Previous studies have postulated the contribution of present-day low-total organic carbon(TOC)marine carbonate source rocks to oil accumulations in the Tabei Uplift,Tarim Basin,China.However,not all present-day low-TO...Previous studies have postulated the contribution of present-day low-total organic carbon(TOC)marine carbonate source rocks to oil accumulations in the Tabei Uplift,Tarim Basin,China.However,not all present-day low-TOC carbonates have generated and expelled hydrocarbons;therefore,to distinguish the source rocks that have already expelled sufficient hydrocarbons from those not expelled hydrocarbons,is crucial in source rock evaluation and resource assessment in the Tabei Uplift.Mass balance can be used to identify modern low-TOC carbonates resulting from hydrocarbon expulsion.However,the process is quite complicated,requiring many parameters and coefficients and thus also a massive data source.In this paper,we provide a quick and cost effective method for identifying carbonate source rock with present-day low TOC,using widely available Rock-Eval data.First,we identify present-day low-TOC carbonate source rocks in typical wells according to the mass balance approach.Second,we build an optimal model to evaluate source rocks from the analysis of the rocks'characteristics and their influencing factors,reported as positive or negative values of a dimensionless index of Rock-Eval data(IR).Positive IR corresponds to those samples which have expelled hydrocarbons.The optimal model optimizes complicated calculations and simulation processes;thus it could be widely applicable and competitive in the evaluation of present-day low TOC carbonates.By applying the model to the Rock-Eval dataset of the Tabei Uplift,we identify present-day iow-TOC carbonate source rocks and primarily evaluate the contribution equivalent of 11.87×10^9 t oil.展开更多
Hydrocarbon source potential of the Paleogene Pabdeh Formation was studied by means of organic geochemistry and distribution of calcareous nannofossils.Based on the results,an Eoceneaged organic matter(OM)-rich interv...Hydrocarbon source potential of the Paleogene Pabdeh Formation was studied by means of organic geochemistry and distribution of calcareous nannofossils.Based on the results,an Eoceneaged organic matter(OM)-rich interval was identified and traced across different parts of the North Dezful zone and partly Abadan Plain.In order to characterize the OM quality and richness of the studied intervals,Rock-Eval pyrolysis and nannofossils evaluation were performed,and the geochemical data collected along selected wells were correlated to capture the variations of thickness and source potential of the OM-rich interval.Accordingly,remarkable variations were identified within the depth ranges of 2480–2552 m and also 2200–2210 m,which were attributed to the maximum increase in the rate of growth R-selected species.This increase in the productivity rate was found to be well correlated to high Rock-Eval total organic carbon(TOC)and hydrogen index(HI)values.Given that the maturity of Pabdeh Formation in the studied area was found to have reached the oil window,we expect significant hydrocarbon generation(Type II kerogen),making the play economically highly promising.展开更多
How to accurately recover the hydrocarbon loss is a crucial step in reservoir evaluation by Rock-Eval pyrolysis. However, it is very difficult to determine the recovering coefficients because there are numerous factor...How to accurately recover the hydrocarbon loss is a crucial step in reservoir evaluation by Rock-Eval pyrolysis. However, it is very difficult to determine the recovering coefficients because there are numerous factors causing the hydrocarbon loss. Aiming at this problem, a new method named critical point analysis is put forward in this paper. The first step of the method is to find the critical point by drawing the scatterplot of hydrocarbon contents versus the ratio of the light component of with the heavy component of;And the second step is to calculate the recovering coefficient by contrasting the pyrolysis parameters at the critical point of different sample types. This method is not only been explained reasonably theoretically,but also has got a good application effect in Huanghua depression.展开更多
