VTI型构造煤地震波各向异性响应特征研究及裂隙预测

There are many kinds of fractures in coal seams. Over the years, many researches have studied coal seam fractures and have achieved fruitful results.But there are not systemic studies in seismic anisotropy explorating in coal seam fractures yet. There are not an efficient，complete method and a set of software in seismic anisotropic detecting in coal seam fractures.Existing methods in anisotropy of coal seam fractions do not meet actural demands because coal is mined in more and more complicate geological conditions. This project mainly discusses techniques of analyzing anisotropic response characteristics of coal seam fractures in VTI tectonic coal. It simulates seismic records by selecting an effective modeling method according to the experiment areas in Shanxi and Shanxi provinces to develop a new seismic data acquisition method in complicated structral background and get seimic records with high resolution and high signal-noise ratio.It does an analyzing research on anisotropic response in VTI coal by comparing the precision among the existing analyzing methods and getting some revised equations in seismic anisotropic response including veloctiy anisotropy,AVO anisotropy and anisotropic parameters,and optimizing calculating method of anisotropic response characteristics,because coal seam's unique features-comparatively thin to seismic wavelet and diffucult to recognize valid information from seismic record.It first discusses the parameters of anisotropic response independently,and then comes to contours of response parameters and overlaps the contours together. It gets the trend and density of fractures by analyzing integrately the corresponding relations between the contours and fractures.It develops a set of anisotopic information analyzing and recognization techinique adapted to VTI coal. Through analyzing the relations of anisotropic response from synthetic data with the model and the relations of anisotropic response parameters from real data with coal seams,it concludes that the correlations between seismic wave anisotropic response and development characteristics of coal seam fractures,providing a new quantitative parameter for fracture prediction for coal mine. All researches are based on the study results in forward and inversion in VTI media during Doctor and funded project by education department of Shanxi provincial government, transforming a developed seismic technique in oil and gas seismic exploration into coal seismic survey.It makes fullest use of seismic exploration in coal mine and it is of great importance for safe production and high efficiency of coal mining.

煤层中裂隙的类型有许多种，多年来，我国有许多知名学者对煤矿裂隙进行了研究，也取得了丰硕的成果，然而对于煤层裂隙地震各向异性勘探技术一直缺乏系统的研究，现有的方法都处于探索性阶段，至今还没有一种完善的，能全面解决裂隙探测的软件和方法，不能满足煤矿开采环境越来越复杂的实际需求。本课题以VTI型构造煤为研究对象，围绕VTI型构造煤中裂隙的特点，以各向异性响应分析技术为突破点，在陕西、山西等地的裂隙型煤矿试验场，研究VTI型构造煤中地震资料采集方法，实现获取煤层高分辨率、高信噪比的地震资料技术；研究适于煤层的各向异性响应分析公式，优化各向异性响应分析算法，实现VTI型构造煤中各向异性信息分析与识别技术；通过理论模型模拟验证和矿区野外试验相结合的方式，探讨各向异性响应与裂隙型煤层之间的关联技术。项目研究结果将进一步挖掘地震勘探技术在煤矿探测上的潜力；给煤矿裂隙探测提供新的定量化参数。

课题以VTI型构造煤为研究对象，研究了地震波的煤层各向异性响应以及各向异性与煤层裂隙之间的关联。在速度各向异性响应方面，从相速度、群速度分别对于不同各向异性参数的响应，以及速度对于不同各向异性参数的综合影响方面分析，阐述了速度与各向异性参数之间的关联：VTI型煤层中P波同时受各向异性参数ε、δ影响，SV波对|ε-δ|的变化更为敏感，随着|ε-δ|的增大，SV波各向异性越来越明显，当二者差值达到一定值时，SV波甚至表现为横波的多值现象，而SH波主要受γ的影响，对γ敏感，基本不受ε、δ的影响；在AVO方面，分析了各向异性参数对PP波、PSV波中反射系数的影响，首次提出了VTI型介质中的各向异性复合反射、透射系数，指出薄层复合反射系数是一个关于子波频率，层速度、薄层厚度、相角等参数的复杂的函数，不能用简单的函数关系式来表示，并分析了VTI型薄煤层复合反射系数随着子波频率、薄层厚度的变化规律，首次采用VTI型煤层复合反射系数等值线图分析煤层复合反射系数与煤层厚度、单界面反射系数的关联；采用人工合成地震记录的方法分析了VTI型薄层介质中地震数据采集的主要影响因素，对于VTI型煤层主要通过提高子波的频率增加地震数据的分辨率，同时各向异性参数估算的稳定性随着偏移距的加大而增加；利用裂隙弱度分析不同裂隙与各向异性参数的关系，裂隙介质中法向弱度和切向弱度同时为0时，介质不表现各向异性，法向弱度的变化对P波速度影响较大，而切向弱度对于SV波的影响更明显，故采用P波数据分析介质法向弱度的变化，通过SV波分析切向弱度的变化；将各向异性分析技术用于实际资料，分析煤层各向异性特点，改善了复杂地区地震资料的成像质量。发表论文9篇，其中以第一作者发表论文5篇，EI中文期刊收录2篇；基于C#和Fortran两种语言实现混合编程，将主要研究成果集于一个软件，开发了一套针对VTI型煤层地震波响应及裂隙参数分析的软件，已申请软件著作权。