摘要
波诱导的孔隙流体流动是造成地震波速度频散与衰减的重要机制,其中孔隙流体性质(尤其是黏度)是影响速度频散变化特征的关键因素之一.为了研究孔隙流体黏度对速度频散的影响,本文在饱和不同黏度流体条件下对2块低孔隙度砂岩和3块中孔隙度砂岩样品进行了低频应力-应变岩石物理测试,获得了岩石样品1~3 kHz的杨氏模量、泊松比和衰减曲线.实验结果发现:两种砂岩样品都表现出随着有效压力增加,杨氏模量增加,频散程度减弱的特征;同时随着流体黏度增大,频散梯度增大,特征频率向较低频率移动.为了更好地解释不同流体黏度条件下的实验数据,本文采用现有经典岩石物理频散模型对实测速度频散进行了描述.研究结果表明,经典的Gurevich喷射流模型、Biot模型、White模型、Gassmann方程和BISQ模型在数值上和趋势上均难以定量刻画实测低频数据,其预测结果存在明显的特征频率且中间过渡频段较小,而实测速度则随频率的增大呈缓慢递增趋势,且具有较宽的中间过渡频段.对于中孔隙度砂岩样品,考虑Biot宏观流作用、软孔与软孔以及软孔与硬孔喷射流效应的扩展Gurevich喷射流模型能够给出与实验数据较为吻合的预测结果;对于低孔隙度砂岩,扩展Gurevich喷射流模型的预测结果也能在趋势上与实验数据保持一致.实验数据和理论模型共同指出归一化参数E(f)/E(1 Hz)具有提高储层流体预测与流体识别精度的潜力和重要意义.
Wave-induced pore fluid flow is an important mechanism that causes seismic wave velocity dispersion and attenuation.Pore fluid properties,especially viscosity,are one of the key factors affecting the variation characteristics of velocity dispersion.In this study,two low-porosity and three medium-porosity sandstone samples were subjected to low-frequency stress-strain rock physics tests.In order to study the effect of pore fluid viscosity on velocity dispersion,experiments were carried out under the condition of saturated fluids of different viscosities.The Young's modulus,Poisson's ratio and attenuation curve of the rock samples at 1~3 kHz are obtained.The experimental results found that:As the effective pressure increases,the Young's modulus increases and the degree of dispersion decreases.As the fluid viscosity increases,the dispersion gradient also increases,and the characteristic frequency moves to a lower frequency.The above phenomena are found in both sandstone samples sets.In order to explain the experimental results better under the different fluid viscosity conditions,the existing classical rock physics dispersion model is used to describe the measured velocity dispersion.The results show that the classical Gurevich squirt model,Biot model,White model,Gassmann equation and BISQ model are difficult to quantitatively characterize the measured low frequency data in terms of numerical value and trend.These model prediction results have obvious characteristic frequencies and small intermediate transition frequency band.However,the measured velocities tend to increase slowly with the frequency increasing and have a wide intermediate transition band.For the medium porosity sandstone samples,the extended Gurevich squirt flow model,which considering the effects of Biot macro-flow,soft pores and soft pores squirt flow,soft pores and hard pores squirt flow,can give predictions that are more consistent with the experimental data.For the low porosity sandstones,the predictions of the extended Gurevich squirt flow model can also be consistent with the experimental data in trend.Normalized parameters have the potential to improve the accuracy of reservoir fluid identification,which is reflected by both experimental data and theoretical models.
作者
李智
欧阳芳
肖增佳
刘欣泽
贺艳晓
赵建国
LI Zhi;OUYANG Fang;XIAO ZengJia;LIU XinZe;HE YanXiao;ZHAO JianGuo(State Key Laboratory of Petroleum Resource and Prospecting,China University of Petroleum(Beijing),Beijing 102249,China;Huanqing Branch,Yumen Oilfield,China National Petroleum Corporation,Qingyang Gansu 745700,China)
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2022年第6期2179-2197,共19页
Chinese Journal of Geophysics
基金
国家自然科学基金联合基金重点基金项目(U20B2015)
国家自然科学基金项目(41574103,41974120)
国家重大专项课题(2016ZX05004-003)联合资助。
关键词
岩石物理实验
频散理论
喷射流模型
孔隙结构
流体黏度
Rock physics experiments
Dispersion theory
Squirt flow model
Pore structure
Fluid viscosity
