Gaomiaozi （GMZ） bentonite is regarded as the favorable candidate backfilling material for a potential repository in China. It is important to understand the diffusion behavior of ^125I in GMZ bentonite and compare t...Gaomiaozi （GMZ） bentonite is regarded as the favorable candidate backfilling material for a potential repository in China. It is important to understand the diffusion behavior of ^125I in GMZ bentonite and compare the diffusion behavior in GMZ and other types of bentonite like MX-80, Avonlea, etc. Therefore, through- and out-diffusion experiments were conducted to obtain the effective diffusion coefficient （De） and distribution coefficient （Kd）. A computer code named Fitting for diffusion coefficient （FDP） was used for the experimental data processing and theoretical modeling. At the dry density of GMZ bentonite from 1600-2000 kg/m^3, the De values of ^125I were （2.4-20.4）×10 ^-12 m^2/s and Ka values were constants. At dry density above 1800 kg/m^3, the diffusion behaviors were almost the same, indicating that the anion exclusion was ineffective. Out-diffusion results showed that the species of ^125I may be changed during the diffusion processing. It was probably caused by some organic mat- ters or reducing substances in GMZ bentonite. Since the main composition of bentonite is montmorillonite, similar diffusion parameters were obtained in GMZ and other types of bentonite. The relationship of DE and accessible porosity （εacc） could be described by Archie＇s law with exponent n = 1.2-2.8 for ^125I diffusion in bentonite, whereas n = 2.0 in GMZ bentonite. Fur- thermore, bentonite with the dry density of 1800 kg/m^3 was proposed as the backfilling materials used in the construction of high level radioactivity waste repository.展开更多
Oil saturation was an important parameter of reservoir evaluation, which had important guiding significance for oilfield development. In this paper, the oil saturation of tight oil in G area was studied, and the origi...Oil saturation was an important parameter of reservoir evaluation, which had important guiding significance for oilfield development. In this paper, the oil saturation of tight oil in G area was studied, and the original oil saturation of the study area was studied by using the comprehensive experimental method. The original oil saturation of tight oil in the study area was determined by J function method, rock electricity method and oil-based mud coring method. The results showed that through the comparison of three experimental methods, it could be concluded that the J function method leads to the low value of oil saturation in the study area. The oil-based mud coring method was more suitable for the determination of oil saturation in this area than the other two methods because it needs to meet too many conditions and the calculation results were also low. G area was located in Qili Village, Ordos Basin.展开更多
This study investigated the application of electrical resistance tomography(ERT)in characterizing the slurry spatial distribution in cemented granular materials(CGMs).For CGM formed by self-flow grouting,the voids in ...This study investigated the application of electrical resistance tomography(ERT)in characterizing the slurry spatial distribution in cemented granular materials(CGMs).For CGM formed by self-flow grouting,the voids in the accumulation are only partially filled and the bond strength is often limited,which results in difficulty in obtaining in situ samples for quality evaluation.Therefore,it is usually infeasible to evaluate the grouting effect or monitor the slurry spatial distribution by a mechanical method.In this research,the process of grouting cement paste into high alumina ceramic beads(HACB)accumulation is reliably monitored with ERT.It shows that ERT results can be used to calculate the cement paste volume in the HACB accumulation,based on calibrating the saturation exponent n in Archie’s law.The results support the feasibility of ERT as an imaging tool in CGM characterization and may provide guidance for engineering applications in the future.展开更多
