页岩气储层水平井压裂分布式光纤邻井微振动监测及震源位置成像

水力压裂是进行非常规油气储层改造，提高单井产量的必备技术.为了实现安全、高效压裂，通常使用地震检波器进行微地震监测和压裂效果评估.一般情况下，井中检波器数量较少且采集方位角较窄，难以获得准确的微地震震源位置，导致无法准确评估储层改造情况.通过将光纤永置式布设于页岩气储层水平井的套管外，我们实现了基于水平井光纤分布式声波传感（Distributed Acoustic Sensing，DAS）的全井段、宽方位、高密度水力压裂过程微振动实时监测，并进一步使用震源扫描算法对监测到的微地震有效事件进行震源位置成像.合成数据算例表明，与常规检波器技术相比，DAS技术具有以下两点优势：（1）DAS技术实现了水平井全井段监测，显著增加了监测数据的采集方位角，可以有效提升震源位置成像的空间分辨率；（2）DAS技术显著增加了监测数据的空间采样密度，可以有效提高低信噪比监测数据的震源位置成像精度.昭通页岩气储层水力压裂监测数据算例进一步验证了DAS技术的有效性，表明了宽方位、高密度的DAS数据可以获得高分辨率的震源位置成像结果，有助于提高储层改造效果评估的准确性.

Distributed fiber optic micro-vibration monitoring in offset-well and microseismic source location imaging during horizontal well fracturing in shale gas reservoir

Hydraulic fracturing is an indispensable technology for unconventional oil and gas reservoir stimulation, and it can increase single well production. To improve the efficiency of fracturing, it usually monitors and evaluates the performance using microseismic data acquired by geophones. Due to the limited number of geophones and narrow azimuths, it is difficult to find the accurate microseismic source locations and evaluate the reservoir stimulation status. By permanently deploying optical fiber outside the casing along horizontal well, we performed entire-well, wide-azimuth and high-density distributed acoustic sensing (DAS) monitoring during hydraulic fracturing, and further estimated the source locations of observed microseismic events using source scanning method. The synthetic examples verify that the DAS has two advantages over geophones: (1) DAS can monitor the entire horizontal well, which increases the acquisition azimuth and improves spatial resolution of the source location images; (2) DAS can greatly improve the data density and reduce the uncertainty of the source location especially for low signal-to-noise ratio data. The Zhaotong shale gas field data result validates the effectiveness of DAS; it shows that the wide-azimuth and high-density DAS data can obtain high resolution source location images, which will improve the evaluation accuracy for reservoir stimulation.