Forty Tertiary coals from Mukah-Balingian and Merit-Pila coalfields of the Sarawak Basin,Malaysia were investigated using bulk and molecular geochemical techniques such as proximate analysis,gas chromatography-mass sp...Forty Tertiary coals from Mukah-Balingian and Merit-Pila coalfields of the Sarawak Basin,Malaysia were investigated using bulk and molecular geochemical techniques such as proximate analysis,gas chromatography-mass spectrometry,elemental analyser,isotope ratio mass spectrometry,and inductively coupled plasma mass spectrometry to reconstruct their paleovegetation,paleoclimate,and environments of deposition.In addition,principal component analysis(PCA)of selected geochemical parameters was carried out to determine the controlling influences on the petroleum potential of the humic coals.s13C values and the abundance of terpenoids imply the predominant contribution of angiosperms to the paleoflora.Bimetal proxies(Sr/Ba,Sr/Cu,and C-value),andδD values are generally suggestive of a warm and humid climate during the accumulation of the paleopeats.However,n-alkane proxies(P_(wax),P_(aq),n-C_(23)/n-C_(29),etc.)and polycyclic aromatic hydrocarbons(PAHs)distribution suggest that Balingian coals accumulated under relatively drier and strongly seasonal palcoclimate in the Late Pliocene.When compared with published global average abundances,the investigated coals are mostly depleted in major oxides and trace elements,suggesting peat accumulation in freshwater-influenced environments.Nonetheless,higher(>0.5 wt%)total sulfur content in some Mukah-Balingian coals suggests some degree of epigenetic marine influence.Fur-thermore,the low to moderately-high ash contents of the Sarawak Basin coals indicate the presence of ombrotrophic and rheotrophic peat deposits.PCA result of selected geochemical proxies suggests that source input,paleoflora,and marine incursions are not major controlling influences on the petroleum potential.However,climatic,and depositional conditions appear to slightly influence the petroleum potential of the studied humic coals.展开更多
Extracting gas from unconventional shale reservoirs with low permeability is challenging.To overcome this,hydraulic fracturing(HF)is employed.Despite enhancing shale gas production,HF has drawbacks like groundwater po...Extracting gas from unconventional shale reservoirs with low permeability is challenging.To overcome this,hydraulic fracturing(HF)is employed.Despite enhancing shale gas production,HF has drawbacks like groundwater pollution and induced earthquakes.Such issues highlight the need for ongoing exploration of novel shale gas extraction methods such as in situ heating through combustion or pyrolysis to mitigate operational and environmental concerns.In this study,thermally immature shales of contrasting organic richness from Rajmahal Basin of India were heated to different temperatures(pyrolysis at 350,500 and 650℃)to assess the temperature protocols necessary for hydrocarbon liberation and investigate the evolution of pore structural facets with implications for CO_(2) sequestration in underground thermally treated shale horizons.Our results from low-pressure N_(2) adsorption reveal reduced adsorption capacity in the shale splits treated at 350 and 500 C,which can be attributed to structural reworking of the organic matter within the samples leading to formation of complex pore structures that limits the access of nitrogen at low experimental temperatures.Consequently,for both the studied samples BET SSA decreased by~58%and 72%at 350℃,and~67%and 68%at 500℃,whereas average pore diameter increased by~45%and 91%at 350℃,and~100%and 94%at 500℃ compared to their untreated counterparts.CO_(2) adsorption results,unlike N_(2),revealed a pronounced rise in micropore properties(surface area and volume)at 500 and 650℃(~30%-35%and~41%63%,respectively for both samples),contradicting the N_(2) adsorption outcomes.Scanning electron microscope(SEM)images complemented the findings,showing pore structures evolving from microcracks to collapsed pores with increasing thermal treatment.Analysis of the SEM images of both samples revealed a notable increase in average pore width(short axis):by~4 and 10 times at 350℃,~5 and 12 times at 500℃,and~10 and 28 times at 650℃ compared to the untreated samples.Rock-Eval analysis demonstrated the liberation of almost all pyrolyzable kerogen components in the shales heated to 650℃.Additionally,the maximum micropore capacity,identified from CO_(2) gas adsorption analysis,indicated 650℃ as the ideal temperature for in situ conversion and CO_(2) sequestration.Nevertheless,project viability hinges on assessing other relevant aspects of shale gas development such as geomechanical stability and supercritical CO_(2) interactions in addition to thermal treatment.展开更多
The extraction of valuables from waste has gained momentum.Thermal infuence alters both the organic and inorganic components of coal.Insufficient knowledge on the association of rare earth elements(REEs)with the paren...The extraction of valuables from waste has gained momentum.Thermal infuence alters both the organic and inorganic components of coal.Insufficient knowledge on the association of rare earth elements(REEs)with the parent matrix of thermally altered high-ash coals(63%ash)limits the potential for such coals being utilized for isolation of valuables.In this study,we analyzed the distribution and occurrence modes of REEs within a magmatically altered high-ash coal via nine-step sequential extraction,combining Tessier and BCR methods.The total concentration of REEs in the coal sample,on whole coal basis,was found to be 820 ppm,which is significantly higher than the world average.Major mineral oxides were deduced to be those of Si,Fe,Al,Ca,Mg,and Ti.Sequential extraction confirmed that about 66%of HREE and 25%of LREE were included in the residual fraction.LREEs were concluded to be primarily in ionic form,whereas HREEs were speculated to be associated with the TiO_(2) phase.XRD analyses showed that thermal alteration affected the dolomite phase specifically,which selectively got removed where carbonate-bound elements were assessed.Petrographic analysis supported the magmatic influence and demonstrated the presence of mosaic structures and pores containing unfused vitrinite,with a reflectance value of 3.6.To summarize,the present study pertaining to delineation of association of valuables in high-ash heat-altered coals from an Eastern coalfeld in India can potentially open up new avenues for utilizing such coals,which are otherwiseconsidered waste.展开更多
基金Lanre Asiwaju received a scholarship for doctorate study from the Nigerian Government through the Petroleum Technology Development Fund(PTDF).
