查看更多>>摘要：Jiaojiang sag in the East China Sea Basin is at the earlier exploration stage,where char-acterizing hydrocarbon generation of source rocks is important to understand oil-gas exploration po-tential.Utilizing geochemical and basin modeling analysis,hydrocarbon generation capacity and pro-cess of the Paleocene E1y,E1l and E1m formations were investigated.Results show that E1y and E1l mud-stones are high-quality source rocks with Type Ⅱ kerogen,which is dominated by both aquatic organ-isms and terrestrial higher plants deposited in sub-reduced environment.E1m mudstone interbedded with thin carbonaceous mudstone and coal is poor-quality source rock with Type Ⅲ kerogen,whose or-ganic matter was originated from terrestrial higher plants under oxidized environment.Controlled by burial and maturity histories,E1y and E1l source rocks experienced two hydrocarbon generation stages,which took place in the Late Paleocene and in the Middle to Late Eocene,respectively,and had high hy-drocarbon generation capacity with cumulative hydrocarbon volume of 363 and 328 mg/g,respectively.E1m source rock only had one hydrocarbon generation process in the Late Eocene,which had low hy-drocarbon generation capacity with cumulative hydrocarbon volume of only 24 mg/g.The future oil-gas exploration in the Jiaojiang sag should focus on hydrocarbon generation center and select targets in the central uplift formed before the Miocene with high-quality traps.
查看更多>>摘要：Paleo-oil reservoir is of great importance to understand hydrocarbon enrichment mecha-nism and hydrocarbon exploration potential,but is yet poorly investigated in Kuqa Depression.The oc-currence of the paleo-oil reservoir in Dabei area was proved by quantitative grain fluorescence(QGF)and fluid inclusion petrography.Development history of the paleo-oil reservoir was reconstructed through:(1)oil-source correlation;(2)time coupling of source rock maturation,porosity evolution and migration pathways.The impact of paleo-oil reservoir on tight-gas accumulation was consequently dis-cussed.Results suggest that considerable oil was accumulated in the K1bs reservoir with paleo oil-water contact in Dabei 2 Well and Dabei 201 Well at 5800 and 6040 m,respectively.Crude oil was primarily sourced from Triassic source rocks with Jurassic source rocks of secondary importance,which was at oil generation window(0.7%-1.1%Ro)during 9-6 and 7.5-5 Ma,respectively.The occurrence of K1bs tight reservoir(porosity<12%)was about 25 Ma,while faults and associated fractures at Kelasue structural belt were developed approximately from 8 to 3.5 Ma.Therefore,the tight oil accumulation was formed during 8-5 Ma.The paleo-oil reservoir in Dabei 1 gas field was destroyed by the evapora-tion fractionation in later stage.
查看更多>>摘要：The tight tuff reservoir is an unusual type of unconventional reservoir with strong hetero-geneity.However,there is a lack of research on the microscopic pore structure that causes the heteroge-neity of tuff reservoirs.Using the Chang 7 Formation in Ordos Basin,China as a case study,carbon-dioxide gas adsorption,nitrogen gas adsorption and high-pressure mercury injection are integrated to investigate the multi-scale pore structure characteristics of tuff reservoirs.Meanwhile,the fractal di-mension is introduced to characterize the complexity of pore structure in tuff reservoirs.By this multi-experimental method,the quantitative characterizations of the full-range pore size distribution of four tuff types were obtained and compared in the size ranges of micropores,mesopores and macropores.Fractal dimension curves derived from full-range pores are divided into six segments as D1,D2,D3,D4,D5 and D6 corresponding to fractal characteristics of micropores,smaller mesopores,larger meso-pores,smaller macropores,medium macropores and larger macropores,respectively.The macropore volume,average macropore radius and fractal dimension D5 significantly control petrophysical proper-ties.The larger macropore volume,average macropore radius and D5 correspond to favorable pore structure and good reservoir quality,which provides new indexes for the tuff reservoir evaluation.This study enriches the understanding of the heterogeneity of pore structures and contributes to unconven-tional oil and gas exploration and development.
查看更多>>摘要：The inland lakes on the Tibetan Plateau(TP)are undergoing significant changes due to their sensitivity to climate.The largest lake in Tibet,Siling Co,has expanded most dramatically during recent decades.Using Landsat,GRACE and meteorological data,the expansion of Siling Co was de-tailed in four stages and the process was further explained.The results show that the lake area in-creased from 1647.30 km2 in 1972 to 2438.99 km2 in 2020.It experienced a slow growth at a rate 6.03 km2/yr from 1972 to 1988,while fluctuating at 1.44 km2/yr during 1989-1997,then accelerated at 60.28 km2/yr between 1998 and 2005,and expanded slowly again at 11.40 km2/yr since 2006.The continued expansion led to its merger with nearby Yagain Co in 2003.Terrestrial water storage(TWS)increase was also observed from GRACE(0.65 cm/yr),with about 0.75 coefficient of determination between the TWS and lake area during 2002-2020.The long-term expansion of Siling Co is related to the increasing trends of temperature and precipitation,but their contributions vary with time span.Specifically,the accelerated stage between 1998 and 2005 can be explained by the increased temperature and precipita-tion accompanied by a drop in evaporation,while the slow expansion since 2006 was due to the de-crease in precipitation and temperature and the rise in evaporation.There is no obvious mass loss of glaciers revealed by GRACE during 2002-2020,which may be related to the negative trend of the tem-perature.Furthermore,the precipitation may still make a major contribution in this phase,as its aver-age is about 93.9 mm higher than that in 1988-1997.
查看更多>>摘要：Mesoscale fracture controls the permeability of shale res-ervoirs,it is one of the main research objectives of natural frac-tures.The length of the mesoscale fracture is less than 1/4 of the seismic eigen wavelength and greater than 1%of the seis-mic eigen wavelength,they cannot be identified in actual seis-mic data and are usually displayed by the azimuthal anisotropy of seismic attributes.In this paper,we propose a calculation process from fracture properties to seismic P-wave velocity and traveltime in anisotropic media induced by multiple sets of arbitrary occurring mesoscale fractures.Based on this process,the variations of the media's Anisotropic(A-)parameters with fracture properties are studied.Furthermore,variation of P-wave NMO elliptical principle axis with the relative fracture density is studied according to the arbitrary anisotropic theory based on A-parameters.
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