气体吸附对页岩裂缝表观渗透率和页岩气采收率的影响
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摘要
页岩气以及无水压裂技术采用的二氧化碳都可使页岩发生吸附变形,影响其裂缝表观渗透率,同时表观渗透率还受到有效应力和流体流态的影响.页岩气渗流过程中多种物理场相互耦合使得吸附应变对表观渗透率的影响不易被分析,常被忽略.本文基于多孔弹性理论和页岩吸附变形的特点,建立了适用于多种边界条件的页岩裂缝表观渗透率模型,提出了分析吸附变形对表观渗透率影响的方案,并分析了一组富有机质页岩样品中吸附应变对其表观渗透率的影响,最终结合页岩气多尺度渗流模型分析了吸附变形对页岩气采收率的影响.研究结果表明:采用不同边界条件和气体测量页岩表观渗透率时,其主控机理并不相同;基于此特点,结合"固定围压"和"固定孔隙压力"条件下的非吸附性气体和吸附性气体测量所得的页岩表观渗透率数据,可以确定内部吸附变形对表观渗透率有较大影响,不可忽略;此外,相较于内部吸附变形,气体吸附引起的页岩整体变形对表观渗透率和页岩气采收率有更大影响.
Shale gas reservoirs can experience adsorption-induced strain due to the in-situ shale gas and the CO2 invasion after anhydrous fracturing. The adsorption-induced strain as well as effective stress and flow regime affect apparent permeability of fractures in shale reservoirs, which makes the impact of adsorption-induced on apparent permeability is difficult to be analyzed and normally ignored in models. In this study, based on poroelastic theory and characteristics of adsorption-induced strain of shale, the analytical apparent permeability model for fractured shale was built to analyze experimental data obtained from various boundary conditions, meanwhile,a experimental method was proposed to investigate the impact of gas adsorption on apparent permeability. With this method, the impact of gas adsorption on organic-rich shale was identified. Finally, the impact of gas adsorption on recovery rate of shale gas reservoirs was analyzed through combining the apparent permeability model and multiscale model of gas flow through fractured media. The analytical model illustrates that the controlling mechanisms of apparent permeability evolutions for different boundary conditions and gases are significantly different. Based on this feature, using the experimental data obtained from non-adsorption phase gas and adsorption-phase gas under conditions of constant confining pressure and constant pore pressure, the impact of internal strain due to adsorption on apparent permeability was identified and cannot be ignored. In additional, compared with the internal strain due to adsorption, the adsorption-induced strain of the whole shale plays a more important role in evolutions of apparent permeability and recovery rate of shale gas reservoirs.
Shale gas reservoirs can experience adsorption-induced strain due to the in-situ shale gas and the CO2 invasion after anhydrous fracturing. The adsorption-induced strain as well as effective stress and flow regime affect apparent permeability of fractures in shale reservoirs, which makes the impact of adsorption-induced on apparent permeability is difficult to be analyzed and normally ignored in models. In this study, based on poroelastic theory and characteristics of adsorption-induced strain of shale, the analytical apparent permeability model for fractured shale was built to analyze experimental data obtained from various boundary conditions, meanwhile,a experimental method was proposed to investigate the impact of gas adsorption on apparent permeability. With this method, the impact of gas adsorption on organic-rich shale was identified. Finally, the impact of gas adsorption on recovery rate of shale gas reservoirs was analyzed through combining the apparent permeability model and multiscale model of gas flow through fractured media. The analytical model illustrates that the controlling mechanisms of apparent permeability evolutions for different boundary conditions and gases are significantly different. Based on this feature, using the experimental data obtained from non-adsorption phase gas and adsorption-phase gas under conditions of constant confining pressure and constant pore pressure, the impact of internal strain due to adsorption on apparent permeability was identified and cannot be ignored. In additional, compared with the internal strain due to adsorption, the adsorption-induced strain of the whole shale plays a more important role in evolutions of apparent permeability and recovery rate of shale gas reservoirs.