The Rock-Eval technique in the last few decades has found extensive application for source rock analysis.The impact of shale particle crush-size and sample weight on key Rock-Eval measurements,viz.the S;curve(heavier ...The Rock-Eval technique in the last few decades has found extensive application for source rock analysis.The impact of shale particle crush-size and sample weight on key Rock-Eval measurements,viz.the S;curve(heavier hydrocarbons released during the non-isothermal pyrolysis-stage)and the S;curve(CO_(2)released from oxidation of organic matter during the oxidation-stage)are investigated in this study.For high and low total organic carbon(TOC)samples of different thermal maturity levels,it is apparent that particle crush-size has a strong influence on the results obtained from RockEval analysis,with the effect being stronger in high-TOC samples.In comparison to the coarser-splits,S;and pyrolyzable carbon(PC)were found to be higher for the finer crush sizes in all the shales studied.The S_(2)CO_(2)oxidation curve shapes of Permian shales show contrasting signatures in comparison to the Paleocene-aged lignitic shale,both from Indian basins.A reduced TOC was observed with rising sample weight for a mature Permian shale from the Jharia basin,while the other shales sampled showed no significant reduction.The results indicate that the S_(2)CO_(2)curve and the S_(2)T_(2),are strongly dependent on the type of organic-matter present and its level of thermal maturity.Sample weight and particle size both influence the S;-curve shapes at different heating rates.With increasing sample weights,an increase in S;-curve magnitude was observed for the shales of diverse maturities.These differences in the S;curve shape lead to substantially different kinetic distributions being fitted to these curves.These findings are considered to have significant implications for the accuracy of reaction kinetics obtained from pyrolysis experiments using different sample characteristics.展开更多
Understanding the origins of potential source rocks and unraveling the intricate connections between reservoir oils and their source formations in the Siwa Basin(Western Desert,Egypt)necessitate a thorough oil-source ...Understanding the origins of potential source rocks and unraveling the intricate connections between reservoir oils and their source formations in the Siwa Basin(Western Desert,Egypt)necessitate a thorough oil-source correlation investigation.This objective is achieved through a meticulous analysis of well-log responses,Rock-Eval pyrolysis,and biomarker data.The analysis of Total Organic Carbon across 31 samples representing Paleozoic formations in the Siwa A-1X well reveals a spectrum of organic richness ranging from 0.17 wt%to 2.04 wt%,thereby highlighting diverse levels of organic content and the presence of both Type II and Type III kerogen.Examination of the fingerprint characteristics of eight samples from the well suggests that the Dhiffah Formation comprises a blend of terrestrial and marine organic matter.Notably,a significant contribution from more oxidized residual organic matter and gas-prone Type III kerogen is observed.Contrarily,the Desouky and Zeitoun formations exhibit mixed organic matter indicative of a transitional environment,and thus featuring a pronounced marine influence within a more reducing setting,which is associated with Type II kerogen.Through analysis of five oil samples from different wells—SIWA L-1X,SIWA R-3X,SIWA D-1X,PTAH 5X,and PTAH 6X,it is evident that terrestrial organic matter,augmented by considerable marine input,was deposited in an oxidizing environment,and contains Type III kerogen.Geochemical scrutiny confirms the coexistence of mixed terrestrial organic matter within varying redox environments.Noteworthy is the uniformity of identified kerogen Types II and III across all samples,known to have potential for hydrocarbon generation.The discovery presented in this paper unveils captivating prospects concerning the genesis of oil in the Jurassic Safa reservoir,suggesting potential links to Paleozoic sources or even originating from the Safa Member itself.These revelations mark a substantial advancement in understanding source rock dynamics and their intricate relationship with reservoir oils within the Siwa Basin.By illuminating the processes of hydrocarbon genesis in the region,this study significantly enriches our knowledge base.展开更多
The Albian-Maastrichtian interval of the Ivorian sedimentary basin has been the subject of numerous sedimentological, biostratigraphic, and geophysical studies. However, its geochemical characteristics remain relative...The Albian-Maastrichtian interval of the Ivorian sedimentary basin has been the subject of numerous sedimentological, biostratigraphic, and geophysical studies. However, its geochemical characteristics remain relatively unexplored. This study aims to determine the oil potential and the nature of the organic matter it contains. It focuses on the geochemical analysis (physicochemical method) of two oil wells located in the offshore sedimentary basin of Côte d’Ivoire, specifically in the Abidjan margin. A total of 154 cuttings samples from wells TMH-1X and TMH-2X were analyzed to determine their oil potential and the nature of the organic matter (OM) they contain. The analyses were performed using Rock-Eval pyrolysis, a method that characterizes the amount of hydrocarbons generated by the organic matter present in the rocks. The key parameters measured include Total Organic Carbon (TOC), Hydrogen Index (HI), oil potential (S2), and maximum pyrolysis temperature (Tmax). These parameters are used to assess the amount of organic matter, its thermal maturity, and