页岩储层吸水能力影响因素实验
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摘要
页岩压裂实践表明,页岩储层压裂后返排率普遍低于30%,涪陵页岩中部核心区块压裂后的返排率甚至低于5%。与常规油气藏相比,页岩返排率与产量之间无明显正相关,甚至可能为负相关,现场实践发现压裂后闷井页岩气产量有增加现象,说明页岩吸水因素对压裂效果的影响很大。因此,针对涪陵志留系龙马溪页岩,建立完善了页岩自吸实验方法,开展了渗透率各向异性、天然微裂缝、围压、和液体类型等页岩自吸实验分析。结果表明:①平行层理面的岩样比垂直层理面的岩样吸水能力强;②围压对页岩自吸能力有一定的抑制作用,相同条件下,深层页岩压裂后的返排率比浅层高;③页岩自吸能力在不同液体中的表现不一,蒸馏水> 2%KCl溶液>煤油;④不同实验条件下的页岩吸水后均能在不同程度上产生诱导微裂缝,对页岩的渗透性有较大的改善。
Some practice shows that, flowback rate after fracturing shale reservoirs is generally less than 30%, in particular below 5%for central Fuling shale block. Different from conventional reservoirs, shale reservoirs represent no significant positive correlation and even negative correlation between flowback rate and production. Field practice illustrates that shale-gas production increases after fracturing and well soaking, indicating that water absorption factors of shale have great effect on fracturing. In this study, the Longmaxi shale in Fuling block was taken as an example to establish and improve an experimental method for shale imbibition and carry out imbibition experimental analysis from four aspects of permeability anisotropy, natural micro-fracture, confining pressure,and liquid type. Results show that,(1) water absorption capacity of rock samples with parallel bedding surface is stronger than that of samples with vertical bedding surface;(2) confining pressure has a certain inhibition effect on imbibition capacity, which indicates that under the same conditions, flowback rate after fracturing deeper shale is higher than that of shallower shale;(3) shale presents different imbibition capacities in different liquids, i.e., distilled water>2% KCl solution>kerosene; and(4) under different experimental conditions, micro-fractures can be induced in various degrees after shale absorbs water, further to significantly improve permeability.
Some practice shows that, flowback rate after fracturing shale reservoirs is generally less than 30%, in particular below 5%for central Fuling shale block. Different from conventional reservoirs, shale reservoirs represent no significant positive correlation and even negative correlation between flowback rate and production. Field practice illustrates that shale-gas production increases after fracturing and well soaking, indicating that water absorption factors of shale have great effect on fracturing. In this study, the Longmaxi shale in Fuling block was taken as an example to establish and improve an experimental method for shale imbibition and carry out imbibition experimental analysis from four aspects of permeability anisotropy, natural micro-fracture, confining pressure,and liquid type. Results show that,(1) water absorption capacity of rock samples with parallel bedding surface is stronger than that of samples with vertical bedding surface;(2) confining pressure has a certain inhibition effect on imbibition capacity, which indicates that under the same conditions, flowback rate after fracturing deeper shale is higher than that of shallower shale;(3) shale presents different imbibition capacities in different liquids, i.e., distilled water>2% KCl solution>kerosene; and(4) under different experimental conditions, micro-fractures can be induced in various degrees after shale absorbs water, further to significantly improve permeability.
引文
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[19]Olafuyi OA,Cinar Y,Knackstedt MA,et al.Spontaneous imbibition in small cores[C]//Asia Pacific Oil and Gas Conference and Exhibition.Jakarta,Indonesia:SPE,2007.
[20]杨柳,葛洪魁,申颍浩.一种评价页岩储层压裂液吸收的新方法[J].科学技术与工程,2016,16(24):48-53.Yang Liu,Ge Hongkui&Shen Yinghao.A new method for evaluating intake of fracturing fluid in shale formations[J].Science Technology and Engineering,2016,16(24):48-53.
[2]Bennion DB,Thomas FB&Bietz RF.Fluid design to minimize invasive damage in horizontal wells[J].Journal of Canadian Petroleum Technology,1996,35(9):45-52.
[3]刘向君,熊健,梁利喜.龙马溪组硬脆性页岩水化实验研究[J].西南石油大学学报(自然科学版),2016,38(3):178-186.Liu Xiangjun,Xiong Jian&Liang Lixi.Hydration experiment of hard brittle shale of the Longmaxi formation[J].Journal of Southwest Petroleum University(Science&Technology Edition),2016,38(3):178-186.
