By measuring the variation of the P-and S-wave velocities of tight sandstone samples under water saturation,it was confirmed that with the decrease in water saturation,the P-wave velocity first decreased and then incr...By measuring the variation of the P-and S-wave velocities of tight sandstone samples under water saturation,it was confirmed that with the decrease in water saturation,the P-wave velocity first decreased and then increased.The variation in velocity was influenced by the sandstone’s porosity.The commonly used Gassmann equation based on fluid substitution theory was studied.Comparing the calculated results with the measured data,it was found that the Gassmann equation agreed well with the measured data at high water saturation,but it could not explain the bending phenomenon of P-wave velocity at low saturation.This indicated that these equations could not accurately describe the relationship between fluid content and rock acoustic velocity.The reasons for this phenomenon were discussed through Taylor’s expansion.The coefficients of the fitting formula were calculated and verified by fitting the measured acoustic velocity changes of the cores.The relationship between P-wave velocity and saturation was discussed,which provides experimental support for calculating saturation using seismic and acoustic logging data.展开更多
Bottom-simulating reflectors (BSRs) in seismic profile always indicate the bottom of gas hydrate stability zone, but is difficult to determine the distribution and features of gas hydrate sediments (GHS). In this stud...Bottom-simulating reflectors (BSRs) in seismic profile always indicate the bottom of gas hydrate stability zone, but is difficult to determine the distribution and features of gas hydrate sediments (GHS). In this study, based on AVA forward modeling and angle-domain common-image gathers we use prestack AVA parameters consistency inversion in predicting gas hydrate sediments in the Shenhu area at northern slope of South China Sea, and obtain the vertical and lateral features and saturation of GHS.展开更多
Acoustic and electrical methods are commonly used to evaluate hydrate saturation based on P-wave velocity(Vp)and resistivity,respectively.We evaluate hydrate saturation using petrophysical parameters directly related ...Acoustic and electrical methods are commonly used to evaluate hydrate saturation based on P-wave velocity(Vp)and resistivity,respectively.We evaluate hydrate saturation using petrophysical parameters directly related to the presence of hydrates.Five petrophysical parameters sensitive to hydrate saturation were first analyzed using the equivalent medium rock physical model,logging intersection plots,and petrophysical parameter inversion.The simulated annealing global optimization method was then used to estimate the hydrate saturation profile in the Shenhu Area,China.The petrophysical parameters Vp,λρ,andλμ,which are associated with the rock elastic and shear moduli,are highly sensitive to hydrate saturation for an estimated saturation range of 0.1-0.44.This range is consistent with that obtained from the original well diameter curves.However,the parameters Vs andμρ,which are only related to the rock shear modulus,yield high hydrate saturation estimates of 0.22-0.43 and exhibit some deviations from the real-time data.Owing to its sensitivity,the Poisson’s ratio is least desired for hydrate evaluation among the studied parameters.The sensitivity of hydrate saturation depends on the petrophysical model used for studying hydrate physical properties and storage analysis.展开更多
In this paper,we introduced parameterizations of the salinity effects(on heat capacity,thermal conductivity,freezing point and saturated vapor pressure) in a lake scheme integrated in the Weather Research and Forecast...In this paper,we introduced parameterizations of the salinity effects(on heat capacity,thermal conductivity,freezing point and saturated vapor pressure) in a lake scheme integrated in the Weather Research and Forecasting model coupled with the Community Land Model(WRF-CLM). This was done to improve temperature simulation over and in a saline lake and to test the contributions of salinity effects on various water properties via sensitivity experiments. The modified lake scheme consists of the lake module in the CLM model,which is the land component of the WRF-CLM model. The Great Salt Lake(GSL) in the USA was selected as the study area. The simulation was performed from September 3,2001 to September 30,2002. Our results show that the modif ied WRF-CLM model that includes the lake scheme considering salinity effects can reasonably simulate temperature over and in the GSL. This model had much greater accuracy than neglecting salinity effects,particularly in a very cold event when that effect alters the freezing point. The salinity effect on saturated vapor pressure can reduce latent heat flux over the lake and make it slightly warmer. The salinity effect on heat capacity can also make lake temperature prone to changes. However,the salinity effect on thermal conductivity was found insignificant in our simulations.展开更多
文摘By measuring the variation of the P-and S-wave velocities of tight sandstone samples under water saturation,it was confirmed that with the decrease in water saturation,the P-wave velocity first decreased and then increased.The variation in velocity was influenced by the sandstone’s porosity.The commonly used Gassmann equation based on fluid substitution theory was studied.Comparing the calculated results with the measured data,it was found that the Gassmann equation agreed well with the measured data at high water saturation,but it could not explain the bending phenomenon of P-wave velocity at low saturation.This indicated that these equations could not accurately describe the relationship between fluid content and rock acoustic velocity.The reasons for this phenomenon were discussed through Taylor’s expansion.The coefficients of the fitting formula were calculated and verified by fitting the measured acoustic velocity changes of the cores.The relationship between P-wave velocity and saturation was discussed,which provides experimental support for calculating saturation using seismic and acoustic logging data.
