In 2012,China's first national shale gas demonstrations areas were set up in the Sichuan Basin.After 10 years'construction and practice,the giant marine shale gas area of 10×10^(12) m^(3) level is built u...In 2012,China's first national shale gas demonstrations areas were set up in the Sichuan Basin.After 10 years'construction and practice,the giant marine shale gas area of 10×10^(12) m^(3) level is built up in the Sichuan Basin,and shale gas steps into a new stage of large-scale benefit exploration and development.In order to systematically summarize the achievements in shale gas exploration and development and provide guidance and reference for the exploration and development of deep shale gas and shale oil&gas in other areas,this paper systematically summarizes the main characteristics,development models and key identification and evaluation technologies for quality reservoirs of Wufeng Formation-Longmaxi Formation shale gas by analyzing the electric property,lithofacies,reservoir parameters and microscopic porosity of key wells in the basin.And the following research results are obtained.First,biogenetic siliceous shale,calcareous shale and mixed shale are main lithofacies types in quality shale gas reservoirs,and they are formed in the environment of semi-deep and deep water continental shelf.Their lateral distribution is controlled by the paleogeomorphology and their vertical development is influenced by provenance,redox condition and paleo productivity.They are 25-90 m thick.Second,in the quality shale gas reservoirs develop organic pores,inorganic pore and microfractures(including lamina/bedding fractures),among which,organic pore is one of the main reservoir spaces and microfracture is not only indispensable reservoir space,but also production pathway.The reservoir space of shale gas is overall micro-nano pore,and macropores play an important role in shale gas enrichment.Third,three development models of quality reservoir are established,including sedimentary type,diagenesis type and reworking type.The sedimentary type is the foundation.Multiple quality reservoirs are developed in the high U/Th interval of graptolite belt at the bottom of Longmaxi Formation,and their thickness is mainly controlled by paleogeomorphology and especially greater in the depression area.The diagenesis type is divided into three forms,i.e.,syngenetic-early diagenetic rigid support,middle-late diagenetic mineral-organic matter transformation,and overpressure relief compaction.The reworking type is dominated by quality reservoirs with microfractures.Fourth,the core technologies for identifying and evaluating quality shale gas reservoir include large-size core and rock slice observation,high-accuracy rock mineral identification,experimental gas content test and simulation,SEM microscopic characterization,3D microscopic pore reconstruction,comprehensive geophysical interpretation and prediction and big data analysis.In conclusion,nearly 10 years'research and practice achievements in demonstration area construction can deepen the understanding on domestic quality shale gas reservoirs,promote the effective development of the theories and technologies related to shale gas reservoirs,improve the prediction accuracy of shale gas sweet spot zones/intervals,and expand the shale gas exploration and development achievements of demonstration areas.展开更多
Deep shale reservoirs(3500–4500 m)exhibit significantly different stress states than moderately deep shale reservoirs(2000–3500 m).As a result,the brittleness response mechanisms of deep shales are also different.It...Deep shale reservoirs(3500–4500 m)exhibit significantly different stress states than moderately deep shale reservoirs(2000–3500 m).As a result,the brittleness response mechanisms of deep shales are also different.It is urgent to investigate methods to evaluate the brittleness of deep shales to meet the increasingly urgent needs of deep shale gas development.In this paper,the quotient of Young’s modulus divided by Poisson’s ratio based on triaxial compression tests under in situ stress conditions is taken as SSBV(Static Standard Brittleness Value).A new and pragmatic technique is developed to determine the static brittleness index that considers elastic parameters,the mineral content,and the in situ stress conditions(BIEMS).The coefficient of determination between BIEMS and SSBV reaches 0.555 for experimental data and 0.805 for field data.This coefficient is higher than that of other brittleness indices when compared to SSBV.BIEMS can offer detailed insights into shale brittleness under various conditions,including different mineral compositions,depths,and stress states.This technique can provide a solid data-based foundation for the selection of‘sweet spots’for single-well engineering and the comparison of the brittleness of shale gas production layers in different areas.展开更多
In this study,a new adaptive morphological filter is developed based on the mathematical morphology algorithm and characteristics of the subtle differences in the waveform morphology in seismic data.The algorithm impr...In this study,a new adaptive morphological filter is developed based on the mathematical morphology algorithm and characteristics of the subtle differences in the waveform morphology in seismic data.The algorithm improves the traditional morphological dilation and corrosion operations.In this study,we propose a multiscale adaptive operator based on the principle of morphological structural“probes”and present the corresponding mathematical proof.Simulation experiments and actual seismic data processing results show that compared with traditional morphological filters,the constructed OCCO-based multistructure adaptive morphological filter can suppress noise to the greatest extent.Moreover,it can effectively improve the SNR of the images,and offers great application prospects.展开更多
