构造煤及夹矸对煤层AVO正演模拟结果影响分析

Analysis on the influence of tectonic coal and parting on AVO forward modeling of coal seam

为研究煤层中夹矸、构造煤对煤层AVO特征的影响,本文建立了4类典型模型并以岩石物理实验数据为依据确定了模型参数,基于反射系数谱理论计算了模型PP波、PS波的反射系数和相位,分析了煤层中夹矸和构造煤对煤层AVO特征的影响.模拟结果表明:夹矸层在煤层中所处空间位置和分层情况对煤层反射系数没有影响,但随夹矸层厚度的增大,煤层PP波PS波反射系数和相位均发生变化;构造煤对煤层PP波、PS波反射系数和相位影响大于夹矸层,构造煤和夹矸层对煤层AVO结果的影响相反;对于即含有夹矸又含有构造煤的厚煤层,夹矸层和构造煤在煤层中所处空间位置对煤层反射系数没有影响;夹矸层与构造煤相对厚度变化会对构造煤AVO地震响应产生影响.煤层中夹矸会减弱构造煤响应识别,在进行构造煤反演时,应结合实际地质资料,排除夹矸影响,提高构造煤预测精度.

To study the AVO characteristic of coal seam under the influence of parting and tectonic coal,four models were established according to the date gained by rock physical experiments. The reflectance and phase of PP-wave and PS-wave were computed in the reflectance spectrum theory and the influence of the interlayer and tectonic coal on the AVO characteristics of the coal seam is analyzed. Results show： the special position of parting and layer features have no impact on the reflectance of coal seam,while the reflection as well as phase of PP-wave and PS-wave changed with the increasing thickness of parting. The impact on the coal reflectance of tectonic coal is dominant compared with parting and the fact are just the opposite when it comes to the phase. The special position of parting and tectonic coal have no impact on the reflectance of thick-layer coal that contain both of them and the AVO characteristics were impacted by the relative thickness of parting and tectonic coal. The parting in the coal seam will weaken the response of the constructed coal. In the process of the tectonic coal inversion,the actual geological data should be combined to remove the influence of the parting and improve the prediction accuracy of the tectonic coal.