Elastic impedance modeling of tight sandstone gas reservoir
Jin Jineng1, Pan Renfang1,2, Zhu Zhengping1, Zhang Liping2
1. Key Laboratory of Oil and Gas Resources and Exploration Technology of Ministry of Education, Yangtze University, Wuhan, Hubei 430100, China;
2. College of Geoscience, Yangtze University, Wuhan, Hubei 430100, China
Abstract:In order to analyze fluid sensitivity characteristics of elastic impedance for tight sandstone gas reservoir identification and its model response trend, an elastic impedance modeling in tight sandstone gas reservoir is conducted. Based on well data statistics of He 8 sandstone in Sulige Gasfield, rock physical model of tight sandstone gas reservoir is established and used in fluid replacement simulation to do the modeling. As the study shows, four types of elastic impedance characteristics for gas reservoirs have been found: Class Ⅰ, positive high elastic impedance difference decreases with incident angle increase; Class Ⅱ, near zero elastic impedance difference decreases from positive to negative with incident angle increase; Class Ⅲ, negative high elastic impedance difference decreases with incident angle increase; and Class Ⅳ, negative high elastic impedance difference increases with incident angle increase. For Classes Ⅰ,Ⅱ, and Ⅲ, the elastic impedance of reservoirs decreases and that of cap rocks increases with incident angle increase while the reflection coefficient decreases with incident angle increase. But for Class Ⅳ, the elastic impedance of reservoirs increases and that of cap rocks decreases with incident angle increase while the reflection coefficient increases with incident angle increase. The elastic impedance and reflection coefficients of the four types of tight gas sandstone reservoirs all show a decreasing trend with gas saturation increase. Larger decreases appear with gas saturation range between 0 and 0.1. In addition, amplitude response characteristics of elastic impedance model can well reflect elastic impedance variation with incident angle and gas saturation, which can serve as a guide for tight gas sandstone reservoir prediction.
Huang Weichuan,Yang Changchun,Fan Taoyuan et al.The application of petrophysical analysis in the reservoir prediction.Progress in Geophysics,2007,22(6):1791-1795.
Pan Renfang,Chen Silu,Zhang Liping et al.Semi-quantitative analysis of gas bearing sand by AVO forward modeling.OGP,2013,48(1):103-108.
[6]
Connolly P.Elastic impedance.The Leading Edge,1999,18(4):438-452.
[7]
Whitcombe D N. Elastic impedance normalization.Geophysics,2002,67(1):60-62.
[8]
倪逸.弹性阻抗计算的一种新方法.石油地球物理勘探,2003,38(2):147-150,155. Ni Yi.A new method for calculation of elastic wave impedance.OGP,2003,38(2):147-150,155.
[9]
马劲风.地震勘探中广义弹性阻抗的正反演.地球物理学报,2003,46(1):118-124.
Ma Jinfeng.Forward modeling and inversion method of generalized elastic impedance in seismic exploration.Chinese Journal of Geophysics,2003,46(1):118-124.
[10]
甘利灯,赵邦六,杜文辉等.弹性阻抗在岩性与流体预测中的潜力分析.石油物探,2005,44(5):504~508. Gan Lideng,Zhao Bangliu,Du Wenhui et al.The potential analysis of elastic impedance in the lithology and fluid prediction.GPP,2005,44(5):504-508.
[11]
张奎,倪逸.三种弹性波阻抗公式比较.石油地球物理勘探,2006,41(增刊):7-11.
Zhang Kui, Ni Yi. Comparison among three elastic wave impedance formulas. OGP,2006,41(S):7-11.
[12]
王浩,罗兵,李霆.弹性阻抗对比分析.岩性油气藏,2010,22(3):110-113.
Wang Hao,Luo Bing,Li Ting.comparative analysis of elastic impedance.Lithologic Reservoirs,2010,22(3):110-113.
Li Aishan,Yin Xingyao,Lu Na et al.Application of elastic impedance inversion with two angle stack gathers to predict gas-bearing reservoir of mid-deep layer.OGP,2009,44(1):87-92.
Gao Gang,He Zhenhua,Cao Junxing et al.The new two-term elastic impedance inversion and its application to predict deep gas-bearing carbonate reservoirs.OGP,2013,48(3):450-457.
[17]
Aki K,Richards P.Quantitative Seismology—Theory and Method.W H Freemall Company,New York,1980.
[18]
Castagna J P,Swan H W.Framework for AVO gradient and intercept interpretation.Geophysics,1998,63(3):948-956.
[19]
Gassmann F.Uber die Elastizitat poroser Medien.Vierteljahrsschrift der Naturforschenden Gesellschaft in Zurich,1951,96:1-23.