塔里木盆地库车坳陷天然裂缝地质力学响应对气井产能的影响
|
摘要
为明确影响库车坳陷深层裂缝性致密砂岩气藏气井产能主控地质因素,在对天然裂缝产状描述和储层地质力学模型建立的基础上,分析了气井中天然裂缝与现今水平主应力之间的关系,定量计算得到了每条裂缝面上的正应力和剪应力,并根据Mohr-Coulomb破坏准则,模拟不同注入压力条件下的天然裂缝的力学响应,据此建立了天然裂缝剪切滑移率的概念。发现其随构造位置的变化而变化,在构造轴部、断层发育处天然裂缝剪切滑移率更大,裂缝的潜在力学活动性更好,渗透率好,单井产能高,反之,单井产能低。另外,开发过程中随地层压力下降,天然裂缝地质力学响应的动态变化也与产能变化密切相关。以3口开发井为例,当孔隙压力下降10MPa时,其中2口井中70%的天然裂缝的剪应力与正应力比值降低,产能也随之降低;而相邻的另一口井中裂缝的剪应力与正应力比值依然保持较高,其产能也保持相对稳定,扭转了传统认为的压力下降产能必然下降的认识。结果表明天然裂缝的地质力学响应是气藏渗透率和气井产能的重要主控因素之一,是该区域储层评价中一个新的指数,也是优化井位部署和压裂改造方案的一个重要补充依据。
To understand key factors to productivity in fractured tight sandstone,based on the description of the occurrence of natural fractures and geomechanical modeling,the interaction between in-situ stress and natural fractures was determined,and the normal stress and shear stress of each fracture plane were calculated to compare the relative mechanical response of natural fractures across the anticline structure in the field.We then simulated mechanical response of natural fractures under different pore pressure according to Mohr-Coulomb failure criterion,and obtained the correlation between geomechanical response and openflow rate of gas wells and built the concept of strike-slip rate depending on the theory.At the crest of structure and faulting area,the favorable combination of in-situ stresses and natural fracture strike results in high shear-to-normal stress ratio and higher strike-slip rate and higher production.Reversely,the wells show lower production.And then with the depletion,the dynamic change of mechanical response of natural fractures is also closely related to productivity.Take 3 new wells for example,as pore pressure of reservoir decreases by 10 MPa,productivity of 2 Wells decreases since the shear-to-normal stress ratio of 70%natural fractures decreases,their productivity is still lower than adjacent wells even after fracturing.The productivity of the third well maintains high because the shear-to-normal stress ratio of all natural fractures increases which changes the traditional point that the productivity decreases following the pressure dropping.It is revealed that the geomechanical response of natural fractures is a controlling factor of well productivity in this reservoir.It is a new index for reservoir evaluation,and is also an important supplementary information for optimizing well placement and stimulation program in the special condition.
To understand key factors to productivity in fractured tight sandstone,based on the description of the occurrence of natural fractures and geomechanical modeling,the interaction between in-situ stress and natural fractures was determined,and the normal stress and shear stress of each fracture plane were calculated to compare the relative mechanical response of natural fractures across the anticline structure in the field.We then simulated mechanical response of natural fractures under different pore pressure according to Mohr-Coulomb failure criterion,and obtained the correlation between geomechanical response and openflow rate of gas wells and built the concept of strike-slip rate depending on the theory.At the crest of structure and faulting area,the favorable combination of in-situ stresses and natural fracture strike results in high shear-to-normal stress ratio and higher strike-slip rate and higher production.Reversely,the wells show lower production.And then with the depletion,the dynamic change of mechanical response of natural fractures is also closely related to productivity.Take 3 new wells for example,as pore pressure of reservoir decreases by 10 MPa,productivity of 2 Wells decreases since the shear-to-normal stress ratio of 70%natural fractures decreases,their productivity is still lower than adjacent wells even after fracturing.The productivity of the third well maintains high because the shear-to-normal stress ratio of all natural fractures increases which changes the traditional point that the productivity decreases following the pressure dropping.It is revealed that the geomechanical response of natural fractures is a controlling factor of well productivity in this reservoir.It is a new index for reservoir evaluation,and is also an important supplementary information for optimizing well placement and stimulation program in the special condition.
