南海神狐海域天然气水合物降压开采过程中储层的稳定性
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摘要
储层稳定性是天然气水合物(以下简称水合物)开采所面临的关键问题之一,也是确保水合物安全高效开采的前提,目前相关的研究较少。为了分析降压法开采南海神狐海域水合物过程中储层的稳定性,根据该海域水合物的钻探资料,建立三维水合物降压开采地质模型,采用非结构网格对模型进行离散;在综合考虑水合物开采过程中的传热传质过程和沉积物变形过程的基础上,建立了热—流—固—化四场耦合的数学模型;基于非结构网格技术,采用有限单元方法对模型求解,获得水合物降压开采条件下的储层孔隙压力、温度、水合物饱和度和应力的时空演化特征,进而分析研究了该海域水合物降压开采过程中储层沉降、应力分布和稳定性。结果表明:(1)储层渗透率越大、井底降压幅度越大,沉降量越大,沉降速度越快;(2)开采过程中储层孔隙压力减小会导致有效应力增加,且近井处剪应力增加较明显,易发生剪切破坏;(3)储层有效应力的增加导致了储层沉降,沉降主要发生在开采的早期,开采60 d,储层最大沉降为32 mm,海底面最大沉降为14 mm。结论认为,南海神狐海域水合物储层渗透率低,储层压力降低的影响范围有限,在60 d的开采时间内,储层不会发生剪切破坏。
Reservoir stability is a key factor in the production of natural gas hydrate(NGH), and also a prerequisite to ensuring safe and efficient NGH production. However, it has been rarely discussed. To analyze the reservoir stability in the process of NGH production by depressurization in the Shenhu area of the South China Sea, we established a 3D geological model of NGH production by depressurization on the basis of NGH drilling data in this area, which was then discretized by means of nonstructural grid. Then, the mathematical model coupling four fields(i.e. thermal, hydraulic, solid and chemical) was established considering the heat and mass transfer process and sediment transformation process during NGH production. The model was solved by the finite element method together with the nonstructural grid technology, and thus the time–space evolution characteristics of reservoir pore pressure, temperature, NGH saturation and stress in the condition of NGH production by depressurization were determined. Finally, reservoir subsidence, stress distribution and stability in the process of NGH production by depressurization in the Shenhu area were analyzed. The results obtained are as follows. First, the higher the reservoir permeability and the larger the bottom hole pressure drop amplitude are, the larger the subsidence amount and the higher the subsiding speed. Second, as the reservoir pore pressure decreases in the process of production, the effective stress increases and the shear stress near the well increases obviously, resulting in shear damage easily. Third, the increase of effective reservoir stress leads to reservoir subsidence, which mainly occurs in the early stage of NGH production. After the production for 60 days, the maximum reservoir subsidence reached 32 mm and the maximum subsidence of seabed surface was 14 mm. In conclusion, the NGH reservoirs in the Shenhu area of the South China Sea are of low permeability and the effect range of reservoir pressure drop is limited, so the reservoirs would not suffer from shear damage in the sixty-day-production period.
Reservoir stability is a key factor in the production of natural gas hydrate(NGH), and also a prerequisite to ensuring safe and efficient NGH production. However, it has been rarely discussed. To analyze the reservoir stability in the process of NGH production by depressurization in the Shenhu area of the South China Sea, we established a 3D geological model of NGH production by depressurization on the basis of NGH drilling data in this area, which was then discretized by means of nonstructural grid. Then, the mathematical model coupling four fields(i.e. thermal, hydraulic, solid and chemical) was established considering the heat and mass transfer process and sediment transformation process during NGH production. The model was solved by the finite element method together with the nonstructural grid technology, and thus the time–space evolution characteristics of reservoir pore pressure, temperature, NGH saturation and stress in the condition of NGH production by depressurization were determined. Finally, reservoir subsidence, stress distribution and stability in the process of NGH production by depressurization in the Shenhu area were analyzed. The results obtained are as follows. First, the higher the reservoir permeability and the larger the bottom hole pressure drop amplitude are, the larger the subsidence amount and the higher the subsiding speed. Second, as the reservoir pore pressure decreases in the process of production, the effective stress increases and the shear stress near the well increases obviously, resulting in shear damage easily. Third, the increase of effective reservoir stress leads to reservoir subsidence, which mainly occurs in the early stage of NGH production. After the production for 60 days, the maximum reservoir subsidence reached 32 mm and the maximum subsidence of seabed surface was 14 mm. In conclusion, the NGH reservoirs in the Shenhu area of the South China Sea are of low permeability and the effect range of reservoir pressure drop is limited, so the reservoirs would not suffer from shear damage in the sixty-day-production period.
