摘要
我们用Stoneley波的衰减系数谱探测地层径向剖面中的连通裂缝.声波测井的Stoneley波只沿井轴传播,幅度在井壁最大,沿径向衰减,波阵面是橄榄型,伸入井内液体,其耦合波的波阵面也是橄榄型,伸入地层;频率不同,伸入地层的径向深度不同,探测深度不一样.连续频率的瞬态Stoneley波能探测不同径向深度剖面的连通裂缝.受开方多值影响,液固平面界面响应的被积函数有一个实极点和8个复极点,实极点对应Stoneley波,在频率f、波数k组成的f-k平面沿直线分布.井内液体的Stoneley波对应圆柱液体响应的被积函数实极点,在f-k平面也沿直线分布.但是被积函数包含Hankel函数,其对数多值产生无数个复极点,其实部也位于直线上,留数也构成Stoneley波响应,复极点的虚部是响应的衰减系数.用改进的矩阵法阶数取2处理阵列声波测井波形,在每个频率均获得两个复波数.其虚部在0.1~6 kHz的区间内一个接近0,是Stoneley波对应的实极点虚部;另一个随频率剧烈变化,是无数复极点的虚部.地层有连通裂缝时这两个虚部均出现异常,其中接近0的虚部异常随频率连续分布,无限延伸裂缝模型的正演结果验证了该连续分布,电成像和试油资料验证了其展现的裂缝及其连通性.
We employ the attenuation coefficient spectrum of Stoneley waves to detect permeable fractures in the radial section of geological formations.Stoneley waves propagate along the wellbore axis,with the greatest amplitude at the borehole wall and a radial decay.Their wavefronts are olive-shaped,penetrating into the borehole fluid,and the wavefronts of the coupled waves of the Stoneley wave also exhibit an olive shape,penetrating into the strata.The penetrating depth varies with frequency,thus altering the exploration depth of the Stoneley wave within the formation.Continuous frequency transient Stoneley waves possess a frequency band that enables the detection of permeable fractures extending in the radial section.The integrand of the liquid-solid plane interface response is influenced by the multivalued property,featuring one real pole and eight complex poles.The real pole corresponds to the Stoneley wave and is distributed along a straight line in the frequencywave number(f-k)plane.The Stoneley wave in the borehole fluid also corresponds to the real pole of the integrand response and is distributed along a straight line in the f-k plane.However,the integrand includes the Hankel function,whose multivalued property generates countless complex poles,with their real parts aligning along the same line as the Stoneley wave in the f-k plane.The residue of each complex pole constitutes the Stoneley wave response in the borehole fluid,and the imaginary part of each complex pole represents the attenuation coefficient of the Stoneley wave response.Utilizing a modified matrix-pencil method with an order of two,we process the full-waveform array sonic data,obtaining two complex wave numbers at each frequency.One complex wave number has an imaginary part that approaches zero in the 0.1~6 kHz frequency range,corresponding to the imaginary part of the real pole for the Stoneley wave.The imaginary part of the other complex wave number fluctuates significantly with frequency,representing the imaginary part of the countless complex poles.When there are permeable fractures in the formation,the imaginary parts of these two complex wave numbers exhibit anomalies.The imaginary part approaching zero varies continuously with frequency,a phenomenon verified by the transmission coefficient of an infinitely extending fracture model in the wellbore.Additionally,the presence and connectivity of fractures are confirmed by electric imaging logs and production test data.
作者
沈永进
苏远大
SHEN YongJin;SU YuanDa(School of Geosciences,China University of Petroleum(East China),Qingdao 266580,China;Key Laboratory of Deep Oil and Gas,China University of Petroleum(East China),Qingdao 266580,China;Qingdao National Laboratory for Marine Science and Technology,Qingdao 266580,China)
出处
《地球物理学报》
北大核心
2025年第9期3651-3663,共13页
Chinese Journal of Geophysics
基金
国家自然科学基金(41821002,42074137)
国家重点研发计划(2019YFC0605504)
中国石油重大科技项目(ZD2019-183-004)联合资助.
关键词
声波测井
Stoneley波
衰减系数
裂缝
连通
波阵面
表面波
Acoustic logging
Stoneley wave
Attenuation coefficient
Fracture
Connectivity
Wave front
Surface wave
