•  
  •  
 

Coal Geology & Exploration

Abstract

Objective To achieve safe and efficient hydraulic fracturing, it is necessary to conduct timely and accurate microseismic monitoring in the reservoir stimulation process. The purpose is to analyze and assess the fracturing effects. Methods Using a permanently deployed fiber-optic cable outside the casing of a coalbed methane (CBM) well, this study employed distributed optical fiber acoustic sensing (DAS)for full-borehole, wide-azimuth, and high-density real-time monitoring of microseismic events induced by the hydraulic fracturing of coal seams. Furthermore, this study proposed a novel method for localizing microseismic sources based on information about wave travel time and a source-constrained mapping algorithm. First, effective microseismic events were identified by calculating the interchannel similarity coefficient from optical fiber data. Second, the incidence locations of microseismic sources in the fiber were obtained based on the P- and S-wave peaks. Third, the wave travel time differences derived using the short term averaging/long term averaging (STA/LTA) algorithm were used to determine the spatial distances between microseismic events and the fiber. Finally, the constrained mapping and localization of microseismic sources were performed by combining the incidence locations in the fiber and the distances from microseismic sources to the monitoring fiber. Results and Conclusion The results indicate that DAS exhibited a strong directional sensitivity to seismic waves in the acquisition process of optical fiber data. Specifically, DAS was sensitive to P-waves with an incidence angle of 0° and S-waves with an incidence angle of 45°but almost insensitive to P-waves with an incidence angle of 90° and S-waves with an incidence angle of 90°. In the case of consistent noise intensity, the sampling effects in the seismic wavefield based on various gauge lengths exhibited decreasing significance in the order of 1 m, 10 m, and 100 m. In the case of a noise intensity of 300%, the spatial sampling data based on a gauge length of 1 m still displayed relatively continuous waveforms, highlighting the seismic source wavelets of 50 Hz. The predicted fracture networks primarily exhibited NNW-SSE-directed distributions, aligning with the direction of the regional maximum principal stress, and prediction errors of within 10 m mostly. The application in wellfield M of the Chuannan coalfield in the Sichuan Basin indicates that the constrained localization algorithm yielded prediction results consistent with the experimental verification results and can effectively indicate the fracture network zones of coal seams. Therefore, this study holds great significance for enhancing the exploitation efficiency of tight hydrocarbon reservoirs with low porosity and permeability.

Keywords

coalbed methane (CBM), hydraulic fracturing, microseismic monitoring, source location, optical fiber distributed acoustic sensing (DAS), constrained mapping

DOI

10.12363/issn.1001-1986.24.06.0403

Reference

[1] 毕彩芹,胡志方,汤达祯,等. 煤系气研究进展与待解决的重要科学问题[J]. 中国地质,2021,48(2):402−423.

BI Caiqin,HU Zhifang,TANG Dazhen,et al. Research progress of coal measure gas and some important scientific problems[J]. Geology in China,2021,48(2):402−423.

[2] 李红梅. 微地震监测技术在非常规油气藏压裂效果综合评估中的应用[J]. 油气地质与采收率,2015,22(3):129−134.

LI Hongmei. Application of micro-seismic monitoring technology to unconventional hydrocarbon reservoir fracturing evaluation[J]. Petroleum Geology and Recovery Efficiency,2015,22(3):129−134.

[3] 张平,吴建光,孙唅森,等. 煤层气井压裂裂缝井下微地震监测技术应用分析[J]. 科学技术与工程,2013,13(23):6681−6685.

ZHANG Ping,WU Jianguang,SUN Hansen,et al. Aanalysis the result of the downhole microseismic monitoring technique in coalbed methane well fracturing[J]. Science Technology and Engineering,2013,13(23):6681−6685.

[4] DUNCAN P M,EISNER L. Reservoir characterization using surface microseismic monitoring[J]. Geophysics,2010,75(5):75A139−75A146.

