深层-超深层复杂孔隙结构碳酸盐岩地震岩石物理及频散特征研究

Study on seismic petrophysics and dispersion characteristics of carbonate rocks with deep ultra-deep complex pore structure in Tarim Basin

碳酸盐岩储层是我国陆上油气勘探的重要储层类型,不同地区的碳酸盐岩储层在沉积、成岩过程存在明显差异,影响其物性及地震弹性性质变化的因素也存在差异,为认识这种机制,针对不同地区碳酸盐岩进行物性与地震弹性性质的对比分析尤为重要.通过对塔里木盆地深层碳酸盐岩储层样品的系统岩石学特征、岩石微观结构特征、物性和地震弹性特征的测试,分析了样品物性和地震弹性特征的变化规律及影响因素.研究结果表明,碳酸盐岩样品物性与地震弹性性质整体变化规律受岩石孔隙结构特征的控制,而难以构建简单的孔隙度~渗透率、孔隙度~速度或密度~速度的准确统计模型.碳酸盐岩样品纵、横波速度具有较好的相关性,在速度比上灰岩、灰质云岩、白云岩以及硅质云岩呈逐渐减小的趋势,可利用速度比及其它含有横波信息的弹性参数进行岩性识别.样品在地震频段表现出明显的频散现象(5~200Hz),微裂隙-溶蚀孔隙型样品、裂隙型样品与溶蚀孔隙型样品在频散与衰减特征上存在明显差异,微裂隙-溶蚀孔隙型样品具有相对较强的频散与衰减特征.依据储层岩石地震弹性性质变化特征给出了深层致密碳酸盐岩岩性、储层类型以及孔隙流体识别与预测的岩石物理标准.基于地震岩石物理模型计算的孔隙纵横比与骨架柔韧性因子可用于定量表征致密碳酸盐岩样品孔隙结构特征的变化,从而反应孔隙结构对岩石样品弹性波速度影响.研究结果可为碳酸盐岩储层的分类以及相关储层的岩性及烃类地震检测提供依据。

Carbonate rock is a critical reservoir for China’s onshore oil and gas exploration.Carbonate reservoirs in different regions significantly differ in sedimentary and diagenesis processes and factors affecting their petrophysical and seismic rock physics properties.Therefore,it is critical to analyze the corresponding properties of carbonate rocks in different regions.Based on systematic petrological,rock microstructure,physical property,and seismic elastic characteristic measurements of deep carbonate reservoir samples in the Tarim Basin,the variation laws and influencing factors of the samples’physical and seismic elastic properties are analyzed.Based on these measurements,the variation patterns and influencing factors of petrophysical and seismic rock properties of rock samples are analyzed.The results show that the carbonate pore structure controls the overall variations of petrophysical and seismic rock physical properties of carbonate samples,and it is challenging to build a simple statistical model of porosity–permeability,porosity–velocity,and density–velocity.P-and S-velocities correlate well,and the P-and S-velocity ratio is a good index for rock typing.For tight carbonate samples,apparent velocity dispersion at a seismic exploration frequency band(5–200 Hz)can be observed,and the pore structure controls the velocity dispersion and attenuation features.Carbonate samples with crack-dissolution pores show moderately stronger velocity dispersion than samples with dissolution and microcrack pores.The pore aspect ratio and the frameflexibility factor(γ)calculated from the seismic rock physics model correlate well with pore structure parameters,such as the characteristic ratio surface.The pore aspect ratio and frame flexibility factor can be used to quantitatively characterize the changes in the pore structure of tight carbonate samples,reflecting the pore structure effects on the elastic wave velocity.This study’s results can provide a basis for rock-typing carbonate reservoirs,lithology,and hydrocarbon detection of relevant reservoirs..