During the Indian National Gas Hydrate Program(NGHP)Expedition 02,Logging-while-drilling(LWD)logs were acquired at three sites(NGHP-02-11,NGHP-02-12,and NGHP-02-13)across the Mahanadi Basin in area A.We applied rock p...During the Indian National Gas Hydrate Program(NGHP)Expedition 02,Logging-while-drilling(LWD)logs were acquired at three sites(NGHP-02-11,NGHP-02-12,and NGHP-02-13)across the Mahanadi Basin in area A.We applied rock physics theory to available sonic velocity logs to know the distribution of gas hydrate at site NGHP-02-11 and NGHP-02-13.Rock physics modeling using sonic velocity at well location shows that gas hydrate is distributed mainly within the depth intervals of 150-265 m and 100 -215 mbsf at site NGHP-02-11 and NGHP-02-13,respectively,with an average saturation of about 4%of the pore space and the maximum concentration of about 40%of the pore space at 250 m depth at site NGHP-02-11,and at site NGHP-02-13 an average saturation of about 2%of the pore space and the maximum concentration of about 20%of the pore space at 246 m depth,as gas hydrate is distributed mainly within 100-246 mbsf at this site.Saturation of gas hydrate estimated from the electrical resistivity method using density derived porosity and electrical resistivity logs from Archie's empirical formula shows high saturation compared to that from the sonic log.However,estimates of hydrate saturation based on sonic P-wave velocity may differ significantly from that based on resistivity,because gas and hydrate have higher resistivity than conductive pore fluid and sonic P-wave velocity shows strong effect on gas hydrate as a small amount of gas reduces the velocity significantly while increasing velocity due to the presence of hydrate.At site NGHP-02-11,gas hydrate saturation is in the range of 15%e30%,in two zones between 150-180 and 245-265 mbsf.Site NGHP-02-012 shows a gas hydrate saturation of 20%e30%in the zone between 100 and 207 mbsf.Site NGHP-02-13 shows a gas hydrate saturation up to 30%in the zone between 215 and 246 mbsf.Combined observations from rock physics modeling and Archie’s approximation show the gas hydrate concentrations are relatively low(<4%of the pore space)at the sites of the Mahanadi Basin in the turbidite channel system展开更多
Geophysical surveys are frequently applied in mining prospection to detect the presence and volume of ore bodies of different nature.Particularly,in gypsum ore bodies exploitation,electrical resistivity measurements a...Geophysical surveys are frequently applied in mining prospection to detect the presence and volume of ore bodies of different nature.Particularly,in gypsum ore bodies exploitation,electrical resistivity measurements are usually the most used methodology.However,it has been observed that different electrical resistivity values can be obtained depending on geometrical features and composition of gypsum.Indeed,electrical resistivity of gypsum rocks depends on several parameters,such as gypsum purity,nature of secondary minerals,porosity,saturation and interstitial fluid properties.Saturation and hydrogeological setting,in particular,were recognized as the most influencing parameters.Hydrogeological conditions of gypsum rock masses are also very relevant for exploitability,safety conditions and economic feasibility and should be accurately known during the prospection and planning phases of the quarries.In this work,a relationship between electrical resistivity and saturation degree of gypsum is proposed.The possibility to estimate gypsum porosity with the use of this relationship is also investigated.The reliability of laboratory measurements is finally verified in comparison with field and modelled resistivity data.The reported results underline the potentiality of the proposed approach to obtain a reliable characterization of the studied ore body.展开更多
Electrical properties are important physical parameters of natural gas hydrate,and,specifically,resistivity has been widely used in the quantitative estimation of hydrate saturation.There are three main methods to stu...Electrical properties are important physical parameters of natural gas hydrate,and,specifically,resistivity has been widely used in the quantitative estimation of hydrate saturation.There are three main methods to study the electrical properties of gas hydrate-bearing sediments:experimental laboratory measurements,numerical simulation,and resistivity logging.Experimental measurements can be divided into three categories:normal electrical measurement,complex resistivity measurement,and electrical resistivity tomography.Experimental measurements show that the resistivity of hydrate-bearing sediment is affected by many factors,and its distribution as well as the hydrate saturation is not uniform;there is a distinct non-Archie phenomenon.The numerical method can simulate the resistivity of sediments by changing the hydrate occurrence state,saturation,distribution,etc.However,it needs to be combined with X-ray CT,nuclear magnetic resonance,and other imaging techniques to characterize the porous characteristics of the hydrate-bearing sediments.Resistivity well logging can easily identify hydrate layers based on their significantly higher resistivity than the background,but the field data of the hydrate layer also has a serious non-Archie phenomenon.Therefore,more experimental measurements and numerical simulation studies are needed to correct the parameters of Archie’s formula.展开更多
