Based on the tortuous capillary network model,the relationship between anisotropic permeability and rock normal strain,namely the anisotropic dynamic permeability model(ADPM),was derived and established.The model was ...Based on the tortuous capillary network model,the relationship between anisotropic permeability and rock normal strain,namely the anisotropic dynamic permeability model(ADPM),was derived and established.The model was verified using pore-scale flow simulation.The uniaxial strain process was calculated and the main factors affecting permeability changes in different directions in the deformation process were analyzed.In the process of uniaxial strain during the exploitation of layered oil and gas reservoirs,the effect of effective surface porosity on the permeability in all directions is consistent.With the decrease of effective surface porosity,the sensitivity of permeability to strain increases.The sensitivity of the permeability perpendicular to the direction of compression to the strain decreases with the increase of the tortuosity,while the sensitivity of the permeability in the direction of compression to the strain increases with the increase of the tortuosity.For layered reservoirs with the same initial tortuosity in all directions,the tortuosity plays a decisive role in the relative relationship between the variations of permeability in all directions during pressure drop.When the tortuosity is less than 1.6,the decrease rate of horizontal permeability is higher than that of vertical permeability,while the opposite is true when the tortuosity is greater than 1.6.This phenomenon cannot be represented by traditional dynamic permeability model.After the verification by experimental data of pore-scale simulation,the new model has high fitting accuracy and can effectively characterize the effects of deformation in different directions on the permeability in all directions.展开更多
BACKGROUND: AND PURPOSE: The measurement of relative cerebral blood volume (rCBV) and the volume transfer constant (K(trans)) by means of dynamic contrast-enhanced (DCE) perfusion MR imaging (pMRI) can be useful in ch...BACKGROUND: AND PURPOSE: The measurement of relative cerebral blood volume (rCBV) and the volume transfer constant (K(trans)) by means of dynamic contrast-enhanced (DCE) perfusion MR imaging (pMRI) can be useful in characterizing brain tumors. The purpose of our study was to evaluate the utility of these measurements in differentiating typical meningiomas and atypical meningiomas. METHODS: Fifteen patients with pathologically confirmed typical meningiomas and seven with atypical meningiomas underwent conventional imaging and DCE pMRI before resection.rCBV measurements were calculated by using standard intravascular展开更多
In order to accurately predict the production performance of coalbed methane(CBM)wells and to formulate a reasonable production system,this paper established a coal reservoir permeability model considering the influen...In order to accurately predict the production performance of coalbed methane(CBM)wells and to formulate a reasonable production system,this paper established a coal reservoir permeability model considering the influence of pulverized coal blockage.Then,on the basis of this model,the flow velocity sensitivity(FVS)experimental data of 15 groups of coal samples taken from the Baode Block,Qinshui Basin,Liulin Block,Hancheng Block,and the Huanglong Coalfield were fitted to determine the permeability models for different coal samples.On this basis,this newly established permeability model was incorporated into a previously developed CBM well performance analysis software,and production history matching was carried out on two CBM wells.Finally,the effects of the parameters of pulverized coal blockage on the permeability of coal reservoirs and the production performance of CBM wells were studied by taking the fitting parameters of CBM Well W1 as the reference.And the following research results are obtained.First,this new model considering the influence of pulverized coal blockage can quantitatively describe the variation of coal reservoir permeability with fluid velocity.In addition,this model can be incorporated into a CBM numerical simulation software or a CBM well performance analysis software to apply it in a wide range.Second,the coal reservoir permeability is less affected by pulverized coal blockage in the Baode Block,but this effect shall not be ignored in the Qinshui Basin and the Huanglong Coalfield.Third,the greater the theoretical maximum permeability damage degree(D_(max))and the permeability damage degree index(n)are,the lower the relative flow velocity(v0.5)corresponding to the critical flow velocity of pulverized coal blockage is and the more obvious the effect of pulverized coal blockage on coal reservoir permeability is.Fourth,in order to reduce the adverse effect of pulverized coal blockage on coal reservoir permeability,it is suggested to reduce the production pressure difference appropriately in the process of production,especially in the initial stage of gas production,so as to avoid severe damage to coal reservoir permeability.展开更多