引文
[1]Harstad H,Teufel L W,Lorenz J C.Characterization and Simulation of Naturally Fractured Tight Gas Sandstone Reservoirs[C].Presented at the SPE Annual Technical Conference&Exhibition held in Dallas,U.S.A.,22-25 October,1995.doi:10.2118/30573-MS.
[2]Gale J F W,Reed R M,Holder J.Natural fractures in the Barnett shale and their importance for hydraulic fracture treatments[J].AAPG Bulletin,2007,91:603-622.
[3]Zhang Hui,Qiu Kaibin,Fuller,et al.Geomechanical-evaluation enabled successful stimulation of a HPHT tight gas reservoir in western China[J].SPE Drilling&Completion,2015(12):274-294.
[4]Teufel L W,Rhett W.“Geomechanical Evidence for Shear Failure of Chalk During Production of the Ekofisk Field”[C].SPE 22755.Presented at the SPE 66th Annual Technical Conference and Exhibition,Dallas,Oct.6-9,1991.
[5]Chen H Y,Teufel L W.Reservoir Stress Changes Induced by Production/Injection[C].Presented at the SPE Rocky Mountain Petroleum Technology Conference held in Keystone,Colorado,21-23May,2001.doi:10.2118/71087-MS.
[6]Zoback M D.Reservoir Geomechanics[M].Cambridge:Cambridge University Press,2007.
[7]Hennings P,Allwardt P,Paul P,et al.Relationship between fractures,fault zones,stress,and reservoir productivity in the Suban Gas Field,Sumatra,Indonesia[J].AAPG Bulletin,201296(4):753-772.
[8]Laubach S E,Gale J F W.Obtaining fracture information for low-permeability(tight)gas sandstones from sidewall cores[J].Journal of Petroleum Geology,2006,29(2):147-158.
[9]Tamagawa T,Pollard D D.Fracture permeability created by perturbed stress fields around active faults in a fractured basement reservoir[J].AAPG Bulletin,2008,92:743-764.
[10]Chang Chandong.Effects of Fractures and Faults on In Situ Stress Magnitudes[C].ARMA 14-7053,American Rock Mechanics Association Minneapolis,MN,USA,1-4June,2014.
[11]Barton C A,Zoback M D,Moos D.Fluid flow along potentially active faults in crystalline rock[J].Geology,1995,23:683-686.
[12]Tao Q,Ehlig-Economides C A,Ghassemi A.Investigation of Stress-Dependent Permeability in Naturally Fractured Reservoirs Using a Fully Coupled Poroelastic Displacement Discontinuity Model[C].Presented at the SPE Annual Technical Conference and Exhibition held in New Orleans,Louisiana,USA,4-7October,2009.doi:10.2118/124745-MS.
[13]Townend J,Zoback M D.How faulting keeps the crust strong[J].Geology,2000,28(5):399-402.
[14]Wang Zhaoming,Li Yong,Xie Huiwen,et al.UItra Deep Oil and Gas Geological Theory and Exploration Practice in Kuqa foreland Basin[M].Beijing:Petroleum Industry Press,2017.王招明,李勇,谢会文,等.库车前陆盆地超深油气地质理论与勘探实践[M].北京:石油工业出版社,2017.
[15]Zhang Huiliang,Zhang Ronghu,Yan haijun,et al.Quantitative evaluation methods and applications of tectonic fracture developed sand reservoir:A cretaceous example from Kuqa foreland basin[J].Acta Petrologica Sinica,2012,28(3):827-835.张惠良,张荣虎,杨海军,等.构造裂缝发育型砂岩储层定量评价方法及应用---以库车前陆盆地白垩系为例[J].岩石学报,2012,28(3):827-835.
