New evidence for the origin of natural gas in Ordos Basin from hydrocarbons of oil water New evidence for the origin of natural gas in Ordos Basin from hydrocarbons of oil water

New evidence for the origin of natural gas in Ordos Basin from hydrocarbons of oil water

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  • 论文作者:Hou Dujie,Li Xianqing,Tang You
  • 作者单位:Jianghan Petroleum University
  • 更新时间:2020-09-15
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论文简介

NOTESthaNew evidence for the origin oftill many disputes about the origin of natural gas. Thnatural gas in Ordos Basinmain focus is two important source rocks, such as UpperPaleozoic strata (Carboniferous Permian system) andLower Paleozoic strata (Ordovician system). Most schol-from hydrocarbons of oilars agree that the gas in Ordovician weathered crust iswaterderived from the mixing source. There are two differentviewpoints about the main source of natural gas. Onel2*HOU Dujie, LI Xianqing & TANG Youjunconsiders that the Changqing gas field is mainly derivedfrom Carboniferous-Permian period coal-bearing strata,Jianghan Petroleum University, Jingzhou 434102, China (e-mail: hdj@mailjhpu.net)belonging to coal-derived gas. For example, Bei9 pro-posed that the carbon isotope of ethane in the side gasAbstract The chief aim of the present work is to investi-field is -25.74 %and -27.14 %in the middle of gas field.gate the controversy origin of natural gas in the Ordos BasinThese characteristics show that the gas has a mixing sour-by using the hydrocarbons of oil water. New evidence hasce which is mainly from humic organic matter. Xial51 sug-been found: There is relatively high content of light hydro-gested that the gas be mainly derived from Upper Paleo-carbons and low content of heavy components in the hydro-zoic strata. Moreover, the Carboniferous carbonate maycarbons fraction of oil water in the middle gas field of theMajiagou Formation, Ordovician reservoir. The hydrocar-also have contribution to the gas generation. Anotherbons of oil water in Well Shan 12 and Well Shan 78 haveviewpoint6" 8] is that the natural gas is mainly from Ordo-relatively high abundance of tricyclic terpane. Tricyclic ter-vician carbonate. Huang'ltries to set up the method andpane/hopane of the two samples are 1.48 and 0.36, respec-parameters of gas correlation for this study. He approvedtively. They also show that pregnane and hompregnane arethat the gas is mainly derived from Ordovician carbonatein relatively high abundance with lower hopane/sterane ratio.by using the carbon isotope data. Actually, he also agreedPr/Ph is less than 2.0. These characteristics reflected thesource input of marine carbonate sedimentary environment.that the gas mainly from Carboniferous Permian coal wasIn contrast, the hydrocarbon of Well Shan 81 is lack of tricy-found in the eastern part of gas field. Li Jian (1998) pro-clic terpane series and pregnane. It has a high ho-posed that the gas is mainly in the range of sapropelicpane/sterane ratio and Pr/Ph is 3.27. These parameters areorganic matter source input based on the carbon isotopetypical character of terrestrial organic matter. Furthermore,data of methane and ethane in the Majiagou Formation,the hydrocarbons of oil water in Well Shan 37 and Well ShanChangqing gas field (personal communication). In addi-34 is between the two typical situations. They have lttlecontent of tricyclic terpanes. They may be derived from ation, some of gases are in the range of mixing source.mixing source of marine carbonate and terrestrial organicThese characteristics prove that gas is mainly from Ordo-matter input. Similarly, the maturity parameters approvevician source rock and parts of gas are derived from Car-this suggestion. The samples of Well Shan 12 and Well Shanboniferous-Permian coal-bearing strata. To sum up, there78 which derived from marine carbonate have relatively highare still lots of dispute about the origin of gas. Some rea-maturity and samples derived from terrestrial organic mat-sons may be multi-explanation of geochemical parameterster have lower maturity. The maturity of the hydrocarbonsand complex source input in this region. Therefore, moreof mixing source is between these two situations. The sugges-tion coincides with the geological background and sourcework is still needed to study the origin of natural gas.rocks distribution.As we know, the formation water plays an importantKeywords: oil water, hydrocarbons of oil water, origin of natural gas,role in the petroleum