文摘Bottom-simulating reflectors (BSRs) in seismic profile always indicate the bottom of gas hydrate stability zone, but is difficult to determine the distribution and features of gas hydrate sediments (GHS). In this study, based on AVA forward modeling and angle-domain common-image gathers we use prestack AVA parameters consistency inversion in predicting gas hydrate sediments in the Shenhu area at northern slope of South China Sea, and obtain the vertical and lateral features and saturation of GHS.
基金The study is supported by the National Natural Science Foundation of China(Nos.91958206,41876053)the National Key Research and Development Plan(2017YFC0307401,2018YFC1405901)+1 种基金the Fund of Acoustics Science and Technology Laboratory(GK2050260214,GK2050260217,GK2050260218,KY10500180084,KY10500190031,6142108200202)Fundamental Research Funds for the Central Universities(HEUCFJ180503,201964016).
文摘Acoustic and electrical methods are commonly used to evaluate hydrate saturation based on P-wave velocity(Vp)and resistivity,respectively.We evaluate hydrate saturation using petrophysical parameters directly related to the presence of hydrates.Five petrophysical parameters sensitive to hydrate saturation were first analyzed using the equivalent medium rock physical model,logging intersection plots,and petrophysical parameter inversion.The simulated annealing global optimization method was then used to estimate the hydrate saturation profile in the Shenhu Area,China.The petrophysical parameters Vp,λρ,andλμ,which are associated with the rock elastic and shear moduli,are highly sensitive to hydrate saturation for an estimated saturation range of 0.1-0.44.This range is consistent with that obtained from the original well diameter curves.However,the parameters Vs andμρ,which are only related to the rock shear modulus,yield high hydrate saturation estimates of 0.22-0.43 and exhibit some deviations from the real-time data.Owing to its sensitivity,the Poisson’s ratio is least desired for hydrate evaluation among the studied parameters.The sensitivity of hydrate saturation depends on the petrophysical model used for studying hydrate physical properties and storage analysis.
基金Supported by the National Natural Science Foundation of China(No.41130961)the Strategic Priority Research Program(B)of Chinese Academy of Sciences(No.XDB03030300)+1 种基金the National Natural Science Foundation of China(Nos.41475011,41275014)Visiting Scholars Program of the Public School Study Abroad Project of Chinese Academy of Sciences(No.2008-No.136)
文摘In this paper,we introduced parameterizations of the salinity effects(on heat capacity,thermal conductivity,freezing point and saturated vapor pressure) in a lake scheme integrated in the Weather Research and Forecasting model coupled with the Community Land Model(WRF-CLM). This was done to improve temperature simulation over and in a saline lake and to test the contributions of salinity effects on various water properties via sensitivity experiments. The modified lake scheme consists of the lake module in the CLM model,which is the land component of the WRF-CLM model. The Great Salt Lake(GSL) in the USA was selected as the study area. The simulation was performed from September 3,2001 to September 30,2002. Our results show that the modif ied WRF-CLM model that includes the lake scheme considering salinity effects can reasonably simulate temperature over and in the GSL. This model had much greater accuracy than neglecting salinity effects,particularly in a very cold event when that effect alters the freezing point. The salinity effect on saturated vapor pressure can reduce latent heat flux over the lake and make it slightly warmer. The salinity effect on heat capacity can also make lake temperature prone to changes. However,the salinity effect on thermal conductivity was found insignificant in our simulations.