引文
1葛洪魁,王小琼,张义.大幅度降低页岩气开发成本的技术途径.石油钻探技术,2013,41:1–5
2 李宗田,苏建政,张汝生.现代页岩油气水平井压裂改造技术.北京:中国石化出版社,2016
3 吴奇,胥云,张守良,等.非常规油气藏体积改造技术核心理论与优化设计关键.石油学报,2014,35:706–714
4 Curtis1 J B.Fractured shale-gas systems.AAPG Bull,2002,86:1921–1938
5 Javadpour F.Nanopores and apparent permeability of gas flow in mudrocks(shales and siltstone).J Can Petrol Technol,2009,48:16–21
6 Peng Y,Liu J,Pan Z,et al.A sequential model of shale gas transport under the influence of fully coupled multiple processes.J Nat Gas Sci Eng,2015,27:808–821
7 冯其红,徐世乾,王森,等.基于嵌入离散裂缝的页岩气藏视渗透率模型.地球科学——中国地质大学学报,2017,42:1301–1313
8 Civan F,Rai C S,Sondergeld C H.Shale-gas permeability and diffusivity inferred by improved formulation of relevant retention and transport mechanisms.Transp Porous Med,2011,86:925–944
9 Moghadam A A,Chalaturnyk R.Expansion of the Klinkenberg’s slippage equation to low permeability porous media.Int J Coal Geol,2014,123:2 –9
10 Guo C,Xu J,Wu K,et al.Study on gas flow through nano pores of shale gas reservoirs.Fuel,2015,143:107–117
11 Vera F E,Ehlig-Economides C.Diagnosing pressure-dependent-permeability in long-term shale gas pressure and production transient analysis.In:Unconventional Resources Technology Conference.Society of Petroleum Engineers,2013
12 Cho Y,Ozkan E,Apaydin O G.Pressure-dependent natural-fracture permeability in shale and its effect on shale-gas well production.SPE Reserv Eval Eng,2013,16:216–228
13 Wang H,Xu W,Zuo J.Compact rock material gas permeability properties.Phys B-Condensed Matter,2014,449:10–18
14 Heller R,Vermylen J,Zoback M.Experimental investigation of matrix permeability of gas shales.AAPG Bull,2014,98:975–995
15 Tinni A,Fathi E,Agarwal R,Sondergeld C H,Akkutlu I Y,Rai C S.Shale permeability measurements on plugs and crushed samples.In:SPE Canadian Unconventional Resources Conference.Society of Petroleum Engineers,2012
16 Ghanizadeh A,Bhowmik S,Haeri-Ardakani O,et al.A comparison of shale permeability coefficients derived using multiple non-steady-state measurement techniques:Examples from the Duvernay Formation,Alberta(Canada).Fuel,2015,140:371–387
17 Wang F P,Reed R M.Pore networks and fluid flow in gas shales.In:SPE Annual Technical Conference and Exhibition.Society of Petroleum Engineers,2009
18 Bustin R M,Bustin A M M,Cui X,et al.Impact of shale properties on pore structure and storage characteristics.In:SPE Shale Gas Production Conference.Fort Worth,Texas,USA,16–18,2008
19 Dong J J,Hsu J Y,Wu W J,et al.Stress-dependence of the permeability and porosity of sandstone and shale from TCDP Hole-A.Int J Rock Mech Min Sci,2010,47:1141–1157
20 Chen D,Pan Z,Ye Z.Dependence of gas shale fracture permeability on effective stress and reservoir pressure:Model match and insights.Fuel,2015,139:383–392
21 周尚文,王红岩,薛华庆,等.基于Ono-Kondo格子模型的页岩气超临界吸附机理探讨.地球科学——中国地质大学学报,2017,42:1421–1430
22 Middleton R S,Carey J W,Currier R P,et al.Shale gas and non-aqueous fracturing fluids:Opportunities and challenges for supercritical CO2.Appl Energ,2015,147:500–509
23 Chen T,Feng X T,Pan Z.Experimental study of swelling of organic rich shale in methane.Int J Coal Geol,2015,150-151:64–73
24 王金杰,于龙,苑庆旺,等.干酪根对页岩基质中甲烷运移规律的影响.地球科学——中国地质大学学报,2017,42:1386–1393