generation, migration, and accumu-Ordos Basin.lation. The composition of formation water has a closerelationship with oil and gas pools. The natural gas mayThe Ordos basin is one of the large and importantdissolve in the formation water which depends on tem-basins in China. It is located in the Paleozoic platform andperature, pressure and character of formation water. Thebelongs to a craton basin, which is congruence of theorganic matter generates hydrocarbons in the media ofPaleozoic depression in the edge of platform and Ceno-water and other geological media and the oil gas pools arezoic and Mesozoic depression within the platform. Thecontacted with formation water in the long geologicalimportant natural gas discovery of Well Shancan 1 andscale. Some of hydrocarbons may exist in oil water whichWell Yu 3 was made in the central part of the basin, incan中国煤 化atural gs oigin. Itis the1989. This opens the prologue of natural gas explorationindicand it is often used forin the Ordos Basin". The Changqing gas field (called thepetrcHCN M H Gation. To our knowledge,Central Gas Field) is one of giant gas fields in China andthe hydrocarbons in oil water have not been used for thisthe study of gas origin arises broad attention. Many scien-study. This note will try to analyze some data of hydro-tists and scholars do a lot of work in this region. So far,carbons in oil water to provide some new geochemicalChinese S府亦数letin Vol. 47 No. 10 May 2002{PAGE }NOTESevidence for the origin of the Changqing gas field.low n-C1s are over dominated and there is a lower content1 Experimentalof n-alkanes above C. The distribution of n-alkane is asNature gas of the Majiagou Formation of theone peak and is narrower than that of the normal crude oil.Changqing gas field is a main research area. 30 oil waterThe n-alkane is in the C1 - C2s range with dominant n-Cjssamples have been analyzed, 5 of which have high abun-or n-C14 members. The parameter n-C2i /n-C22* is above10 and this reveals more light n-alkanes components. OEPdance of hydrocarbons.(_ 1) SPME and SPME/GC analysis. SPME is ais 0.98- -1.32. By using SPME/GC analysis, it has beennew technique used in geochemistry. It is mainly used forfound that hydrocarbons in oil water have relatively highrapid analysis of hydrocarbons in the formation water.abundance n-alkanes and branched alkane. There is a lttleSPME/GC analysis was carried out using Hewlett Packardcontent of cyclic alkane and aromatics. High abundance of6890 gas chromatograph. The extraction of SPME was 20hydrocarbons in oil water appears in Well Shan 37, Shanmin. Sample injection was for 4 min. The GC was fitted34, Shan 81, Shan 17 and Shan 11 -14. The distributionwith HP-5 capillary columns (30 m_ >0.32 mm. >0.25 um).of n-alkane is in the range of n-C3" -n-C17 with high n-The temperature of FID was 300.( and the oven tem-C2[ /C22+ value. There is a lower content of hydrocarbonsperature program was from 100.( to 300.( at 4.V/min.in Well Shancan 1, Shan 45 with dominant n-C1o member.Nitrogen was used as carried gas (1.0 mI /min).3 Characteristics of biomarker in the hydrocarbons .(- i) Bulk composition of hydrocarbons in oil water.of oil waterThe hydrocarbons of water have been separated by using(. 1) Terpanes.As a whole, an obvious differencechloroform extraction. Then the extract was separated intooccurs in the terpanes series, especially in the relativethree fractions by column chromatograph over silicaabundance of tricyclic terpanes to hopanes series. Highgel/AI2O3. The saturate fraction was eluted with ether, theabundance tricyclic terpanes appear in the samples of Wellaromatic hydrocarbons with dichloromethane and theShan 12 and Shan 78 (fig. (a)). The ratio tricyclic ter-polar compounds with chloroform/ethanol .pane/hopanes of two samples is 1 .48 and 0.36, respec-(i i) Gas chromatography (GC)._ The GC of satu-tively. The tricyclic terpane is in the Co-E29 range. C2rate was performed by using Hewlett Packard 6890. Theand C23 tricyclic terpane is relatively high in hydrocarbonsGC was ftted with HP-5MS capillary columns 30 m. >of Well Shan 12. Futhermore, the Co tricyclic terpane0.25 mm. >0.25 um). The sample injection temperatureis relatively high in the sample of Well Shan 78.was 300!( and the oven temperature programmedThe distribution of tricyclic terpane is in variousprogram was from 100.( to 300.