非均质厚储层多级射孔压裂裂缝扩展规律
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摘要
为研究常规压裂与多级压裂两种不同改造方式下的裂缝扩展规律及增产机理,制备力学参数接近真实地层的人造岩心,采用真三轴加载方式模拟地层真实三向地应力环境,自主设计并开展了常规射孔压裂与多级射孔压裂物理模拟实验。研究结果表明:多级射孔笼统压裂时纵向应力均质情况下,岩石在射孔位置同时起裂,产生的多条裂缝在垂直方向同时扩展,扩展的裂缝会在裂缝尖端周围产生局部应力,从而彼此干扰,出现复杂裂缝情况。多级射孔分段压裂当第一条裂缝存在时,缝内的压力会改变周围的应力场,进而改变局部最大和最小主应力的方向,进行第二次压裂时,新的裂缝会受到第一条裂缝的局部应力场影响,沿着新的应力方向扩展,并不会与第一条裂缝重合,从而引起空间裂缝的形态变化。相同条件下多级射孔压裂比集中射孔笼统压裂的裂缝面积大,相同施工规模条件下射孔分段数目越多裂缝越复杂,裂缝与储层接触面积越大。针对低渗透非均质厚储层而言,推荐采用多级射孔、分段注入方式进行压裂。
To compare the crack propagation law and production increase mechanism under conventional perforated fracturing and multi-stage perforated fracturing,the physical simulation experiments are independently designed and conducted by preparing artificial cores whose mechanical parameters are close to the real strata,the true triaxial loading method is used to simulate the true three-dimensional ground stress environment. The results of the study indicate that in the case of homogeneous stress in the longitudinal fracturing,the rock starts to crack at the same time as the perforation. The multiple cracks produced expand in the vertical direction simultaneously. The extended cracks will generate local stress around the crack tip and thus interfere with each other. So there will be complex cracks. In the case of multi-stage perforated fracturing,when the first crack exists,the pressure in the seam will change the surrounding stress field,and then change the direction of the local maximum and minimum principal stress.During the second fracturing,the new crack will be affected by the local stress field of the first crack,spread along the new stress direction,and will not coincide with the first crack,causing the form of the space crack to change. Under the same conditions,multi-stage perforated fracturing has a larger crack area than centralized perforation general fracturing. Under the condition of the same construction scale,the more number of perforation subdivisions,the more complex the cracks and the greater the contact area between fractures and reservoirs. For the heterogeneous and low permeability reservoir,multi-stage perforated segmented fracturing technology is recommended.
To compare the crack propagation law and production increase mechanism under conventional perforated fracturing and multi-stage perforated fracturing,the physical simulation experiments are independently designed and conducted by preparing artificial cores whose mechanical parameters are close to the real strata,the true triaxial loading method is used to simulate the true three-dimensional ground stress environment. The results of the study indicate that in the case of homogeneous stress in the longitudinal fracturing,the rock starts to crack at the same time as the perforation. The multiple cracks produced expand in the vertical direction simultaneously. The extended cracks will generate local stress around the crack tip and thus interfere with each other. So there will be complex cracks. In the case of multi-stage perforated fracturing,when the first crack exists,the pressure in the seam will change the surrounding stress field,and then change the direction of the local maximum and minimum principal stress.During the second fracturing,the new crack will be affected by the local stress field of the first crack,spread along the new stress direction,and will not coincide with the first crack,causing the form of the space crack to change. Under the same conditions,multi-stage perforated fracturing has a larger crack area than centralized perforation general fracturing. Under the condition of the same construction scale,the more number of perforation subdivisions,the more complex the cracks and the greater the contact area between fractures and reservoirs. For the heterogeneous and low permeability reservoir,multi-stage perforated segmented fracturing technology is recommended.
引文
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[16]张矿生,唐梅荣,杜现飞,等.致密薄互层缝高扩展影响因素的试验研究[J].科学技术与工程,2017,17(22):197-203.Zhang Kuangsheng,Tang Meirong,Du Xianfei,et al.The Experimental Investigation of Hydraulic Fracture Height Propagation in Tight Thin Interbeds[J].Science Technology and Engineering,2017,17(22):197-203.
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[19]赵振峰,唐梅荣,逄铭玉,等.定面射孔对压裂初始裂缝形态的影响研究[J].科学技术与工程,2016,16(22):60-63.Zhao Zhenfeng,Tang Meirong,Pang Mingyu,et al.Impact of Transverse Perforations on the Initial Fracture Shape of Hydraulic Fracturing[J].Science Technology and Engineering,2016,16(22):60-63.
[20]Fallahzadeh S H,Rasouli V,Sarmadivalen M.An Investigation of Hydraulic Fracturing Initiation and Near-Wellbore Propagation from Perforated Boreholes in Tight Formations[J].Rock Mechanics and Rock Engineering,2015,48(2):573-584.
[2]刘建伟,张佩玉,廖天彬,等.马58 H致密油藏水平井分段多簇射孔压裂技术[J].石油钻采工艺,2015,37(3):88-92.Liu Jianwei,Zhang Peiyu,Liao Tianbin,et al.Staged Multi-Cluster Perforation Fracturing Technology for Horizontal Well Ma-58 H in Tight Reservoir[J].Oil Drilling&Production Technology,2015,37(3):88-92.