Carbonate gas reservoir in the eastern area on the Right Bank of the Amu Darya River,Turkmenistan,are of low-porosity and with developed fractures.In this area,fractures control reservoir properties and natural gas pr...Carbonate gas reservoir in the eastern area on the Right Bank of the Amu Darya River,Turkmenistan,are of low-porosity and with developed fractures.In this area,fractures control reservoir properties and natural gas production,and karst fractures are the most important kind of fractures,so their identification and evaluation are quite necessary.In this paper,fracture types were identified and their occurrence was extracted by using conventional logging and image logging data after core calibration.Then,the distribution characteristics of karst fractures and their controlling effect on reservoirs were studied according to the identification results.And the following research results were obtained.First,karst fractures are mainly of high angle with the characteristic of mono system and the interactive relation of genesis.Second,they are mainly distributed in the upper XVhp layer of CallovianeOxford Stage and the lower XVa2eXVI layer.Third,they are the main effective fractures in this area.The dissolved pores are connected effectively through the expanded karst fractures by dissolution,and consequently reservoirs of high porosity and permeability are formed and they are the important reservoir type and high-yield gas reservoir in this area.Fourth,karst fractures are related to high-yield wells and high-yield layers in this area,and they also control the distribution of high-yield reservoirs in the lower part of CallovianeOxford Stage.It is concluded that by virtue of imaging logging and conventional logging data,karst fractures,unfilled fractures,semi-filled fractures and fullyfilled fractures can be identified and evaluated better.Furthermore,the identification and evaluation of karst fractures deepen the understanding on fractured reservoirs in this area,improve the reservoir evaluation effect,and provide the basis for the target horizon and azimuth optimization of horizontal wells and highly deviated wells.And it is also indicated that the reservoirs with developed karst fractures are the subsequent important drilling targets.展开更多
Through the field emission scanning electronic microscope(FESEM)and the nitrogen adsorption test,pore type and structure of shale reservoir in the Longmaxi Formation in the Sichuan Basin were well studied.Result showe...Through the field emission scanning electronic microscope(FESEM)and the nitrogen adsorption test,pore type and structure of shale reservoir in the Longmaxi Formation in the Sichuan Basin were well studied.Result showed that the pore type includes organic pore,intercrystalline pore,dissolution intracrystalline pore and interparticle pore,and the organic pore was one of major pore types;among the organic pore,the micropore had large pore volume and specific surface area,and was the main storage space of shale gas.Through study on effect of total organic carbon(TOC),organic matter maturity(Ro),diagenesis and tectonism on shale porosity,influence of TOC on porosity could be divided into four stages:the rapid increasing stage(TOC from 0 to 2%),the slow decreasing stage(TOC from 2 to 3%),the rapid increasing stage(TOC from 3 to 4%or 6%)and the rapid decreasing stage(TOC>4%or 6%);influence of the maturity on porosity of shale could be divided into three stages:the rapid decreasing stage(Ro from 1.5 to 2.2%),the rapid increasing stage(Ro from 2.2 to 2.7%)and the rapid decreasing stage(Ro>2.7%);during the high thermal evolution stage,the organic diagenesis was stronger than the inorganic diagenesis;the tectonism had a great impact on porosity,and the more intense the tectonism was,the smaller the porosity would be.The evolution of shale porosity of the Longmaxi Formation underwent five stages:the immature rapid compaction stage(Ro<0.7%),the mature hydrocarbon generation and dissolution stage(Ro from 0.7 to 1.3%),the high mature pore closed stage(Ro from 1.3 to 2.2%),the overmature secondary pyrolysis stage(Ro from 2.2 to 2.7%)and the overmature slow compaction stage(Ro>2.7%);among which the mature hydrocarbon generation and dissolution stage and the overmature secondary pyrolysis stage were the most favorable shale pore development stages。展开更多
The performance of nano-cellulose fluid as a"green"flooding agent in enhancing oil recovery was evaluated in our previous study.Expanding upon our prior findings,in this study the physical properties of nano...The performance of nano-cellulose fluid as a"green"flooding agent in enhancing oil recovery was evaluated in our previous study.Expanding upon our prior findings,in this study the physical properties of nano-cellulose were further improved through chemical grafting with 2-acrylamido-2-methylpropane sulfonic acid monomer(AMPS)and alkyl chain.Scanning electron microscopy(SEM)observation indicated that the morphology of the nano-cellulose maintained fibrillar and was not altered after the chemical modification.The thermal stability of the AMPS and alkyl chain grafted nano-cellulose was investigated through thermogravimetric analysis(TGA).A similar thermal response behavior was observed for the three evaluated samples.Compared to the non-grafted nano-cellulose,the grafted nano-cellulose remained homogenous in an electrolyte solution against storage time,suggesting a superior sanity-tolerance.Rheological analysis also proved the advanced viscoelastic properties of the nano-cellulose dispersion.展开更多