[16]Wang Zhaoming.Formation mechanism and enrichment regularities of Kelasu subsalt deep large gasfield in Kuqa Depression,Tarim Basin[J].Natural Gas Geoscience,2014,25(2):153-166.王招明.塔里木盆地库车坳陷克拉苏盐下深层大气田形成机制与富集规律[J].天然气地球科学,2014,25(2):153-166.
[17]Jia Chengzao.Tectonic Characteristics and Petroleum Tarim Basin China[M].Beijing:Petroleum Industry Press,1997.贾承造.中国塔里木盆地构造特征与油气[M].北京:石油工业出版社,1997.
[18]He Dengfa,Zhou Xinyuan,Yang Haijun,et al.Geological structure and its controls on giant oil and gas fields in Kuqa Depression,Tarim Basin:A clue from new shot seismic data[J].Geotectonica et Metallogenia,2009,33(1):19-32.何登发,周新源,杨海军,等.库车坳陷的地质结构及其对大油气田的控制作用[J].大地构造与成矿学,2009,33(1):19-32.
[19]Neng Yuan,Xie Huiwen,Li Yong,et al.The character of deformation style and its distribution law in the middle part of Kuqa Depression,northern margin of Tarim Basin,NW China[J].Chinese Journal of Geology:Scientia Geologica Sinica,2012,47(3):629-639.能源,谢会文,李勇,等.塔里木盆地库车坳陷中部构造变形样式及分布特征[J].地质科学,2012,47(3):629-639.
[20]Zhang Fuxiang,Zhang Hui.Geomechanical Mechanism of Hydraulic Fracturing and Fracability of Natural Fractured Tight Sandstone Reservoir in Keshen Gasfield in Tarim Basin[C].Presented at the SPE Abu Dhabi International Petroleum Exhibition and Conference,2015,SPE-177457-MS.doi:10.2118/177457-MS.
[21]Jaeger J C,Cook N G W.Fundamentals of Rock Mechanics[M].First Edition.London:Chapman and Hall,1979.
[2]Gale J F W,Reed R M,Holder J.Natural fractures in the Barnett shale and their importance for hydraulic fracture treatments[J].AAPG Bulletin,2007,91:603-622.
[3]Zhang Hui,Qiu Kaibin,Fuller,et al.Geomechanical-evaluation enabled successful stimulation of a HPHT tight gas reservoir in western China[J].SPE Drilling&Completion,2015(12):274-294.
[4]Teufel L W,Rhett W.“Geomechanical Evidence for Shear Failure of Chalk During Production of the Ekofisk Field”[C].SPE 22755.Presented at the SPE 66th Annual Technical Conference and Exhibition,Dallas,Oct.6-9,1991.
[5]Chen H Y,Teufel L W.Reservoir Stress Changes Induced by Production/Injection[C].Presented at the SPE Rocky Mountain Petroleum Technology Conference held in Keystone,Colorado,21-23May,2001.doi:10.2118/71087-MS.
[6]Zoback M D.Reservoir Geomechanics[M].Cambridge:Cambridge University Press,2007.
[7]Hennings P,Allwardt P,Paul P,et al.Relationship between fractures,fault zones,stress,and reservoir productivity in the Suban Gas Field,Sumatra,Indonesia[J].AAPG Bulletin,201296(4):753-772.
[8]Laubach S E,Gale J F W.Obtaining fracture information for low-permeability(tight)gas sandstones from sidewall cores[J].Journal of Petroleum Geology,2006,29(2):147-158.
[9]Tamagawa T,Pollard D D.Fracture permeability created by perturbed stress fields around active faults in a fractured basement reservoir[J].AAPG Bulletin,2008,92:743-764.
