The origin and migration of natural gas and the accumulation of gas hydrates within the Pearl River Mouth Basin of the northern South China Sea are poorly understood. Based on high-resolution 2D/3D seismic data, three...The origin and migration of natural gas and the accumulation of gas hydrates within the Pearl River Mouth Basin of the northern South China Sea are poorly understood. Based on high-resolution 2D/3D seismic data, three environments of focused fluid flow： gas chimneys, mud diapirs and active faults have been identified. Widespread gas chimneys that act as important conduits for fluid flow are located below bottom simulating reflections and above basal uplifts. The occurrence and evolution of gas chimneys can be divided into a violent eruptive stage and a quiet seepage stage. For most gas chimneys, the strong eruptions are deduced to have happened during the Dongsha Movement in the latest Miocene, which are observed below Pliocene strata and few active faults develop above the top of the Miocene. The formation pressures of the Baiyun Sag currently are considered to be normal, based on these terms： 1） Borehole pressure tests with pressure coefficients of 1.043-l.047; 2） The distribution of gas chimneys is limited to strata older than the Pliocene; 3） Disseminated methane hydrates, rather than fractured hydrates, are found in the hydrate samples; 4） The gas hydrate is mainly charged with biogenic gas rather than thermogenic gas based on the chemical tests from gas hydrates cores. However, periods of quiet focused fluid flow also enable the establishment of good conduits for the migration of abundant biogenic gas and lesser volumes ofthermogenic gas. A geological model goveming fluid flow has been proposed to interpret the release of overpressure, the migration of fluids and the formation of gas hydrates, in an integrated manner. This model suggests that gas chimneys positioned above basal uplifts were caused by the Dongsha Movement at about 5.5 Ma. Biogenic gas occupies the strata above the base of the middle Miocene and migrates slowly into the gas chimney columns. Some of the biogenic gas and small volumes ofthermogenic gas eventually contribute to the formation of the gas hydrates.展开更多
The three-dimensional structures of summer precipitation over the South China Sea （SCS） and the East China Sea （ECS） are investigated based on tropical rainfall measurement mission （TRMM）. The primary results ar...The three-dimensional structures of summer precipitation over the South China Sea （SCS） and the East China Sea （ECS） are investigated based on tropical rainfall measurement mission （TRMM）. The primary results are as follows. First, both the convective and stratiform precipitation rates in the SCS are much higher than those of the ECS. The contribution of the convective cloud precipitation to the surface precipitation is primarily over the SCS and the ECS with a proportion of about 70%, but the contribution of convective cloud precipitation is slightly larger in the SCS than the ECS. The contribution of stratus precipitation is slightly larger in the ECS than that in the SCS. Second, the content of cloud particles and precipitation particles in the ECS in June was greater than that in the SCS, while in July and August, the content of cloud and precipitation particles in the ECS was less than that in the SCS. Third, the latent heat profile of the ECS is quite different from that of the SCS. In June, the peak values of evaporation and condensation latent heating rates in the ECS are greater than those in the SCS. In July and August, however, the peak values of evaporation and condensation latent heating rates in the ECS are about 0.05°/h less than those in the SCS.展开更多
In situ data are employed to evaluate five gridded surface heat flux datasets over the South China Sea. The surface heat budgets for these gridded datasets are computed. The authors find that the gridded datasets tend...In situ data are employed to evaluate five gridded surface heat flux datasets over the South China Sea. The surface heat budgets for these gridded datasets are computed. The authors find that the gridded datasets tend to underestimate both the solar radiation and sensible heat flux in general, while the latent heat fluxes are close to the observations, except for that of NOC unadjusted version 2 （NOC2）, which overestimates both the latent and sensible heat flux. The underestimation of solar radiation also indicates that the gridded datasets might underestimate the surface heat budget. The net surface heat flux of the five gridded datasets is always positive. However, the net surface heat flux of COADS, NOC1, NOC2, and OAFlux, in the range 48-56 W m-2, is around twofold more than that of NOC1 a （22 W m-2）. The budget for NOC2 is smaller than that of NOC1 and OAFlux, by approximately 49 W m-2, because of the large release of latent heat flux. Based on the comparison, the authors believe that the net surface heat flux over the South China Sea should be higher than 56 W m-2, which is significantly larger （around 10%-20%） than previous estimations.展开更多
南海北部大陆边缘的许多盆地都发现了裂后沉降异常,位于深水陆坡区的白云凹陷是其中的典型代表。本文采用盆模软件Temis Suite 2007对穿过白云凹陷的3条地震剖面进行回剥分析,观测其不同时间基底的垂向运动特征,并将其与MCKENZIE经典拉...南海北部大陆边缘的许多盆地都发现了裂后沉降异常,位于深水陆坡区的白云凹陷是其中的典型代表。本文采用盆模软件Temis Suite 2007对穿过白云凹陷的3条地震剖面进行回剥分析,观测其不同时间基底的垂向运动特征,并将其与MCKENZIE经典拉张模型计算的理论裂后沉降值进行对比,发现白云主凹中心的裂后异常沉降量最大超过2.6km,白云南凹最大异常沉降量接近2km,高于白云凹陷北部边缘的异常沉降。凹陷东部的裂后沉降作用强于凹陷西部。对沉降曲线的研究发现,白云凹陷在中中新世(16.5～10.5Ma)期间有一段沉降明显加速的过程,白云南凹尤为明显,可能与南海扩张停止事件有关。白云凹陷发育了巨厚的沉积,并且呈韧性伸展状态,本文认为下地壳流可能是导致白云凹陷裂后异常沉降最主要的因素。展开更多