[3]任飞,张遂安,李辛子,等.煤层气水平井分段压裂裂缝参数优化设计[J].天然气与石油,2014,32(1):58-62.Ren Fei,Zhang Suian,Li Xinzi,et al.Optimization Design of Fracture Parameters in Coalbed Methane(CBM)Horizontal Well Staged Fracturing[J].Natural Gas and Oil,2014,32(1):58-62.
[4]Warpinski N R,Clark J A,Schmidt R A,et al.Laboratory Investigation on the Effect of In-Situ Stresses on Hydraulic Fracture Containment[J].Society of Petroleum Engineers Journal,1982,22(3):333-340.
[5]Teufel L W,Clark J A.Hydraulic Fracture Propagation in Layered Rock:Experimental Studies of Fracture Containment[J].Society of Petroleum Engineers Journal,1984,24(1):19-32.
[6]Cleary M P.Analysis of Mechanics and Production for Producing Favourable Shapes of Hydraulic Fractures[C]//Proceedings of the SPE Annual Technical Conference and Exhibition,21-24 September,1980,Dallas,Texas,USA.New York:SPE,1980.
[7]Biot M A,Medlin W L,Masse L.Fracture Penetration Through an Interface[J].Society of Petroleum Engineers Journal,1983,23(6):857-868.
[8]Hanson M E,Shaffer R J.Some Results from Continuum Mechanics Analyses of the Hydraulic Fracture Process[J].Society of Petroleum Engineers Journal,1980,20(2):86-94.
[9]Simonson E R,Abou-Sayed A S,Clifton R J.Containment of Massive Hydraulic Fractures[J].Society of Petroleum Engineers Journal,1978,18(1):27-32.
[10]刘玉章,付海峰,丁云宏,等.层间应力差对水力裂缝扩展影响的大尺度实验模拟与分析[J].石油钻采工艺,2014,36(4):88-92.Liu Yuzhang,Fu Haifeng,Ding Yunhong,et al.Large Scale Experimental Simulation and Analysis of Interlayer Stress Difference Effect on Hydraulic Fracture Extension[J].Oil Drilling&Production Technology,2014,36(4):88-92.
[11]王文东,苏玉亮,慕立俊,等.致密油藏直井体积压裂储层改造体积的影响因素[J].中国石油大学学报(自然科学版),2013,37(3):93-97.Wang Wendong,Su Yuliang,Mu Lijun,et al.Influencing Factors of Stimulated Reservoir Volume of Vertical Wells in Tight Oil Reservoirs[J].Journal of China University of Petroleum(Edition of Natural Science),2013,37(3):93-97.
[12]陈军斌,魏波,王汉青.定向射孔参数对压裂裂缝扩展规律的影响[J].断块油气田,2017,24(3):391-395.Chen Junbin,Wei Bo,Wang Hanqing.Influence of Directional Perforation Parameters on Fracture Propagation[J].Fault-Block Oil and Gas Field,2017,24(3):391-395.
[13]Bai J,Martysevich V,Walters H,et al.Laboratory-Scale Hydraulic Fracturing:Experiment and Numerical Modeling[C]//Proceedings of 50th U.S.Rock Mechanics/Geomechanics Symposium,26-29 June,2016,Houston,Texas,USA.Alexandria:American Rock Mechanics Association,2016.
[14]常琨.疏松砂岩人工裂缝起裂及延伸规律研究[D].东营:中国石油大学(华东),2013.Chang Kun.Study on the Fracture Initiation and Propagation Law for Unconsolidated Sandstone[D].Dongying:China University of Petroleum(East China),2013.
[15]刘鹏.砂砾岩水压致裂机理的实验与数值模拟研究[D].北京:中国矿业大学(北京),2017.Liu Peng.Experimental and Numerical Simulating Studies on Hydrofracturing Mechanism of Glutenite[D].Beijing:China University of Mining&Technology(Beijing),2017.
[16]张矿生,唐梅荣,杜现飞,等.致密薄互层缝高扩展影响因素的试验研究[J].科学技术与工程,2017,17(22):197-203.Zhang Kuangsheng,Tang Meirong,Du Xianfei,et al.The Experimental Investigation of Hydraulic Fracture Height Propagation in Tight Thin Interbeds[J].Science Technology and Engineering,2017,17(22):197-203.
[17]Daneshy A A.Experimental Investigation of Hydraulic Fracture Extension in Isotropic Media[M]:Texas:Society of Petroleum Engineers,1971.
[18]Bunger A P,Kear J,Jeffrey R G,et al.Laboratory Investigation of Hydraulic Fracture Growth Through Weak Discontinuities with Active Ultrasound Monitoring[C]//Proceedings of the 13th ISRM International Congress of Rock Mechanics,10-13 May,2015,Montreal,Canada.Montreal:International Society for Rock Mechanics,2015.
[19]赵振峰,唐梅荣,逄铭玉,等.定面射孔对压裂初始裂缝形态的影响研究[J].科学技术与工程,2016,16(22):60-63.Zhao Zhenfeng,Tang Meirong,Pang Mingyu,et al.Impact of Transverse Perforations on the Initial Fracture Shape of Hydraulic Fracturing[J].Science Technology and Engineering,2016,16(22):60-63.
[20]Fallahzadeh S H,Rasouli V,Sarmadivalen M.An Investigation of Hydraulic Fracturing Initiation and Near-Wellbore Propagation from Perforated Boreholes in Tight Formations[J].Rock Mechanics and Rock Engineering,2015,48(2):573-584.