its potential to generate hydrocarbons in the studied wells. The results show significant variations between different stratigraphic levels. In well TMH-1X, the Cenomanian and Campanian intervals stand out with very good quantities of organic matter (OM) with good oil potential, although often immature. In contrast, other stages such as the Albian and Turonian contain organic matter in moderate to low quantities, often immature and of continental type, which limits their capacity to generate hydrocarbons. In well TMH-2X, a similar trend is observed. Despite an abundance of organic matter, the oil potential remains low in most of the studied stages. The organic matter is primarily of type III (continental origin) and thermally immature, indicating a low potential for hydrocarbon generation. The study reveals that, although some intervals exhibit high-quality organic matter, the majority of the samples show insufficient maturity for effective hydrocarbon production. Wells TMH-1X and TMH-2X offer limited oil potential, requiring more advanced maturation conditions to fully exploit the hydrocarbon resources.展开更多
The contamination of cuttings and side wall core (SWC) samples in the Bambra 2 well by drilling mud additives and natural hydrocarbons may cause Rock Eval T max (℃) data to be suspect, and affect its uti...The contamination of cuttings and side wall core (SWC) samples in the Bambra 2 well by drilling mud additives and natural hydrocarbons may cause Rock Eval T max (℃) data to be suspect, and affect its utility in the assessment of thermal maturity. The Rock Eval results of 284 cuttings samples, 31 side wall core samples and conventional core samples from the Jurassic Cretaceous sedimentary sequences in the Bambra 2 well are presented in this paper. Significantly lower T max values from cuttings samples compared with T max values from conventional core samples and solvent extracted SWC samples, from the deeper and higher maturity interval, are thought to have been caused by contamination by diesel and other drilling mud additives. The cuttings samples in the Barrow Group of Cretaceous may be contaminated by natural hydrocarbons, resulting their T max values to be 2-10 ℃ lower than a regularly increased T max trend from core samples. This study indicates that more reliable Rock Eval T max data are obtained from the conventional core samples and solvent extracted SWC samples. This study also indicates that the T max values from some SWC samples were also affected by free hydrocarbons, due to the use of diesel as a mud additive as well.展开更多
This article prognosticates the hydrocarbon generation potential of core samples from fields A, B, C and D in Niger delta, Nigeria. The objectives of this study are to characterize the quality of these core samples by...This article prognosticates the hydrocarbon generation potential of core samples from fields A, B, C and D in Niger delta, Nigeria. The objectives of this study are to characterize the quality of these core samples by organic geochemical analyses. A total of ten core samples collected from fields A, B, C and D in Niger delta were analyzed using total organic carbon(TOC) content analysis, rock-eval pyrolysis technique. The analytical results of the studied core samples reveal that they have generally high total organic carbon contents(TOC), suggesting that conditions in the Niger delta favour organic matter production and preservation. There is a variation in the kerogen types and this may be attributed to the relative stratigraphic positions of the core samples within the Niger delta. The rock-eval results indicate that the samples from fields C and D contain predominantly Type II kerogen with a capacity to generate oil and gas and hence have good generative potential. The samples from fields A and B contain mainly Type III kerogen and are gas-prone with moderate generative potential.展开更多
Controlled by fluctuating paleoclimates and sedimentary environments,the organic and inorganic features of the Lucaogou Formation exhibit strong heterogeneity in the vertical profile,challenging conventional geologica...Controlled by fluctuating paleoclimates and sedimentary environments,the organic and inorganic features of the Lucaogou Formation exhibit strong heterogeneity in the vertical profile,challenging conventional geological interpretation.To elucidate the possible influence of heterogeneity on resource evaluation,a high-resolution sampling approach was applied to an 86.2 cm long core from the Lucaogou Formation of the Jimsar sag in the Junggar Basin.86 sets of samples were micro-drilled from the core and subjected to comparative Rock-Eval pyrolysis.Following the classical guidelines,the organic abundance,kerogen type,and maturity of source rocks were exhaustively analyzed.Experimental results revealed that organic richness and composition vary significantly under different sedimentary backgrounds,which in turn leads to differential hydrocarbon generation.The combination of hydrocarbon generation,transport,and expulsion results in peculiar patterns for hydrocarbon accumulation in the Lucaogou Formation.Laminated shales in the Lucaogou Formation serve as both hydrocarbon source rocks and reservoirs,with laminae being migration pathways.Organic-rich dolomites in the Lucaogou Formation have a considerable hydrocarbon-generating capacity and present the characteristics of self-generation and self-storage.However,massive mudstones act purely as hydrocarbon source rocks.展开更多