25 Beskok A,Karniadakis G E.Report:A model for flows in channels,pipes,and ducts at micro and nano scales.Microscale Thermophys Eng,1999,3:43–77
26 Cui X,Bustin R M.Volumetric strain associated with methane desorption and its impact on coalbed gas production from deep coal seams.AAPG Bull,2005,89:1181–1202
27 Peng Y,Liu J,Wei M,et al.Why coal permeability changes under free swellings:New insights.Int J Coal Geol,2014,133:35–46
28 Peng Y,Liu J,Zhu W,et al.Benchmark assessment of coal permeability models on the accuracy of permeability prediction.Fuel,2014,132:194 –203
29 Peng Y,Liu J,Pan Z,et al.Impact of coal matrix strains on the evolution of permeability.Fuel,2016,189:270–283
30 Pan Z,Connell L D.A theoretical model for gas adsorption-induced coal swelling.Int J Coal Geol,2007,69:243–252
31 Wang S,Elsworth D,Liu J.Permeability evolution in fractured coal:The roles of fracture geometry and water-content.Int J Coal Geol,2011,87:13 –25
32 Ghanizadeh A,Amann-Hildenbrand A,Gasparik M,et al.Experimental study of fluid transport processes in the matrix system of the European organic-rich shales:II.Posidonia Shale(Lower Toarcian,northern Germany).Int J Coal Geol,2014,123:20–33
33 Aljamaan H,Alnoaimi K,Kovscek A R.In-depth experimental investigation of shale physical and transport properties.In:Unconventional Resources Technology Conference.Denver.2013:1120–1129
34 Pan Z,Connell L D.Reservoir simulation of free and adsorbed gas production from shale.J Nat Gas Sci Eng,2015,22:359–370
35 Sone H,Zoback M D.Mechanical properties of shale-gas reservoir rocks—Part 1:Static and dynamic elastic properties and anisotropy.Geophysics,2013,78:D381–D392
2 李宗田,苏建政,张汝生.现代页岩油气水平井压裂改造技术.北京:中国石化出版社,2016
3 吴奇,胥云,张守良,等.非常规油气藏体积改造技术核心理论与优化设计关键.石油学报,2014,35:706–714
4 Curtis1 J B.Fractured shale-gas systems.AAPG Bull,2002,86:1921–1938
5 Javadpour F.Nanopores and apparent permeability of gas flow in mudrocks(shales and siltstone).J Can Petrol Technol,2009,48:16–21
6 Peng Y,Liu J,Pan Z,et al.A sequential model of shale gas transport under the influence of fully coupled multiple processes.J Nat Gas Sci Eng,2015,27:808–821
7 冯其红,徐世乾,王森,等.基于嵌入离散裂缝的页岩气藏视渗透率模型.地球科学——中国地质大学学报,2017,42:1301–1313
8 Civan F,Rai C S,Sondergeld C H.Shale-gas permeability and diffusivity inferred by improved formulation of relevant retention and transport mechanisms.Transp Porous Med,2011,86:925–944
9 Moghadam A A,Chalaturnyk R.Expansion of the Klinkenberg’s slippage equation to low permeability porous media.Int J Coal Geol,2014,123:2 –9
10 Guo C,Xu J,Wu K,et al.Study on gas flow through nano pores of shale gas reservoirs.Fuel,2015,143:107–117
11 Vera F E,Ehlig-Economides C.Diagnosing pressure-dependent-permeability in long-term shale gas pressure and production transient analysis.In:Unconventional Resources Technology Conference.Society of Petroleum Engineers,2013
12 Cho Y,Ozkan E,Apaydin O G.Pressure-dependent natural-fracture permeability in shale and its effect on shale-gas well production.SPE Reserv Eval Eng,2013,16:216–228
13 Wang H,Xu W,Zuo J.Compact rock material gas permeability properties.Phys B-Condensed Matter,2014,449:10–18
14 Heller R,Vermylen J,Zoback M.Experimental investigation of matrix permeability of gas shales.AAPG Bull,2014,98:975–995
