页岩气和天然气的区别_页岩气渗流数学模型

  本文关键词：页岩气渗流数学模型，由笔耕文化传播整理发布。

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误差.

(ⅳ) 裂缝中解吸附过程对页岩气产量的影响. 本文中基质采用了非平衡解吸附理论, 而裂缝则采用平衡态(也即瞬时)解吸附模型进行模拟. 对比不考虑裂缝中的解吸附过程计算的累积产量, 结果如图

14所示. 可以看出人工裂缝内解吸附过程对页岩气产量几乎没有影响: 生产150天后考虑人工裂缝内解吸附过程的累计产量为153492.9 m3, 不考虑人工裂缝内解吸附过程的累计产量为153490.2 m3, 相差仅为2.7 m3, 这说明人工裂缝内的吸附气量并不多(人工裂缝的容积本身很小), 所以人工裂缝内的解吸附过程可以忽略.

图14 (网络版彩色)人工裂缝内解吸附过程对页岩气产量的影响 Figure 14 (Color online) Impact of desorption process in hydraulic fracture on shale gas production

5 结论

针对页岩气渗流机理复杂的特点, 综合考虑了自由气的黏性流动、Knudsen扩散、滑脱流和吸附气的表面扩散以及岩石变形引起的吸附气滑移, 建立了页岩气渗流数学模型, 采用非线性非平衡Langmuir吸附理论分析了渗流过程中的解吸附机理. 通过数值模拟, 得到以下结论:

自由气的黏性流动与Knudsen扩散主导页岩气产量, 无因次变量既可分析主导流动机制, 也可计算等效渗透率.

(3) 非平衡解吸附过程相较于传统瞬时解吸附理论, 会降低页岩气产量, 解吸附速率越慢, 页岩气产量越低.

(4) 由于人工裂缝容积有限, 在模拟多级压裂水平井页岩气产量时可以忽略人工裂缝中的解吸附过程.

(1) 页岩气在原始储层条件下几乎不流动, 在多级压裂水平井的产能计算中, 可以只考虑SRV区域内气体的流动.

(5) 建立的数学模型能够分析自由气、吸附气以及净解吸附速率在生产过程中的时空分布规律, 为多级压裂水平井中页岩气的渗流问题提供了科学

(2) 数值模拟结果显示, 吸附气的表面扩散与滑

移对页岩气产量的影响均在0.1%以下,

可以忽略

.

基础.

参考文献

1 Yao J, Sun H, Huang Z Q, et al. Key mechanical problems in the development of shale gas reservoirs (in Chinese). Sci Sin-Phys Mech Astron, 2013, 43: 1527–1547 [姚军, 孙海, 黄朝琴, 等. 页岩气藏开发中的关键力学问题. 中国科学: 物理学 力学 天文学, 2013, 43: 1527–1547]

2 Tang Y, Tang X, Wang G Y, et al. Summary of hydraulic fracturing technology in shale gas development (in Chinese). Geol Bull China, 2011, 30: 393–399 [唐颖, 唐玄, 王广源, 等. 页岩气开发水力压裂技术综述. 地质通报, 2011, 30: 393–399]

3 Guo C, Wei M, Chen H, et al. Improved numerical simulation for shale gas reservoirs. In: Offshore Technology Conference Asia, Kuala Lumpur, 2014

4 Javadpour F, Fisher D, Unsworth M. Nanoscale gas flow in shale gas sediments. J Can Petrol Technol, 2007, 46: 55–61

5 Freeman C M, Moridis G, Llk D, et al. A numerical study of performance for tight gas and shale gas reservoir systems. J Petrol Sci Eng, 2013, 108: 22–39

6 Kast W, Hohenthanner C R. Mass transfer within the gas-phase of porous media. Int J Heat Mass Tran, 2000, 43: 807–823

7 Guo J J, Zhang L H, Wang H T, et al. Pressure transient analysis for multi-stage fractured horizontal wells in shale gas reservoirs. Transp Porous Med, 2012, 93: 635–653

8 Nobakht M, Clarkson C R, Kaviani D. New type curves for analyzing horizontal well with multiple fractures in shale gas reservoirs. J Nat Gas Sci Eng, 2013, 10: 99–112

9 Zhao Y L, Zhang L H, Zhao J Z, et al. “Triple porosity” modeling of transient well test and rate decline analysis for multi-fractured hori-zontal well in shale gas reservoirs. J Petrol Sci Eng, 2013, 110: 253–262

2269

2015年8月 第60卷 第24期

10 Yu W, Sepehrnoori K. Numerical evaluation of the impact of geomechanics on well performance in shale gas reservoirs. In: 47th US Rock

Mechanics/Genomechanics Symposium, San Francisco, 2013

11 Huang J, Ghassemi A. Poroelastic analysis of gas production from shale. In: 47th US Rock Mechanics/Genomechanics Symposium, San

Francisco, 2011

12 Mongalvy V, Chaput E, Agarwal S, et al. A new numerical methodology for shale reservoir performance evaluation. In: SPE North