According to the capillary theory,an equivalent capillary model of micro-resistivity imaging logging was built.On this basis,the theoretical models of porosity spectrum(Ф_(i)),permeability spectrum(K_(i))and equivale...According to the capillary theory,an equivalent capillary model of micro-resistivity imaging logging was built.On this basis,the theoretical models of porosity spectrum(Ф_(i)),permeability spectrum(K_(i))and equivalent capillary pressure curve(pe)were established to reflect the reservoir heterogeneity.To promote the application of the theoretical models,the Archie's equation was introduced to establish a general model for quantitatively characterizing bi,K,and pei.Compared with the existing models,it is shown that:(1)the existing porosity spectrum model is the same as the general equation of gi;(2)the Ki model can display the permeability spectrum as compared with Purcell's permeability model;(3)the per model is constructed on a theoretical basis and avoids the limitations of existing models that are built only based on the component of porosity spectrum,as compared with the empirical model of capillary pressure curve.The application in the Permian Maokou Formation of Well TsX in the Central Sichuan paleo-uplift shows that the Ф_(i),K_(i),and p_(ci) models can be effectively applied to the identification of reservoir types,calculation of reservoir properties and pore structure parameters,and evaluation of reservoir heterogeneity.展开更多
Accurate quantification of the gas hydrate content in the deep sea is useful for assessing the resource potential and understanding the role of gas hydrates in the global carbon cycle.Resistivity logging data combined...Accurate quantification of the gas hydrate content in the deep sea is useful for assessing the resource potential and understanding the role of gas hydrates in the global carbon cycle.Resistivity logging data combined with Archie’s equation are often used to calculate gas hydrate saturation,but the reliability is dependent on the rationality of the empirical parameter cementation factor and saturation index.At present,an increasing number of fine-grained hydrate-rich sediment regions have been discovered worldwide through drilling efforts,and the reservoir types and hydrate distribution are diverse,which differs greatly from that of coarse-grained reservoirs of hydrate-bearing sediment.This results in vertical variations in m and n through stratigraphy.At present,the saturation evaluation effect of these reservoirs cannot be improved.In this work,a theory for the determination of the cementation factor and saturation index was first proposed to obtain reliable and variable values of the empirical parameters.Then,a hydrate saturation evaluation technique with variables m and n was formed based on the well logging data.This technique was used to evaluate complex fine-grained hydrate-bearing reservoirs in several regions worldwide.It was found that the highest n could be 16,and the log calculation results were more consistent with the core hydrate saturation.Additionally,the cause of the excessively high n values was explained from physical principles,and the result was verified with actually well log data.In future evaluations of the amount of hydrate resources in fine-grained sediment reservoirs worldwide,new saturation estimation methods should be taken into account to advance hydrate research.展开更多