( at 4:C/min.geological samples. Therefore, many scientists believeNitrogen was used as carried gas (1.0 mI /min). .that it may originate from cell membrane of protozoa(- i1) Gas chromatography/mass spectrometry (GC/based on their distribution and characteristic of the tricy-MS). GCMS analyses were performed by using Hewlettclic isoprenoid molecular structure. However, more andPackard 6890GC/5973MSD. The GC was fitted with HP-more researches concentrated on the tasmanite shale in the5MS capillary columns (30 m. >0.25 mm. >0.25 um). The10 years which verified high abundance of tricyclic ter-temperature of sample injection was 305'. ( and the ovenpane in tasmanite shale and its close relation with al-was held at 50.( for 2 min. The temperature programgl1 Paul recently detected very high abundance ofwas from 50.( to 100.( at 20.V/min and from 100.( to .C19一C28 tricyclic terpane in the separated tasmanite by310..( at 3!C/min. The temperature was then held atusing laser mirco-pyrolysis GCMS analysisl21. This result310( for 15.5 min. Helium was used as carried gas (1.0confirmed that algae is the main source of tricyclic tmL/min). Operating conditions were: ion source 230_(;panes. Based on the statistical results by Wang [13), someemission current, 34.6 μA; quadrupole temperature 150.(characteristics appear in the tricyclic terpane of carbonate.and electron energy 70 eV.The Paleozoic marine carbonate in northern China, the2 Chemical gross composition and n-alkane distribu-Ordos Basin and the Tarim Basin have relatively hightion of hydrocarbonsabundance of tricyclic terpane. Most of the samples haveThe bulk composition of hydrocarbons in oil water23 predominance and the ratio of tricyclic ter-has shown that there are high saturate (72.94%- -90.7 1%),pane/ petacyclic terpane is about 0.35 - -0.5. To sum uptheseappropriate content aromatics (4.29%- 1 7.77%) and non-中国煤化r)undance of tricyclic ter-hydrocarbons (5.00% - - 18.3%), very limited asphltene.panefrom marine carbonateCNMHGThe saturates/aromatics are in the range of 4.34- 21.15.:TYHLower molecular weight normal alkane is dominated inThere is a low content of tricyclic terpane in thethe whole-hydrocarbons GC analysis. The n-alkanes behydrocarbons of Well Shan 37 and Well Shan 34. Thehydrocarbons may derive from the mixing source of{PAGE } Chinese Science Bulletin Vol. 47 No. 10 May 2002NOTESmarine carbonate and terrestrial organic matter. In contrast,lower Pr/Ph ratios (- <2) in marine organic matter and highthe hydrocarbons in Well Shan 81 may be mainly relatedhopane/sterane and high Pr/Ph (. >3). The hydrocarbons into the terrestrial organic matter because this sample has aoil water of Well Shan 12 have relatively high abundanceminor content of tricyclic terpane and high Pr/Ph ratio.of tricyclic terpane and pregnane series, lower hopane/sterane (fig. 1(). Pr/Ph is 1.7. The overall charac-teristics reflected the marine carbonate source organic3.4 7matter input. On the other aspects, the samples in WellShan 8]Shan 81 do not have any tricyclic terpane and pregnane3.0-series and high hopane/sterane. Pr/Ph is about 3.27. This2.8-shows a feature of terrestrial organic matter source input.2.6-Based on this character, the hydrocarbons of Well Shan 372.4-nd Well Shan 34 have mixing source input.It should be mentioned that maturity could provide2.0-another evidence for this deduction. The maturity of Well1.8-Shan 34●Shan 78Shan 12Shan 12 and Well Shan 78 mainly derived from marine1.6Shan 37(8organic matter have relatively high maturity and Well0.0 0.20.40.60.8101.214 1.6Shan 81 derived from terrestrial organic matter has lowerTricyclic tepanes/hopanematurity. The maturity of hydrocarbons from the mixing0.5 7source is between these two extreme members. This coin-cides with the geological background because marine■Shan12.source rocks (Ordovician) have higher maturity than themain terrestrial source rock (Carboniferous-Permian).0.3-In general, the ratio of diasterane/regular steraneoften is used as identification of the source rock type of.2-oil, i.e. carbonate or clastic rock[141. The lower ratio indi-cates the anoxic and deficient-clay environments andcarbonate source rocks. Overall, the hydrocarbon in this. Shan 78region has a lower content of diasteranes series and theShan37{b0.0ratio of diasterane/regular sterane is lower than 0.1. This1.2 14 1.6 1.8 2.0 2.2 2.4 2.6 2.8may also shed light on the origin of hydrocarbons thatHopane/sterancmarine organic matter may play an important role in hy-0.50-drocarbon generation.0.48 -画0.46-4 Results出0.44-The formation water is an important media for三0.42.petroleum generation and migration. The formation waterShan 78盎0.40is contacted with oil and gas, so some organic matter is首0.38left in oil water. Analysis of this kind of organic matter员0.36can also give us some hints for natural gas origin.