[5] 梁雪莉,刘海龙,承宁,等. 微地震监测解释技术在非常规油气储层的研究与应用[J]. 新疆石油天然气,2021,17(3):53−58.

LIANG Xueli,LIU Hailong,CHENG Ning,et al. Study and application of microseismic monitoring and interpretation technology in unconventional oil and gas reservoirs[J]. Xinjiang Oil & Gas,2021,17(3):53−58.

[6] MOLENAAR M M,FIDAN E,HILL D J. Real-time downhole monitoring of hydraulic fracturing treatments using fibre optic distributed temperature and acoustic sensing[C]//All Days. Vienna,Austria. SPE,2012 DOI:10.2118/152981-MS.

[7] WEBSTER P,COX B,MOLENAAR M. Developments in diagnostic tools for hydraulic fracture geometry analysis[C]//Society of Exploration Geophysicists,American Association of Petroleum Geologists,Society of Petroleum Engineers. Unconventional Resources Technology Conference,12-14 August 2013. Denver,Colorado,USA. 2013. DOI:10.1190/urtec2013-025.

[8] KARRENBACH M,COLE S,RIDGE A,et al. Fiber-optic distributed acoustic sensing of microseismicity,strain and temperature during hydraulic fracturing[J]. Geophysics,2019,84(1):D11−D23.

[9] RICHTER P,PARKER T,WOERPEL C,et al. Hydraulic fracture monitoring and optimization in unconventional completions using a high-resolution engineered fibre-optic distributed acoustic sensor[J]. First Break,2019,37(4):63−68.

[10] WU Shaojiang,WANG Yibo,XIE Fei,et al. Crosscorrelation migration of microseismic source locations with hybrid imaging condition[J]. Geophysics,2022,87(1):KS17−KS31.

[11] BARNOSKI M K,MD R,SM J. A novel technique for investigating attenuation characteristics of fiber waveguides[J]. Applied Optics,1976,15(9):2112–2115.

[12] KUVSHINOV B N. Interaction of helically wound fibre-optic cables with plane seismic waves[J]. Geophysical Prospecting,2016,64(3):671−688.

[13] WILLIS M E,ELLMAUTHALER A,LEBLANC M,et al. Comparing distributed acoustic sensing,vertical seismic profile data acquired with single- and multi-mode fiber optic cables[C]//Society of Exploration Geophysicists. SEG Technical Program Expanded Abstracts 2018. Anaheim,California,2018. DOI:10.1190/segam2018-29962121..

[14] MOLENAAR M M,HILL D,WEBSTER P,et al. First downhole application of distributed acoustic sensing (DAS) for hydraulic fracturing monitoring and diagnostics[C]//All Days. The Woodlands,Texas,USA. SPE,2011. DOI:10.2118/140561-MS.

[15] BORODIN I,SEGAL A. Real-time hydraulic fracture monitoring and wellbore characterization with distributed acoustic sensing of pumping noise[J]. The Leading Edge,2020,39(11):785−792.

[16] WILLIS M E,BARFOOT D,ELLMAUTHALER A,et al. Quantitative quality of distributed acoustic sensing vertical seismic profile data[J]. The Leading Edge,2016,35(7):605−609.

[17] MADSEN K N,TØNDEL R,KVAM Ø. Data-driven depth calibration for distributed acoustic sensing[J]. The Leading Edge,2016,35(7):610−614.

[18] CONSTANTINOU A,FARAHANI A,CUNY T,et al. Improving DAS acquisition by real-time monitoring of wireline cable coupling[C]//Society of Exploration Geophysicists. SEG Technical Program Expanded Abstracts 2016. Dallas,Texas. 2016 DOI:10.1190/segam2016-13950092.1.

[19] WILLIS M,PALACIOS W,ELLMAUTHALER A,et al. Mitigation of zigzag noise on DAS VSP records acquired in vertical wells[C]//European Association of Geoscientists & Engineers. EAGE 2020 Annual Conference & Exhibition Online. Online,2020 DOI:10.3997/2214-4609.202011089.