The formation factor relates bulk resistivity to pore fluid resistivity in porous materials. Understanding the formation factor is essential in using electrical and electromagnetic methods to monitor ieachate accumula...The formation factor relates bulk resistivity to pore fluid resistivity in porous materials. Understanding the formation factor is essential in using electrical and electromagnetic methods to monitor ieachate accumulations and movements both within and around landfills. Specifically, the formation factor allows leachate resistivity, the degree of saturation, and, possibly, even the hydraulic conductivity of the waste to be estimated from non-invasive surface measurements. In this study, apparent formation factors are computed for three landfills with different types of waste as well as sediments contaminated by landfill leachate. Resistivity soundings at the closed Mallard North landfill in suburban Chicago （Illinois, USA） mapped leachate surfaces that were confirmed by monitoring wells. The resistivity of leachate-saturated waste from resistivity sounding inversions was then divided by the leachate resistivity values measured in-situ to compute apparent formation factors （Fa） ranging from 1.6 to 4.9. A global Fa of 3.0±1.9 was computed for the entire monitored portion of this landfill. At a nearby mixed laboratory waste landfill, a 2D inverted resistivity section was used to compute an Fa of 2.9. Finally, a distinctly different Fa value of 10.6±2.8 was computed for leachate-saturated retorted oil shale wastes north of Maoming （茂名）, Guangdong （广东） Province, China. Shallow aquifers in the Laohuling （老虎岭） Formation near this landfill are polluted by acidic leachate containing heavy metals and organic compounds. The Fa for aquifers containing contaminated groundwater fall in the same range as aquifers with normal groundwater, 1.7-3.9. However, models from inverted sounding curves over these contaminated areas exhibit unusually low resistivity layers, which may be diagnostic of contamination.展开更多
Accurate laboratory measurements and analysis of electrical properties of core samples are a prerequisite step to the evaluation of oil and gas reserves. In recent times, this evaluation technique has been adopted in ...Accurate laboratory measurements and analysis of electrical properties of core samples are a prerequisite step to the evaluation of oil and gas reserves. In recent times, this evaluation technique has been adopted in carbon dioxide sequestration projects for estimating and monitoring carbon dioxide (CO2) accumulation in saline aquifers. Several papers have reported laboratory success in the use of resistivity measurements to monitor the flow and also estimate the volume of CO2 plume in geological formations. Such laboratory experiments did not capture the effect of CO2 -brine-rock interaction (CBRI) on saturation estimation. The possibility of a change in value resistivity due to CO2/brine/rock interactions, and the possible effect on CO2 monitoring and estimation are of immediate interest here. Preliminary results of an ongoing research work showed that a much longer experiment time accommodates CO2-brine-rock interaction which ultimately lead to change in rock resistivity. We hereby present the electrical behavior of carbonates to CO2/ brine/rock interaction during prolonged CO2 sequestration and the effect on saturation estimation. This electrical behavior and its possible effect on CO2 monitoring and estimation are discussed.展开更多
To solve the problem that it is difficult to identify carbonate low resistivity pays(LRPs) by conventional logging methods in the Rub Al Khali Basin, the Middle East, the variation of fluid distribution and rock condu...To solve the problem that it is difficult to identify carbonate low resistivity pays(LRPs) by conventional logging methods in the Rub Al Khali Basin, the Middle East, the variation of fluid distribution and rock conductivity during displacement were analyzed by displacement resistivity experiments simulating the process of reservoir formation and production, together with the data from thin sections, mercury injection and nuclear magnetic resonance experiments. In combination with geological understandings, the genetic mechanisms of LRPs were revealed, then the saturation interpretation model was selected, the variation laws and distribution range of the model parameters were defined, and finally an updated comprehensive saturation interpretation technique for the LRPs has been proposed. In the study area, the LRPs have resistivity values of less than 1 Ω·m, similar to or even slightly lower than that of the water layers. Geological research reveals that the LRPs were developed in low-energy depositional environment and their reservoir spaces are controlled by micro-scale pore throats, with an average radius of less than 0.7 μm, so they are typical microporous LRPs. Different from LRPs of sandstone and mudstone, they have less tortuous conductive paths than conventional reservoirs, and thus lower resistivity value under the same saturation. Archie’s formula is applicable to the saturation interpretation of LRPs with a cementation index value of 1.77-1.93 and a saturation index value of 1.82-2.03 that are 0.2-0.4 lower than conventional reservoirs respectively. By using interpretation parameters determined by classification statistics of petrophysical groups(PGs), oil saturations of the LRPs were calculated at bout 30%-50%,15% higher than the results by conventional methods, and basically consistent with the data of Dean Stark, RST, oil testing and production. The 15 wells of oil testing and production proved that the coincidence rate of saturation interpretation is over 90%and the feasibility of this method 展开更多
