advances in unconventional shale gas resources_lectures910_gas generation kinetics anddetermination of gas maturity and agin

,*,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,Click to edit Master title style,Click to edit Master text styles,Second level,Third level,Fourth level,Fifth level,Click to edit Master title style,Oct. 04, 2010,*,Oct. 04, 2010,Gas Generation Kinetics and,Determination of Gas Maturity and Aging,Tongwei Zhang et al.,Bureau of Economic Geology,The University of Texas at Austin,Oct. 04, 2010,Principle of Petroleum Generation Kinetics,Theorems,petroleum generation is the result of a large number of chemical reactions leading from kerogen to liquid and gaseous products of lower molecular weight and to residues of increasing degree of condensation,these reactions are governed by the basic laws of chemical kinetics,Sedimentary basins as chemical reactors,feedstock,products,T, P, catalysts, transport,SOM,petroleum,Lack of active process control must becompensated by intelligent analysis and reconstruction of reaction conditions in time and space,active process control,Order of Reactions,1,st,order,2,nd,order,n,th,order,TTI Approach (empirical),Reaction rate doubles at 10 C temperature increase (”rule of thumb”),Lopatin (1971); Waples (1980),Statistical thermodynamics; partition functions,Activated complex,E,A,- activation energy bond energy,A,- pre-exponential factor (“frequency factor”) probability of bond cleavage,Arrhenius relationship (semi-empirical),Comparison TTI - Arrhenius Approach,Arrhenius diagram,Kerogen degradation and hydrocarbon generation (activation energy distribution),kerogen,oil,CO,2,H,2,O, etc.,carbon residue,after Tissot & Welte (1984),CO,2,H,2,O, H,2,S, etc.,gas,carbon residue,k,11,k,12,k,1i,k,1m,k,21,k,22,k,2j,k,2n,Activation energy distribution,Kinetic isotope effects during natural gas generation,Individual 1st order reaction rate coefficients for,12,C and,13,C,isotopic species,Kinetic isotope effects during natural gas generation,Assuming:,Isotope fractionation,Oct. 04, 2010,Gas Geochemistry in Tarim Basin, China,Tectonic Elements and Gas Fields in the Tarim Basin, China,A,A,A Main Component is Methane in Natural Gases, Tarim Basin,Contents of Ethane and Propane are varied significantly in the Natural Gases,No obvious difference in ethane and propane contents was observed for coal-type gas and oil-type gas in the Tarim basin. So, it is hard to differentiate gas types based on the gas chemical composition,Carbon Isotopic Compositions are Effective Indicators for Gas Origin Identification,Coal-type gas posses heavier carbon isotopes of ethane and propane compared with oil-type gas.,A positive relationship of,d,13,C,2,and,d,13,C,1,and,d,13,C,3,suggests that the thermal genetic gases from organic matter cracking under high temperature and pressure are a dominant source in the Tarim basin.,GOR-isotope quantitative model can apply to the understanding of natural gas formation and gas filling history.,Kerogen,+,Primary Remain Gas,Secondary C racking,Gas/Oil,Primary Expelled Gas,Gas/Oil,Gas/Oil,Secondary Remain Gas,Gas/Oil,Secondary Expelled Gas,Possible Scenario of Gas Generation and Modeling,Flow Chart for Gas Generation Kinetics Investigation,kerogen,gold-tube,pyrolysis,kinetics fitting,extrapolation,Immature source,Gas Yields and Carbon,Isotopes Measurement,Ea: activation energy,Af: frequency factor,Timing of gas generation,migration and accumulation,Geochemical Properties of Jurassic Coal Selected for Simulation,sample,percentage,TOC,d,13,C,HI,(%),(%),(,),(mgHC/gTOC),Coal (Ro =0.4%),67.4,-24.3,238,vitrinite,42.3,66.1,-24.8,157.8,fusinite,42.3,68.3,-24.6,32.6,semi-fusinite,70.4,-24.6,33.7,Exinite,10,74.5,-24.8,464.2,Mathematical Expression for,Gas Generation