Based on the hydro-geological conditions of 1028 mining face in Suntuan Coal Mine, mining seepage strain mechanism of seam floor was simulated by a nonlinear coupling method, which applied fluid-solid coupling analysi...Based on the hydro-geological conditions of 1028 mining face in Suntuan Coal Mine, mining seepage strain mechanism of seam floor was simulated by a nonlinear coupling method, which applied fluid-solid coupling analysis module of FLAC^3D. The results indicate that the permeability coefficient of adjoining rock changes a lot due to mining. The maximum value reaches 1 379.9 times to the original value, where it is at immediate roof of the mined-out area. According to the analysis on the seepage field, mining does not destroy water resistance of the floor aquiclude. The mining fissure does not conduct lime-stone aquifer, and it is less likely to form damage. The plastic zone does not exactly correspond to the seepage area, and the scope of the altered seepage area is much larger than the plastic zone.展开更多
Karaganda Coal Basin bears the largest undeveloped reserve of coalbed methane(CBM)in Kazakhstan,which lacks water resources for implementing large-volume hydraulic fracturing.Cryogenic fracturing utilizing liquid nitr...Karaganda Coal Basin bears the largest undeveloped reserve of coalbed methane(CBM)in Kazakhstan,which lacks water resources for implementing large-volume hydraulic fracturing.Cryogenic fracturing utilizing liquid nitrogen(LN_(2))has been trialled in fields and is a waterless fracturing technique under intensive research these days.This study aimed to evaluate the cryogenic treatment efficacy of Karaganda coal samples as well as to understand the coal permeability evolution during the thawing period.X-ray fluorescent spectrometry(XRF)and microscope imaging identified the compositional and structural heterogeneities of coal specimens mined from different interlayers.Acoustic emission test,permeability measurement,and microscope imaging comparatively characterized the dry coal structure alteration before and after immersion into LN_(2).Cryogenic treatment slowed down the S-wave velocity through coal specimens,enhanced permeability by over 65%after temperature recovery as well as created new fractures,enlarged existing ones,and spalled coal particles.Dynamic permeability evolution against temperature rise during the thawing process has been successfully captured for the first time.Overall,the experimental measurements support that the LN_(2) cryogenic fracturing technique would be effective in stimulating coalbeds for CBM production in Karaganda Coal Basin.展开更多
基金Supported by the National Natural Science Foundation of China(52274048)Beijing Natural Science Foundation Project of China(3222037)Shaanxi Provincial Technical Innovation Project of China(2023-YD-CGZH-02).
文摘Based on the tortuous capillary network model,the relationship between anisotropic permeability and rock normal strain,namely the anisotropic dynamic permeability model(ADPM),was derived and established.The model was verified using pore-scale flow simulation.The uniaxial strain process was calculated and the main factors affecting permeability changes in different directions in the deformation process were analyzed.In the process of uniaxial strain during the exploitation of layered oil and gas reservoirs,the effect of effective surface porosity on the permeability in all directions is consistent.With the decrease of effective surface porosity,the sensitivity of permeability to strain increases.The sensitivity of the permeability perpendicular to the direction of compression to the strain decreases with the increase of the tortuosity,while the sensitivity of the permeability in the direction of compression to the strain increases with the increase of the tortuosity.For layered reservoirs with the same initial tortuosity in all directions,the tortuosity plays a decisive role in the relative relationship between the variations of permeability in all directions during pressure drop.When the tortuosity is less than 1.6,the decrease rate of horizontal permeability is higher than that of vertical permeability,while the opposite is true when the tortuosity is greater than 1.6.This phenomenon cannot be represented by traditional dynamic permeability model.After the verification by experimental data of pore-scale simulation,the new model has high fitting accuracy and can effectively characterize the effects of deformation in different directions on the permeability in all directions.
文摘BACKGROUND: AND PURPOSE: The measurement of relative cerebral blood volume (rCBV) and the volume transfer constant (K(trans)) by means of dynamic contrast-enhanced (DCE) perfusion MR imaging (pMRI) can be useful in characterizing brain tumors. The purpose of our study was to evaluate the utility of these measurements in differentiating typical meningiomas and atypical meningiomas. METHODS: Fifteen patients with pathologically confirmed typical meningiomas and seven with atypical meningiomas underwent conventional imaging and DCE pMRI before resection.rCBV measurements were calculated by using standard intravascular
基金supported by the National Major Science and Technology Project“Development of CBM quantitative production technology and equipment”(No.:2016ZX05042-004).