基金supported by Qianjiang Talents Project in Zhejiang ProvinceProject Supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry
文摘Gaomiaozi （GMZ） bentonite is regarded as the favorable candidate backfilling material for a potential repository in China. It is important to understand the diffusion behavior of ^125I in GMZ bentonite and compare the diffusion behavior in GMZ and other types of bentonite like MX-80, Avonlea, etc. Therefore, through- and out-diffusion experiments were conducted to obtain the effective diffusion coefficient （De） and distribution coefficient （Kd）. A computer code named Fitting for diffusion coefficient （FDP） was used for the experimental data processing and theoretical modeling. At the dry density of GMZ bentonite from 1600-2000 kg/m^3, the De values of ^125I were （2.4-20.4）×10 ^-12 m^2/s and Ka values were constants. At dry density above 1800 kg/m^3, the diffusion behaviors were almost the same, indicating that the anion exclusion was ineffective. Out-diffusion results showed that the species of ^125I may be changed during the diffusion processing. It was probably caused by some organic mat- ters or reducing substances in GMZ bentonite. Since the main composition of bentonite is montmorillonite, similar diffusion parameters were obtained in GMZ and other types of bentonite. The relationship of DE and accessible porosity （εacc） could be described by Archie＇s law with exponent n = 1.2-2.8 for ^125I diffusion in bentonite, whereas n = 2.0 in GMZ bentonite. Fur- thermore, bentonite with the dry density of 1800 kg/m^3 was proposed as the backfilling materials used in the construction of high level radioactivity waste repository.
文摘Oil saturation was an important parameter of reservoir evaluation, which had important guiding significance for oilfield development. In this paper, the oil saturation of tight oil in G area was studied, and the original oil saturation of the study area was studied by using the comprehensive experimental method. The original oil saturation of tight oil in the study area was determined by J function method, rock electricity method and oil-based mud coring method. The results showed that through the comparison of three experimental methods, it could be concluded that the J function method leads to the low value of oil saturation in the study area. The oil-based mud coring method was more suitable for the determination of oil saturation in this area than the other two methods because it needs to meet too many conditions and the calculation results were also low. G area was located in Qili Village, Ordos Basin.
基金The authors thank to the financial support from the National Natural Science Foundation of China(Grant Nos.52039005 and 51861165102)Scientific Research Project of State Key Laboratory of Hydroscience and Engineering(No.2022-KY-01)Beijing Sinoconfix Co.,Ltd.provides all of the polycarboxylate-based superplasticizer for the research.Mr.Weihua Zeng and Guiwen Li are gratefully acknowledged for their help in performing the experiments.
文摘This study investigated the application of electrical resistance tomography(ERT)in characterizing the slurry spatial distribution in cemented granular materials(CGMs).For CGM formed by self-flow grouting,the voids in the accumulation are only partially filled and the bond strength is often limited,which results in difficulty in obtaining in situ samples for quality evaluation.Therefore,it is usually infeasible to evaluate the grouting effect or monitor the slurry spatial distribution by a mechanical method.In this research,the process of grouting cement paste into high alumina ceramic beads(HACB)accumulation is reliably monitored with ERT.It shows that ERT results can be used to calculate the cement paste volume in the HACB accumulation,based on calibrating the saturation exponent n in Archie’s law.The results support the feasibility of ERT as an imaging tool in CGM characterization and may provide guidance for engineering applications in the future.
