In the calculation of shale gas resources/reserves,isothermal adsorption parameters are mainly determined by dry sample data at the laboratory temperature,and the regression effect of total organic carbon content(TOC)...In the calculation of shale gas resources/reserves,isothermal adsorption parameters are mainly determined by dry sample data at the laboratory temperature,and the regression effect of total organic carbon content(TOC)isothermal adsorption parameters is poor.Based on the physical significance of key parameters in Langmuir and Henry adsorption models,the problems in determining the isothermal adsorption parameters in the calculation of shale gas reserves/reserves are analyzed by taking the marine shale in the Upper Ordovician Wufeng FormingeLower Silurian Longmaxi Formation in the Sichuan Basin as an example.Based on a large number of measured isothermal adsorption data,the effects of TOC,temperature and water saturation on the shale gas adsorption parameters are analyzed.The influence model of TOC,temperature and water saturation on isothermal adsorption parameters of shale gas is established,and a novel method for calculating the adsorption parameters of shale gas from under experimental conditions to original reservoir conditions is proposed.The results are obtained as follows.First,there are problems in the calculation of shale gas resources/reserves,such as poor and contradictoryfitting relation between isothermal adsorption parameters and TOC,difficulty in the conversion of Van't Hoff equation,and difficulty in direct application of water saturation(Sw)in resource/reserves calculation.Second,the problem of poor directfitting relation between Langmuir pressure(pL)and TOC is solved by integrating the Langmuir adsorption model with the Henry adsorption model and by establishing a new parameter e Henry constant a for methane adsorption capacity of shale.Third,when Sw<40%,the Langmuir volume(VL)is linearly negatively correlated with Sw;when Sw<20%,a is constant relatively;by establishing the relationship between the normalized absolute adsorption capacity and Sw(<50%)under the pressure exceeding 30 MPa,the effect of Sw on the isothermal adsorption capacity can be calculated.Fourth,the in-situ stress in the Wufeng FormationeLongmaxi Formation shale reservoir affects the adsorption capacity of shale.For shale reservoirs with the same TOC,the higher the in-situ stress,the smaller the VL and a values.Under high pressure(>30 MPa),the effect of Sw on the methane adsorption capacity of shale shows a similar trend,and the effect of water molecules on the adsorption capacity on shale pore surface is constant.It is concluded that the proposed novel method for determining the isothermal adsorption parameters of shale with different TOC,temperature and water saturation conditions provides a technical support for the accurate calculation of shale gas resources/reserves and contributes to the scientific development of shale gas industry.展开更多
Analyzes on solid potassium mineral reserves calculation methods and existing problems of chaerhan salt lake,t with many parameters comparison solid potassium mineral reserves calculation results are reliable,the
Porosity is a key parameter in shale gas reservoir evaluation and reserve calculation and its accurate test is the basis for calculating geological reserves of shale gas and determining development plans.In order to c...Porosity is a key parameter in shale gas reservoir evaluation and reserve calculation and its accurate test is the basis for calculating geological reserves of shale gas and determining development plans.In order to clarify the differences between different porosity test methods and their influences on the calculation results of shale gas reserves,we collected 65 shale samples of Lower Silurian Longmaxi Formation from six shale gas wells in the Zhaotong National Shale Gas Demonstration Area of the southern Sichuan Basin for comparative experiments using three porosity test method,including gas injection porosimetry(GIP)method,water immersion porosimetry(WIP)method and nuclear magnetic resonance(NMR)method.Then,these three methods were comparatively analyzed based on the test results.Finally,it was proposed to optimize the key parameters of these three shale porosity test methods.And the following research results were obtained.First,in terms of the GIP method,the particle size of shale sample shall be in the range of 20–60 mesh and the helium saturation equilibrium time shall be over 1800 s.Second,in terms of the WIP method,the sample shall be dried for at least 48 h under 110°C and saturated for 24 h under the confining pressure of 15 MPa.Third,in terms of the NMR method,NMR porosity calculation shall not be conducted until the NMR signal of the dried sample is deducted,on the basis of echo time and waiting time optimization.Fourth,porosity average and median value obtained by these three shale porosity test methods follow the relationship of WIP porosity>NMR porosity>particle GIP porosity>plunger GIP porosity.Fifth,different shale porosity test methods have greater influences on the calculation results of shale gas geological reserves,whose difference can reach 20%.In conclusion,during the application of NMR method and WIP method,fluid is introduced for saturation,which may damage the shale pores.However,the particle GIP porosity can reflect the entire space of shale more comprehensively and is not influenced by the properties of the applied fluid.Therefore,it is suggested to adopt the particle GIP method to calculate shale gas geological reserves.展开更多