引文
[1]Klauda JB&Sandler SI.Global distribution of methane hydrate in ocean sediment[J].Energy&Fuels,2016,19(2):459-470.
[2]Dubreuil-Boisclair C,Gloaguen E,Bellefleur G&Marcotte D.Non-Gaussian gas hydrate grade simulation at the Mallik site,Mackenzie Delta,Canada[J].Marine and Petroleum Geology,2012,35(1):20-27.
[3]Uddin M,Wright F,Dallimore S&Coombe D.Gas hydrate dissociations in Mallik hydrate bearing zones A,B,and C by depressurization:Effect of salinity and hydration number in hydrate dissociation[J].Journal of Natural Gas Science and Engineering,2014,21:40-63.
[4]Schoderbek D,Martin KL,Howard J,Silpngarmlert S&Hester K.North Slope hydrate field trial:CO2/CH4 exchange[C]//OTC Arctic Technology Conference,3-5 December 2012,Houston,Texas,USA.DOI:http://dx.doi.org/10.4043/23725-MS.
[5]Yamamoto K,Terao Y,Fujii T,Terumichi I,Seki M,Matsuzawa M,et al.Operational overview of the first offshore production test of methane hydrates in the Eastern Nankai Trough[C].Offshore Technology Conference,5-8 May,Texas,USA.
[6]陈惠玲,朱夏.南海神狐海域天然气水合物试采60天关井[N].中国国土资源报,2017-07-10(1).Chen Huiling&Zhu Xia.The trial production well of gas hydrate from Shenhu area,South China Sea,shut down on the 60th day of production[N].China Land Resource Report,2017-07-10(1).
[7]Kurihara M,Sato A,Ouchi H,Narita H,Masuda Y,Saeki T,et al.Prediction of gas productivity from eastern Nankai trough methane-hydrate reservoirs[J].SPE Reservoir Evaluation&Engineering,2009,12(3):477-499.
[8]梁金强,王宏斌,苏新,付少英,王力峰,郭依群,等.南海北部陆坡天然气水合物成藏条件及其控制因素[J].天然气工业,2014,34(7):128-135.Liang Jinqiang,Wang Hongbin,Su Xin,Fu Shaoying,Wang Lifeng,Guo Yiqun,et al.Natural gas hydrate formation conditions and the associated controlling factors in the northern slope of the South China Sea[J].Natural Gas Industry,2014,34(7):128-135.
[9]于兴河,王建忠,梁金强,李顺利,曾小明,沙志彬,等.南海北部陆坡天然气水合物沉积成藏特征[J].石油学报,2014,35(2):253-264.Yu Xinghe,Wang Jianzhong,Liang Jinqiang,Li Shunli,Zeng Xiaoming,Sha Zhibin,et al.Depositional accumulation characteristics of gas hydrate in the northern continental slope of South China Sea[J].Acta Petrolei Sinica,2014,35(2):253-264.
[10]Zhang KN,Moridis GJ,Wu NY,Li XS&Reagan MT.Evaluation of alternative horizontal well designs for gas production from hydrate deposits in the Shenhu area,South China Sea[C]//International Oil and Gas Conference&Exhibition,8-10 June 2010,Beijing,China.DOI:http://dx.doi.org/10.2118/131151-MS.
[11]胡立堂,张可霓,高童.南海神狐海域天然气水合物注热降压开采数值模拟研究[J].现代地质,2011,25(4):675-681.Hu Litang,Zhang Keni&Gao Tong.Numerical studies of gas production from gas hydrate zone using heat injection and depressurization in Shenhu area,the South China Sea[J].Geoscience,2011,25(4):675-681.
[12]李刚,李小森,Zhang Keni,Moridis GJ.水平井开采南海神狐海域天然气水合物数值模拟[J].地球物理学报,2011,54(9):2325-2337.Li Gang,Li Xiaosen,Zhang KN&Moridis GJ.Numerical simulation of gas production from hydrate accumulations using a single horizontal well in Shenhu area,South China Sea[J].Chinese Journal of Geophysics,2011,54(9):2325-2337.
[13]李刚,李小森,陈琦,陈朝阳.南海神狐海域天然气水合物开采数值模拟[J].化学学报,2010,68(11):1083-1092.Li Gang,Li Xiaosen,Chen Qi&Chen Zhaoyang.Numerical simulation of gas production from gas hydrate zone in Shenhu area,South China Sea[J].Acta Chimica Sinica,2010,68(11):1083-1092.