[4]黄睿哲,姜振学,高之业,等.页岩储层组构特征对自发渗吸的影响[J].油气地质与采收率,2017,24(1):111-115.Huang Ruizhe,Jiang Zhenxue,Gao Zhiye,et al.Effect of composition and structural characteristics on spontaneous imbibition of shale reservoir[J].Petroleum Geology and Recovery Efficiency,2017,24(1):111-115.
[5]Makhanov KK.An experimental study of spontaneous imbibition in Horn River shales[D].Edmonton,Alberta:University of Alberta,2013.
[6]任凯,葛洪魁,杨柳,等.页岩自吸实验及其在返排分析中的应用[J].科学技术与工程,2015,15(30):106-109,123.Ren Kai,Ge Hongkui,Yang Liu,et al.Imbibition experiment of shale and its application in flowback analysis[J].Science Technology and Engineering,2015,15(30):106-109,123.
[7]Ghanbari E&Dehghanpour H.Impact of rock fabric on water imbibition and salt diffusion in gas shales[J].International Journal of Coal Geology,2015,138:55-67.
[8]Zolfaghari A,Dehghanpour H,Noel M et al.Laboratory and field analysis of flowback water from gas shales[J].Journal of Unconventional Oil and Gas Resources,2016,14:113-127.
[9]刘向君,熊健,梁利喜,等.川南地区龙马溪组页岩润湿性分析及影响讨论[J].天然气地球科学,2014,25(10):1644-1652.Liu Xiangjun,Xiong Jian,Liang Lixi,et al.Analysis of the wettability of Longmaxi formation shale in the south region of Sichuan Basin and its influence[J].Natural Gas Geoscience,2014,25(10):1644-1652.
[10]Dehghanpour H,Zubair HA,Chhabra A,et al.Liquid intake of organic shales[J].Energy&Fuels,2012,26(9):5750-5758.
[11]Engelder T,Cathles LM&Bryndzia LT.The fate of residual treatment water in gas shale[J].Journal of Unconventional Oil&Gas Resources,2014,7:33-48.
[12]高树生,胡志明,郭为,等.页岩储层吸水特征与返排能力[J].天然气工业,2013,33(12):71-76.Gao Shusheng,Hu Zhiming,Guo Wei,et al.Water absorption characteristics of gas shale and the fracturing fluid flowback capacity[J].Natural Gas Industry,2013,33(12):71-76.
[13]Scott H,Patey ITM&Byrne MT.Return permeability measurements-Proceed with caution[C]//European Formation Damage Conference.Scheveningen,The Netherlands:SPE,2007.
[14]Zhou Z,Abass H,Li XP,et al.Experimental investigation of the effect of imbibition on shale permeability during hydraulic fracturing[J].Journal of Natural Gas Science and Engineering,2016,29:413-430.
[15]Yan Q,Lemanski C,Karpyn ZT,et al.Experimental investigation of shale gas production impairment due to fracturing fluid migration during shut-in time[J].Journal of Natural Gas Science&Engineering,2015,24:99-105.
[16]Wang DM,Butler R,Liu H,et al.Flow-rate behavior and imbibition in shale[J].SPE Reservoir Evaluation&Engineering,2011,14(4):485-492.
[17]Sun Hong,STEVEN Dick,Cutler Jennifer,et al.A novel nondamaging friction reducer:development and successful slickwater frac applications[C]//Tight Gas Completions Conference.San Antonio,Texas,USA:SPE,2010
[18]章哲宇.滑溜水对页岩储层渗透率的影响实验研究[D].重庆:重庆科技学院,2017.Zhang Zheyu.Experimental study on the effect of slickwater on shale reservoir permeability[D].Chongqing:Chongqing University of Science&Technology,2017.
[19]Olafuyi OA,Cinar Y,Knackstedt MA,et al.Spontaneous imbibition in small cores[C]//Asia Pacific Oil and Gas Conference and Exhibition.Jakarta,Indonesia:SPE,2007.
[20]杨柳,葛洪魁,申颍浩.一种评价页岩储层压裂液吸收的新方法[J].科学技术与工程,2016,16(24):48-53.Yang Liu,Ge Hongkui&Shen Yinghao.A new method for evaluating intake of fracturing fluid in shale formations[J].Science Technology and Engineering,2016,16(24):48-53.