致密砂岩储层CO_2压裂裂缝扩展实验研究
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摘要
为提高天然裂缝和层理不发育致密储层压裂裂缝的复杂性,基于真三轴压裂模拟实验系统,开展了致密砂岩储层CO_2压裂实验研究,分析了水平应力差、压裂液类型和排量对压裂裂缝扩展规律的影响。研究表明,超临界CO_2压裂形成的水力裂缝形态最复杂,液态CO_2次之,滑溜水压裂产生的水力裂缝形态简单;采用液态CO_2压裂时,低水平应力差(≤3 MPa)有利于提高水力裂缝的复杂程度;液态CO_2压裂的起裂压力相比于滑溜水压裂降低22.1%,超临界CO_2压裂的起裂压力相比于滑溜水压裂降低28.2%;提高排量会加快井筒内流体增压速率,起裂压力升高。实验证明超临界CO_2压裂能够有效提高裂缝复杂性。
In order to improve the complexity of hydraulic fractures in the tight reservoirs with undeveloped natural fractures and beddings, CO_2 based tight sandstone fracturing was experimentally studied in the true triaxial fracturing simulation experiment system to analyze the effects of horizontal stress difference, fracturing fluid type and displacement on the propagation laws of hydraulic fractures. It is shown that the hydraulic fractures generated by supercritical CO_2 fracturing are morphologically the most complex, followed by those generated by liquid CO_2 fracturing and those generated by slick-water fracturing are the simplest. When liquid CO_2 fracturing is carried out, low horizontal stress difference(≤3 MPa) is beneficial to increasing the complexity of hydraulic fractures. Compared with the initial pressure of slick-water fracturing, that of liquid CO_2 fracturing is 22.1% lower and that of supercritical CO_2 fracturing is 28.2% lower. The fluid pressure increasing rate inside the wellbore and the initial pressure can be increased by increasing the displacement. It is experimentally proved that supercritical CO_2 fracturing can improve the complexity of fractures effectively.
In order to improve the complexity of hydraulic fractures in the tight reservoirs with undeveloped natural fractures and beddings, CO_2 based tight sandstone fracturing was experimentally studied in the true triaxial fracturing simulation experiment system to analyze the effects of horizontal stress difference, fracturing fluid type and displacement on the propagation laws of hydraulic fractures. It is shown that the hydraulic fractures generated by supercritical CO_2 fracturing are morphologically the most complex, followed by those generated by liquid CO_2 fracturing and those generated by slick-water fracturing are the simplest. When liquid CO_2 fracturing is carried out, low horizontal stress difference(≤3 MPa) is beneficial to increasing the complexity of hydraulic fractures. Compared with the initial pressure of slick-water fracturing, that of liquid CO_2 fracturing is 22.1% lower and that of supercritical CO_2 fracturing is 28.2% lower. The fluid pressure increasing rate inside the wellbore and the initial pressure can be increased by increasing the displacement. It is experimentally proved that supercritical CO_2 fracturing can improve the complexity of fractures effectively.
引文
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[2]陈玉良.鄂尔多斯盆地盒8期原型盆地沉积体系及岩相古地理研究[D].西安:长安大学,2015.CHEN Yuliang.Study on depositional systems and lithofacies paleogeography of He-8 period,Erdos prototype basin[D].Xi’an:Chang’an University,2015.
[3]魏元龙,杨春和,郭印同,刘伟,王磊,侯振坤,徐峰.须家河组致密砂岩水力压裂裂缝形态的试验研究[J].岩石力学与工程学报,2016,35(增刊1):2720-2731.WEI Yuanlong,YANG Chunhe,GUO Yintong,LIU Wei,WANG Lei,HOU Zhenkun,XU Feng.Experimental study on hydraulic fracture geometry of tight sandstone from Xujiahe group[J].Chinese Journal of Rock Mechanics and Engineering,2016,35(S1):2720-2731.
[4]SINAL M L,LANCASTER G.Liquid CO2 fracturing:advantages and limitations[J].Journal of Canadian Petroleum Technology,1987,26(5):26-30.
[5]刘合,王峰,张劲,孟思炜,段永伟.二氧化碳干法压裂技术--应用现状与发展趋势[J].石油勘探与开发,2014,41(4):466-472.LIU He,WANG Feng,ZHANG Jin,MENG Siwei,DUANYongwei.Fracturing with carbon dioxide:Application status and development trend[J].Petroleum Exploration and Development,2014,41(4):466-472.
[6]ISHIDA T,AOYAGI K,NIWA T,CHEN Y,MURATA S,CHEN Q,NAKAYAMA Y.Acoustic emission monitoring of hydraulic fracturing laboratory experiment with supercritical and liquid CO2[J].Geophysical Research Letters,2012,39(16):L16309.
[7]KIZAKIA A,TANAKA H,OHASHI K,SAKAGUCHIK,MATSUKI K.Hydraulic fracturing in Inada granite and Ogino tuff with super critical carbon dioxide[R].ISRM-ARMS7-2012-109,2012.
[8]ZHANG Xinwei,LU Yiyu,TANG Jiren,ZHOU Zhe,LIAO Yin.Experimental study on fracture initiation and propagation in shale using supercritical carbon dioxide fracturing[J].Fuel,2017,190:370-378.
[9]BENNOUR Z,ISHIDA T,NAGAYA Y,CHEN Youqing,NARA Yoshitaka,CHEN Qu,SEKINE Kotaro,NAGANOYu.Crack extension in hydraulic fracturing of shale cores using viscous oil,water,and liquid carbon dioxide[J].Rock Mechanics&Rock Engineering,2015,48(4):1463-1473.
[10]ZOU Yushi,LI Ning,MA Xinfang,ZHANG Shicheng,LI Sihai.Experimental study on the growth behavior of supercritical CO2-induced fractures in a layered tight sandstone formation[J].Journal of Natural Gas Science&Engineering,2018,49:145-156.
[11]HUCKA V,DAS B.Brittleness determination of rocks by different methods[J].International Journal of Rock Mechanics and Mining Sciences and Geomechanics Abstracts,1974,11(10):389-392.
[12]张士诚,郭天魁,周彤,邹雨时,牟松茹.天然页岩压裂裂缝扩展机理试验[J].石油学报,2014,35(3):496-503.ZHANG Shicheng,GUO Tiankui,ZHOU Tong,ZOUYushi,MU Songru.Fracture propagation mechanism experiment of hydraulic fracturing in natural shale[J].Acta Petrolei Sinica,2014,35(3):496-503.
[13]BEUGELSDIJK LJL,PATER De C J,SATO K.Experimental hydraulic fracture propagation in a multifractured medium[R].SPE 59419,2000.
[14]AHMED MG,QI Q,RUSSELL M,SCOTT N,TEDR.New insights into hydraulic fracturing of shale formations[R].IPTC 17594,2014.
[15]GARAGASH D,DETOURNAY E.The tip region of a fl uid-driven fracture in an elastic medium[J].Journal Applied Mechanics,2000,67(1):183-192.
[16]DETOURNAY E.Propagation regimes of fluid-driven fractures in impermeable rocks[J].International Journal of Geomechanics,2004,4:35-45.
[17]TUDOR R,VOZNIAK C,PETERS W,BANKS M-L.Technical advances in liquid CO2 fracturing[R].PETSOC-94-36,1994.
[18]ITO T.Effect of pore pressure gradient on fracture initiation in fluid saturated porous media:Rock[J].Engineering Fracture Mechanics,2008,75(7):1753-1762.