Petrophysical modeling for offshore natural gas hydrates
ZHANG Jinqiang1,2, HAN Lei1,2,3, LIU Junzhou1,2, LIU Xiwu1,2
1. Sinopec Key Laboratory of Shale Oil/Gas Exploration and Production Technology, Beijing 102206, China; 2. Sinopec Petroleum Exploration and Production Research Institute, Beijing 102206, China; 3. Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou, Guangdong 511458, China
Abstract：As offshore natural gas hydrates occur in unconsolidated sediments,the petrophysical model of unconsolidated sediments should be built before the petrophysical modeling of natural gas hydrates. The traditional petrophysical model of unconsolidated sediments,however,faces the pro-blems of a high error in the estimation of shear wave velocity and a non-self-consistent modeling process. Taking account of the lubrication effect of brine on sediment particles,this study introduces the modified Hertz-Mindlin equation in the mode-ling process to improve accuracy. During the mo-deling of unconsolidated sediments,the modified Hertz-Mindlin equation is used to calculate the elastic moduli of sediments under critical porosity,and then Hashine-Shtrikman bounds are applied to calculate the elastic moduli of the skeleton of unconsolidated sediments. Furthermore,this paper discusses the influence of different occurrence forms of hydrates on the elastic properties of sediments,as well as the applicable models and discrimination criteria. On this basis,for natural hydrates existing as supporting grains and pore-filling fluids,the petrophysical modeling method and process that suits the two occurrence forms are designed. The modeling results are highly consistent with the measured curves of shallow drilling,which verifies the applicability of this method.
MAKOGON Y F,HOLDITCH S A,MAKOGON T Y. Natural gas-hydrates—a potential energy source for the 21st Century[J]. Journal of Petroleum Science and Engineering,2007,56(1-3):14-31.
[2]
BOSWELL R,COLLETT T S. Current perspectives on gas hydrate resources[J]. Energy & Environmental Science,2011,4(4):1206-1215.
[3]
SLOAN E D. Clathrate Hydrates of Natural Gases[M]. Marcel Dekker,New York,1998.
[4]
梁金强,王宏斌,苏新,等. 南海北部陆坡天然气水合物成藏条件及其控制因素[J]. 天然气工业,2014,34(7):128-135.LIANG Jinqiang,WANG Hongbin,SU Xin,et al. Natural gas hydrate formation conditions and the associated controlling factors in the northern slope of the South China Sea[J]. Natural Gas Industry,2014,34(7):128-135.
[5]
张光学,梁金强,陆敬安,等. 南海东北部陆坡天然气水合物藏特征[J]. 天然气工业,2014,34(11):1-10.ZHANG Guangxue,LIANG Jinqiang,LU Jing’an,et al. Characteristics of natural gas hydrate reservoirs on the northeastern slope of the South China Sea[J]. Natural Gas Industry,2014,34(11):1-10.
[6]
杜浩,石万忠,梁金强,等. 琼东南盆地块体搬运沉积体系成因及其对水合物成藏的影响[J]. 石油地球物理勘探,2021,56(4):869-881.DU Hao,SHI Wanzhong,LIANG Jinqiang,et al. Genesis of mass transport deposits and their effect on gas hydrate accumulation in the Qiongdongnan Basin[J]. Oil Geophysical Prospecting,2021,56(4):869-881.
[7]
CARCIONE J M,TINIVELLA U. Bottom-simulating reflectors:seismic velocities and AVO effects [J]. Geophysics,2000,65(1):54-67.
[8]
赵群,郭建,郝守玲,等. 模拟天然气水合物的岩石物理特性模型实验[J]. 地球物理学报,2005,48(3):649-655.ZHAO Qun,GUO Jian,HAO Shouling,et al. Experiments of physical modeling for petrophysical properties of natural gas hydrate[J]. Chinese Journal of Geophysics,2005,48(3):649-655.
[9]
张如伟,张宝金,黄捍东,等. 天然气水合物沉积层的AVA特征[J]. 石油地球物理勘探,2011,46(4):634-639.ZHANG Ruwei,ZHANG Baojin,HUANG Handong,et al. AVA characters on gas hydrate-bearing sedimentary deposit[J]. Oil Geophysical Prospecting,2011,46(4):634-639.
[10]
王新全,刘晖,王林,等. 南祁连盆地天然气水合物地震勘探技术[J]. 石油地球物理勘探,2017,52(4):644-650.WANG Xinquan,LIU Hui,WANG Lin,et al. Seismic exploration for natural gas hydrate in the South Qilian Basin[J]. Oil Geophysical Prospecting,2017,52(4):644-650.
