Research On Logging Recognition Method For Complex Fluid Properties

As a new clean energy,natural gas is consuming more and more in domestic and global areas.In recent years,the consumption and exploitation of natural gas in China are increasing rapidly,and the demand market for natural gas has great potential for development.The fluid properties in the study area are extremely complex,including conventional gas reservoir,condensate gas reservoir,light oil reservoir and high CO₂-bearing gas reservoir.For a long time,how to effectively distinguish CO₂ non-hydrocarbon gas reservoir and hydrocarbon gas reservoir,as well as oil reservoir,condensate gas reservoir and conventional gas reservoir by logging method is the key problem to be solved urgently in the study area,and its accurate identification is the key of subsequent production evaluation and development means.Firstly,a fine interpretation model of reservoir parameters is established,and the accurate calculation of these parameters is the basis of the quantitative evaluation method of fluid properties.The calculation model of regional porosity is based on the idea of optimization,and the formation component analysis model is adopted.This method takes into account a variety of logging and geological factors.The calculation results are more accurate than single logging method.Permeability is first divided into two types of reservoir by flow unit,one is the first type of reservoir and the other is the second type of reservoir.The intersection chart method is used to realize automatic identification of reservoir types,and the permeability model is constructed according to reservoir types.Because the reservoirs in this area are sandstone and mudstone reservoirs,the mudstone content in the reservoir section is less,and some wells contain a small amount of limestone,the classical Archie formula is used to calculate water saturation and the results are consistent and reliable compared with those calculated by non-electric method.This study evaluates reservoir fluid properties from qualitative and quantitative aspects.Qualitatively,the logging response characteristics of different fluid properties are analyzed,and the applicability of various logging methods to fluid properties identification is analyzed from the principle.Finally,apparent porosity and light-heavy hydrocarbon ratio are selected as characteristic parameters,and a qualitative identification chart of fluid properties is established,which can qualitatively distinguish hydrocarbon gas reservoir,CO₂ non-hydrocarbon gas reservoir,conventional gas reservoir,condensate gas reservoir and oil reservoir.Quantitative aspects include the calculation of hydrocarbon gas content and the quantitative calculation of gas-oil ratio.The method of calculating hydrocarbon gas content is firstly studied and the method of calculating the density of methane,carbon dioxide,neutron and acoustic logging response values under formation conditions is obtained.Quantitative calculation of hydrocarbon gas and non-hydrocarbon gas content can be made by means of formation component analysis model and optimization theory,and hydrocarbon gas and non-hydrocarbon gas can be well distinguished by logging data.Quantitative calculation method of gas-oil ratio is studied and the method of calculating gas-oil ratio under surface conditions by using gas state equation is obtained.Then the correlation between derived parameters and gas-oil ratio is analyzed.The quantitative relationship between gas-oil ratio and derived parameters Xh and Yh is fitted.This equation can be used in the calculation of optimum component content and realizes the comprehensive utilization of logging data to calculate the gas-oil ratio.Finally,the reliability of calculating reservoir parameters and identification of fluid properties are analyzed.Errors in calculating porosity and permeability are within the limits prescribed by the state.Hydrocarbon gas and non-hydrocarbon gas identification,in the 16 statistical layers,15 fluid types identified by logging are consistent with the results of testing fluid types,which shows that calculating hydrocarbon gas content can better distinguish hydrocarbon gas and CO₂ gas layers.Conventional gas reservoir,condensate gas reservoir and oil reservoir identification.Among the 20 statistical layers,16 layers,accounting for 80%of the total,consistent with the result of testing data by calculating gas-oil ratio from logging data.Finally,it provides a reliable method and technology for the identification of regional fluid properties,and has a good application value.