近年来,随着微地震技术发展，微地震的应用深度也在不断拓展。如微地震监测从最初简单的震源点定位到震源机制反演、地层主应力状态以及储层渗透率等高级解释参数。在众多解释参数中，微地震事件震级是一种极为重要的震源参数，它是表征在生产作业中诱发震源强度大小的物理量。不同地区诱发事件震级分布特点不尽相同，目前对于震级大小的影响因素尚不十分明确。以山西沁水盆地南部煤层气井水力压裂地面微地震监测为例，综合现有资料对该井压裂事件震级的影响因素进行了分析。首先，通过压裂施工曲线定量统计了施工中油压的平均压力和峰值压力，然后分别与微地震事件震级进行交汇分析;其次，应用Gutenberg-Richter定律研究事件震级在空间和时间频率的分布特征。最后基于三维地震相干体属性解释储层天然裂缝，应用摩尔库伦破裂准则分析天然裂缝对破裂压力的影响。分析表明:① 水力压裂中事件的平均震级或峰值震级都与水力压裂压力具有明显的正相关关系，压力是影响微地震事件震级的大小的直接因素。② 强震级集中区域表现为明显的低b值特点，表明该区域附近岩性相对更偏脆性，应力积累能力大于周围区域。③ 天然裂缝会降低地层的破裂压力，因此在煤层中裂缝发育区域诱发事件震级较低。水力压裂施工中诱发事件是一个复杂的过程，限于资料的限制，尚有一些影响震级的因素未进行分析，如地应力、储层脆性等。下一步工作将搜集尽可能多的资料，对震级影响进行更全面的分析。通过对水力压裂事件震级影响因素进行分析，有助于掌握事件震级的发生规律，从而保障水力压裂施工安全以及顺利进行。

In recent years,with the development of microseismic technology,the application depth of microseismic is also expanding,for example,microseismic monitoring from the initial simple source locating to source mechanism inversion,formation main stress state and reservoir permeability and other highlevel interpretation parameters.Among many interpretation parameters,the magnitude of microseismic events is a very important source parameter,which is representing the intensity of induced source in production.The magnitude distribution characteristics of induced events in different regions are different.At present,the influencing factors of magnitude are not very clear.Taking the surface microseismic monitoring of hydraulic fracturing of coalbed methane wells in the south of Qinshui Basin as an example,the influencing factors of the magnitude of fracturing events in this well were analyzed based on the existing data.First of all,the average pressure and peak pressure of oil pressure during the hydraulic fracturing were calculated quantitatively through the fracturing hydraulic fracturing curve,and then the intersection analysis was carried out with the magnitude of microseismic events respectively.Secondly,GutenbergRichter law was applied to study the distribution characteristics of events magnitude in space and time frequency.Finally,based on the attributes of threedimensional seismic coherence body,the natural fracture of reservoir was interpreted,and the influence of natural fracture on fracture pressure was analyzed by using Mohr Coulomb fracture criterion.The results show that ① the average magnitude or peak magnitude of the events in hydraulic fracturing has a significant positive correlation with the hydraulic fracturing pressure,and the pressure is the direct factor affecting the magnitude of the microseismic events.② The area with strong magnitude concentration is characterized by obvious low b value,which indicates that the lithology near the area is relatively more brittle,and the stress accumulation capacity is greater than the surrounding area.③ The natural fractures will reduce the fracture open pressure of the formation,so the induced events magnitude in the fracture development area of the coal seam is relatively low.The induced events in hydraulic fracturing is a complex process,limited by the data,there are still some factors affecting the magnitude that have not been analyzed,such as insitu stress,reservoir brittleness and so on.The next step is to collect as much data as possible to make a more comprehensive analysis of the magnitude impact.Through the analysis of the factors influencing the magnitude of the hydraulic fracturing events,it is helpful to understand the occurrence law of the magnitude of the events,so as to ensure the safety and smooth progress of the hydraulic fracturing

1 工区概况

2 M井组事件震级计算

3 事件震级影响因素分析

    3.1 压裂施工曲线与事件震级关系

    3.2 微地震事件b值与震级关系

    3.3 天然裂缝与震级关系

4 结论