[11]
霍元媛,张明. 基于遗传算法的天然气水合物似海底反射层速度结构全波形反演[J]. 石油地球物理勘探,2010,45(1):55-59.HUO Yuanyuan,ZHANG Ming. The genetic algorithm based velocity structure waveform inversion for gas hydrate bottom simulating reflection (BSR)[J]. Oil Geophysical Prospecting,2010,45(1):55-59.
[12]
杨静,张雷,王九拴,等. 基于模型正演的天然气水合物定量描述[J]. 石油地球物理勘探,2020,55(2):419-425.YANG Jing,ZHANG Lei,WANG Jiushuan,et al. Quantitative characterization of gas hydrate based on forward modeling[J]. Oil Geophysical Prospecting,2020,55(2):419-425.
[13]
张聿文,刘学伟,金玉洁. 含天然气水合物地层的速度和衰减研究[J]. 石油地球物理勘探,2004,39(2):205-214.ZHANG Yuwen,LIU Xuewei,JIN Yujie. Study of velocity and attenuation for gas-bearing hydrate formation[J]. Oil Geophysical Prospecting,2004,39(2):205-214.
[14]
LEE M W,HUTCHINSON D R,COLLETT T S,et al. Seismic velocities for hydrate-bearing sediments using weighted equation[J]. Journal of Geophysical Research-Solid Earth,1996,101(B9):20347-20358.
[15]
HELGERUD M B,DVORKIN J,NUR A,et al. Elastic-wave velocity in marine sediments with gas hydrates:effective medium modeling[J]. Geophysical Research Letters,1999,26(13):2021-2024.
[16]
ECKER C,DVORKIN J,NUR A. Sediments with gas hydrates:internal structure from seismic AVO[J]. Geophysics,1998,63(5):1659-1669.
[17]
宋海斌,OSAMU M,杨胜雄,等. 含天然气水合物沉积物的岩石物性模型与似海底反射层的AVA特征[J]. 地球物理学报,2002,45(4):546-556.SONG Haibin,OSAMU M,YANG Shengxiong,et al. Physical property models of gas hydrate-bearing sediments and AVA character of bottom simulating reflector[J]. Chinese Journal of Geophysics,2002,45(4):546-556.
[18]
刘欣欣,印兴耀,栾锡武. 天然气水合物地层岩石物理模型构建[J]. 中国科学(地球科学),2018,48(9):1248-1266.LIU Xinxin,YIN Xingyao,LUAN Xiwu. Seismic rock physical modelling for gas hydrate-bearing sediments[J]. Scientia Sinica(Terrae),2018,48(9):1248-1266.
[19]
孟大江,文鹏飞,张如伟,等. 天然气水合物横波速度等效介质模型预测方法[J]. 石油地球物理勘探,2020,55(1):117-125.MENG Dajiang,WEN Pengfei,ZHANG Ruwei,et al. Gas hydrate S-wave velocity prediction method based on effective medium model[J]. Oil Geophysical Prospecting,2020,55(1):117-125.
[20]
AVSETH P,MUKERJI T,MAVKO G. Quantitative Seismic Interpretation:Applying Rock Physics Tools to Reduce Interpretation Risk[M]. Cambridge University Press,Cambridge,2010.
[21]
MAVKO G,MUKERJI T,DVORKIN J. The Rock Physics Handbook:Tools for Seismic Analysis in Porous Media[M]. Cambridge University Press,Cambridge,1998.
[22]
HASHIN Z,SHTRIKMAN S. A variational approach to the theory of the elastic behaviour of multiphase materials[J]. Journal of the Mechanics and Physics of Solids,1963,11(2):127-140.
[23]
DAI J C,SNYDER F,GILLESPIE D,et al. Exploration for gas hydrates in the deepwater,northern Gulf of Mexico:Part I. A seismic approach based on geologic model,inversion,and rock physics principles[J]. Marine and Petroleum Geology,2008,25(9):830-844.
[24]
DVORKIN J,NUR A. Elasticity of high-porosity sandstones:theory for two North Sea data sets[J]. Geophysics,1996,61(5):1363-1370.
[25]
WADELL H. Volume,shape,and roundness of rock particles[J]. The Journal of Geology,1932,40(5):443-451.
[26]
GARCIA X,MEDINA E A. Hysteresis effects stu-died by numerical simulations:cyclic loading-unloading of a realistic sand model[J]. Geophysics,2006,71(2):F13-F20.