Shale gas,a type of unconventional natural gas found within shale formations,has emerged as a significant source of energy globally.The West Bokaro Basin,part of the Damodar Valley,is known for its rich coal deposits ...Shale gas,a type of unconventional natural gas found within shale formations,has emerged as a significant source of energy globally.The West Bokaro Basin,part of the Damodar Valley,is known for its rich coal deposits and complex geological history.The basin's stratigraphy includes significant coal-bearing formations interbedded with shales,which may be potential sources of shale gas.The key formations in the basin include the Barakar Formation,which is the primary coal-bearing unit,and the Raniganj Formation,which contains substantial shale intervals.These formations exhibit varying thicknesses,organic content,thermal maturity,and mechanical strength,all of which are critical factors influencing shale gas potential.The assessment of shale gas potential in the West Bokaro Basin involves evaluating the organic richness,thermal maturity,pore characteristics,geochemistry,and mineralogy of the shale formations.Apart from organic richness and thermal maturity,the shale formations must be friable,as they generally lack natural permeability.This study aims to present a comprehensive analysis of the prospects of shale gas in the West Bokaro Basin based on the organic petrography,geochemistry,mineralogical study,Fourier Transform Infrared Spectroscopy(FTIR)analysis,and low-pressure N_(2) adsorption analysis.The dark color,greasy touch,and high total organic carbon(TOC)content(5.88%-22.84%)provided an initial clue for the shale's potential as a source rock.Results from organic petrographic analysis suggest that these shales contain kerogen type Ⅲ,which is a known indicator of gas-prone zones.The random vitrinite reflectance(R_(o),0.80%-0.91%)and the temperature of maximum pyrolysis yield(Tmax,434-448℃)indicate that the organic matter has attained the sufficient thermal maturity required for the generation of hydrocarbons.FTIR and X-ray diffraction(XRD)analyses identified inorganic entities and high quartz content in the shale samples,confirming their friability.The brittleness index(BI)calculated using X-ray fluorescence(XRF)data showed BI values above 0.48,indicating that the shales are brittle,which is advantageous for hydraulic fracturing.The high quartz content in the shale might act as a natural proppant,enhancing gas extraction efficiency.These findings suggest that the West Bokaro shales hold promise for economically viable shale gas production.展开更多
基金supported by the China Postdoctoral Science Foundation(grant No.2017M611108)the National Science and Technology Major Project of China(grant No.2016ZX05006006-001)the National Basic Research Program of China(grant Nos.2011CB2011-02 and 2014CB239100)
文摘Previous studies have postulated the contribution of present-day low-total organic carbon(TOC)marine carbonate source rocks to oil accumulations in the Tabei Uplift,Tarim Basin,China.However,not all present-day low-TOC carbonates have generated and expelled hydrocarbons;therefore,to distinguish the source rocks that have already expelled sufficient hydrocarbons from those not expelled hydrocarbons,is crucial in source rock evaluation and resource assessment in the Tabei Uplift.Mass balance can be used to identify modern low-TOC carbonates resulting from hydrocarbon expulsion.However,the process is quite complicated,requiring many parameters and coefficients and thus also a massive data source.In this paper,we provide a quick and cost effective method for identifying carbonate source rock with present-day low TOC,using widely available Rock-Eval data.First,we identify present-day low-TOC carbonate source rocks in typical wells according to the mass balance approach.Second,we build an optimal model to evaluate source rocks from the analysis of the rocks'characteristics and their influencing factors,reported as positive or negative values of a dimensionless index of Rock-Eval data(IR).Positive IR corresponds to those samples which have expelled hydrocarbons.The optimal model optimizes complicated calculations and simulation processes;thus it could be widely applicable and competitive in the evaluation of present-day low TOC carbonates.By applying the model to the Rock-Eval dataset of the Tabei Uplift,we identify present-day iow-TOC carbonate source rocks and primarily evaluate the contribution equivalent of 11.87×10^9 t oil.
