The Qilian Mountain permafrost area located in the northern of Qinghai-Tibet Plateau is a favorable place for natural gas hydrate formation and enrichment,due to its well-developed fractures and abundant gas sources.U...The Qilian Mountain permafrost area located in the northern of Qinghai-Tibet Plateau is a favorable place for natural gas hydrate formation and enrichment,due to its well-developed fractures and abundant gas sources.Understanding the formation and distribution of multi-component gas hydrates in fractures is crucial in accurately evaluating the hydrate reservoir resources in this area.The hydrate formation experiments were carried out using the core samples drilled from hydrate-bearing sediments in Qilian Mountain permafrost area and the multi-component gas with similar composition to natural gas hydrates in Qilian Mountain permafrost area.The formation and distribution characteristics of multi-component gas hydrates in core samples were observed in situ by X-ray Computed Tomography(X-CT)under high pressure and low temperature conditions.Results show that hydrates are mainly formed and distributed in the fractures with good connectivity.The ratios of volume of hydrates formed in fractures to the volume of fractures are about 96.8%and 60.67%in two different core samples.This indicates that the fracture surface may act as a favorable reaction site for hydrate formation in core samples.Based on the field geological data and the experimental results,it is preliminarily estimated that the inventory of methane stored in the fractured gas hydrate in Qilian Mountain permafrost area is about 8.67×1013 m3,with a resource abundance of 8.67×108 m3/km2.This study demonstrates the great resource potential of fractured gas hydrate and also provides a new way to further understand the prospect of natural gas hydrate and other oil and gas resources in Qilian Mountain permafrost area.展开更多
The Early Cambrian Yuertusi Formation(Є_(1)y)in the Tarim Basin of China deposits a continuously developed suite of organic-rich black mudstones,which constitute an important source of oil and gas reservoirs in the Pa...The Early Cambrian Yuertusi Formation(Є_(1)y)in the Tarim Basin of China deposits a continuously developed suite of organic-rich black mudstones,which constitute an important source of oil and gas reservoirs in the Paleozoic.However,its hydrocarbon generation and evolution characteristics and resource potential have long been constrained by deeply buried strata and previous research.In this paper,based on the newly obtained ultra-deep well drilling data,the hydrocarbon generation and expulsion model ofЄ_(1)y shale was established by using data-driven Monte Carlo simulation,upon which the hydrocarbon generation,expulsion,and retention amounts were calculated by using the diagenetic method.The research indicates that theЄ_(1)y shale reaches the hydrocarbon generation and expulsion threshold at equivalent vitrinite reflectances of 0.46%and 0.72%,respectively.The cumulative hydrocarbon generation is 68.88×10^(10)t,the cumulative hydrocarbon expulsion is 35.59×10^(10)t,and the cumulative residual hydrocarbon is 33.29×10^(10)t.This paper systematically and quantitatively calculates the hydrocarbon expulsion at various key geological periods for theЄ_(1)y source rocks in the study area for the first time,more precisely confirming that the black shale of theЄ_(1)y is the most significant source rock contributing to the marine oil and gas resources in the Tarim Basin,filling the gap in hydrocarbon expulsion calculation in the study area,and providing an important basis for the formation and distribution of Paleozoic hydrocarbon reservoirs.The prospect of deep ultra-deep oil and gas exploration in the Tarim Basin is promising.Especially,the large area of dolomite reservoirs under the Cambrian salt and source rock interiors are the key breakthrough targets for the next exploration in the Tarim Basin.展开更多
