致密砂岩多频段岩石物理特征与流体检测应用

Compared with the conventional sandstone, the tight sandstone has the characteristics of low porosity and low permeability, and the pore structure is complex with development of micro-fractures. Therefore, its seismic rock physic characteristics are different from those of the conventional sandstone reservoir. Furthermore, fluid flow interactions with the solid phase make the variation of the elastic parameters more complicated. Consequently, we have poor understanding of the seismic response caused by fluids in the tight sandstone reservoirs, thus often leading to the failure of the conventional reservoir prediction and fluid detection methods. To this end, we plan to make experiments on tight sandstone samples, using the rock physics measurement techniques at multi-frequency bands, to measure their elastic properties in the seismic and ultrasonic frequency bands. In combination with the sonic frequency results, we will investigate the effect of lithology, petrophysical properties, pore structure, fluid type, saturation, viscosity, effective pressure among other factors on the P and S wave velocity dispersions. On this basis, by considering the geometrical and physical characteristics of the pores, we will build a theoretical model for the tight sandstones with the constraints of the velocity data measured at different frequencies. In the seismic frequency band, we will analyze fluid sensitivity factors and establish rock physics templates, which will be applied to quantitative seismic interpretation and analysis of frequency-dependent seismic amplitude attributes, and ultimately develop a new frequency-dependent fluid detection method. This study provides a new idea for fluid detection in tight sandstone reservoirs, which is of great theoretical and practical values in promoting the quantification of seismic interpretation and reducing the oil/gas development risk.

不同于常规砂岩，致密砂岩具有低孔、低渗的特点，孔隙结构比较复杂、微裂隙发育，因此其地震岩石物理特征迥异于常规砂岩储层，加之孔隙流体作用使弹性参数变化更为复杂，人们对储层中流体的地震响应规律认识不清，往往造成常规储层预测和流体检测方法失效。为此，本研究拟利用多频段岩石物理实验技术，针对致密砂岩样品进行地震和超声频段的岩石物理测量，并结合测井频段结果，考察岩性、物性、孔隙结构、流体类型、饱和度、黏度、有效压力等因素对纵、横波速度频散的影响；在此基础上，考虑孔隙几何和物理特征，对致密砂岩进行理论模型建模并利用实测速度频散数据约束；进而在地震频段内，分析流体敏感因子，建立岩石物理量版，并应用于定量地震解释和地震振幅频变属性分析，最终发展新的频变流体检测方法。该研究为致密砂岩储层流体检测提供了新的思路，对推动地震解释定量化、降低油气开发风险等方面具有重要的理论与应用价值。

致密砂岩具有低孔、低渗的特点，孔隙结构比较复杂、微裂隙发育，因此其地震岩石物理特征迥异于常规砂岩储层，加之孔隙流体作用使弹性参数变化更为复杂，人们对储层中流体的地震响应规律认识不清，往往造成常规储层预测和流体检测方法失效。本项目针对致密砂岩岩石物理性质和规律开展实验和理论研究，探索孔隙流体、孔隙结构、有效压力条件对弹性参数频散的作用机理，基于波致流理论构建致密砂岩岩石物理模型，分析流体敏感性因子，构建对应的岩石物理解释量版，探索流体地震检测方法。研究成果包括：（1）建立了致密砂岩多频段岩石物理规律，明确了饱和致密砂岩弹性参数频散和衰减的主要控制因素；（2） 发现了部分饱和的微裂隙-孔隙型致密砂岩“双台阶频散、双衰减峰”现象，揭示了中观和微观波致流相互作用的耦合机理，其结果可用于推断微裂隙和流体的存在性；（3）实现了致密砂岩干燥、饱和、部分饱和状态下岩石物理理论建模和不同尺度流体流动耦合效应的有限元数值模拟，可定量描述不同尺度波致流引起的弹性参数频散规律；（4）基于实验结果和模型预测结果，明确了致密岩石储层流体敏感因子，建立了可用于流体检测的岩石物理解释量版，指导致密砂岩储层岩性和流体预测。依托这些研究成果，发表期刊论文14篇，会议论文8篇，授权实用新型专利1项，申请国家发明专利3项，特邀报告2个。本项目在实施过程中，相关致密砂岩岩石物理建模技术、流体敏感因子表征方法及地震频段岩石物理频变量版技术应用油气企业、研究院的横向委托项目，在致密砂岩油气勘探开发中得到有效应用。