[14]Li G,Moridis GJ,Zhang KN&Li XS.Evaluation of gas production potential from marine gas hydrate deposits in Shenhu area of South China Sea[J].Energy&Fuels,2010,24(11):6018-6033.
[15]苏正,何勇,吴能友.南海北部神狐海域天然气水合物热激发开采潜力的数值模拟分析[J].热带海洋学报,2012,31(5):74-82.Su Zheng,He Yong&Wu Nengyou.Numerical simulation on production potential of hydrate deposits by thermal stimulation[J].Journal of Tropical Oceanography,2012,31(5):74-82.
[16]沈海超,程远方,胡晓庆.天然气水合物藏降压开采近井储层稳定性数值模拟[J].石油钻探技术,2012,40(2):76-81.Shen Haichao,Cheng Yuanfang&Hu Xiaoqing.Numerical simulation of near wellbore reservoir stability during gas hydrate production by depressurization[J].Petroleum Drilling Techniques,2012,40(2):76-81.
[17]程家望,苏正,吴能友.天然气水合物降压开采储层稳定性模型分析[J].新能源进展,2016,4(1):33-41.Cheng Jiawang,Su Zheng&Wu Nengyou.A geomechanical stability model analysis of hydrate reservoir for gas hydrate production by depressurization[J].Advances in New and Renewable Energy,2016,4(1):33-41.
[18]孙可明,王婷婷,翟诚,罗慧玉.天然气水合物加热分解储层变形破坏规律研究[J].特种油气藏,2017,24(5):91-96.Sun Keming,Wang Tingting,Zhai Cheng&Luo Huiyu.Patterns of reservoir deformation due to thermal decomposition of natural gas hydrates[J].Special Oil&Gas Reservoirs,2017,24(5):91-96.
[19]Sun JX,Zhang L,Ning FL,Lei HW,Liu TL,Hu GW,et al.Production potential and stability of hydrate-bearing sediments at the site GMGS3-W19 in the South China Sea:A preliminary feasibility study[J].Marine and Petroleum Geology,2017,86:447-473.
[20]Yang S,Zhang M,Liang J,Lu J,Zhang Z,Melanie H,et al.Preliminary results of China's third gas hydrate drilling expedition:A critical step from discovery to development in the South China Sea[J].Fire in the Ice,2015,15(2):1-5.
[21]Kim HC,Bishnoi PR,Heidemann RA&Rizvi SSH.Kinetics of methane hydrate decomposition[J].Chemical Engineering Science,1985,42(7):1645-1653.
[22]Biot MA&Willis DG.The elastic coefficients of the theory of consolidation[J].Journal of Applied Mechanics,1957,15(2):594-601.
[23]Masuda Y,Naganawa S&Ando S.Numerical calculation of gas production performance from reservoirs containing natural gas hydrates[J].SPE Journal,1997,29(3):201-210.
[24]Sun XF&Mohanty KK.Kinetic simulation of methane hydrate formation and dissociation in porous media[J].Chemical Engineering Science,2006,61(11):3476-3495.
[25]Duan ZH&Sun R.A model to predict phase equilibrium of CH4and CO2 clathrate hydrate in aqueous electrolyte solutions[J].American Mineralogist,2006,91(8/9):1346-1354.
[26]Esmaeilzadeh F,Zeighami ME&Fathi J.1-D modeling of hydrate decomposition in porous media[C]//Proceedings of World Academy of Science:Engineering&Technology,2013,43:648.
[27]Soga K,Lee SL,Ng MYA&Klar A.Characterisation and engineering properties of methane hydrate soils[C]//Proceedings of the 2nd International Workshop on Characterisation and Engineering Properties of Natural Soils,29 November-1 December 2006,Singapore.London:CRC Press,2006.
[28]Santamarina JC&Ruppel C.The impact of hydrate saturation on the mechanical,electrical,and thermal properties of hydrate-bearing sand,silts,and clay[C]//Proceedings of the 6th International Conference on Gas Hydrate,6-10 July 2008,Vancouver,British Columbia,Canada.
[29]Clarke M&Bishnoi PR.Determination of the intrinsic rate of gas hydrate decomposition using particle size analysis[J].Annals of the New York Academy of Sciences,2000,912:556-563.