文摘Forty Tertiary coals from Mukah-Balingian and Merit-Pila coalfields of the Sarawak Basin,Malaysia were investigated using bulk and molecular geochemical techniques such as proximate analysis,gas chromatography-mass spectrometry,elemental analyser,isotope ratio mass spectrometry,and inductively coupled plasma mass spectrometry to reconstruct their paleovegetation,paleoclimate,and environments of deposition.In addition,principal component analysis(PCA)of selected geochemical parameters was carried out to determine the controlling influences on the petroleum potential of the humic coals.s13C values and the abundance of terpenoids imply the predominant contribution of angiosperms to the paleoflora.Bimetal proxies(Sr/Ba,Sr/Cu,and C-value),andδD values are generally suggestive of a warm and humid climate during the accumulation of the paleopeats.However,n-alkane proxies(P_(wax),P_(aq),n-C_(23)/n-C_(29),etc.)and polycyclic aromatic hydrocarbons(PAHs)distribution suggest that Balingian coals accumulated under relatively drier and strongly seasonal palcoclimate in the Late Pliocene.When compared with published global average abundances,the investigated coals are mostly depleted in major oxides and trace elements,suggesting peat accumulation in freshwater-influenced environments.Nonetheless,higher(>0.5 wt%)total sulfur content in some Mukah-Balingian coals suggests some degree of epigenetic marine influence.Fur-thermore,the low to moderately-high ash contents of the Sarawak Basin coals indicate the presence of ombrotrophic and rheotrophic peat deposits.PCA result of selected geochemical proxies suggests that source input,paleoflora,and marine incursions are not major controlling influences on the petroleum potential.However,climatic,and depositional conditions appear to slightly influence the petroleum potential of the studied humic coals.
文摘Extracting gas from unconventional shale reservoirs with low permeability is challenging.To overcome this,hydraulic fracturing(HF)is employed.Despite enhancing shale gas production,HF has drawbacks like groundwater pollution and induced earthquakes.Such issues highlight the need for ongoing exploration of novel shale gas extraction methods such as in situ heating through combustion or pyrolysis to mitigate operational and environmental concerns.In this study,thermally immature shales of contrasting organic richness from Rajmahal Basin of India were heated to different temperatures(pyrolysis at 350,500 and 650℃)to assess the temperature protocols necessary for hydrocarbon liberation and investigate the evolution of pore structural facets with implications for CO_(2) sequestration in underground thermally treated shale horizons.Our results from low-pressure N_(2) adsorption reveal reduced adsorption capacity in the shale splits treated at 350 and 500 C,which can be attributed to structural reworking of the organic matter within the samples leading to formation of complex pore structures that limits the access of nitrogen at low experimental temperatures.Consequently,for both the studied samples BET SSA decreased by~58%and 72%at 350℃,and~67%and 68%at 500℃,whereas average pore diameter increased by~45%and 91%at 350℃,and~100%and 94%at 500℃ compared to their untreated counterparts.CO_(2) adsorption results,unlike N_(2),revealed a pronounced rise in micropore properties(surface area and volume)at 500 and 650℃(~30%-35%and~41%63%,respectively for both samples),contradicting the N_(2) adsorption outcomes.Scanning electron microscope(SEM)images complemented the findings,showing pore structures evolving from microcracks to collapsed pores with increasing thermal treatment.Analysis of the SEM images of both samples revealed a notable increase in average pore width(short axis):by~4 and 10 times at 350℃,~5 and 12 times at 500℃,and~10 and 28 times at 650℃ compared to the untreated samples.Rock-Eval analysis demonstrated the liberation of almost all pyrolyzable kerogen components in the shales heated to 650℃.Additionally,the maximum micropore capacity,identified from CO_(2) gas adsorption analysis,indicated 650℃ as the ideal temperature for in situ conversion and CO_(2) sequestration.Nevertheless,project viability hinges on assessing other relevant aspects of shale gas development such as geomechanical stability and supercritical CO_(2) interactions in addition to thermal treatment.
文摘The extraction of valuables from waste has gained momentum.Thermal infuence alters both the organic and inorganic components of coal.Insufficient knowledge on the association of rare earth elements(REEs)with the parent matrix of thermally altered high-ash coals(63%ash)limits the potential for such coals being utilized for isolation of valuables.In this study,we analyzed the distribution and occurrence modes of REEs within a magmatically altered high-ash coal via nine-step sequential extraction,combining Tessier and BCR methods.The total concentration of REEs in the coal sample,on whole coal basis,was found to be 820 ppm,which is significantly higher than the world average.Major mineral oxides were deduced to be those of Si,Fe,Al,Ca,Mg,and Ti.Sequential extraction confirmed that about 66%of HREE and 25%of LREE were included in the residual fraction.LREEs were concluded to be primarily in ionic form,whereas HREEs were speculated to be associated with the TiO_(2) phase.XRD analyses showed that thermal alteration affected the dolomite phase specifically,which selectively got removed where carbonate-bound elements were assessed.Petrographic analysis supported the magmatic influence and demonstrated the presence of mosaic structures and pores containing unfused vitrinite,with a reflectance value of 3.6.To summarize,the present study pertaining to delineation of association of valuables in high-ash heat-altered coals from an Eastern coalfeld in India can potentially open up new avenues for utilizing such coals,which are otherwiseconsidered waste.