文摘During the Indian National Gas Hydrate Program(NGHP)Expedition 02,Logging-while-drilling(LWD)logs were acquired at three sites(NGHP-02-11,NGHP-02-12,and NGHP-02-13)across the Mahanadi Basin in area A.We applied rock physics theory to available sonic velocity logs to know the distribution of gas hydrate at site NGHP-02-11 and NGHP-02-13.Rock physics modeling using sonic velocity at well location shows that gas hydrate is distributed mainly within the depth intervals of 150-265 m and 100 -215 mbsf at site NGHP-02-11 and NGHP-02-13,respectively,with an average saturation of about 4%of the pore space and the maximum concentration of about 40%of the pore space at 250 m depth at site NGHP-02-11,and at site NGHP-02-13 an average saturation of about 2%of the pore space and the maximum concentration of about 20%of the pore space at 246 m depth,as gas hydrate is distributed mainly within 100-246 mbsf at this site.Saturation of gas hydrate estimated from the electrical resistivity method using density derived porosity and electrical resistivity logs from Archie's empirical formula shows high saturation compared to that from the sonic log.However,estimates of hydrate saturation based on sonic P-wave velocity may differ significantly from that based on resistivity,because gas and hydrate have higher resistivity than conductive pore fluid and sonic P-wave velocity shows strong effect on gas hydrate as a small amount of gas reduces the velocity significantly while increasing velocity due to the presence of hydrate.At site NGHP-02-11,gas hydrate saturation is in the range of 15%e30%,in two zones between 150-180 and 245-265 mbsf.Site NGHP-02-012 shows a gas hydrate saturation of 20%e30%in the zone between 100 and 207 mbsf.Site NGHP-02-13 shows a gas hydrate saturation up to 30%in the zone between 215 and 246 mbsf.Combined observations from rock physics modeling and Archie’s approximation show the gas hydrate concentrations are relatively low(<4%of the pore space)at the sites of the Mahanadi Basin in the turbidite channel system
文摘Geophysical surveys are frequently applied in mining prospection to detect the presence and volume of ore bodies of different nature.Particularly,in gypsum ore bodies exploitation,electrical resistivity measurements are usually the most used methodology.However,it has been observed that different electrical resistivity values can be obtained depending on geometrical features and composition of gypsum.Indeed,electrical resistivity of gypsum rocks depends on several parameters,such as gypsum purity,nature of secondary minerals,porosity,saturation and interstitial fluid properties.Saturation and hydrogeological setting,in particular,were recognized as the most influencing parameters.Hydrogeological conditions of gypsum rock masses are also very relevant for exploitability,safety conditions and economic feasibility and should be accurately known during the prospection and planning phases of the quarries.In this work,a relationship between electrical resistivity and saturation degree of gypsum is proposed.The possibility to estimate gypsum porosity with the use of this relationship is also investigated.The reliability of laboratory measurements is finally verified in comparison with field and modelled resistivity data.The reported results underline the potentiality of the proposed approach to obtain a reliable characterization of the studied ore body.
基金the financial support provided by the National Natural Science Foundation of China(Grant Nos.42174133 and 41676032)China Geological Survey(Grant No.DD20190234)。
文摘Electrical properties are important physical parameters of natural gas hydrate,and,specifically,resistivity has been widely used in the quantitative estimation of hydrate saturation.There are three main methods to study the electrical properties of gas hydrate-bearing sediments:experimental laboratory measurements,numerical simulation,and resistivity logging.Experimental measurements can be divided into three categories:normal electrical measurement,complex resistivity measurement,and electrical resistivity tomography.Experimental measurements show that the resistivity of hydrate-bearing sediment is affected by many factors,and its distribution as well as the hydrate saturation is not uniform;there is a distinct non-Archie phenomenon.The numerical method can simulate the resistivity of sediments by changing the hydrate occurrence state,saturation,distribution,etc.However,it needs to be combined with X-ray CT,nuclear magnetic resonance,and other imaging techniques to characterize the porous characteristics of the hydrate-bearing sediments.Resistivity well logging can easily identify hydrate layers based on their significantly higher resistivity than the background,but the field data of the hydrate layer also has a serious non-Archie phenomenon.Therefore,more experimental measurements and numerical simulation studies are needed to correct the parameters of Archie’s formula.