心0.34- Shan 81The light n-alkane components are rich and limited0.32■Shan 37heavy n-alkane components are typical characteristics of(e)0.30hydrocarbon of oil water in the Majiagou Formation, Or-0.34 0.36 0.38 0.40 0.42 0.44 0.46 0.48 0.50 0.52 0.54 0.56dovician. Most of samples have light n-alkanes (- C20 n-Fig.1. The geochemical parameters of hydrocarbons in oil water.alkanes).The sample of Well Shan 12 and Well Shan 78 have(- i) Steranes. Sterane is a typical biomarker de-rived from eukaryote and hopane is another kind of bio-relatively high abundance of tricyclic terpane. The ratio oftricy1.48 and 0.36. These twomarker from prokaryote. Therefore, the ratio of ho中国煤化工samDlarine organic matter. Thepane/sterane can clearly indicate the source input differ-YHCNMHGellShan34haveamixingence of hydrocarbons. Peters and Moldowan summarizesource. In contrast, the sample of Well Shan 81 is derivedthe characteristics of global marine and terrestrial organicfrom terrestrial organic matter because this sample doesmatter as follows!l4l: It often has lower hopane/sterane andnot have tricyclic terpane, with the highest Pr/Ph ratio.Chinese S府亦数letin Vol. 47 No. 10 May 2002{PAGE }NOTESThe hydrocarbons of Well Shan 12 have high abun-the Central gas field, Ordos basin, Acta Petrolei Sinica (in Chi-dance of pregnane series and lower hopane/sterane, lowernese), 1994, 15(2): 17. Huang Difan, Xong Chuanwu, Yang Junje, The origin type andPr/Ph. These characteristics reflected marine source input.source of natural gas in the Central gas field, Ordos basin, NaturalThe hydrocarbons of Well Shan 81 presents the feature ofGas Industry (in Chinese), 1996, 16(6): 1.high hopane/sterane, high Pr/Ph, traces of tricyclic terpane8. Xu Rongchang, The Theory of Natural Gas and Its Application (inand pregnane, which indicated terrestrial source input.Chinese), Bijing: Science Press, 1994.The maturity of biomarker and the ratio of diaster-9. Bei Feng, Wu Zheng, Song Zhenya, Organic Petrology Study ofane/regular sterane support the above hypothesis.Source Rock and Evaluation of Natural Gas Generation in the Or-dos Basin (in Chinese), Chengdu: Chengdu University of ScienceAcknowledgements This work was supported by the National“95"and Technology Press, 1995, 11 - 59.Science and Technology Research Project (Grant No. 99-1 10-01-03-02).10. Volkman, J. K., Banks, M. R.. Denwer, K. et al., Biomarker com-Referencesposition and depositional setting Tasmanite oil shale from north-ermn Tasmania, Australia, 14th International Meeting on Orgainc1. Dai Jinxing, Wang Tingbin, Song Yan, The Distribution and For-Geochemistry, Paris, September 18- -22, 1989, Abstract No.168mation Condition of Large and Medium-sized Gas Field in China11. Aquino Neto, F. R., Tniguis, J., Azevedo, D. A. et al, Organic(in Chinese), Beiing: Geological Publishing House, 1997, 81一geochemnistry of geographically unrelated Tasmanites, 14th Inter-100.national Meeting on Organic Geochemitry, Paris, September 182. Guan Deshi, Zhang Wenzheng, Pei Ge, Source rock of Ordovi--22, 1989, Abstract No.189.cian reservoir in the Central gas field, Ordos basin, Oil and Gas12. Paul, F. G., Khaled, R. A., Simon, C. G.,, Tricyclic terpenoid com-Geology (in Chinese), 1993, 14(3): 191.position of Tasmanited kerogen as determined by pyrolysis GC-. Zhang Wenzheng, Guan Deshi, Carbon Isotope Geochemistry ofMS, 2000, Geochimica Cosmochimica Acta, 2000, 64(7): 1249.Liquid Hydrocarbon Molecular Series (in Chinese), Beijing,13. Wang Tao, The Geological Theory and Practicse of Natural Gas inPetroleum Industry Press, 1997, 130- -162.China (in Chinese), Bejing: Petroleum Industry Press, 1997, 1041. Dai Jinxing, Xia Xinyu, Gas reservoir and source rock of Ordov--128.cian weathering crust, Front of Geology (in Chinese), 1999(6):195.4. Peters, K. E, Moldowan, J M., The Biomarker Guide: Interpret-5. Xia Xinyu, Hydrocarbon Potential Evaluation of Carbonates andng Molecular Fossils in Petroleum and Ancient Sediments, NJ:Source Rock Correlation of the Changqing Gas Field (in Chinese),Englewood Cliffs, Prentice Hall, Inc., 1993.Beijing: Petroleum Industry Press, 2000, 99 - -122.(Received September 13, 2001)Cheng Anding, Origin and migration of Ordovician natural gas in中国煤化工MHCNMHG{PAGE } Chinese Science Bulletin Vol. 47 No. 10 May 2002

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