[30]Rutqvist J,Moridis GJ,Grover T,Silpngarmlert S,Collett TS&Holdich SA.Coupled multiphase fluid flow and wellbore stability analysis associated with gas production from oceanic hydrate-bearing sediments[J].Journal of Petroleum Science&Engineering,2012(92/93):65-81.
[2]Dubreuil-Boisclair C,Gloaguen E,Bellefleur G&Marcotte D.Non-Gaussian gas hydrate grade simulation at the Mallik site,Mackenzie Delta,Canada[J].Marine and Petroleum Geology,2012,35(1):20-27.
[3]Uddin M,Wright F,Dallimore S&Coombe D.Gas hydrate dissociations in Mallik hydrate bearing zones A,B,and C by depressurization:Effect of salinity and hydration number in hydrate dissociation[J].Journal of Natural Gas Science and Engineering,2014,21:40-63.
[4]Schoderbek D,Martin KL,Howard J,Silpngarmlert S&Hester K.North Slope hydrate field trial:CO2/CH4 exchange[C]//OTC Arctic Technology Conference,3-5 December 2012,Houston,Texas,USA.DOI:http://dx.doi.org/10.4043/23725-MS.
[5]Yamamoto K,Terao Y,Fujii T,Terumichi I,Seki M,Matsuzawa M,et al.Operational overview of the first offshore production test of methane hydrates in the Eastern Nankai Trough[C].Offshore Technology Conference,5-8 May,Texas,USA.
[6]陈惠玲,朱夏.南海神狐海域天然气水合物试采60天关井[N].中国国土资源报,2017-07-10(1).Chen Huiling&Zhu Xia.The trial production well of gas hydrate from Shenhu area,South China Sea,shut down on the 60th day of production[N].China Land Resource Report,2017-07-10(1).
[7]Kurihara M,Sato A,Ouchi H,Narita H,Masuda Y,Saeki T,et al.Prediction of gas productivity from eastern Nankai trough methane-hydrate reservoirs[J].SPE Reservoir Evaluation&Engineering,2009,12(3):477-499.
[8]梁金强,王宏斌,苏新,付少英,王力峰,郭依群,等.南海北部陆坡天然气水合物成藏条件及其控制因素[J].天然气工业,2014,34(7):128-135.Liang Jinqiang,Wang Hongbin,Su Xin,Fu Shaoying,Wang Lifeng,Guo Yiqun,et al.Natural gas hydrate formation conditions and the associated controlling factors in the northern slope of the South China Sea[J].Natural Gas Industry,2014,34(7):128-135.
[9]于兴河,王建忠,梁金强,李顺利,曾小明,沙志彬,等.南海北部陆坡天然气水合物沉积成藏特征[J].石油学报,2014,35(2):253-264.Yu Xinghe,Wang Jianzhong,Liang Jinqiang,Li Shunli,Zeng Xiaoming,Sha Zhibin,et al.Depositional accumulation characteristics of gas hydrate in the northern continental slope of South China Sea[J].Acta Petrolei Sinica,2014,35(2):253-264.
[10]Zhang KN,Moridis GJ,Wu NY,Li XS&Reagan MT.Evaluation of alternative horizontal well designs for gas production from hydrate deposits in the Shenhu area,South China Sea[C]//International Oil and Gas Conference&Exhibition,8-10 June 2010,Beijing,China.DOI:http://dx.doi.org/10.2118/131151-MS.
[11]胡立堂,张可霓,高童.南海神狐海域天然气水合物注热降压开采数值模拟研究[J].现代地质,2011,25(4):675-681.Hu Litang,Zhang Keni&Gao Tong.Numerical studies of gas production from gas hydrate zone using heat injection and depressurization in Shenhu area,the South China Sea[J].Geoscience,2011,25(4):675-681.
[12]李刚,李小森,Zhang Keni,Moridis GJ.水平井开采南海神狐海域天然气水合物数值模拟[J].地球物理学报,2011,54(9):2325-2337.Li Gang,Li Xiaosen,Zhang KN&Moridis GJ.Numerical simulation of gas production from hydrate accumulations using a single horizontal well in Shenhu area,South China Sea[J].Chinese Journal of Geophysics,2011,54(9):2325-2337.
[13]李刚,李小森,陈琦,陈朝阳.南海神狐海域天然气水合物开采数值模拟[J].化学学报,2010,68(11):1083-1092.Li Gang,Li Xiaosen,Chen Qi&Chen Zhaoyang.Numerical simulation of gas production from gas hydrate zone in Shenhu area,South China Sea[J].Acta Chimica Sinica,2010,68(11):1083-1092.
