Font Size: a A A

Mechanism Of The Shale Gas And Oil Accumulation Of YanChang Formation In The Southeast Ordos Basin

Posted on:2013-01-03Degree:DoctorType:Dissertation
Country:ChinaCandidate:Y X YuFull Text:PDF
GTID:1220330482462958Subject:Mineral prospecting and exploration
Abstract/Summary:PDF Full Text Request
The Ordos Basin is rich in oil and gas resources and it is one of the largest superimposed basins in China. Although it is well known to geologist that the organic-rich shale is widely distributed in the upper Triassic Yanchang formation and it has great hydrocarbon potential, the mechanism of its self-contained, continental source-reservoir system, has not been studied. This article apply to dynamic analysis of the process of hydrocarbon generating as research ideas, using shale petrology and petroleum geochemistry analysis as main research method, combined physical simulation and comprehensive geological analysis to study on the generation conditions, reservoir characteristic, main controlling factors and mechanism of shale gas and oil in the southeast Ordos Basin. The main conclusions are following:The shale gas is existed chiefly as sorption state in the southeast of Ordos Basin, it is about 46.8% to 75.2% in total gas content and that number come from quantitative analysis of gas content which through field desorption test and absorption isotherm test in the same rock sample and combined the research of the formation temperature and pressure. Try to study the oil content in shale through the evaluation of source rock by the technique of extraction soluble organic matters and pyrolysis which are corrected, then the gas-oil ratio in the shale can be predicted.The shale gas and oil content depends on the various characteristics and processes, including (1) excellent original organic richness and generation potential; (2) specific kerogen type with moderate maturity of organic matter;(3) the shale has high adsorption ability with the increasing of illite-smectite mixed-layer clay mineral;(4) the specific expulsion unit combination and anomalous low pressure and anomalous low temperature of the formation which is the external controlling factors.The characteristics and degree of the carbon isotope fractionation of desorbed methane from shale can be applied to predicate the gas content and the theory basis is that the proportion of residual gas consisted by the 12C and 13C is specific when the organic matters which has a specific pore configuration reach in a specific stage. The features of the carbon isotope fractionation from the same shale formation also reflect the dynamic process of the gas generated from the source and adsorbed, saturated, diffusive transport, diffusive loss, biodegradation in the shale internal formation.Established the model of coexisting relationship between shale gas and oil by the simulation of source rock for hydrocarbon generation and expulsion combined with transformation ratio which based on restoring mature present-day HI to original HI, it revealed that when the TR is between 30% and 70%(0.6%<Ro<1.12%), the gas/oil ratio (GOR) in shale is between 130m3/t to 550m3/t and the shale is mainly containted oil and oil-associated gas; when the TR is between 70% to 90%(1.12%<Ro<1.60%), the GOR will be as high as from 600m3/t to 2200 m3/t and the shale is mainly containted wet gas and some condensate; when the TR is more than 90%, the GOR will be much more higher, the shale is mainly containted dry gas.The research of this paper enriches the theory of the continental shale gas and oil in China and it will be of importance in guiding the shale gas and oil exploration and development in China.
Keywords/Search Tags:Ordos Basin, shale gas and oil, shale gas and oil content, transformation ratio, coexisting relationship between shale gas and oil
PDF Full Text Request
Related items