[20] GE M. Analysis of source location algorithms Part I:Overview and non-iterative methods[J]. Journal of Acoustic Emission,2003,21(1):14−28.

[21] GE M. Analysis of source location algorithms:Part II. Iterative methods[J]. Journal of Acoustic Emission,2003,21(1):29−51.

[22] 李楠,王恩元,GE Maochen. 微震监测技术及其在煤矿的应用现状与展望[J]. 煤炭学报,2017,42(增刊1):83−96.

LI Nan,WANG Enyuan,GE Maochen. Microseismic monitoring technology and its application status and prospect in coal mine[J]. Journal of China Coal Society,2017,42(Sup.1):83−96.

[23] 武绍江,王一博,梁兴,等. 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[J]. 地球物理学报,2022,65(7):2756−2765.

WU Shaojiang,WANG Yibo,LIANG Xing,et al. Distributed fiber optic micro-vibration monitoring in offset-well and microseismic source location imaging during horizontal well fracturing in shale gas reservoir[J]. Chinese Journal of Geophysics,2022,65(7):2756−2765.

[24] 曾志毅,张建中. 利用微地震记录互相关成像的震源定位方法[J]. 石油地球物理勘探,2020,55(2):360−372.

ZENG Zhiyi,ZHANG Jianzhong. Source location through microseismic cross-correlation imaging[J]. Oil Geophysical Prospecting,2020,55(2):360−372.

[25] MATEEVA A,MESTAYER J,COX B,et al. Advances in distributed acoustic sensing (DAS) for VSP[C]//Society of Exploration Geophysicists. SEG Technical Program Expanded Abstracts 2012. 2012:1–5.

[26] BUTTER C D,HOCKER G B. Fiber optics strain gauge[J]. Applied Optics,1978,17(18):2867.

[27] MASOUDI A,NEWSON T P. Analysis of distributed optical fibre acoustic sensors through numerical modelling[J]. Optics Express,2017,25(25):32021−32040.

[28] 刘辉,李静,迟本鑫. 基于应变率的分布式光纤声波传感全波形反演研究[J]. 地球物理学报,2022,65(9):3584−3598.

LIU Hui,LI Jing,CHI Benxin. Study of distributed acoustic sensing data waveform inversion based on strain rate[J]. Chinese Journal of Geophysics,2022,65(9):3584−3598.

[29] 马国旗,曹丹平,尹教建,等. 分布式声传感井中地震信号检测数值模拟方法[J]. 石油地球物理勘探,2020,55(2):311−320.

MA Guoqi,CAO Danping,YIN Jiaojian,et al. Numerical simulation of detecting seismic signals in DAS wells[J]. Oil Geophysical Prospecting,2020,55(2):311−320.

[30] DEAN T,CUNY T,HARTOG A H. The effect of gauge length on axially incident P-waves measured using fibre optic distributed vibration sensing[J]. Geophysical Prospecting,2017,65(1):184−193.

[31] BAKKU S K. Fracture characterization from seismic measurements in a borehole[D]. Massachusetts:Massachusetts Institute of Technology,2015.

[32] 卢晨刚,张遂安,白铁峰,等. 川南筠连区块煤层三维含气量属性精细建模[J]. 煤炭科学技术,2019,47(8):219−225.

LU Chengang,ZHANG Sui’an,BAI Tiefeng,et al. Improved modeling of 3D gas content attributes of CBM in Junlian Region of southern Sichuan[J]. Coal Science and Technology,2019,47(8):219−225.

[33] 彭丽莎,张毅敏,熊威,等. 四川筠连地区高阶煤煤层气井解堵技术及应用[J]. 煤田地质与勘探,2021,49(5):132−138.

PENG Lisha,ZHANG Yimin,XIONG Wei,et al. De-blocking technology and application of high-rank CBM well in Junlian region in Sichuan Province[J]. Coal Geology & Exploration,2021,49(5):132−138.

Share

COinS
 
 

To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.