基于shearlet 变换的微地震噪声压制方法研究

The rich reserves of unconventional oil and gas resources have been a new highlight in the global oil and gas exploration recent years with the shortage of conventional hydrocarbon resources increasingly getting serious. Microseismic technique is the important mean in unconventional oil and gas reservoir exploration. However, the energy of effective signals in microseismic data is extremely weak and the signals are contaminated by strong interference which brings difficulties for data processing and interpretation. This project aims to develop shearlet transform based microseismic noise attenuation technique. For the microseismic data from well and surface, we first achieve the condition of the proposed method applied to microseismic signals extraction and noise suppression by taking the multiscale and multidirectional characteristic of shearlet transform. Then we analyze the characteristic of microseismic signals and noise in shearlet domain at different scales, directions and locations and study mathematic model for shearlet coefficients reconstruction. Finally we construct a filtering scheme and make it suitable for microseismic signals multidimensional detection with variable window and irregular noise attenuation. Techniques in this project will provide reliable support for the identification of microseismic signals, accurate source localizations and oil and gas basin fine structure reconstruction, which also raises development effectiveness of unconventional oil and gas reservoirs.

随着常规油气勘探资源的日益紧缺，储备量丰富的非常规油气资源已经成为近年来全球油气资源勘探开发新亮点。微地震技术是非常规油气储层开采的重要手段，然而微地震信号一般呈现“弱信号，强干扰”的特征，微地震监测所采集到的数据有效信号能量极其微弱，给数据的处理解释带来较大困难，本项目立意开展基于Shearlet变换的微地震噪声压制技术研究。针对井中和地面的微地震资料，利用Shearlet变换特点（多尺度、多方向等），获得该方法可应用微地震有效信号提取及噪声压制的应用条件；分析微震有效信号和噪声在Shearlet变换域中尺度、方向和位置的特征；研究Shearlet变换域系数重建的数学模型；构建适用于非常规油气开采中微地震微弱有效信号的多方位变时窗检测与复杂非规则噪声滤波方案。为微地震有效信号的识别与震源的准确定位、提高非常规油气藏开发成效以及油气盆地精细结构重建提供可靠的技术支撑。

随着常规油气勘探资源的日益紧缺，储备量丰富的非常规油气资源已经成为近年来全球油气资源勘探开发新亮点。微地震技术是非常规油气储层开采的重要手段，微地震检测技术主要采用水力压裂、注气注水作为震源。因此与常规地震资料相比，实际微地震资料的有效信号能量极其微弱，这导致了实际微地震资料的信噪比要远低于常规地震资料。此外，微地震资料中噪声类型较为复杂，因此很难通过常规的滤波方法对其进行处理。本项目将多尺度几何分析方法Shearlet变换引入到非常规油气开采的微地震资料消噪中。从正演模拟入手，建立微地震记录有效信号和噪声在Shearlet域的多尺度多方向表征模型；针对传统初至拾取方法对于强噪声记录处理过程中出现的退化问题，提出基于谱多流形聚类（SMMC）、模糊C-均值聚类等微地震信号初至拾取检测方法，将从相似性矩阵中提取到的本征维度流形特征抽象为噪声类和信号类，进而对微地震初至时刻进行有效拾取判断；研究微地震信号时空域和Shearlet变换域特征以及有效信号和噪声在Shearlet域中能量、相关性以及高阶统计量等方面的差异，提出了多种适合微地震资料去噪和初至拾取的阈值函数模型，从而得到Shearlet域中每个尺度方向的系数重建方案及最优阈值设置方案，实现极低信噪比下的有效信号识别与重建；研究三维Shearlet变换原理及其在多分量多维度的微地震数据噪声压制原理，基于三维Shearlet变换和改进阈值函数，对井中三维微地震数据噪声压制得到较好效果，最终建立一套适用于井中和地面的微地震资料噪声压制方法以及初至拾取方法技术。将该项目成果应用于实际微地震勘探资料处理，试处理井中和地面的微地震实际资料，可以有效提高实际地震资料信噪比6-8dB，初至拾取准确率提高20%-30%。该研究为微地震有效信号的识别与震源的准确定位、提高非常规油气藏开发以及油气盆地精细结构重建提供较为可靠的技术支撑。