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871.
872.
Kang Ping Chen 《International Journal of Coal Geology》2011,87(2):72-79
An instantaneous coal outburst is a sudden and violent simultaneous ejection of large amounts of coal and gas (methane, carbon dioxide) from the working coalface during underground mining. The occurrence of such an outburst usually leads to a gas explosion and pollution of the mine. Despite extensive research efforts in the past 150 years, the physical mechanisms causing coal outbursts are still poorly understood. Here we present a new model combining fracture mechanics, gas dynamics and rock mechanics to elucidate the physical mechanisms leading to instantaneous outbursts. This model suggests a domino effect that leads to a catastrophic failure of the coal and an instantaneous outburst. The model identifies a critical condition for the onset of instantaneous outbursts, and it successfully predicts all of the observed phenomena preceding outbursts, most of which are explained for the first time. The model also predicts a fracture aperture size effect which is confirmed by the existing observation-based fracture classification scheme used to assess outburst proneness. 相似文献
873.
东台坳陷现今地温场特征与油藏分布关系 总被引:1,自引:0,他引:1
东台坳陷为中国东部苏北盆地油气资源最丰富的地区。为了加深对东台坳陷地温场和油藏关系的理解,根据符合地温场研究要求的54口井连续测温资料和243口井试油温度数据,获得了深度1000~3500m地温、E2s-K2t各层位界面地温和各层地温梯度。地温场分布以凹陷或次凹成独立单元,地温随深度加深而线性增高,地温异常不明显。地温梯度总体呈现"浅层低、深层高"的特点,E2s-E2d地温梯度总体在22~30℃/km之间,E1f-K2t在28~38℃/km之间,平均约为30℃/km。不同深度的地温和地温梯度分布模式相似,正向构造单元高,负向构造单元低;而不同层位的地温分布规律则相反,即凹陷内温度高,凸起和隆起上的温度低。基底构造形态、沉积盖层厚度、深大断裂、地下水、地层放射性生热等因素决定了该坳陷总体为温盆特征。大部分地区目前还处在油气液态窗内,绝大多数油藏分布高于60℃的油气勘探开发黄金区域。 相似文献
874.
利用AVO正反演技术识别深水凹陷气层 总被引:1,自引:0,他引:1
针对深水凹陷莺二段地质条件复杂,地震资料信噪比较低、烃检困难等难点,利用琼东南盆地陵水凹陷地气勘探阶段的钻孔资料及测井资料,应用zoeppritz方程进行射线数字模拟,研究该区典型气层及水层段的反射特征和AVO特征,对深水区坡折带低信噪比资料进行了保幅去噪及道集拉平处理,对常规的碳氢指示因子进行了改进.经结果表明:改进的碳氢指示因子对第三类及第四类AVO异常检测卓有成效,第四类AVO异常对于深水勘探有重要意义. 相似文献
875.
南海A区某开发气田为岩性一断圈气藏,受断层影响,为多个小型断块气藏的集合,每块气水界面不统一,气藏情况复杂。常规的AVO反演技术往往只能定性地识别含气性,无法定量地识别储层的含水饱和度。为了满足气田合理高效开发的需求,查清每块气藏的气水充注程度,在高分辨率三维地震资料中,采用了EEI反演技术来预测储层的含水饱和程度。研究结果表明,在该区运用EEI反演技术得到的EEI属性,能有效地识别出含水饱和度低于60%的气层,研究成果对气田进入开发后期调整井布署、提高采收率具有不可替代的作用。 相似文献
876.
877.
针对复杂流体运动中物质输运方程的数值求解面临地形复杂、数值阻尼过大以及数值振荡等难题,建立了Godunov格式下求解二维水流-输运方程的高精度耦合数学模型,提出了集成输运对流项的HLLC (Harten-Lax-van Leer-Contact)型近似黎曼算子,可同时计算水流通量及输运通量,不仅有效模拟了复杂地形上水流运动,而且解决了输运方程中对流项产生的数值阻尼过大和不稳定振荡等难题。采用水深-水位加权重构技术和Minmod限制器,提高了模型处理复杂混合流态的能力,同时结合Hancock预测-校正方法,使模型具有时空二阶精度。算例结果表明,模型精度高、稳定性好,能有效抑制数值阻尼,适合模拟实际复杂流体运动中物质的输运过程,具有较好的推广应用价值。 相似文献
878.
Impact of the Ice-albedo Feedback on Meridional Temperature Gradient of Northern Hemisphere 总被引:1,自引:0,他引:1
This paper analyzes the variation of meridional temperature gradient (MTG) over mid-latitude and high-latitude of Northern Hemisphere continents during last 100 years using observational data. It is found that MTG over high-latitude of Northern Hemisphere continents has an increasing trend, but the simulation results of CMIP5 models show a decreasing trend. Results of this study showed the decrease of MTG over the high-latitude continents of Northern Hemisphere calculated by CMIP5 historical simulations mainly because the models of CMIP5 exaggerated ice-albedo feedback over high-latitude regions. A series of simulation results by energy balance climate models showed that ice-albedo feedback amplified the magnitude of warming in the global warming induced only by carbon dioxide, and the magnitude of warming in high latitude was much larger than that in low-latitude regions. Along with global warming, ice-albedo feedback has little influence on MTG in low-latitude, but can induce the decrease of MTG in high-latitude regions. 相似文献
879.
880.
Presence of gas hydrate and free gas in Iranian part of Makran accretionary prism changes the elastic properties of unconsolidated sediments and produces sharp bottom simulating reflectors (BSRs) which are observed on the 2-D seismic data. Different methods have been applied to estimate the gas hydrate and free gas saturations in marine sediments based on seismic measurements. Most of these methods are based on relating the elastic properties to the hydrate and free gas saturations and remotely estimating their concentration. In this regard, using the effective medium theory (EMT) which was developed for different modes of hydrate distribution is more considered among other rock physics theories. The main concern about saturation estimations based on EMT is that the velocities of the hydrate-bearing sediments primarily depend on how they are distributed within the pore space. Therefore, understanding the modes of hydrate distribution (at least cementing or non-cementing modes) is necessary to decrease the estimation uncertainties.The first intention of paper is to investigate amplitude variation versus offset (AVO) analysis of BSR to determine the hydrate distribution modes. The results from the probable saturation revealed that if the hydrate cements the sediment grains, BSR would show the AVO class IV and if hydrate does not cement the sediment grains, then BSR would show either the AVO class II or class III depending on the free gas saturation just beneath the BSR. The second intention of paper is to introduce some templates called reflectivity templates (RTs) for quantitative study of hydrate resources. These templates are provided based on the EMT to quantify the hydrate and free gas near the BSR. Validation of this approach by synthetic data showed that a reliable quantification could be achieved by intercept-gradient RTs, only if these attributes are determined with a high accuracy and good assumptions are made about the mineralogical composition and porosity of the unconsolidated host sediments. The results of this approach applied to a 2-D marine pre-stack time migrated seismic line showed that less than 10% of the gas hydrate accumulated near to the BSR in anticlinal-ridge type structure of Iranian deep sea sediments. The free gas saturation near to the BSR by assuming a homogeneous distribution was less than 3% and by assuming patchy distribution was about 3–10%. 相似文献