[10]Chang Chandong.Effects of Fractures and Faults on In Situ Stress Magnitudes[C].ARMA 14-7053,American Rock Mechanics Association Minneapolis,MN,USA,1-4June,2014.
[11]Barton C A,Zoback M D,Moos D.Fluid flow along potentially active faults in crystalline rock[J].Geology,1995,23:683-686.
[12]Tao Q,Ehlig-Economides C A,Ghassemi A.Investigation of Stress-Dependent Permeability in Naturally Fractured Reservoirs Using a Fully Coupled Poroelastic Displacement Discontinuity Model[C].Presented at the SPE Annual Technical Conference and Exhibition held in New Orleans,Louisiana,USA,4-7October,2009.doi:10.2118/124745-MS.
[13]Townend J,Zoback M D.How faulting keeps the crust strong[J].Geology,2000,28(5):399-402.
[14]Wang Zhaoming,Li Yong,Xie Huiwen,et al.UItra Deep Oil and Gas Geological Theory and Exploration Practice in Kuqa foreland Basin[M].Beijing:Petroleum Industry Press,2017.王招明,李勇,谢会文,等.库车前陆盆地超深油气地质理论与勘探实践[M].北京:石油工业出版社,2017.
[15]Zhang Huiliang,Zhang Ronghu,Yan haijun,et al.Quantitative evaluation methods and applications of tectonic fracture developed sand reservoir:A cretaceous example from Kuqa foreland basin[J].Acta Petrologica Sinica,2012,28(3):827-835.张惠良,张荣虎,杨海军,等.构造裂缝发育型砂岩储层定量评价方法及应用---以库车前陆盆地白垩系为例[J].岩石学报,2012,28(3):827-835.
[16]Wang Zhaoming.Formation mechanism and enrichment regularities of Kelasu subsalt deep large gasfield in Kuqa Depression,Tarim Basin[J].Natural Gas Geoscience,2014,25(2):153-166.王招明.塔里木盆地库车坳陷克拉苏盐下深层大气田形成机制与富集规律[J].天然气地球科学,2014,25(2):153-166.
[17]Jia Chengzao.Tectonic Characteristics and Petroleum Tarim Basin China[M].Beijing:Petroleum Industry Press,1997.贾承造.中国塔里木盆地构造特征与油气[M].北京:石油工业出版社,1997.
[18]He Dengfa,Zhou Xinyuan,Yang Haijun,et al.Geological structure and its controls on giant oil and gas fields in Kuqa Depression,Tarim Basin:A clue from new shot seismic data[J].Geotectonica et Metallogenia,2009,33(1):19-32.何登发,周新源,杨海军,等.库车坳陷的地质结构及其对大油气田的控制作用[J].大地构造与成矿学,2009,33(1):19-32.
[19]Neng Yuan,Xie Huiwen,Li Yong,et al.The character of deformation style and its distribution law in the middle part of Kuqa Depression,northern margin of Tarim Basin,NW China[J].Chinese Journal of Geology:Scientia Geologica Sinica,2012,47(3):629-639.能源,谢会文,李勇,等.塔里木盆地库车坳陷中部构造变形样式及分布特征[J].地质科学,2012,47(3):629-639.
[20]Zhang Fuxiang,Zhang Hui.Geomechanical Mechanism of Hydraulic Fracturing and Fracability of Natural Fractured Tight Sandstone Reservoir in Keshen Gasfield in Tarim Basin[C].Presented at the SPE Abu Dhabi International Petroleum Exhibition and Conference,2015,SPE-177457-MS.doi:10.2118/177457-MS.
[21]Jaeger J C,Cook N G W.Fundamentals of Rock Mechanics[M].First Edition.London:Chapman and Hall,1979.
© 2004-2018 中国地质图书馆版权所有 京ICP备05064691号 京公网安备11010802017129号 地址：北京市海淀区学院路29号 邮编：100083 电话：办公室：(+86 10)66554848；文献借阅、咨询服务、科技查新：66554700 |