文摘In order to accurately predict the production performance of coalbed methane(CBM)wells and to formulate a reasonable production system,this paper established a coal reservoir permeability model considering the influence of pulverized coal blockage.Then,on the basis of this model,the flow velocity sensitivity(FVS)experimental data of 15 groups of coal samples taken from the Baode Block,Qinshui Basin,Liulin Block,Hancheng Block,and the Huanglong Coalfield were fitted to determine the permeability models for different coal samples.On this basis,this newly established permeability model was incorporated into a previously developed CBM well performance analysis software,and production history matching was carried out on two CBM wells.Finally,the effects of the parameters of pulverized coal blockage on the permeability of coal reservoirs and the production performance of CBM wells were studied by taking the fitting parameters of CBM Well W1 as the reference.And the following research results are obtained.First,this new model considering the influence of pulverized coal blockage can quantitatively describe the variation of coal reservoir permeability with fluid velocity.In addition,this model can be incorporated into a CBM numerical simulation software or a CBM well performance analysis software to apply it in a wide range.Second,the coal reservoir permeability is less affected by pulverized coal blockage in the Baode Block,but this effect shall not be ignored in the Qinshui Basin and the Huanglong Coalfield.Third,the greater the theoretical maximum permeability damage degree(D_(max))and the permeability damage degree index(n)are,the lower the relative flow velocity(v0.5)corresponding to the critical flow velocity of pulverized coal blockage is and the more obvious the effect of pulverized coal blockage on coal reservoir permeability is.Fourth,in order to reduce the adverse effect of pulverized coal blockage on coal reservoir permeability,it is suggested to reduce the production pressure difference appropriately in the process of production,especially in the initial stage of gas production,so as to avoid severe damage to coal reservoir permeability.
文摘Based on the hydro-geological conditions of 1028 mining face in Suntuan Coal Mine, mining seepage strain mechanism of seam floor was simulated by a nonlinear coupling method, which applied fluid-solid coupling analysis module of FLAC^3D. The results indicate that the permeability coefficient of adjoining rock changes a lot due to mining. The maximum value reaches 1 379.9 times to the original value, where it is at immediate roof of the mined-out area. According to the analysis on the seepage field, mining does not destroy water resistance of the floor aquiclude. The mining fissure does not conduct lime-stone aquifer, and it is less likely to form damage. The plastic zone does not exactly correspond to the seepage area, and the scope of the altered seepage area is much larger than the plastic zone.
基金support of the Collaborative Research Grant"Development of cryogenic fracturing technology for coalbed methane production in Karaganda Coal Basin,Kazakhstan" (Reference Number:021220CRP2022)by Nazarbayev University,Kazakhstanthe Open Fund of Engineering Research Center of Development and Management for Low to Ultra-Low Permeability Oil&Gas Reservoirs in West China,Ministry of Education,China。
文摘Karaganda Coal Basin bears the largest undeveloped reserve of coalbed methane(CBM)in Kazakhstan,which lacks water resources for implementing large-volume hydraulic fracturing.Cryogenic fracturing utilizing liquid nitrogen(LN_(2))has been trialled in fields and is a waterless fracturing technique under intensive research these days.This study aimed to evaluate the cryogenic treatment efficacy of Karaganda coal samples as well as to understand the coal permeability evolution during the thawing period.X-ray fluorescent spectrometry(XRF)and microscope imaging identified the compositional and structural heterogeneities of coal specimens mined from different interlayers.Acoustic emission test,permeability measurement,and microscope imaging comparatively characterized the dry coal structure alteration before and after immersion into LN_(2).Cryogenic treatment slowed down the S-wave velocity through coal specimens,enhanced permeability by over 65%after temperature recovery as well as created new fractures,enlarged existing ones,and spalled coal particles.Dynamic permeability evolution against temperature rise during the thawing process has been successfully captured for the first time.Overall,the experimental measurements support that the LN_(2) cryogenic fracturing technique would be effective in stimulating coalbeds for CBM production in Karaganda Coal Basin.