基金supported by the Exploration Directorate of National Iranian Oil Company(NIOC)。
文摘Hydrocarbon source potential of the Paleogene Pabdeh Formation was studied by means of organic geochemistry and distribution of calcareous nannofossils.Based on the results,an Eoceneaged organic matter(OM)-rich interval was identified and traced across different parts of the North Dezful zone and partly Abadan Plain.In order to characterize the OM quality and richness of the studied intervals,Rock-Eval pyrolysis and nannofossils evaluation were performed,and the geochemical data collected along selected wells were correlated to capture the variations of thickness and source potential of the OM-rich interval.Accordingly,remarkable variations were identified within the depth ranges of 2480–2552 m and also 2200–2210 m,which were attributed to the maximum increase in the rate of growth R-selected species.This increase in the productivity rate was found to be well correlated to high Rock-Eval total organic carbon(TOC)and hydrogen index(HI)values.Given that the maturity of Pabdeh Formation in the studied area was found to have reached the oil window,we expect significant hydrocarbon generation(Type II kerogen),making the play economically highly promising.
文摘How to accurately recover the hydrocarbon loss is a crucial step in reservoir evaluation by Rock-Eval pyrolysis. However, it is very difficult to determine the recovering coefficients because there are numerous factors causing the hydrocarbon loss. Aiming at this problem, a new method named critical point analysis is put forward in this paper. The first step of the method is to find the critical point by drawing the scatterplot of hydrocarbon contents versus the ratio of the light component of with the heavy component of;And the second step is to calculate the recovering coefficient by contrasting the pyrolysis parameters at the critical point of different sample types. This method is not only been explained reasonably theoretically,but also has got a good application effect in Huanghua depression.
基金awarding BH the CSIR-CIMFR in-house research grant(No.MLP-93/2019-20),the funds of which were utilized to purchase the Rock-Eval 6 device at CSIR-CIMFR and conduct the research。
文摘The Rock-Eval technique in the last few decades has found extensive application for source rock analysis.The impact of shale particle crush-size and sample weight on key Rock-Eval measurements,viz.the S;curve(heavier hydrocarbons released during the non-isothermal pyrolysis-stage)and the S;curve(CO_(2)released from oxidation of organic matter during the oxidation-stage)are investigated in this study.For high and low total organic carbon(TOC)samples of different thermal maturity levels,it is apparent that particle crush-size has a strong influence on the results obtained from RockEval analysis,with the effect being stronger in high-TOC samples.In comparison to the coarser-splits,S;and pyrolyzable carbon(PC)were found to be higher for the finer crush sizes in all the shales studied.The S_(2)CO_(2)oxidation curve shapes of Permian shales show contrasting signatures in comparison to the Paleocene-aged lignitic shale,both from Indian basins.A reduced TOC was observed with rising sample weight for a mature Permian shale from the Jharia basin,while the other shales sampled showed no significant reduction.The results indicate that the S_(2)CO_(2)curve and the S_(2)T_(2),are strongly dependent on the type of organic-matter present and its level of thermal maturity.Sample weight and particle size both influence the S;-curve shapes at different heating rates.With increasing sample weights,an increase in S;-curve magnitude was observed for the shales of diverse maturities.These differences in the S;curve shape lead to substantially different kinetic distributions being fitted to these curves.These findings are considered to have significant implications for the accuracy of reaction kinetics obtained from pyrolysis experiments using different sample characteristics.