文摘In 2012,China's first national shale gas demonstrations areas were set up in the Sichuan Basin.After 10 years'construction and practice,the giant marine shale gas area of 10×10^(12) m^(3) level is built up in the Sichuan Basin,and shale gas steps into a new stage of large-scale benefit exploration and development.In order to systematically summarize the achievements in shale gas exploration and development and provide guidance and reference for the exploration and development of deep shale gas and shale oil&gas in other areas,this paper systematically summarizes the main characteristics,development models and key identification and evaluation technologies for quality reservoirs of Wufeng Formation-Longmaxi Formation shale gas by analyzing the electric property,lithofacies,reservoir parameters and microscopic porosity of key wells in the basin.And the following research results are obtained.First,biogenetic siliceous shale,calcareous shale and mixed shale are main lithofacies types in quality shale gas reservoirs,and they are formed in the environment of semi-deep and deep water continental shelf.Their lateral distribution is controlled by the paleogeomorphology and their vertical development is influenced by provenance,redox condition and paleo productivity.They are 25-90 m thick.Second,in the quality shale gas reservoirs develop organic pores,inorganic pore and microfractures(including lamina/bedding fractures),among which,organic pore is one of the main reservoir spaces and microfracture is not only indispensable reservoir space,but also production pathway.The reservoir space of shale gas is overall micro-nano pore,and macropores play an important role in shale gas enrichment.Third,three development models of quality reservoir are established,including sedimentary type,diagenesis type and reworking type.The sedimentary type is the foundation.Multiple quality reservoirs are developed in the high U/Th interval of graptolite belt at the bottom of Longmaxi Formation,and their thickness is mainly controlled by paleogeomorphology and especially greater in the depression area.The diagenesis type is divided into three forms,i.e.,syngenetic-early diagenetic rigid support,middle-late diagenetic mineral-organic matter transformation,and overpressure relief compaction.The reworking type is dominated by quality reservoirs with microfractures.Fourth,the core technologies for identifying and evaluating quality shale gas reservoir include large-size core and rock slice observation,high-accuracy rock mineral identification,experimental gas content test and simulation,SEM microscopic characterization,3D microscopic pore reconstruction,comprehensive geophysical interpretation and prediction and big data analysis.In conclusion,nearly 10 years'research and practice achievements in demonstration area construction can deepen the understanding on domestic quality shale gas reservoirs,promote the effective development of the theories and technologies related to shale gas reservoirs,improve the prediction accuracy of shale gas sweet spot zones/intervals,and expand the shale gas exploration and development achievements of demonstration areas.
文摘Deep shale reservoirs(3500–4500 m)exhibit significantly different stress states than moderately deep shale reservoirs(2000–3500 m).As a result,the brittleness response mechanisms of deep shales are also different.It is urgent to investigate methods to evaluate the brittleness of deep shales to meet the increasingly urgent needs of deep shale gas development.In this paper,the quotient of Young’s modulus divided by Poisson’s ratio based on triaxial compression tests under in situ stress conditions is taken as SSBV(Static Standard Brittleness Value).A new and pragmatic technique is developed to determine the static brittleness index that considers elastic parameters,the mineral content,and the in situ stress conditions(BIEMS).The coefficient of determination between BIEMS and SSBV reaches 0.555 for experimental data and 0.805 for field data.This coefficient is higher than that of other brittleness indices when compared to SSBV.BIEMS can offer detailed insights into shale brittleness under various conditions,including different mineral compositions,depths,and stress states.This technique can provide a solid data-based foundation for the selection of‘sweet spots’for single-well engineering and the comparison of the brittleness of shale gas production layers in different areas.
基金This work was supported National Key R&D Program of China(2017YFC0601505).
文摘In this study,a new adaptive morphological filter is developed based on the mathematical morphology algorithm and characteristics of the subtle differences in the waveform morphology in seismic data.The algorithm improves the traditional morphological dilation and corrosion operations.In this study,we propose a multiscale adaptive operator based on the principle of morphological structural“probes”and present the corresponding mathematical proof.Simulation experiments and actual seismic data processing results show that compared with traditional morphological filters,the constructed OCCO-based multistructure adaptive morphological filter can suppress noise to the greatest extent.Moreover,it can effectively improve the SNR of the images,and offers great application prospects.
