摘要
在非常规油气开发中,水力压裂技术可以极大地提高油气开采的效率。在压裂过程中,伴随着新的裂缝产生或已经存在裂缝的重新激活,会诱发大量微地震事件。对我国西南地区某垂直页岩气井水力压裂地面微地震监测数据进行了处理和分析。与常规微地震数据处理过程相比,在进行微地震事件定位的同时,利用微地震信号对储层由于压裂导致的速度变化进行了成像分析。采用双差地震成像算法,利用绝对到时和波形互相关得到的相对到时数据联合反演速度结构及震源位置。反演结果显示,微地震定位精度与传统网格搜索法相比有较大改善。对于不同的压裂深度,微地震空间分布和速度异常呈现出不同的特点。整体上由于裂缝的存在,微地震位于低v_P区域。而对于v_S来说,在深部微地震位于低速异常区域,但在浅部则位于高速异常区域。结合岩石物理实验结果和波形分析,推测在浅部微地震和高v_S关联是由于该区域天然裂缝发育并且气体处于饱和状态。研究结果表明,综合微地震定位和速度成像可以更加全面地刻画页岩气水力压裂过程和裂缝分布。
In unconventional oil and gas development,hydraulic fracturing can greatly improve the efficiency of oil and gas production.During the fracturing process,microseismic events is easily induced along with the generation of new cracks or reactivation of existing cracks.This study analyzes the surface microseismic monitoring data recorded during hydraulic fracturing in a shale gas production well in southwest China.This study first detects and locates microseismic events,and then images the velocity changes of the reservoir caused by hydraulic fracturing.A double-difference(DD) seismic tomography is adopted to identify the event locations and velocity structure simultaneously using both absolute arrival and differential times estimated from waveform cross correlation.The results showed that the identification of event locations was more accurate than when using conventional grid-search location algorithms.The distribution of microseismic events and velocity anomalies showed different characteristics at different depths.The microseismic events were associated with low v_P anomalies because of the existence of fractures.However,for v_S,the microseismic events were associated with low and high v_S anomalies at deeper and shallower zones,respectively.Combining the results of rock physics experiments and waveform analysis,we inferred that the relation between microseismic events and high v_S anomalies was due to the existence of intensive fractures and saturation of gas.This study demonstrated that comprehensive microseismic event locations and velocity imaging can more fully indicate the hydraulic fracturing process and fracture distribution in shale gas reservoir.
作者
缪思钰
张海江
陈余宽
谭玉阳
苗园园
黄振华
王飞
谢庆明
MIAO Siyu;ZHANG Haijiang;CHEN Yukuan;TAN Yuyang;MIAO Yuanyuan;HUANG Zhenhua;WANG Fet;XIE Qingming(Laboratory of Seismology and Physics of Earth’s Interiors University of Science and Technology of China Hefei 230020, China;Anhui Wantai Geophysical Technology Co.,Ltd .,He fei 230020,China;Chongqing Institute of Geology & Mineral Resources,Chongqing 401120,China;Chongqing Design Institute of Huadi Engineering Survey,Chongqing 404100 ,China)
出处
《石油物探》
EI
CSCD
北大核心
2019年第2期262-271,284,共11页
Geophysical Prospecting For Petroleum
基金
重庆市科学技术委员会重点专项"盆缘山区页岩气地球物理探测装置研发与应用示范"(cstc2016zdcy-zd90002)资助~~
关键词
微地震
震源定位
波形互相关
双差成像
页岩气
水力压裂
microseismic
event location
waveform cross-correlation
double-difference tomography
shale gas
hydraulic fracturing
