【摘要】 随着非常规致密砂岩气、页岩气藏的开采开发,压裂技术在储层改造中起着举足轻重的作用,而微地震监测技术是评价压裂施工效果的关键且即时的技术之一.根据微地震监测处理高精度地反演微震位置,从而预测压裂裂缝的发展趋势及区域,对压裂施工效果进行跟踪及评判,同时也为后期油气藏的开采和开发提供技术指导.定位精度直接影响地下裂缝的分布特征,错误或精度不高的定位结果,必将导致对裂缝趋势的误判.文章结合理论和数值模拟方法,对初至拾取精度的影响因素进行了分析,讨论初至误差对定位精度的影响.同时结合地层岩石物理特性、射孔资料对速度模型的校正、速度各向异性、地层倾角、多段压裂等因素,分析了这些因素对精细速度模型及定位精度的影响.最后结合定位方法本身所存在的局限,探讨反演方法及方位角对定位精度的影响.通过理论及数值模拟分析表明,初至误差、速度模型精度及定位方法对定位精度有着紧密关系,并将其归类为可控误差及系统误差,通过区别对待可控误差和系统误差,可最终为高精度微地震监测定位技术的研究及应用提供指导.更多还原

【Abstract】 With the exploitation of the unconventional reservoirs such as tight sand and shale,fracturing technique plays an important role in the reservoir reconstruction.Through inverting the microseismic(MS) location effectively,it can forecast the development tendency of manmade fracture and becomes one of the key and immediate techniques to provide the evaluations for the post-fracture response,directions for the exploitation and designs for the re-fracturing.The key role of the MS monitoring is both inverting the location of the microfracture which triggers the MS signal and describing the geometry of the fracture system effectively,therefore,it is important to get a high precision location.The location precision directly affects the distribution of the manmade fracture,and the false or low precision location will result in the misjudgment of the fracture tendency.However,it is very difficult to get a high precision MS location because it is very sensitive to the first arrival,velocity,inversion algorithm and so on.This paper firstly discusses the first arrival influence on the location precision.Through the numerical simulation it can get that the first arrival has a strong effect on the location precision,and there exists a proximate proximatey linear relation between the first arrival error and the location error.The paper discusses the influences of rock property,the calibrated velocity,anisotropy velocity,the layer dip,multi-stage fracture on the velocity and location precision.Before the fracturing,the bulk and shear modulus can be considered to be constant.With the liquid and filling material injection,the density and the modulus increase and they may result in the change of velocity.The static velocity model may result in the location error because a static velocity is used in the location.In addition,a horizontal isotropy velocity is usually used in the location and may result in the location error because of dip and anisotropy in the real layer.Moreover,it is easy to ignore that a fixed velocity model is used in multi-stages fracture and may result in the location error.Finally,the paper analyses the location algorithm influence on the location error.The inversion is the universal location method,but the inappropriate option function and criteria which may result in the local extremum.Meanwhile,the azimuth also has a strong effect on the location precision.Through the theoretical analysis and numerical simulation,the first arrival error,velocity error and location algorithm have a tight relationship with the location precision.Some kinds of location errors are controllable,and some errors are systematic.Through differentiating the controllable and systematic errors,it can give some suggestions for the high precision processing flow research and the actual data processing.更多还原