页岩气井压裂后焖排模式
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摘要
页岩气井水力压裂过程中注入液量大,但压裂后返排率往往较低,滞留压裂液对储层的影响仍不清晰。针对该问题,选取永川新店子构造YY1井龙马溪组的岩心,开展压裂液渗吸实验,并对比渗吸前后岩心物性、孔隙结构特征及电子显微镜下微观结构等参数的变化规律。实验结果表明:永川新店子构造岩心压裂液渗吸后,岩心平均孔隙度增大了50%,平均渗透率增大了25%,气体吸附量减少了35%,比表面积降低了40%;岩心沿层理方向产生了新的裂缝,并随着渗吸的持续进行,裂缝发生扩展和延伸,逐步沟通裂缝网络,增大了液体的渗吸面积;通过YY1HF井的现场试验发现,焖井30 d后再控产(6万m~3/d)试采,产液量大幅度降低,气井生产稳定。研究认为,压裂后焖井有利于改善储层物性,增加渗流通道,压裂后返排应由小到大逐级控制油嘴排液,以提高气井采收率。
Horizontal well staged fracturing is the main technical mean of shale gas reservoir reformation,the large fracturing fluid was injected into the formation but the flow-back rate was relatively low. The pros and cons are still unclear about the retention fracturing fluid in the formation. In order to solve this problem,cores of Longmaxi Formation from well YY1 in Xindianzi structure of Yongchuan were selected to carry out imbibition experiment with slick-water,and the variation rules of core physical properties,pore structure characteristics and micro-structure were compared. The results show that after fracturing fluid imbibition,the average porosity and permeability increased by 50% and 25% respectively,while gas adsorption capacity and specific surface area decreased by 35% and 40% respectively. Micro fissures were created along the bedding direction after imbibition test,and with the continuous infiltration,the fissures expanded and extended,gradually communicated the fracture network,and increased the infiltration area of liquid. Through field test of well YY1HF,it is found that after 30 days of shut-in test under the production rate of 60 000 m~3/d,the production of liquid is greatly reduced,and the production of gas wells is stable. Therefore,post-frac shut-in is beneficial to improve reservoir physical properties and increase seepage channels,and gradual enlargement flow-back strategy is better for gas recovery.
Horizontal well staged fracturing is the main technical mean of shale gas reservoir reformation,the large fracturing fluid was injected into the formation but the flow-back rate was relatively low. The pros and cons are still unclear about the retention fracturing fluid in the formation. In order to solve this problem,cores of Longmaxi Formation from well YY1 in Xindianzi structure of Yongchuan were selected to carry out imbibition experiment with slick-water,and the variation rules of core physical properties,pore structure characteristics and micro-structure were compared. The results show that after fracturing fluid imbibition,the average porosity and permeability increased by 50% and 25% respectively,while gas adsorption capacity and specific surface area decreased by 35% and 40% respectively. Micro fissures were created along the bedding direction after imbibition test,and with the continuous infiltration,the fissures expanded and extended,gradually communicated the fracture network,and increased the infiltration area of liquid. Through field test of well YY1HF,it is found that after 30 days of shut-in test under the production rate of 60 000 m~3/d,the production of liquid is greatly reduced,and the production of gas wells is stable. Therefore,post-frac shut-in is beneficial to improve reservoir physical properties and increase seepage channels,and gradual enlargement flow-back strategy is better for gas recovery.
引文
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[15]YAN Q,LEMANSKI C,KARPYN Z T,et al.Experimental investigation of shale gas production impairment due to fracturing fluid migration during shut-in time.Journal of Natural Gas Science and Engineering,2015,24:99-105.
[16]王跃鹏,刘向君,梁利喜.页岩力学特性的层理效应及脆性预测.岩性油气藏,2018,30(4):149-160.WANG Y P,LIU X J,LIANG L X.Influences of bedding planes on mechanical properties and prediction method of brittleness index in shale.Lithologic Reservoirs,2018,30(4):149-160.
[17]孙文峰,李玮,董智煜,等.页岩孔隙结构表征方法新探索.岩性油气藏,2017,29(2):125-130.SUN W F,LI W,DONG Z Y,et al.A new approach to the characterization of shale pore structure.Lithologic Reservoirs,2017,29(2):125-130.
[18]徐祖新.基于CT扫描图像的页岩储层非均质性研究.岩性油气藏,2014,26(6):46-49.XU Z X.Heterogeneity of shale reservoirs based on CT images.Lithologic Reservoirs,2014,26(6):46-49.
[19]余川,周洵,方光建,等.地层温压条件下页岩吸附性能变化特征:以渝东北地区龙马溪组为例.岩性油气藏,2018,30(6):10-17.YU C,ZHOU X,FANG G J,et al.Adsorptivity of shale under the formation temperature and pressure:a case of Longmaxi Formation in northeastern Chongqing.Lithologic Reservoirs,2018,30(6):10-17.
[20]何彦庆,郑丽,闫长辉,等.页岩储层标准等温吸附曲线的建立:以鄂尔多斯盆地长7页岩储层为例.岩性油气藏,2018,30(3):92-99.HE Y Q,ZHENG L,YAN C H,et al.Establishment of standard adsorption isotherms for shale reservoirs:a case of Chang7 shale reservoir in Ordos Basin.Lithologic Reservoirs,2018,30(3):92-99.
