Seepage-type gas hydrate accumulation in subsea shallow formations involves complicated thermohydro-solid coupling processes and matching problem between various accumulation elements.Theformation physical properties ...Seepage-type gas hydrate accumulation in subsea shallow formations involves complicated thermohydro-solid coupling processes and matching problem between various accumulation elements.Theformation physical properties control local natural gas migration pathway and thus the final reservoircharacteristics of hydrates.In this paper,a novel mixed-flux model for gas hydrate accumulation isestablished and then used to simulate the process of methane gas migration into the shallow stratum toform a hydrate reservoir.The effects of reservoir heterogeneity and gas source conditions on the distribution of pore fluid and hydrate accumulation are examined.The simulation results show thatreservoir heterogeneity is conducive to the retention and lateral migration of CH4 in a hydrate stabilityzone.CH4 can contact more pore water to form a large hydrate reserve,but the formed hydrate is oftendispersed.Low-permeability layers enhance the trapping of CH4 and form a uniform and large hydratesaturation.Besides,gas source conditions have an important impact on the hydrate accumulation inreservoirs.Large gas flux,small pore water flux,continuous gas supply,high content of heavy components in natural gas,and numerous gas source points contribute to large amounts of hydrates generationin a certain time period.The presented work will deepen our understanding of the controls of natural gashydrate systems in subea shallow formations.展开更多
The current study tested the gas component and carbon isotopic composition of gas samples from 6 oilgas fields at the northern margin of Qaidam Basin, and established a chart to quantitatively identify the mixing rati...The current study tested the gas component and carbon isotopic composition of gas samples from 6 oilgas fields at the northern margin of Qaidam Basin, and established a chart to quantitatively identify the mixing ratio of source-mixed gas. Besides, this research quantitatively investigated the natural gas generated by different types of organic matter. The results show that different ratios of source-mixed gas exist in the 6 oil-gas fields at the northern margin of Qaidam Basin. Among them, Mabei has the highest mixing ratio of coal-type gas, followed by Nanbaxian, Mahai, Lenghu-4, Lenghu-3 and Lenghu-5, with the ratios of coal-type gas 91%, 87%, 83%, 66%, 55% and 36%, respectively. Lenghu-3 and Lenghu-4 oil-gas fields were mainly filled by coal-type gas earlier. For Lenghu-3, the gas was mainly generated from low matured source rocks in lower Jurassic Series of Lengxi sub-sag. For Lenghu-4, the gas was mainly generated from humus-mature source rocks in lower Jurassic Series of the northern slope of Kunteyi sub-sag. Gas in Lenghu-5 was mainly later filled oil-type gas, which was generated from high matured sapropelics in lower Jurassic Series of Kunteyi sub-sag. Earlier filled coal-type gas was the main part of Mahai, Nanbaxian and Mabei oil-gas fields. Gas source of Mahai was mainly generated from high mature humics in lower Jurassic Series of Yibei sub-sag; for Nanbaxian, the gas was mainly generated from high matured humics in middle-lower Jurassic Series of Saishiteng sub-sag; for Mabei, the gas was mainly generated from humus-mature source rocks in middle Jurassic Series of Yuqia sub-sag.展开更多
基金This research is supported by the Fundamental Research Funds for the Central Universities(No.15CX05036A,18CX05009A)the National Key Basic Research Program 973 project(No.2015CB251201)+2 种基金It is also partially financed by the National Major S&T Project(No.2016ZX05056004-003)the General Project of Shandong Natural Science Foundation(ZR2020ME090)the National Natural Science Foundation of China(No.51974347)。
文摘Seepage-type gas hydrate accumulation in subsea shallow formations involves complicated thermohydro-solid coupling processes and matching problem between various accumulation elements.Theformation physical properties control local natural gas migration pathway and thus the final reservoircharacteristics of hydrates.In this paper,a novel mixed-flux model for gas hydrate accumulation isestablished and then used to simulate the process of methane gas migration into the shallow stratum toform a hydrate reservoir.The effects of reservoir heterogeneity and gas source conditions on the distribution of pore fluid and hydrate accumulation are examined.The simulation results show thatreservoir heterogeneity is conducive to the retention and lateral migration of CH4 in a hydrate stabilityzone.CH4 can contact more pore water to form a large hydrate reserve,but the formed hydrate is oftendispersed.Low-permeability layers enhance the trapping of CH4 and form a uniform and large hydratesaturation.Besides,gas source conditions have an important impact on the hydrate accumulation inreservoirs.Large gas flux,small pore water flux,continuous gas supply,high content of heavy components in natural gas,and numerous gas source points contribute to large amounts of hydrates generationin a certain time period.The presented work will deepen our understanding of the controls of natural gashydrate systems in subea shallow formations.
基金Financial support from the National Natural Science Foundation of China (No. 40730422)the Priority Academic Program Development of Jiangsu Higher Education Institutions of Chinadata provided by Jurassic Project Department in Research Institute of Petroleum Exploration and Development of China are gratefully acknowledged
文摘The current study tested the gas component and carbon isotopic composition of gas samples from 6 oilgas fields at the northern margin of Qaidam Basin, and established a chart to quantitatively identify the mixing ratio of source-mixed gas. Besides, this research quantitatively investigated the natural gas generated by different types of organic matter. The results show that different ratios of source-mixed gas exist in the 6 oil-gas fields at the northern margin of Qaidam Basin. Among them, Mabei has the highest mixing ratio of coal-type gas, followed by Nanbaxian, Mahai, Lenghu-4, Lenghu-3 and Lenghu-5, with the ratios of coal-type gas 91%, 87%, 83%, 66%, 55% and 36%, respectively. Lenghu-3 and Lenghu-4 oil-gas fields were mainly filled by coal-type gas earlier. For Lenghu-3, the gas was mainly generated from low matured source rocks in lower Jurassic Series of Lengxi sub-sag. For Lenghu-4, the gas was mainly generated from humus-mature source rocks in lower Jurassic Series of the northern slope of Kunteyi sub-sag. Gas in Lenghu-5 was mainly later filled oil-type gas, which was generated from high matured sapropelics in lower Jurassic Series of Kunteyi sub-sag. Earlier filled coal-type gas was the main part of Mahai, Nanbaxian and Mabei oil-gas fields. Gas source of Mahai was mainly generated from high mature humics in lower Jurassic Series of Yibei sub-sag; for Nanbaxian, the gas was mainly generated from high matured humics in middle-lower Jurassic Series of Saishiteng sub-sag; for Mabei, the gas was mainly generated from humus-mature source rocks in middle Jurassic Series of Yuqia sub-sag.