[14]Li G,Moridis GJ,Zhang KN&Li XS.Evaluation of gas production potential from marine gas hydrate deposits in Shenhu area of South China Sea[J].Energy&Fuels,2010,24(11):6018-6033.
[15]苏正,何勇,吴能友.南海北部神狐海域天然气水合物热激发开采潜力的数值模拟分析[J].热带海洋学报,2012,31(5):74-82.Su Zheng,He Yong&Wu Nengyou.Numerical simulation on production potential of hydrate deposits by thermal stimulation[J].Journal of Tropical Oceanography,2012,31(5):74-82.
[16]沈海超,程远方,胡晓庆.天然气水合物藏降压开采近井储层稳定性数值模拟[J].石油钻探技术,2012,40(2):76-81.Shen Haichao,Cheng Yuanfang&Hu Xiaoqing.Numerical simulation of near wellbore reservoir stability during gas hydrate production by depressurization[J].Petroleum Drilling Techniques,2012,40(2):76-81.
[17]程家望,苏正,吴能友.天然气水合物降压开采储层稳定性模型分析[J].新能源进展,2016,4(1):33-41.Cheng Jiawang,Su Zheng&Wu Nengyou.A geomechanical stability model analysis of hydrate reservoir for gas hydrate production by depressurization[J].Advances in New and Renewable Energy,2016,4(1):33-41.
[18]孙可明,王婷婷,翟诚,罗慧玉.天然气水合物加热分解储层变形破坏规律研究[J].特种油气藏,2017,24(5):91-96.Sun Keming,Wang Tingting,Zhai Cheng&Luo Huiyu.Patterns of reservoir deformation due to thermal decomposition of natural gas hydrates[J].Special Oil&Gas Reservoirs,2017,24(5):91-96.
[19]Sun JX,Zhang L,Ning FL,Lei HW,Liu TL,Hu GW,et al.Production potential and stability of hydrate-bearing sediments at the site GMGS3-W19 in the South China Sea:A preliminary feasibility study[J].Marine and Petroleum Geology,2017,86:447-473.
[20]Yang S,Zhang M,Liang J,Lu J,Zhang Z,Melanie H,et al.Preliminary results of China's third gas hydrate drilling expedition:A critical step from discovery to development in the South China Sea[J].Fire in the Ice,2015,15(2):1-5.
[21]Kim HC,Bishnoi PR,Heidemann RA&Rizvi SSH.Kinetics of methane hydrate decomposition[J].Chemical Engineering Science,1985,42(7):1645-1653.
[22]Biot MA&Willis DG.The elastic coefficients of the theory of consolidation[J].Journal of Applied Mechanics,1957,15(2):594-601.
[23]Masuda Y,Naganawa S&Ando S.Numerical calculation of gas production performance from reservoirs containing natural gas hydrates[J].SPE Journal,1997,29(3):201-210.
[24]Sun XF&Mohanty KK.Kinetic simulation of methane hydrate formation and dissociation in porous media[J].Chemical Engineering Science,2006,61(11):3476-3495.
[25]Duan ZH&Sun R.A model to predict phase equilibrium of CH4and CO2 clathrate hydrate in aqueous electrolyte solutions[J].American Mineralogist,2006,91(8/9):1346-1354.
[26]Esmaeilzadeh F,Zeighami ME&Fathi J.1-D modeling of hydrate decomposition in porous media[C]//Proceedings of World Academy of Science:Engineering&Technology,2013,43:648.
[27]Soga K,Lee SL,Ng MYA&Klar A.Characterisation and engineering properties of methane hydrate soils[C]//Proceedings of the 2nd International Workshop on Characterisation and Engineering Properties of Natural Soils,29 November-1 December 2006,Singapore.London:CRC Press,2006.
[28]Santamarina JC&Ruppel C.The impact of hydrate saturation on the mechanical,electrical,and thermal properties of hydrate-bearing sand,silts,and clay[C]//Proceedings of the 6th International Conference on Gas Hydrate,6-10 July 2008,Vancouver,British Columbia,Canada.
[29]Clarke M&Bishnoi PR.Determination of the intrinsic rate of gas hydrate decomposition using particle size analysis[J].Annals of the New York Academy of Sciences,2000,912:556-563.
[30]Rutqvist J,Moridis GJ,Grover T,Silpngarmlert S,Collett TS&Holdich SA.Coupled multiphase fluid flow and wellbore stability analysis associated with gas production from oceanic hydrate-bearing sediments[J].Journal of Petroleum Science&Engineering,2012(92/93):65-81.