The petroliferous province of the Western Desert comprises several sedimentary basins with different hydrocarbon potentiality and production capability.The middle Jurassic Khatatba Formation was proved a potential sou...The petroliferous province of the Western Desert comprises several sedimentary basins with different hydrocarbon potentiality and production capability.The middle Jurassic Khatatba Formation was proved a potential source rock in some basins and active/effective in others.The current study aims to give a comprehensive assessment and evaluation of the potential organic-rich intervals of the Khatatba Formation across JG and JD fields,northeast Abu Gharadig Basin(NEAG).The hydrocarbon generating capability and sourcing of the Khatatba Formation studied through organic geochemistry calibrated with well logging.However,the efficiency of some widely used plots of geochemistry is re-evaluated according to their accuracy and consistency.Forty cuttings,thirteen cores and two oil samples obtained from three wells(JG-2,JG-3 and JD-4)were evaluated.The samples revealed total organic carbon(TOC)values ranging from 1 to 9 wt%,exhibiting a good-excellent potential source rock.A single sample in the JD-4 well attained a TOC value of 21.3 wt%with a generating potential(represented by S2 parameter)exceeding 146 mgHc/g rock required a special evaluation.Most of the samples(mainly in the JD-4 well)attained a sufficient level of thermal maturity for hydrocarbon generation with a Tmax up to 449C.The vitrinite reflectance(%Ro)values(a common maturity-related indicator)acquired from the JD-4 well ranging between 0.76%and 0.92%.These values are tediously increasing with depth indicating a uniform geothermal regime.The Khatatba organofacies,with wide variety of kerogen types(I,II,II-S and II/III),contain marine organic matter with a slight terrigenous input,exhibiting anoxic-suboxic environmental conditions.Oil-source correlations define the organic-rich intervals responsible for charging the accumulated hydrocarbon in the NEAG concession.展开更多
Western Desert represents a major oil and gas province in Egypt producing more than 50%of the country’s oil production.Oil and gas blend occurs in most producing fields,however,the genetic link between gas and liquid...Western Desert represents a major oil and gas province in Egypt producing more than 50%of the country’s oil production.Oil and gas blend occurs in most producing fields,however,the genetic link between gas and liquid hydrocarbon phases are not well-constrained.Obayied sub-basin in the Western Desert where oil and gas phases coexist in the Middle Jurassic sandstones of the Khatatba Formation provides an ideal place to investigate the link between oil and gas generation.Geochemical analyses on rock samples(Rock–Eval pyrolysis,vitrinite reflectance,R_(o))and gases(molecular and isotopic composition)were conducted in order to identify the genetic characteristics of the hydrocarbon phases produced.Maturity-relevant parameters(Rock–Eval T_(max),vitrinite reflectance R_(o))elucidate that only Middle Jurassic Khatatba organofacies capable of generating wet and dry hydrocarbon gases.Additionally,the enrichment of C_(7)normal alkanes,mono-branched alkanes relative to polybranched components in the Obayied gases reflect their generation via cracking of oil.Basin modelling results confirm gas generation through both primary and secondary cracking.However,secondary cracking of liquid hydrocarbon phases is volumetrically more significant.Primary cracking of the Khatatba organofacies likely predate and catalyze the secondary cracking of the liquid phases and therefore the volume of generated gas increases incrementally eastward where both processes coexist.The present study highlights the significant role of secondary cracking in the generation and accumulation of huge gas accumulations in the basins containing oil-prone source intervals.展开更多
文摘The petroliferous province of the Western Desert comprises several sedimentary basins with different hydrocarbon potentiality and production capability.The middle Jurassic Khatatba Formation was proved a potential source rock in some basins and active/effective in others.The current study aims to give a comprehensive assessment and evaluation of the potential organic-rich intervals of the Khatatba Formation across JG and JD fields,northeast Abu Gharadig Basin(NEAG).The hydrocarbon generating capability and sourcing of the Khatatba Formation studied through organic geochemistry calibrated with well logging.However,the efficiency of some widely used plots of geochemistry is re-evaluated according to their accuracy and consistency.Forty cuttings,thirteen cores and two oil samples obtained from three wells(JG-2,JG-3 and JD-4)were evaluated.The samples revealed total organic carbon(TOC)values ranging from 1 to 9 wt%,exhibiting a good-excellent potential source rock.A single sample in the JD-4 well attained a TOC value of 21.3 wt%with a generating potential(represented by S2 parameter)exceeding 146 mgHc/g rock required a special evaluation.Most of the samples(mainly in the JD-4 well)attained a sufficient level of thermal maturity for hydrocarbon generation with a Tmax up to 449C.The vitrinite reflectance(%Ro)values(a common maturity-related indicator)acquired from the JD-4 well ranging between 0.76%and 0.92%.These values are tediously increasing with depth indicating a uniform geothermal regime.The Khatatba organofacies,with wide variety of kerogen types(I,II,II-S and II/III),contain marine organic matter with a slight terrigenous input,exhibiting anoxic-suboxic environmental conditions.Oil-source correlations define the organic-rich intervals responsible for charging the accumulated hydrocarbon in the NEAG concession.
文摘Western Desert represents a major oil and gas province in Egypt producing more than 50%of the country’s oil production.Oil and gas blend occurs in most producing fields,however,the genetic link between gas and liquid hydrocarbon phases are not well-constrained.Obayied sub-basin in the Western Desert where oil and gas phases coexist in the Middle Jurassic sandstones of the Khatatba Formation provides an ideal place to investigate the link between oil and gas generation.Geochemical analyses on rock samples(Rock–Eval pyrolysis,vitrinite reflectance,R_(o))and gases(molecular and isotopic composition)were conducted in order to identify the genetic characteristics of the hydrocarbon phases produced.Maturity-relevant parameters(Rock–Eval T_(max),vitrinite reflectance R_(o))elucidate that only Middle Jurassic Khatatba organofacies capable of generating wet and dry hydrocarbon gases.Additionally,the enrichment of C_(7)normal alkanes,mono-branched alkanes relative to polybranched components in the Obayied gases reflect their generation via cracking of oil.Basin modelling results confirm gas generation through both primary and secondary cracking.However,secondary cracking of liquid hydrocarbon phases is volumetrically more significant.Primary cracking of the Khatatba organofacies likely predate and catalyze the secondary cracking of the liquid phases and therefore the volume of generated gas increases incrementally eastward where both processes coexist.The present study highlights the significant role of secondary cracking in the generation and accumulation of huge gas accumulations in the basins containing oil-prone source intervals.