基金the research project is funded by Abdullah Alrushaid Chair for Earth Science Remote Sensing Research at King Saud University,Riyadh,Saudi Arabia.。
文摘Understanding the origins of potential source rocks and unraveling the intricate connections between reservoir oils and their source formations in the Siwa Basin(Western Desert,Egypt)necessitate a thorough oil-source correlation investigation.This objective is achieved through a meticulous analysis of well-log responses,Rock-Eval pyrolysis,and biomarker data.The analysis of Total Organic Carbon across 31 samples representing Paleozoic formations in the Siwa A-1X well reveals a spectrum of organic richness ranging from 0.17 wt%to 2.04 wt%,thereby highlighting diverse levels of organic content and the presence of both Type II and Type III kerogen.Examination of the fingerprint characteristics of eight samples from the well suggests that the Dhiffah Formation comprises a blend of terrestrial and marine organic matter.Notably,a significant contribution from more oxidized residual organic matter and gas-prone Type III kerogen is observed.Contrarily,the Desouky and Zeitoun formations exhibit mixed organic matter indicative of a transitional environment,and thus featuring a pronounced marine influence within a more reducing setting,which is associated with Type II kerogen.Through analysis of five oil samples from different wells—SIWA L-1X,SIWA R-3X,SIWA D-1X,PTAH 5X,and PTAH 6X,it is evident that terrestrial organic matter,augmented by considerable marine input,was deposited in an oxidizing environment,and contains Type III kerogen.Geochemical scrutiny confirms the coexistence of mixed terrestrial organic matter within varying redox environments.Noteworthy is the uniformity of identified kerogen Types II and III across all samples,known to have potential for hydrocarbon generation.The discovery presented in this paper unveils captivating prospects concerning the genesis of oil in the Jurassic Safa reservoir,suggesting potential links to Paleozoic sources or even originating from the Safa Member itself.These revelations mark a substantial advancement in understanding source rock dynamics and their intricate relationship with reservoir oils within the Siwa Basin.By illuminating the processes of hydrocarbon genesis in the region,this study significantly enriches our knowledge base.
文摘The Albian-Maastrichtian interval of the Ivorian sedimentary basin has been the subject of numerous sedimentological, biostratigraphic, and geophysical studies. However, its geochemical characteristics remain relatively unexplored. This study aims to determine the oil potential and the nature of the organic matter it contains. It focuses on the geochemical analysis (physicochemical method) of two oil wells located in the offshore sedimentary basin of Côte d’Ivoire, specifically in the Abidjan margin. A total of 154 cuttings samples from wells TMH-1X and TMH-2X were analyzed to determine their oil potential and the nature of the organic matter (OM) they contain. The analyses were performed using Rock-Eval pyrolysis, a method that characterizes the amount of hydrocarbons generated by the organic matter present in the rocks. The key parameters measured include Total Organic Carbon (TOC), Hydrogen Index (HI), oil potential (S2), and maximum pyrolysis temperature (Tmax). These parameters are used to assess the amount of organic matter, its thermal maturity, and its potential to generate hydrocarbons in the studied wells. The results show significant variations between different stratigraphic levels. In well TMH-1X, the Cenomanian and Campanian intervals stand out with very good quantities of organic matter (OM) with good oil potential, although often immature. In contrast, other stages such as the Albian and Turonian contain organic matter in moderate to low quantities, often immature and of continental type, which limits their capacity to generate hydrocarbons. In well TMH-2X, a similar trend is observed. Despite an abundance of organic matter, the oil potential remains low in most of the studied stages. The organic matter is primarily of type III (continental origin) and thermally immature, indicating a low potential for hydrocarbon generation. The study reveals that, although some intervals exhibit high-quality organic matter, the majority of the samples show insufficient maturity for effective hydrocarbon production. Wells TMH-1X and TMH-2X offer limited oil potential, requiring more advanced maturation conditions to fully exploit the hydrocarbon resources.
文摘The contamination of cuttings and side wall core (SWC) samples in the Bambra 2 well by drilling mud additives and natural hydrocarbons may cause Rock Eval T max (℃) data to be suspect, and affect its utility in the assessment of thermal maturity. The Rock Eval results of 284 cuttings samples, 31 side wall core samples and conventional core samples from the Jurassic Cretaceous sedimentary sequences in the Bambra 2 well are presented in this paper. Significantly lower T max values from cuttings samples compared with T max values from conventional core samples and solvent extracted SWC samples, from the deeper and higher maturity interval, are thought to have been caused by contamination by diesel and other drilling mud additives. The cuttings samples in the Barrow Group of Cretaceous may be contaminated by natural hydrocarbons, resulting their T max values to be 2-10 ℃ lower than a regularly increased T max trend from core samples. This study indicates that more reliable Rock Eval T max data are obtained from the conventional core samples and solvent extracted SWC samples. This study also indicates that the T max values from some SWC samples were also affected by free hydrocarbons, due to the use of diesel as a mud additive as well.
