Quantitative Reserch Of Fluid Inclusions By Laser Raman And Infrared Spectroscopy

The various geological information contained in fluid inclusions is the code of relevant geological processes?P,T,pH,X,W,S etc.?.Various data of fluid inclusions obtained by spectral quantitative analysis and study of geological processes in the crust and mantle in combination with other geological technology,have always been the frontier and hotspot in earth science research.In this paper,the quantitative technique of laser Raman spectroscopy is used to study several CO₂-bearing oil and gas reservoirs in Lishui sag,East China Sea Basin.This paper not only discussed the Raman quantitative method of different material composition in CH₄-CO₂-H₂O-NaCl geological fluid system,but also makes use of comprehensive methods such as carbon isotope analysis,petrography of inclusions,microthermometry data,burial history simulation,seismic interpretation and tectonic evolution,etc to solve the charging regularity of hydrocarbon gas and carbon dioxide accumulation in Lishui sag and can provide a new technical research method for fluid accumulation rules in this kind of carbon-bearing oil and gas sedimentary basin.A Fourier transform infrared spectroscopy?FT-IR?quantitative model of single component for methane?at 40-200?,2-50 MPa?and carbon dioxide?at 40-120?,6-50 MPa?were established for the first time.Quantitative method of Fourier infrared spectroscopy were applied to several natural methane fluid inclusions in quartz veins of central Alps and synthetic carbon dioxide inclusions?FSCC?.This technique opens the door of Fourier infrared spectroscopy quantitative technology,and compares the advantages and disadvantages between Fourier infrared spectroscopy and Laser Raman technology,which lays a foundation for further Fourier infrared spectroscopy quantification of methane and carbon dioxide system.Several following insights were finally achieved:Spectral quantitative analysis of fluid inclusions:1.Raman quantitative calibration curve of pure CO₂ system?at 160?,3-50 MPa?and H₂O dissloved in CO₂ system?at 160?,10-50 MPa?have been established.The quantitative method of fluid inclusions under the seven kinds of material composition system of CO₂,CO₂-H₂O,CO₂-H₂O-NaCl,CH₄,CH₄-H₂O,CH₄-H₂O-NaCl,CH₄-CO₂are discussed,which are the theoretical basis for further geological application.2.Micro FT-IR combine with HPOC technology were used to study the variation characteristics of the methane stretching vibration bands?P,Q,R?in the temperature range from 40 to 200? and pressure range from 2 to 50 MPa for the first time.Area,Full Width Half Maximum?FHWM?,Height Ratio?R/Q,P/Q?and peak shifts?P,Q,R?were used to study the relation between the quantitative infrared parameters and pressure/density.Methane calibration models with different infrared parameters were established.3.Through Micro-FT-IR and HPOC technology,to study variation characteristics of vibration stretching band?2v₂+v₃ and v₁+v₃?CO₂ under temperature scope?40 to 120??and pressure scope?2 to 50 MPa?,the relationship between area and pressure/density are established.Calibration model of infrared area parameters was set up and discussed the peak shift variation.Geological applications:There are many CH₄ and CO₂ mixed gas reservoirs in Lishui sag of the East China Sea basin.The Laser Raman quantitative analysis of fluid inclusions is the core method combined with the lithofacies analysis under the microscope,comprehensive methods of burial history evolution and tectonic and sedimentary evolution of sedimentary basins are as follows:1.By polarizing microscope,scanning electron microscope and observation of mineral cathodic luminescence,it is found that the reservoir sandstone in Lishui sag is mainly volcanic clastic sandstone,a few is feldspathic lithic sandstone.The pyroclastic content of well LS35-7-1d and WZ13-1-1 are higher than that in the LS36-1 structure.The main minerals include quartz,feldspar,cuttings,calcite,dolomite,sapphire,etc.Mineral paragenetic sequence is clay mineral cladding,siderite,pyrite,kaolinite,secondary quartz growths,micro-crystalline,ankerite,bitumen,dawsonite,calcite.2.CO₂ gas reservoirs in Lishui sag can be divided into two categories according to the CO₂ content:Type I content is between 90%and 100%;Type II content is between30%and 60%.On the plane,CO₂ gas reservoirs are mainly distributed in the western depression and the Lingfeng buried hill,longitudinally,mainly distributed in Mingyunfeng formation and Lingfeng formation.The CO₂ gas in Lishui sag is mainly inorganic,and the gas source is mainly derived from the mantle,which is closely related to mantle-magmatic activity.In the LS 36-1 tectonic zone,CH₄ is an organic origin,CO₂is organic and inorganic mixed origin,it is dominated by inorganic origin.Inorganic CO₂is derived from crust-mantle source and dominated by mantle