基金Supported by the National Natural Science Foundation of China(U2003102,41974117)China National Science and Technology Major Project(2016ZX05052001).
文摘According to the capillary theory,an equivalent capillary model of micro-resistivity imaging logging was built.On this basis,the theoretical models of porosity spectrum(Ф_(i)),permeability spectrum(K_(i))and equivalent capillary pressure curve(pe)were established to reflect the reservoir heterogeneity.To promote the application of the theoretical models,the Archie's equation was introduced to establish a general model for quantitatively characterizing bi,K,and pei.Compared with the existing models,it is shown that:(1)the existing porosity spectrum model is the same as the general equation of gi;(2)the Ki model can display the permeability spectrum as compared with Purcell's permeability model;(3)the per model is constructed on a theoretical basis and avoids the limitations of existing models that are built only based on the component of porosity spectrum,as compared with the empirical model of capillary pressure curve.The application in the Permian Maokou Formation of Well TsX in the Central Sichuan paleo-uplift shows that the Ф_(i),K_(i),and p_(ci) models can be effectively applied to the identification of reservoir types,calculation of reservoir properties and pore structure parameters,and evaluation of reservoir heterogeneity.
基金This project was funded by the National Natural Science Foundation of China(No.42106213)the China Postdoctoral Science Foundation(Nos.2021M690161 and 2021T140691)+1 种基金the National Key Research and Development Program of China(No.2021YFC3100601)the Postdoctorate Funded Project in Hainan Province.
文摘Accurate quantification of the gas hydrate content in the deep sea is useful for assessing the resource potential and understanding the role of gas hydrates in the global carbon cycle.Resistivity logging data combined with Archie’s equation are often used to calculate gas hydrate saturation,but the reliability is dependent on the rationality of the empirical parameter cementation factor and saturation index.At present,an increasing number of fine-grained hydrate-rich sediment regions have been discovered worldwide through drilling efforts,and the reservoir types and hydrate distribution are diverse,which differs greatly from that of coarse-grained reservoirs of hydrate-bearing sediment.This results in vertical variations in m and n through stratigraphy.At present,the saturation evaluation effect of these reservoirs cannot be improved.In this work,a theory for the determination of the cementation factor and saturation index was first proposed to obtain reliable and variable values of the empirical parameters.Then,a hydrate saturation evaluation technique with variables m and n was formed based on the well logging data.This technique was used to evaluate complex fine-grained hydrate-bearing reservoirs in several regions worldwide.It was found that the highest n could be 16,and the log calculation results were more consistent with the core hydrate saturation.Additionally,the cause of the excessively high n values was explained from physical principles,and the result was verified with actually well log data.In future evaluations of the amount of hydrate resources in fine-grained sediment reservoirs worldwide,new saturation estimation methods should be taken into account to advance hydrate research.