文摘This article prognosticates the hydrocarbon generation potential of core samples from fields A, B, C and D in Niger delta, Nigeria. The objectives of this study are to characterize the quality of these core samples by organic geochemical analyses. A total of ten core samples collected from fields A, B, C and D in Niger delta were analyzed using total organic carbon(TOC) content analysis, rock-eval pyrolysis technique. The analytical results of the studied core samples reveal that they have generally high total organic carbon contents(TOC), suggesting that conditions in the Niger delta favour organic matter production and preservation. There is a variation in the kerogen types and this may be attributed to the relative stratigraphic positions of the core samples within the Niger delta. The rock-eval results indicate that the samples from fields C and D contain predominantly Type II kerogen with a capacity to generate oil and gas and hence have good generative potential. The samples from fields A and B contain mainly Type III kerogen and are gas-prone with moderate generative potential.
基金supported by the National Natural Science Foundation of China(No.U22B6004)the Basic Research and Strategic Reserve Technology Research Project of CNPC(No.2020D-5008-01)the Scientific Research and Technology Development Project of PetroChina Exploration&Development Research Institute(Nos.2021DJ0104 and 2021DJ1808)。
文摘Controlled by fluctuating paleoclimates and sedimentary environments,the organic and inorganic features of the Lucaogou Formation exhibit strong heterogeneity in the vertical profile,challenging conventional geological interpretation.To elucidate the possible influence of heterogeneity on resource evaluation,a high-resolution sampling approach was applied to an 86.2 cm long core from the Lucaogou Formation of the Jimsar sag in the Junggar Basin.86 sets of samples were micro-drilled from the core and subjected to comparative Rock-Eval pyrolysis.Following the classical guidelines,the organic abundance,kerogen type,and maturity of source rocks were exhaustively analyzed.Experimental results revealed that organic richness and composition vary significantly under different sedimentary backgrounds,which in turn leads to differential hydrocarbon generation.The combination of hydrocarbon generation,transport,and expulsion results in peculiar patterns for hydrocarbon accumulation in the Lucaogou Formation.Laminated shales in the Lucaogou Formation serve as both hydrocarbon source rocks and reservoirs,with laminae being migration pathways.Organic-rich dolomites in the Lucaogou Formation have a considerable hydrocarbon-generating capacity and present the characteristics of self-generation and self-storage.However,massive mudstones act purely as hydrocarbon source rocks.
文摘Shale gas,a type of unconventional natural gas found within shale formations,has emerged as a significant source of energy globally.The West Bokaro Basin,part of the Damodar Valley,is known for its rich coal deposits and complex geological history.The basin's stratigraphy includes significant coal-bearing formations interbedded with shales,which may be potential sources of shale gas.The key formations in the basin include the Barakar Formation,which is the primary coal-bearing unit,and the Raniganj Formation,which contains substantial shale intervals.These formations exhibit varying thicknesses,organic content,thermal maturity,and mechanical strength,all of which are critical factors influencing shale gas potential.The assessment of shale gas potential in the West Bokaro Basin involves evaluating the organic richness,thermal maturity,pore characteristics,geochemistry,and mineralogy of the shale formations.Apart from organic richness and thermal maturity,the shale formations must be friable,as they generally lack natural permeability.This study aims to present a comprehensive analysis of the prospects of shale gas in the West Bokaro Basin based on the organic petrography,geochemistry,mineralogical study,Fourier Transform Infrared Spectroscopy(FTIR)analysis,and low-pressure N_(2) adsorption analysis.The dark color,greasy touch,and high total organic carbon(TOC)content(5.88%-22.84%)provided an initial clue for the shale's potential as a source rock.Results from organic petrographic analysis suggest that these shales contain kerogen type Ⅲ,which is a known indicator of gas-prone zones.The random vitrinite reflectance(R_(o),0.80%-0.91%)and the temperature of maximum pyrolysis yield(Tmax,434-448℃)indicate that the organic matter has attained the sufficient thermal maturity required for the generation of hydrocarbons.FTIR and X-ray diffraction(XRD)analyses identified inorganic entities and high quartz content in the shale samples,confirming their friability.The brittleness index(BI)calculated using X-ray fluorescence(XRF)data showed BI values above 0.48,indicating that the shales are brittle,which is advantageous for hydraulic fracturing.The high quartz content in the shale might act as a natural proppant,enhancing gas extraction efficiency.These findings suggest that the West Bokaro shales hold promise for economically viable shale gas production.