基金Supported by the National Natural Science Foundation of China (Nos.40930845 and 41006031)the International Science & Technology Cooperation Program of China (No. 2010DFA21740)the National Science and Technology Major Project (No. 2011ZX05026-004-06)
文摘The origin and migration of natural gas and the accumulation of gas hydrates within the Pearl River Mouth Basin of the northern South China Sea are poorly understood. Based on high-resolution 2D/3D seismic data, three environments of focused fluid flow： gas chimneys, mud diapirs and active faults have been identified. Widespread gas chimneys that act as important conduits for fluid flow are located below bottom simulating reflections and above basal uplifts. The occurrence and evolution of gas chimneys can be divided into a violent eruptive stage and a quiet seepage stage. For most gas chimneys, the strong eruptions are deduced to have happened during the Dongsha Movement in the latest Miocene, which are observed below Pliocene strata and few active faults develop above the top of the Miocene. The formation pressures of the Baiyun Sag currently are considered to be normal, based on these terms： 1） Borehole pressure tests with pressure coefficients of 1.043-l.047; 2） The distribution of gas chimneys is limited to strata older than the Pliocene; 3） Disseminated methane hydrates, rather than fractured hydrates, are found in the hydrate samples; 4） The gas hydrate is mainly charged with biogenic gas rather than thermogenic gas based on the chemical tests from gas hydrates cores. However, periods of quiet focused fluid flow also enable the establishment of good conduits for the migration of abundant biogenic gas and lesser volumes ofthermogenic gas. A geological model goveming fluid flow has been proposed to interpret the release of overpressure, the migration of fluids and the formation of gas hydrates, in an integrated manner. This model suggests that gas chimneys positioned above basal uplifts were caused by the Dongsha Movement at about 5.5 Ma. Biogenic gas occupies the strata above the base of the middle Miocene and migrates slowly into the gas chimney columns. Some of the biogenic gas and small volumes ofthermogenic gas eventually contribute to the formation of the gas hydrates.
基金The National Key Basic Research Program of China under contract No.2014CB953903the National Basic Research Programof China under contract No.2011CB403500+1 种基金the National Natural Science Foundation of China under contract Nos 40775066 and 41275145the Fundamental Research Funds for the Central Universities under contract No.13lgjc03
文摘The three-dimensional structures of summer precipitation over the South China Sea （SCS） and the East China Sea （ECS） are investigated based on tropical rainfall measurement mission （TRMM）. The primary results are as follows. First, both the convective and stratiform precipitation rates in the SCS are much higher than those of the ECS. The contribution of the convective cloud precipitation to the surface precipitation is primarily over the SCS and the ECS with a proportion of about 70%, but the contribution of convective cloud precipitation is slightly larger in the SCS than the ECS. The contribution of stratus precipitation is slightly larger in the ECS than that in the SCS. Second, the content of cloud particles and precipitation particles in the ECS in June was greater than that in the SCS, while in July and August, the content of cloud and precipitation particles in the ECS was less than that in the SCS. Third, the latent heat profile of the ECS is quite different from that of the SCS. In June, the peak values of evaporation and condensation latent heating rates in the ECS are greater than those in the SCS. In July and August, however, the peak values of evaporation and condensation latent heating rates in the ECS are about 0.05°/h less than those in the SCS.
基金supported by the National Key Basic Research Program of China[grant number 2013CB956204]the National Natural Science Foundation of China[grant number 41576025],[grant number 41275084],[grant number 41075059]the Strategic Priority Research Program entitled‘Western Pacific Ocean System:Structure,Dynamics and Consequences’of the Chinese Academy of Sciences[grant number XDA11010304]
文摘In situ data are employed to evaluate five gridded surface heat flux datasets over the South China Sea. The surface heat budgets for these gridded datasets are computed. The authors find that the gridded datasets tend to underestimate both the solar radiation and sensible heat flux in general, while the latent heat fluxes are close to the observations, except for that of NOC unadjusted version 2 （NOC2）, which overestimates both the latent and sensible heat flux. The underestimation of solar radiation also indicates that the gridded datasets might underestimate the surface heat budget. The net surface heat flux of the five gridded datasets is always positive. However, the net surface heat flux of COADS, NOC1, NOC2, and OAFlux, in the range 48-56 W m-2, is around twofold more than that of NOC1 a （22 W m-2）. The budget for NOC2 is smaller than that of NOC1 and OAFlux, by approximately 49 W m-2, because of the large release of latent heat flux. Based on the comparison, the authors believe that the net surface heat flux over the South China Sea should be higher than 56 W m-2, which is significantly larger （around 10%-20%） than previous estimations.
文摘南海北部大陆边缘的许多盆地都发现了裂后沉降异常,位于深水陆坡区的白云凹陷是其中的典型代表。本文采用盆模软件Temis Suite 2007对穿过白云凹陷的3条地震剖面进行回剥分析,观测其不同时间基底的垂向运动特征,并将其与MCKENZIE经典拉张模型计算的理论裂后沉降值进行对比,发现白云主凹中心的裂后异常沉降量最大超过2.6km,白云南凹最大异常沉降量接近2km,高于白云凹陷北部边缘的异常沉降。凹陷东部的裂后沉降作用强于凹陷西部。对沉降曲线的研究发现,白云凹陷在中中新世(16.5～10.5Ma)期间有一段沉降明显加速的过程,白云南凹尤为明显,可能与南海扩张停止事件有关。白云凹陷发育了巨厚的沉积,并且呈韧性伸展状态,本文认为下地壳流可能是导致白云凹陷裂后异常沉降最主要的因素。