[2]张小龙,张同伟,李艳芳,等.页岩气勘探和开发进展综述.岩性油气藏,2013,25(2):116-122.ZHANG X L,ZHANG T W,LI Y F,et al.Research advance in exploration and development of shale gas.Lithologic Reservoirs,2013,25(2):116-122.
[3]徐勇,吕成福,陈国俊,等.川东南龙马溪组页岩孔隙分形特征.岩性油气藏,2015,27(4):32-39.XU Y,LYU C F,CHEN G J,et al.Fractal characteristics of shale pores of Longmaxi Formation in southeast Sichuan Basin.Lithologic Reservoirs,2015,27(4):32-39.
[4]CRAFTON J W,NOE S L.Factors affecting early well productivity in six shale plays.SPE 166101,2013.
[5]WANG D M,BUTLER R,LIU H,et al.Flow-rate behavior and imbibition in shale.SPE Reservoir Evaluation&Engineering,2011,14(4):485-492.
[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.科学技术与工程,2015,15(30):106-109.REN K,GE H K,YANG L,et al.Imbibition experiment of shale and its application in flowback analysis.Science Technology and Engineering,2015,15(30):106-109.
[7]MAKHANOV K,DEHGHANPOUR H,KURU E.An experimental study of spontaneous imbibition in Horn River Shales.SPE 162650,2012.
[8]DEHGHANPOUR H,LAN Q,SAEED Y,et al.Spontaneous imbibition of brine and oil in gas shales:Effect of water adsorption and resulting microfractures.Energy&Fuels,2013,27(6):3039-3049.
[9]ZHOU Z,ABASS H,LI X P,et al.Experimental investigation of the effect of imbibition on shale permeability during hydraulic fracturing.Journal of Natural Gas Science and Engineering,2016,29:413-430.
[10]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.科学技术与工程,2016,16(24):48-53.YANG L,GE H K,SHEN Y H.A new method for evaluating intake of fracturing fluid in shale formations.Science Technology and Engineering,2016,16(24):48-53.
[11]钱斌,朱炬辉,杨海,等.页岩储集层岩心水化作用实验.石油勘探与开发,2017,44(4):615-621.QIAN B,ZHU J H,YANG H,et al.Experiments on shale reservoirs plugs hydration.Petroleum Exploration and Development,2017,44(4):615-621.
[12]SCOTT H E,PATEY I T M,BYRNE M T.Return permeability measurements-Proceed with caution.SPE 107812,2007.
[13]高树生,胡志明,郭为,等.页岩储层吸水特征与返排能力.天然气工业,2013,33(12):71-76.GAO S S,HU Z M,GUO W,et al.Water absorption characteristics of gas shale and the fracturing fluid flowback capacity.Natural Gas industry,2013,33(12):71-76.
[14]DUTTA R,LEE C H,ODUMABO S,et al.Experimental investigation of fracturing-fluid migration caused by spontaneous imbibition in fractured low-permeability sands.SPE Reservoir Evaluation&Engineering,2014,17(1):74-81.
[15]YAN Q,LEMANSKI C,KARPYN Z T,et al.Experimental investigation of shale gas production impairment due to fracturing fluid migration during shut-in time.Journal of Natural Gas Science and Engineering,2015,24:99-105.
[16]王跃鹏,刘向君,梁利喜.页岩力学特性的层理效应及脆性预测.岩性油气藏,2018,30(4):149-160.WANG Y P,LIU X J,LIANG L X.Influences of bedding planes on mechanical properties and prediction method of brittleness index in shale.Lithologic Reservoirs,2018,30(4):149-160.
[17]孙文峰,李玮,董智煜,等.页岩孔隙结构表征方法新探索.岩性油气藏,2017,29(2):125-130.SUN W F,LI W,DONG Z Y,et al.A new approach to the characterization of shale pore structure.Lithologic Reservoirs,2017,29(2):125-130.
[18]徐祖新.基于CT扫描图像的页岩储层非均质性研究.岩性油气藏,2014,26(6):46-49.XU Z X.Heterogeneity of shale reservoirs based on CT images.Lithologic Reservoirs,2014,26(6):46-49.
[19]余川,周洵,方光建,等.地层温压条件下页岩吸附性能变化特征:以渝东北地区龙马溪组为例.岩性油气藏,2018,30(6):10-17.YU C,ZHOU X,FANG G J,et al.Adsorptivity of shale under the formation temperature and pressure:a case of Longmaxi Formation in northeastern Chongqing.Lithologic Reservoirs,2018,30(6):10-17.
[20]何彦庆,郑丽,闫长辉,等.页岩储层标准等温吸附曲线的建立:以鄂尔多斯盆地长7页岩储层为例.岩性油气藏,2018,30(3):92-99.HE Y Q,ZHENG L,YAN C H,et al.Establishment of standard adsorption isotherms for shale reservoirs:a case of Chang7 shale reservoir in Ordos Basin.Lithologic Reservoirs,2018,30(3):92-99.