The Jiaoshiba shale gasfield is located in the Fuling area of the Sichuan Basin,with the Upper Ordovician Wufeng-Lower Silurian Longmaxi Fm as the pay zone.At the bottom of the pay zone,a high-quality shale gas reserv...The Jiaoshiba shale gasfield is located in the Fuling area of the Sichuan Basin,with the Upper Ordovician Wufeng-Lower Silurian Longmaxi Fm as the pay zone.At the bottom of the pay zone,a high-quality shale gas reservoir about 20 m thick is generally developed with high organic contents and gas abundance,but its resistivity is relatively low.Accordingly,the gas saturation calculated by formulas(e.g.Archie)using electric logging data is often much lower than the experiment-derived value.In this paper,a new method was presented for calculating gas saturation more accurately based on non-electric logging data.Firstly,the causes for the low resistivity of shale gas reservoirs in this area were analyzed.Then,the limitation of traditional methods for calculating gas saturation based on electric logging data was diagnosed,and the feasibility of the neutronedensity porosity overlay method was illustrated.According to the response characteristics of neutron,density and other porosity logging in shale gas reservoirs,a model for calculating gas saturation of shale gas was established by core experimental calibration based on the density logging value,the density porosity and the difference between density porosity and neutron porosity,by means of multiple methods(e.g.the dual-porosity overlay method by optimizing the best overlay coefficient).This new method avoids the effect of low resistivity,and thus can provide normal calculated gas saturation of high-quality shale gas reservoirs.It works well in practical application.This new method provides a technical support for the calculation of shale gas reserves in this area.展开更多
基金supported by the Scientific Research and Technol-ogy Development Project of PetroChina Company Limited,"Research on Geological Activity Evaluation Technology of shale gas Development Zone"(No.2022DJ80)"Research on Exploration and Development Technology of Marine shale gas"(No.2021DJ19).
文摘In the calculation of shale gas resources/reserves,isothermal adsorption parameters are mainly determined by dry sample data at the laboratory temperature,and the regression effect of total organic carbon content(TOC)isothermal adsorption parameters is poor.Based on the physical significance of key parameters in Langmuir and Henry adsorption models,the problems in determining the isothermal adsorption parameters in the calculation of shale gas reserves/reserves are analyzed by taking the marine shale in the Upper Ordovician Wufeng FormingeLower Silurian Longmaxi Formation in the Sichuan Basin as an example.Based on a large number of measured isothermal adsorption data,the effects of TOC,temperature and water saturation on the shale gas adsorption parameters are analyzed.The influence model of TOC,temperature and water saturation on isothermal adsorption parameters of shale gas is established,and a novel method for calculating the adsorption parameters of shale gas from under experimental conditions to original reservoir conditions is proposed.The results are obtained as follows.First,there are problems in the calculation of shale gas resources/reserves,such as poor and contradictoryfitting relation between isothermal adsorption parameters and TOC,difficulty in the conversion of Van't Hoff equation,and difficulty in direct application of water saturation(Sw)in resource/reserves calculation.Second,the problem of poor directfitting relation between Langmuir pressure(pL)and TOC is solved by integrating the Langmuir adsorption model with the Henry adsorption model and by establishing a new parameter e Henry constant a for methane adsorption capacity of shale.Third,when Sw<40%,the Langmuir volume(VL)is linearly negatively correlated with Sw;when Sw<20%,a is constant relatively;by establishing the relationship between the normalized absolute adsorption capacity and Sw(<50%)under the pressure exceeding 30 MPa,the effect of Sw on the isothermal adsorption capacity can be calculated.Fourth,the in-situ stress in the Wufeng FormationeLongmaxi Formation shale reservoir affects the adsorption capacity of shale.For shale reservoirs with the same TOC,the higher the in-situ stress,the smaller the VL and a values.Under high pressure(>30 MPa),the effect of Sw on the methane adsorption capacity of shale shows a similar trend,and the effect of water molecules on the adsorption capacity on shale pore surface is constant.It is concluded that the proposed novel method for determining the isothermal adsorption parameters of shale with different TOC,temperature and water saturation conditions provides a technical support for the accurate calculation of shale gas resources/reserves and contributes to the scientific development of shale gas industry.