source.CO₂ in WZ 13-1-1and LS35-7-1d are inorganic origin?mantle-derived?.Carbon isotope analysis shows that the source of CO₂ in two kinds of CO₂-bearing wells is mainly inorganic-mantle source.3.The secondary fluid inclusions in Paleocene reservoirs of Lishui sag mainly exist in quartz grain fractures and quartz growths.Fluid inclusions can be mainly divided into four categories:First type is brine solution inclusions.It is liquid phase saline solution inclusions;Second type is CO₂-bearing fluid inclusions,which is divided into pure CO₂inclusions,rich CO₂ inclusions,dissolved CO₂ in water inclusions;Third type is CH₄-bearing fluid inclusions,which is divided into pure CH₄ inclusions,rich CH₄ inclusions,dissolved CH₄ in water inclusions and CH₄ aqueous inclusions containing solid organic particles;Fourth type is CO₂ and CH₄ mixed gas fluid inclusions,including CO₂ and CH₄mixed gas inclusions and CO₂ and CH₄ aqueous inclusions.Homogenization temperature?T_h?distribution of the CO₂-bearing fluid inclusions in the three structures is relatively consistent.It mainly focuses on 120 to 160? and 200 to 230?.The homogenization temperature of CH₄-bearing fluid inclusions of LS 36-1 structure and LS 35-7-1d are mainly in the range of 100 to 130? and 140 to 160?.The homogenization temperature of CO₂ and CH₄ mixed inclusions were mainly 80 to 100?.4.The total density of CO₂-rich inclusions and pure CO₂ inclusions in the western depression of Lishui sag are mainly divided into three categories:Low-density CO₂ fluid?⁰.15 g/cm³ or less?,medium-density CO₂ fluid?⁰.45 g/cm³?,and high-density CO₂fluid?⁰.75 g/cm³?.Variation of density shows a decreasing trend with the increase of homogenization temperature.The salinity values of aqueous inclusions in LS36-1 and LS35-7-1d range from 0.6 to 6.6 wt%,the salinity values of aqueous inclusions in WZ13-1-1 less than 2.4 wt%.The homogenization temperature of low-salinity inclusions is 112to 146?,but homogenization temperature of high-salinity inclusions?<6.6 wt%?is 122to 153?.Overall,homogenization temperature increases as salinity increases.Methane gas inclusions in LS 36-1 can be divided into two types:low-density methane fluids?approximately 0.1 g/cm³ or lower?,homogenization temperature range of coeval saline inclusions is 92.3 to 107.3?,and high-density methane fluids?higher than 0.115 g/cm³?,the homogenization temperature range of coeval saline inclusions is 97.8 to 116.9?.5.First charging stage of CO₂ fluid in LS36-1 was in the Late-Paleocene?58-57 Ma?,and second charging stage of CO₂ fluid was in the Miocene?21-4 Ma?.LS35-7-1d also recorded two stages of CO₂ injection events,the first stage in the Late-Paleocene?61-59Ma?,and the second stage of CO₂ injection in the pliocene?5-3 Ma?.WZ13-1-1 has two stages of CO₂ injection,the first stage was in the Late-Paleocene?⁶0 Ma?,and the second stage was in the Pliocene?3-1 Ma?.In LS36-1 structure,the first stage of methane fluid injected in gas reservoir in Late-Oligocene,during which traps were formed,CO₂ was formed in the 21-4 Ma reservoir,and methane gas in the first stage was displaced;after secondary hydrocarbon generation,the second stage of methane fluid injected in gas reservoir?8-1 Ma?,partially displacing early CO₂ fluid and forming current gas reservoir.In LS35-7-1d,methane gas was formed in Oligocene,and CO₂ injection in the late stage occurred at 5-3 Ma,displacing early methane gas reservoirs formed and forming present gas reservoirs.Pure CH₄ natural fluid inclusions in the quartz vein of central Alps region are applied in geology by method of micro-fourier infrared spectroscopic quantitative analysis,and the feasibility of Fourier infrared quantitative analysis is compared.6.In the central Alps region of Switzerland,there are four fluid regions,among which methane fluids undergoed oxidation reaction,and the fluid moves to the water area and carbon dioxide area.At 40?,the Q peak shifts of methane?v₃?band were collected to determine densities and trapped pressures of natural methane fluid inclusions.These pressure intervals are located at the end of the methane zone,indicating that the transition from CH₄ to H₂O-?CO₂?zone is not pressure-controlled.At the same time,the Fourier infrared spectra and Raman spectra at room temperature of a single pure methane natural inclusion were collected at the same time to determine its density.Meanwhile,the density deviation obtained by the two type spectral analysis techniques were very small.7.By Fourier infrared spectrum quantitative techniques of single CO₂ component,collecting 2v₂+v₃ and v₁+v₃ stretching vibration double bands area to determine FSCC synthetic pure CO₂ inclusions density under 40?.And at room temperature,collect the Raman spectra of inclusions to compare their data.Density calculation of two kinds of spectrum analysis technology have small deviation,in the range of allowable error.