Paleofluid-rock interaction results in the modification of the ultra-deep reservoir quality,but the coupling effects of the paleofluid evolution on reservoir quality modification are still underestimated.Here,the mult...Paleofluid-rock interaction results in the modification of the ultra-deep reservoir quality,but the coupling effects of the paleofluid evolution on reservoir quality modification are still underestimated.Here,the multi-stage dolomite cements have been studied by means of core observations,thin section identification,fluid inclusions,and in situ elements and isotopic analyses in order to reaveal the paleofluid evolution processes and their effects on the reservoir quality.The fibrous dolomite cement(FDC)and bladed dolomite cement(BDC)both have similar geochemical properties and homogenization temperature(Th)to the matrix dolostone.Subsequent early silicification occurs(QZ1).However,silt-to fine-sized crystalline dolomite cement(CD2)has higher concentration of Fe and medium rare earth element,more negativeδ^(18)O than for FDC and BDC,and 103.4-150.2℃in Th.The first petroleum charge episode solid bitumen 1(SB1)followed the CD2.The medium to coarse sized crystalline dolomite cement(CD3)is characterized by the higher Mn and lower Sr concentration than CD2,positiveδEu anomaly,negativeδ^(13)C andδ^(18)O,high^(87)Sr/^(86)Sr ratio and 138.9℃-184.3℃in Th.The solid bitumen 2(SB2)occurs after CD3.Subsequently,the saddle dolomite(SD)has higher Fe and Mn concentration and lower Na and Sr than others cement,δEu positive anomaly,negativeδ^(13)C andδ^(18)O,high ^(87)Sr/^(86)Sr ratio and 177.5℃-243.6℃in Th.Eventually massive silicification(QZ2)took place.The FDC,BDC,QZ1 and SB1 formed in the early diagenetic stage and have little negative effect on the reservoir quality.But the CD2 and CD3 dramatically decreased the reservoir quality related to a quantity of hydrothermal fluids entrance in the mesodiagenetic stage along the strike-slip faults and the unconformity surface at top of the Deng-2 Member during the late stage of the Caledonian orogeny.The reservoir spaces were retained and enlarged during the late diagenetic stage when the peak petroleum charge occurred,massive silicification and thermochemical sulfate reduction took place with SB2,SD and QZ2 being formed.The research outcome may update our understanding on the retention mechanism and the insights for further hydrocarbon exploration of Precambrian ultra-deep microbial reservoirs.展开更多
基金the financial support of the National Natural Science Foundation of China(42176212,41976074 and 41302034)the Marine S&T Fund of Shandong Province for Laoshan Laboratory(2021QNLM020002)the Marine Geological Survey Program(DD20221704)。
文摘The Qilian Mountain permafrost area located in the northern of Qinghai-Tibet Plateau is a favorable place for natural gas hydrate formation and enrichment,due to its well-developed fractures and abundant gas sources.Understanding the formation and distribution of multi-component gas hydrates in fractures is crucial in accurately evaluating the hydrate reservoir resources in this area.The hydrate formation experiments were carried out using the core samples drilled from hydrate-bearing sediments in Qilian Mountain permafrost area and the multi-component gas with similar composition to natural gas hydrates in Qilian Mountain permafrost area.The formation and distribution characteristics of multi-component gas hydrates in core samples were observed in situ by X-ray Computed Tomography(X-CT)under high pressure and low temperature conditions.Results show that hydrates are mainly formed and distributed in the fractures with good connectivity.The ratios of volume of hydrates formed in fractures to the volume of fractures are about 96.8%and 60.67%in two different core samples.This indicates that the fracture surface may act as a favorable reaction site for hydrate formation in core samples.Based on the field geological data and the experimental results,it is preliminarily estimated that the inventory of methane stored in the fractured gas hydrate in Qilian Mountain permafrost area is about 8.67×1013 m3,with a resource abundance of 8.67×108 m3/km2.This study demonstrates the great resource potential of fractured gas hydrate and also provides a new way to further understand the prospect of natural gas hydrate and other oil and gas resources in Qilian Mountain permafrost area.