文摘Analyzes on solid potassium mineral reserves calculation methods and existing problems of chaerhan salt lake,t with many parameters comparison solid potassium mineral reserves calculation results are reliable,the
基金supported by the National Major Science and Technology Project“Quantitative characterization and evaluation of shale reservoirs”(No.2017ZX05035002-002).
文摘Porosity is a key parameter in shale gas reservoir evaluation and reserve calculation and its accurate test is the basis for calculating geological reserves of shale gas and determining development plans.In order to clarify the differences between different porosity test methods and their influences on the calculation results of shale gas reserves,we collected 65 shale samples of Lower Silurian Longmaxi Formation from six shale gas wells in the Zhaotong National Shale Gas Demonstration Area of the southern Sichuan Basin for comparative experiments using three porosity test method,including gas injection porosimetry(GIP)method,water immersion porosimetry(WIP)method and nuclear magnetic resonance(NMR)method.Then,these three methods were comparatively analyzed based on the test results.Finally,it was proposed to optimize the key parameters of these three shale porosity test methods.And the following research results were obtained.First,in terms of the GIP method,the particle size of shale sample shall be in the range of 20–60 mesh and the helium saturation equilibrium time shall be over 1800 s.Second,in terms of the WIP method,the sample shall be dried for at least 48 h under 110°C and saturated for 24 h under the confining pressure of 15 MPa.Third,in terms of the NMR method,NMR porosity calculation shall not be conducted until the NMR signal of the dried sample is deducted,on the basis of echo time and waiting time optimization.Fourth,porosity average and median value obtained by these three shale porosity test methods follow the relationship of WIP porosity>NMR porosity>particle GIP porosity>plunger GIP porosity.Fifth,different shale porosity test methods have greater influences on the calculation results of shale gas geological reserves,whose difference can reach 20%.In conclusion,during the application of NMR method and WIP method,fluid is introduced for saturation,which may damage the shale pores.However,the particle GIP porosity can reflect the entire space of shale more comprehensively and is not influenced by the properties of the applied fluid.Therefore,it is suggested to adopt the particle GIP method to calculate shale gas geological reserves.
文摘The Jiaoshiba shale gasfield is located in the Fuling area of the Sichuan Basin,with the Upper Ordovician Wufeng-Lower Silurian Longmaxi Fm as the pay zone.At the bottom of the pay zone,a high-quality shale gas reservoir about 20 m thick is generally developed with high organic contents and gas abundance,but its resistivity is relatively low.Accordingly,the gas saturation calculated by formulas(e.g.Archie)using electric logging data is often much lower than the experiment-derived value.In this paper,a new method was presented for calculating gas saturation more accurately based on non-electric logging data.Firstly,the causes for the low resistivity of shale gas reservoirs in this area were analyzed.Then,the limitation of traditional methods for calculating gas saturation based on electric logging data was diagnosed,and the feasibility of the neutronedensity porosity overlay method was illustrated.According to the response characteristics of neutron,density and other porosity logging in shale gas reservoirs,a model for calculating gas saturation of shale gas was established by core experimental calibration based on the density logging value,the density porosity and the difference between density porosity and neutron porosity,by means of multiple methods(e.g.the dual-porosity overlay method by optimizing the best overlay coefficient).This new method avoids the effect of low resistivity,and thus can provide normal calculated gas saturation of high-quality shale gas reservoirs.It works well in practical application.This new method provides a technical support for the calculation of shale gas reserves in this area.