American Unconventional Gas Conference and Exhibition, Woodlands, 2011

13 Srinivasan R, Auvil S R, Schork J M. Mass transfer in Carbon molecular sieves-an interpretation of Langmuir kinetics. The Chem Eng J,

1995, 57: 137–144

14 Do D D, Wang K. A new model for the description of adsorption kinetics in heterogeneous activated carbon. Carbon, 1998, 36:

1539–1554

15 Nikolai S, Wolf K A A, Bruining J. Interpretation of carbon dioxide diffusion behavior in coals. Int J Coal Geol, 2007, 72: 315–324 16 Jin Y, Chen M. Wellbore Stability Mechanics (in Chinese). Beijing: Science Press, 2012 [金衍, 陈勉. 井壁稳定力学. 北京: 科学出版

社, 2012]

17 Zhang H, Liu J, Elsworth D. How sorption-induced matrix deformation affects gas flow in coal seams: A new FE model. Int J Rock Mech

Min, 2008, 45: 1226–1236

18 Warren J E, Root P J. The behavior of naturally fractured reservoirs. Soc Pet Eng J, 1963, 3: 245–255

19 Zhang Y T. Rock Hydraulics and Engineering (in Chinese). Beijing: China Water Power Press, 2005 [张有天. 岩石水力学与工程. 北

京: 中国水利水电出版社, 2005]

20 Xia Y, Jin Y, Chen M, et al. Hydrodynamic modeling of mud loss controlled by the coupling of discrete fracture and matrix. J Petrol Sci

Eng, 2014, doi:10.1016/j.petrol.2014.07.026

21 Biryukov D, Kuchuk F J. Transient pressure behavior of reservoirs with discrete conductive faults and fractures. Transp Porous Med,

2012, 95: 239–268

22 Chen M, Jin Y, Zhang G Q. Rock Mechanics in Petroleum Engineering (in Chinese). Beijing: Science Press, 2008 [陈勉, 金衍, 张广清.

石油工程岩石力学. 北京: 科学出版社, 2008]

23 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: 181–202

24 Harpalani S, Schraufnagel A. Measurement of parameters impacting methane recovery from coal seams. Int J Min Geol Eng, 1990, 28:

369–384

25 Robertson E P, Christiansen R L. Modeling permeability in coal using sorption-induced strain data. In: SPE Annual Technical Conference

and Exhibition, Dallas, 2005

26 Bello R O, Wattenbarger R A. Multi-stage hydraulically fractured shale gas rate transient analysis. In: SPE North Africa Technical Con-ference and Exhibition, Cairo, 2010

27 Stalgorova E, Mattar L. Practical analytical model to simulate production of horizontal wells with branch fractures. In: SPE Canadian

Unconventional Resources Conference, Calgary, 2012

28 Stalgorova E, Mattar L. Analytical model for history matching and forecasting production in multifrac composite systems. In: SPE Cana-dian Unconventional Resources Conference, Calgary, 2012

29 Brohi I, Mehran P D, Roberto A. Modeling fractured horizontal wells as dual porosity composite reservoirs—Application to tight gas,

shale gas and tight oil cases. In: SPE Western North American Regional Meeting, Anchorage, 2011

30 Ozkan E, Raghavan R. New solutions for well-test-analysis problems: Part 1—Analytical considerations. SPE Formation Evaluation,

1991, 6: 359–368

31 Ozkan E, Raghavan R. New solutions for well-test-analysis Problems: Part 2—Computational considerations and applications. SPE For-mation Evaluation, 1991, 6: 369–378

32 Ozkan E, Raghavan R. New solutions for well-test-analysis problems: Part 3—Additional algorithms. In: SPE Annual Tech Conf Exhibit,

1994, doi.org/10.2118/28424-MS

33 Guo J J, Zhang L H, Wang H T, et al. Pressure transient analysis for multi-stage fractured horizontal wells in shale gas reservoirs. Transp

Porous Med, 2012, 93: 635–653

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Gas flow in shale reservoirs

XIA Yang1, JIN Yan1, CHEN Mian1 & CHEN KangPing1,2

1 2

State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China; School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe AZ 85287-6101, USA

This study incorporates various gas transport mechanisms in shale nanopores with nonlinear and non-equilibrium gas adsorption- desorption kinetics. We formulate a simplified model for matrix and hydraulic fractures to study the dynamic production performance of multi-stage fractured horizontal wells in shale gas reservoirs. The gas transport mechanisms include viscous flow, Knudsen diffusion of free gas, surface diffusion, and slippage of adsorbed gas whilerock deformation is coupled in the flow equations. The sensitivity of the production rate to key physical parameters is examined through numerical simulation. Our results indicate that the viscous flow and Knudsen diffusion dominate the production of shale gas. The production rate was sensitive to the desorption rate while largely unaffected by the surface diffusion and slippage of the adsorbed gas, given that the transport process of adsorbed gas is a much slower process than the diffusion of free gas.

shale gas, flow mechanism, non-equilibrium desorption, numerical simulation

doi: 10.1360/N972014-01175

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  本文关键词：页岩气渗流数学模型，由笔耕文化传播整理发布。