15 Tinni A,Fathi E,Agarwal R,Sondergeld C H,Akkutlu I Y,Rai C S.Shale permeability measurements on plugs and crushed samples.In:SPE Canadian Unconventional Resources Conference.Society of Petroleum Engineers,2012
16 Ghanizadeh A,Bhowmik S,Haeri-Ardakani O,et al.A comparison of shale permeability coefficients derived using multiple non-steady-state measurement techniques:Examples from the Duvernay Formation,Alberta(Canada).Fuel,2015,140:371–387
17 Wang F P,Reed R M.Pore networks and fluid flow in gas shales.In:SPE Annual Technical Conference and Exhibition.Society of Petroleum Engineers,2009
18 Bustin R M,Bustin A M M,Cui X,et al.Impact of shale properties on pore structure and storage characteristics.In:SPE Shale Gas Production Conference.Fort Worth,Texas,USA,16–18,2008
19 Dong J J,Hsu J Y,Wu W J,et al.Stress-dependence of the permeability and porosity of sandstone and shale from TCDP Hole-A.Int J Rock Mech Min Sci,2010,47:1141–1157
20 Chen D,Pan Z,Ye Z.Dependence of gas shale fracture permeability on effective stress and reservoir pressure:Model match and insights.Fuel,2015,139:383–392
21 周尚文,王红岩,薛华庆,等.基于Ono-Kondo格子模型的页岩气超临界吸附机理探讨.地球科学——中国地质大学学报,2017,42:1421–1430
22 Middleton R S,Carey J W,Currier R P,et al.Shale gas and non-aqueous fracturing fluids:Opportunities and challenges for supercritical CO2.Appl Energ,2015,147:500–509
23 Chen T,Feng X T,Pan Z.Experimental study of swelling of organic rich shale in methane.Int J Coal Geol,2015,150-151:64–73
24 王金杰,于龙,苑庆旺,等.干酪根对页岩基质中甲烷运移规律的影响.地球科学——中国地质大学学报,2017,42:1386–1393
25 Beskok A,Karniadakis G E.Report:A model for flows in channels,pipes,and ducts at micro and nano scales.Microscale Thermophys Eng,1999,3:43–77
26 Cui X,Bustin R M.Volumetric strain associated with methane desorption and its impact on coalbed gas production from deep coal seams.AAPG Bull,2005,89:1181–1202
27 Peng Y,Liu J,Wei M,et al.Why coal permeability changes under free swellings:New insights.Int J Coal Geol,2014,133:35–46
28 Peng Y,Liu J,Zhu W,et al.Benchmark assessment of coal permeability models on the accuracy of permeability prediction.Fuel,2014,132:194 –203
29 Peng Y,Liu J,Pan Z,et al.Impact of coal matrix strains on the evolution of permeability.Fuel,2016,189:270–283
30 Pan Z,Connell L D.A theoretical model for gas adsorption-induced coal swelling.Int J Coal Geol,2007,69:243–252
31 Wang S,Elsworth D,Liu J.Permeability evolution in fractured coal:The roles of fracture geometry and water-content.Int J Coal Geol,2011,87:13 –25
32 Ghanizadeh A,Amann-Hildenbrand A,Gasparik M,et al.Experimental study of fluid transport processes in the matrix system of the European organic-rich shales:II.Posidonia Shale(Lower Toarcian,northern Germany).Int J Coal Geol,2014,123:20–33
33 Aljamaan H,Alnoaimi K,Kovscek A R.In-depth experimental investigation of shale physical and transport properties.In:Unconventional Resources Technology Conference.Denver.2013:1120–1129
34 Pan Z,Connell L D.Reservoir simulation of free and adsorbed gas production from shale.J Nat Gas Sci Eng,2015,22:359–370
35 Sone H,Zoback M D.Mechanical properties of shale-gas reservoir rocks—Part 1:Static and dynamic elastic properties and anisotropy.Geophysics,2013,78:D381–D392