throats and the movable fluid saturation, the less the pseudo threshold pressure to flow. The pseudo threshold pressure gradient to flow is a characteristic parameter of nonlinear flow degree and seepage ability and it is a synthetic symbol of pore structure and movable fluid saturation.
石油工程
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  Security and stability control system for offshore platform power grid

  Zhang Jifen; Hu Peng and Liu Jun

  , 2009, 36(2): 1708-0.

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  The key technology for offshore platform power grid interlinked-Energy Management System (EMS) is studied in this paper. The perfect EMS control solutions are formulated and carried on by the studies of the control strategies of frequency control, voltage control, precedence load shedding, high frequency trip generator and communication failure etc. according to the power flow and fault simulation calculations against all kinds of working modes of the grid. The power supply effects before and after using the power grid interlink and EMS control are contrasted. Their application has improved the power supply reliability, boosting up the ability against impacts, decreasing the spare capability of generators, reducing the maintenance work, and saving investment.
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  Study on casing load in a casing-stratum system by elastoplastic theory

  Chen Zhaowei and Cai Yongen

  , 2009, 36(2): 1709-0.

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  Casing load is studied with the elastoplastic theory in a casing-stratum system under uniform in-situ stress. The solutions of displacements and stresses of the elastic and plastic region for a thick-walled cylinder are deduced with the Mohr-Coulomb criterion, from which the solutions for the Tresca criterion can be deduced directly. On the basis of the solutions, the casing load and the limit in-situ stress are studied in a casing-stratum system when stratum or casing is in plasticity separately. Analysis shows that when stratum is in plasticity, casing load is lager than that of elastic solution (3%), while, when casing is in plasticity, casing load is less than that of elastic solution (6%). The results can be applied in casing design and casing load calculating under uniform in-situ stress.
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  Experiment and finite element model for optimizing pressure difference of hydraulic fracture well test

  Zhao Haifeng; Chen Mian and Jin Yan

  , 2009, 36(2): 1710-0.

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  After studying the shut-in pressure sensitivity of fracture capacity through experiment, a monoletus finite element model and a finite element model considering natural fractures are established to optimize pressure difference of hydraulic fracture well test. The finite element models established can simulate the stress distribution around hydraulic fractures and the production rate. Taking Well A in the Tazhong Oilfield as an example, there are two key factors in determining the reasonable pressure difference. One is to avoid the collapse of proppant and acid etching formation, and one upper limit of pressure difference can be drawn from the strength check of proppant and acid etching formation, which is 9.0 MPa. The other is that the selected pressure difference should produce high well test rate, the inflexion on well test rate-pressure difference curve corresponds to another upper limit of pressure difference, which are 8.8, 8.2 and 6.6 MPa for monoletus model, model with parallel natural fractures and model with vertical natural fractures, respectively. The smaller upper limit is the optimized value. From comparing calculation and actual data, it is shown that the relative positions of natural and hydraulic fractures affect the rate prediction.
学术讨论
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  Review on inorganic origin of oil and gas in China: Reply to Mr. Zhang Jinglian

  Wang Lansheng

  , 2009, 36(2): 1711-0.

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  Argument on organic or inorganic origin of oil and gas should be based on scientific methods and practices. Metal-organic compounds are formed by metal and organic compound coexisted. There is no sufficient evidence proving that the isotope assay for Pb, Sr and Nd can reveal the age and formation conditions of metal-organic compounds, or that they can indicate the age and formation conditions of the organic compounds. Metal-organic compound is not the source of crude oil, and the metal can not be deemed to generate crude oil. It just can be considered that the crude oil evolves from the organic compound in metal-organic compound; however, it is not sufficient to prove the inorganic origin of oil and gas. Besides, Fischer Tropsch reaction has a relatively simple procedure which needs strict conditions such as catalysts, temperature and pressure, and its reactants and products are simple. The reactants are only CO (or CO2) and H2, and the products are hydrocarbons with low molecular weight. Fischer Tropsch reaction can not generate all hydrocarbon components in oil and gas widely used as energy today. So Fischer Tropsch reaction can not prove that all oil and gas is of inorganic origin either.