Kinetics,is the conversion of CH,4, k is rate constant, R is gas mole constant, E is activation energy. E,0,is mean activation energy.,controls the shape and is activation threshold. controls the width of the distribution.,is the gamma function, 01/1. A is the prefactor.,Gas Generation From Coal Anhydrous Pyrolysis at Two Different Heating Rates,Gas Yield (mg/g TOC),Temperature (C),C,1,C,2,C,3,Activation Energy Distribution of Gas Generation From Jurassic Coal,Carbon isotopes of C,1,C,2, C,3,from organic matter thermal cracking under non-isothermal,pyrolysis,Theoretical basis for carbon isotope fractionation model,Carbon isotope kinetics model of C,1, C,2,and C,3,generation from organic matter thermal cracking,Carbon Isotope Kinetics of Natural Gas Generation,Carbon Isotopes of Gases From Coal Anhydrous Pyrolysis at Two Different Heating Rates,13,C (, PDB,),Temperature (C),C,1,C,2,C,3,The fractionation factor between,13,C-,12,C bond and,12,C-,12,C becomes less with heated temperature decreasing, and this shows that large fractionation exists at lower temperature and small fractionations exists at higher temperature.,According to Tang et al, GCA 2000,Laboratory pyrolysis data can not be directly compared with geological data. Only through extrapolation of kinetic gas isotope fractionation, can one use pyrolysis data to predict gas isotope changes with time and temperature.,Observed Gas Isotope Fractionations in the Laboratory and Nature,d,13,C,Geological Temperatures,Laboratory Temperatures,Smaller Fractionation,Larger Fractionation,Temperature,d,13,C,Temperature,Extrapolation of kinetic gas isotope fractionation obtained from pyrolysis data is able to predict gas isotope changes with time and temperature under geological condition.,Kinetics Parameters of Isotope Fractionations For Basin Modeling,d,13,C,C,1,C,2,C,3,Alpha(1),1.02,1.02,1.02,BetaLow (cal/mol),1,10,10,BetaHigh (cal/mol),85,80,80,Eo (kcal/mol),59.4,61.4,61.6,Sigma (% Eo),22.3,37.9,30.9,Gamma (,),-30.1,-21.2,-23.0,Oct. 04, 2010,Geological Application of GOR-Isotope Model in Tarim Basin,Timing of Gas formation and Expulsion,Gas filling history,Gas thermal maturity,Gas reserves estimation,Gas recharging time,Burial Thermal History of Jurassic Source Rock in the Tarim Basin,Time-Temperature curve of the bottom of Jurassic source,Burial history curve,According to Liang et al. 2003,Modeling Carbon Isotopes of Expelled Gases from Jurassic Coal Match with Geological Observation of Natural Gases in Reservoirs,d,13,C,1,d,13,C,2,d,13,C,3,d,13,C,2,Carbon isotope model of expelled gases from Jurassic coal,Thermal Maturity of Coal-type Gas in Tarim Basin,significant contribution from secondary cracking,1.17,1.35,1.5,1.6,1.83,2.02,Primary gas from kerogen cracking,C,1,/(C,2,+C,3,) vs,d,13,C,2,Gas Reserves Prediction By Gas Geochemistry Isotope Model,Expelled gas amount from the Jurassic coal,500,1000,1500,2000,2500,Kela 2 Large-size Gas Field Was Probably Charged About 2 mybp,Ro 2.2%,KL2 gas field was charged about 2mybp,Conclusions,Petroleum and natural gas generation in sedimentary basins is a kinetically controlled process which can be simulated at laboratorys high temperature condition.,Kinetically fractionation model on gas composition and isotopes derived from laboratory simulation can be extrapolated to geological condition at a given geological heating history.,Quantitative kinetics model provides a useful tool for dynamically understanding gas recharging history, determining gas maturity, predicting gas reserves and recharging time in an effective trap.,The recharging of Kela 2 large-sized gas field probably occurred about 2my before present time.,Expelled gas retained in the Jurassic coal until faults as gas migration pathway became available at about 2mybp.,