文摘Carbonate gas reservoir in the eastern area on the Right Bank of the Amu Darya River,Turkmenistan,are of low-porosity and with developed fractures.In this area,fractures control reservoir properties and natural gas production,and karst fractures are the most important kind of fractures,so their identification and evaluation are quite necessary.In this paper,fracture types were identified and their occurrence was extracted by using conventional logging and image logging data after core calibration.Then,the distribution characteristics of karst fractures and their controlling effect on reservoirs were studied according to the identification results.And the following research results were obtained.First,karst fractures are mainly of high angle with the characteristic of mono system and the interactive relation of genesis.Second,they are mainly distributed in the upper XVhp layer of CallovianeOxford Stage and the lower XVa2eXVI layer.Third,they are the main effective fractures in this area.The dissolved pores are connected effectively through the expanded karst fractures by dissolution,and consequently reservoirs of high porosity and permeability are formed and they are the important reservoir type and high-yield gas reservoir in this area.Fourth,karst fractures are related to high-yield wells and high-yield layers in this area,and they also control the distribution of high-yield reservoirs in the lower part of CallovianeOxford Stage.It is concluded that by virtue of imaging logging and conventional logging data,karst fractures,unfilled fractures,semi-filled fractures and fullyfilled fractures can be identified and evaluated better.Furthermore,the identification and evaluation of karst fractures deepen the understanding on fractured reservoirs in this area,improve the reservoir evaluation effect,and provide the basis for the target horizon and azimuth optimization of horizontal wells and highly deviated wells.And it is also indicated that the reservoirs with developed karst fractures are the subsequent important drilling targets.
基金supported by the National Natural Science Foundation of China(No.41502150)Major science and technology special projects of PetroChina Co.Ltd(No.2016E-0611)Stra-tegic Priority Research Programof the Chinese Academy of Sciences(No.XDB10010504).
文摘Through the field emission scanning electronic microscope(FESEM)and the nitrogen adsorption test,pore type and structure of shale reservoir in the Longmaxi Formation in the Sichuan Basin were well studied.Result showed that the pore type includes organic pore,intercrystalline pore,dissolution intracrystalline pore and interparticle pore,and the organic pore was one of major pore types;among the organic pore,the micropore had large pore volume and specific surface area,and was the main storage space of shale gas.Through study on effect of total organic carbon(TOC),organic matter maturity(Ro),diagenesis and tectonism on shale porosity,influence of TOC on porosity could be divided into four stages:the rapid increasing stage(TOC from 0 to 2%),the slow decreasing stage(TOC from 2 to 3%),the rapid increasing stage(TOC from 3 to 4%or 6%)and the rapid decreasing stage(TOC>4%or 6%);influence of the maturity on porosity of shale could be divided into three stages:the rapid decreasing stage(Ro from 1.5 to 2.2%),the rapid increasing stage(Ro from 2.2 to 2.7%)and the rapid decreasing stage(Ro>2.7%);during the high thermal evolution stage,the organic diagenesis was stronger than the inorganic diagenesis;the tectonism had a great impact on porosity,and the more intense the tectonism was,the smaller the porosity would be.The evolution of shale porosity of the Longmaxi Formation underwent five stages:the immature rapid compaction stage(Ro<0.7%),the mature hydrocarbon generation and dissolution stage(Ro from 0.7 to 1.3%),the high mature pore closed stage(Ro from 1.3 to 2.2%),the overmature secondary pyrolysis stage(Ro from 2.2 to 2.7%)and the overmature slow compaction stage(Ro>2.7%);among which the mature hydrocarbon generation and dissolution stage and the overmature secondary pyrolysis stage were the most favorable shale pore development stages。
基金The authors would like to acknowledge the financial support from PetroChina Innovation Foundation(2015D-5006-0212).
文摘The performance of nano-cellulose fluid as a"green"flooding agent in enhancing oil recovery was evaluated in our previous study.Expanding upon our prior findings,in this study the physical properties of nano-cellulose were further improved through chemical grafting with 2-acrylamido-2-methylpropane sulfonic acid monomer(AMPS)and alkyl chain.Scanning electron microscopy(SEM)observation indicated that the morphology of the nano-cellulose maintained fibrillar and was not altered after the chemical modification.The thermal stability of the AMPS and alkyl chain grafted nano-cellulose was investigated through thermogravimetric analysis(TGA).A similar thermal response behavior was observed for the three evaluated samples.Compared to the non-grafted nano-cellulose,the grafted nano-cellulose remained homogenous in an electrolyte solution against storage time,suggesting a superior sanity-tolerance.Rheological analysis also proved the advanced viscoelastic properties of the nano-cellulose dispersion.
