天然气水合物和游离气层的弹性参数异常特征及其在饱和度估算中的应用
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摘要
与水饱和沉积层相比,天然气水合物和游离气储集层的地震波速度、泊松比、弹性模量及其比值等弹性参数具有明显的异常特征。对于接触胶结水合物层来说,对饱和度变化最为敏感的弹性参数是横波速度和横波波阻抗;对于非接触胶结水合物层来说,对饱和度变化最为敏感的参数是弹性模量比和纵波速度;对于游离气层来说,对饱和度变化最为敏感的弹性参数是弹性模量比和泊松比。当水合物与岩石骨架呈接触胶结时,水合物层在速度和波阻抗剖面上表现为近似平行于海底的高值异常带,而泊松比剖面却无明显异常。利用对饱和度变化敏感的弹性参数估算水合物和游离气饱和度的精度较高。依据对美国布莱克海台区USGS95-1测线的地震数据进行水合物分析研究,发现该地区的水合物是接触胶结类型,得到该地区的水合物饱和度最大可达20%;下伏游离气层的含量小于2%。
Comparing with water-saturated sediments, such elastic parameters as velocity of seismic waves, Poisson ratio, elastic module and ratio of elastic module in sediments with gas-hydrate and free gas have clearly anomalous feature. For contact-cemented gas hydrate layer, the elastic parameters most sensitive to change of saturation are S-wave velocity and wave impedance; For non-contact cemented gas hydrate layer, the elastic parameters most sensitive to change of saturation are ratio of elastic module and P-wave velocity; and for free gas layer, the elastic parameters most sensitive to change of saturation are ratio of elastic module and Poisson ratio. When contact cement of gas hydrate with rock frame, the show of gas hydrate layer on velocity and wave impedance sections is high-value anomalous zone near parallel to sea bottom and without clear anomaly on Poisson ratio section. Using elastic parameters sensitive to the change of saturation to estimate the saturation of gas-hydrate and free gas has higher precision. Based on the analysis and study of gas hydrate for seismic data from line USGS95-1 in Blake ridge, it discovered that the gas-hydrate in the region is contact cemented type, and the max saturation of gas hydrate can reach to 20 and content of free gas in underlying layer is less than 2.
Comparing with water-saturated sediments, such elastic parameters as velocity of seismic waves, Poisson ratio, elastic module and ratio of elastic module in sediments with gas-hydrate and free gas have clearly anomalous feature. For contact-cemented gas hydrate layer, the elastic parameters most sensitive to change of saturation are S-wave velocity and wave impedance; For non-contact cemented gas hydrate layer, the elastic parameters most sensitive to change of saturation are ratio of elastic module and P-wave velocity; and for free gas layer, the elastic parameters most sensitive to change of saturation are ratio of elastic module and Poisson ratio. When contact cement of gas hydrate with rock frame, the show of gas hydrate layer on velocity and wave impedance sections is high-value anomalous zone near parallel to sea bottom and without clear anomaly on Poisson ratio section. Using elastic parameters sensitive to the change of saturation to estimate the saturation of gas-hydrate and free gas has higher precision. Based on the analysis and study of gas hydrate for seismic data from line USGS95-1 in Blake ridge, it discovered that the gas-hydrate in the region is contact cemented type, and the max saturation of gas hydrate can reach to 20 and content of free gas in underlying layer is less than 2.
引文
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[15]Lu Shaoming,Mcmechan G A.Elastic i mpedance in-version of multichannel seismic data from unconsoli-dated sedi ments containing gas hydrate and free gas.Geophysics,2004,69(1):164~179
[16]Ecker C,Dvorkin J,Nur A M.Esti mating the amount of gas hydrate and free gas from marine seismic data,Geophysics,2000,65:565~573
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[20]ODP Leg164Shipboard Scientific Party.Methane gas hydrate drilled at Blake Ridge.Eos Transactions,American Geophysical Union,1996,77(23):219
[21]Ecker C,Dvorkin J,Nur A M.Sedi ments with gas hydrates:Internal structure fromseismic AVO.Geo-physics,1998,63(5):1659~1669
[2]蒋少涌,杨涛,薛紫晨等.南海北部海区海底沉积物中孔隙水的Cl-和SO24-浓度异常特征及其对天然气水合物的指示意义.现代地质,2005,19(1):45~54
[3]杨涛,蒋少涌,杨竞红等.孔隙水中NH4+和HPO42-浓度异常:一种潜在的天然气水合物地球化学勘查新指标.现代地质,2005,19(1):55~60
[4]牛滨华,孙春岩,苏新等.勘查地球化学方法适用于勘查天然气水合物的依据.现代地质,2005,19(1):61~66
[5]刘海生,王南萍,侯胜利等.海洋沉积物热释光——潜在的天然气水合物找矿方法.物探与化探,2002,26(4):264~267
[6]王宏斌,梁劲,龚跃华等.基于天然气水合物地震数据计算南海北部陆坡海底热流.现代地质,2005,19(1):67~73
[7]卢振权,吴必豪,强祖基.利用卫星热红外遥感探测南海天然气水合物.地质学报,2002,76(1):100~106
[8]卢振权,吴必豪,强祖基等.中国近海海域卫星热红外亮温增温异常探讨.现代地质,2005,19(1):74~82
[9]Shipley T H,Houston M H.Seismic reflection evi-dence from widespread occurrence of possible gas-hy-drate horizons on continental slopes and rises.AAPG Bulletin,1979,63(12):2204~2213
[10]Holbrook W S,Hoskins H.Methane hydrate and free gas on the Blake Ridge fromvertical seismic pro-file.Science,1996,273:1840~1843
[11]孙春岩,黄新武,章明昱等.天然气水合物及其地球物理识别方法的研究进展.现代地质,2003,17(2):195~201
[12]Li Minfeng,Liu Xuewei.An AVOinversion method for identifying gas hydrate and free gas.Society of Exploration Geophysicists of Japan,2004,72~77
[13]李敏锋,李灿苹,刘学伟等.基于小波变换的天然气水合物层地震数据多尺度分析——布莱克海台USGS95-1测线应用实例.现代地质,2006,20(1):109~114
[14]刘学伟,李敏锋,张聿文等.天然气水合物地震响应研究——中国南海HD152测线.现代地质,2005,19(1):33~38.
[15]Lu Shaoming,Mcmechan G A.Elastic i mpedance in-version of multichannel seismic data from unconsoli-dated sedi ments containing gas hydrate and free gas.Geophysics,2004,69(1):164~179
[16]Ecker C,Dvorkin J,Nur A M.Esti mating the amount of gas hydrate and free gas from marine seismic data,Geophysics,2000,65:565~573
[17]Tinivella U,Jose M.Esti mating of gas-hydrate con-centration and free-gas saturation fromlog and seis-mic data.The Leading Edge,2001,200~203
[18]宋海斌,耿建华.天然气水合物的地震响应,反射地震学论文集.上海:同济大学出版社,2000,227~231
[19]Helgerud M,Dvorkin J,Nur A M et al.Elastic-wave velocity in marine sedi ments with gas hydrates:Effective medium modeling.Geophys Res Lett,1999,26:2021~2024
[20]ODP Leg164Shipboard Scientific Party.Methane gas hydrate drilled at Blake Ridge.Eos Transactions,American Geophysical Union,1996,77(23):219
[21]Ecker C,Dvorkin J,Nur A M.Sedi ments with gas hydrates:Internal structure fromseismic AVO.Geo-physics,1998,63(5):1659~1669
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