基金supported by the National Natural Science Foundation of China (No. 40873076)Science & Technology Project of Guangdong Province (2KM06506S)+1 种基金the Environmental Protection Bureau of Maoming for funding the Maoming work and providing logistical support in the fieldThe Department of Geology and Environmental Geosciences, Graduate School, School of Liberal Arts and Sciences, Northern Illinois University, and Argonne National Laboratory provided support for the Mallard North project and provided travel support to China during a research sabbatical
文摘The formation factor relates bulk resistivity to pore fluid resistivity in porous materials. Understanding the formation factor is essential in using electrical and electromagnetic methods to monitor ieachate accumulations and movements both within and around landfills. Specifically, the formation factor allows leachate resistivity, the degree of saturation, and, possibly, even the hydraulic conductivity of the waste to be estimated from non-invasive surface measurements. In this study, apparent formation factors are computed for three landfills with different types of waste as well as sediments contaminated by landfill leachate. Resistivity soundings at the closed Mallard North landfill in suburban Chicago （Illinois, USA） mapped leachate surfaces that were confirmed by monitoring wells. The resistivity of leachate-saturated waste from resistivity sounding inversions was then divided by the leachate resistivity values measured in-situ to compute apparent formation factors （Fa） ranging from 1.6 to 4.9. A global Fa of 3.0±1.9 was computed for the entire monitored portion of this landfill. At a nearby mixed laboratory waste landfill, a 2D inverted resistivity section was used to compute an Fa of 2.9. Finally, a distinctly different Fa value of 10.6±2.8 was computed for leachate-saturated retorted oil shale wastes north of Maoming （茂名）, Guangdong （广东） Province, China. Shallow aquifers in the Laohuling （老虎岭） Formation near this landfill are polluted by acidic leachate containing heavy metals and organic compounds. The Fa for aquifers containing contaminated groundwater fall in the same range as aquifers with normal groundwater, 1.7-3.9. However, models from inverted sounding curves over these contaminated areas exhibit unusually low resistivity layers, which may be diagnostic of contamination.
文摘Accurate laboratory measurements and analysis of electrical properties of core samples are a prerequisite step to the evaluation of oil and gas reserves. In recent times, this evaluation technique has been adopted in carbon dioxide sequestration projects for estimating and monitoring carbon dioxide (CO2) accumulation in saline aquifers. Several papers have reported laboratory success in the use of resistivity measurements to monitor the flow and also estimate the volume of CO2 plume in geological formations. Such laboratory experiments did not capture the effect of CO2 -brine-rock interaction (CBRI) on saturation estimation. The possibility of a change in value resistivity due to CO2/brine/rock interactions, and the possible effect on CO2 monitoring and estimation are of immediate interest here. Preliminary results of an ongoing research work showed that a much longer experiment time accommodates CO2-brine-rock interaction which ultimately lead to change in rock resistivity. We hereby present the electrical behavior of carbonates to CO2/ brine/rock interaction during prolonged CO2 sequestration and the effect on saturation estimation. This electrical behavior and its possible effect on CO2 monitoring and estimation are discussed.
基金Supported by the CNPC Scientific Research and Technology Development Project (2019D-4410)。
文摘To solve the problem that it is difficult to identify carbonate low resistivity pays(LRPs) by conventional logging methods in the Rub Al Khali Basin, the Middle East, the variation of fluid distribution and rock conductivity during displacement were analyzed by displacement resistivity experiments simulating the process of reservoir formation and production, together with the data from thin sections, mercury injection and nuclear magnetic resonance experiments. In combination with geological understandings, the genetic mechanisms of LRPs were revealed, then the saturation interpretation model was selected, the variation laws and distribution range of the model parameters were defined, and finally an updated comprehensive saturation interpretation technique for the LRPs has been proposed. In the study area, the LRPs have resistivity values of less than 1 Ω·m, similar to or even slightly lower than that of the water layers. Geological research reveals that the LRPs were developed in low-energy depositional environment and their reservoir spaces are controlled by micro-scale pore throats, with an average radius of less than 0.7 μm, so they are typical microporous LRPs. Different from LRPs of sandstone and mudstone, they have less tortuous conductive paths than conventional reservoirs, and thus lower resistivity value under the same saturation. Archie’s formula is applicable to the saturation interpretation of LRPs with a cementation index value of 1.77-1.93 and a saturation index value of 1.82-2.03 that are 0.2-0.4 lower than conventional reservoirs respectively. By using interpretation parameters determined by classification statistics of petrophysical groups(PGs), oil saturations of the LRPs were calculated at bout 30%-50%,15% higher than the results by conventional methods, and basically consistent with the data of Dean Stark, RST, oil testing and production. The 15 wells of oil testing and production proved that the coincidence rate of saturation interpretation is over 90%and the feasibility of this method