基金supported by the CNPC Science and Technology Major Project of the Fourteenth Five-Year Plan(2021DJ0101)the National Natural Science Foundation of China(U19B600302,41872148)。
文摘The Early Cambrian Yuertusi Formation(Є_(1)y)in the Tarim Basin of China deposits a continuously developed suite of organic-rich black mudstones,which constitute an important source of oil and gas reservoirs in the Paleozoic.However,its hydrocarbon generation and evolution characteristics and resource potential have long been constrained by deeply buried strata and previous research.In this paper,based on the newly obtained ultra-deep well drilling data,the hydrocarbon generation and expulsion model ofЄ_(1)y shale was established by using data-driven Monte Carlo simulation,upon which the hydrocarbon generation,expulsion,and retention amounts were calculated by using the diagenetic method.The research indicates that theЄ_(1)y shale reaches the hydrocarbon generation and expulsion threshold at equivalent vitrinite reflectances of 0.46%and 0.72%,respectively.The cumulative hydrocarbon generation is 68.88×10^(10)t,the cumulative hydrocarbon expulsion is 35.59×10^(10)t,and the cumulative residual hydrocarbon is 33.29×10^(10)t.This paper systematically and quantitatively calculates the hydrocarbon expulsion at various key geological periods for theЄ_(1)y source rocks in the study area for the first time,more precisely confirming that the black shale of theЄ_(1)y is the most significant source rock contributing to the marine oil and gas resources in the Tarim Basin,filling the gap in hydrocarbon expulsion calculation in the study area,and providing an important basis for the formation and distribution of Paleozoic hydrocarbon reservoirs.The prospect of deep ultra-deep oil and gas exploration in the Tarim Basin is promising.Especially,the large area of dolomite reservoirs under the Cambrian salt and source rock interiors are the key breakthrough targets for the next exploration in the Tarim Basin.
基金supported by the National Natural Science Foundation of China(Nos.41872150,42230310)the Joint Funds of National Natural Science Foundation of China(Grant No.U19B6003)。
文摘Paleofluid-rock interaction results in the modification of the ultra-deep reservoir quality,but the coupling effects of the paleofluid evolution on reservoir quality modification are still underestimated.Here,the multi-stage dolomite cements have been studied by means of core observations,thin section identification,fluid inclusions,and in situ elements and isotopic analyses in order to reaveal the paleofluid evolution processes and their effects on the reservoir quality.The fibrous dolomite cement(FDC)and bladed dolomite cement(BDC)both have similar geochemical properties and homogenization temperature(Th)to the matrix dolostone.Subsequent early silicification occurs(QZ1).However,silt-to fine-sized crystalline dolomite cement(CD2)has higher concentration of Fe and medium rare earth element,more negativeδ^(18)O than for FDC and BDC,and 103.4-150.2℃in Th.The first petroleum charge episode solid bitumen 1(SB1)followed the CD2.The medium to coarse sized crystalline dolomite cement(CD3)is characterized by the higher Mn and lower Sr concentration than CD2,positiveδEu anomaly,negativeδ^(13)C andδ^(18)O,high^(87)Sr/^(86)Sr ratio and 138.9℃-184.3℃in Th.The solid bitumen 2(SB2)occurs after CD3.Subsequently,the saddle dolomite(SD)has higher Fe and Mn concentration and lower Na and Sr than others cement,δEu positive anomaly,negativeδ^(13)C andδ^(18)O,high ^(87)Sr/^(86)Sr ratio and 177.5℃-243.6℃in Th.Eventually massive silicification(QZ2)took place.The FDC,BDC,QZ1 and SB1 formed in the early diagenetic stage and have little negative effect on the reservoir quality.But the CD2 and CD3 dramatically decreased the reservoir quality related to a quantity of hydrothermal fluids entrance in the mesodiagenetic stage along the strike-slip faults and the unconformity surface at top of the Deng-2 Member during the late stage of the Caledonian orogeny.The reservoir spaces were retained and enlarged during the late diagenetic stage when the peak petroleum charge occurred,massive silicification and thermochemical sulfate reduction took place with SB2,SD and QZ2 being formed.The research outcome may update our understanding on the retention mechanism and the insights for further hydrocarbon exploration of Precambrian ultra-deep microbial reservoirs.
