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作者简介:

陈元千(1933—),男,河南兰考人,教授级高级工程师,1952年考入清华大学石油工程系,1956年毕业于北京石油学院钻采系,长期从事油气藏工程、油气田开发和油气储量评价工作。E-mail:525980269@qq.com。

中图分类号:TE32+8

文献标识码:A

文章编号:1009-9603(2021)01-0132-05

DOI:10.13673/j.cnki.cn37-1359/te.2021.01.016

参考文献 1
陈元千,周翠.线性递减类型的建立、对比与应用[J].石油学报,2015,36(8):983-987.CHEN Yuanqian,ZHOU Cui.Establishment,comparison and ap⁃ plication of the linear decline type[J].Acta Petrolei Sinica,2015,36(8):983-987.
参考文献 2
陈元千,齐亚东,傅礼兵,等.井控页岩气可动地质储量和可采储量的评价方法[J].油气地质与采收率,2018,25(4):73-78.CHEN Yuanqian,QI Yadong,FU Libing,et al.Methods for esti⁃ mating well-controlled movable in-place and recoverable re⁃ serves of shale gas[J].Petroleum Geology and Recovery Efficien⁃ cy,2018,25(4):73-78.
参考文献 3
陈元千,唐玮.广义递减模型的建立及应用[J].石油学报,2016,37(11):1 410-1 413.CHEN Yuanqian,TANG Wei.Establishment and application of generalized decline model[J].Acta Petrolei Sinica,2016,37(11):1 410-1 413.
参考文献 4
陈元千,傅礼兵.幂函数递减模型的建立、对比与应用[J].油气地质与采收率,2019,26(6):87-91.CHEN Yuanqian,FU Libing.Establishment,comparison and ap⁃ plication of power function decline model[J].Petroleum Geology and Recovery Efficiency,2019,26(6):87-91.
参考文献 5
陈元千,郝明强.多峰预测模型的建立与应用[J].新疆石油地质,2013,34(3):296-299.CHEN Yuanqian,HAO Mingqiang.Establishment and application of the multi⁃peak forecasting model[J].Xinjiang Petroleum Geolo⁃ gy,2013,34(3):296-299.
参考文献 6
陈元千.对翁氏预测模型的推导及应用[J].天然气工业,1996,16(2):22-26,102.CHEN Yuanqian.Derivation and application of Weng’s predica⁃ tion model[J].Natural Gas Industry,1996,16(2):22-26,102.
参考文献 7
陈元千,胡建国.预测油气田产量和储量的Weibull模型(为纪念克拉玛依油田勘探开发40周年而作)[J].新疆石油地质,1995,16(3):250-255,287.CHEN Yuanqian,HU Jianguo.Weibull model for predicting out⁃ put and reserve in an oil and gas field[J].Xinjiang Petroleum Ge⁃ ology,1995,16(3):250-255,287.
参考文献 8
陈元千.瑞利模型的完善推导与应用[J].油气地质与采收率,2004,11(4):39-41.CHEN Yuanqian.The perfect derivation of Rayleigh model and its application[J].Petroleum Geology and Recovery Efficiency,2004,11(4):39-41.
参考文献 9
LANCZOS C A.Precision approximation of gamma function[J].Journal of the Society for Industrial and Applied Mathematics:Se⁃ ries B,Numerical Analysis,1964:1 186-1 196.
参考文献 10
ARPS J J.Analysis of decline curves,Trans[J].AIME,1945,160:228-247.
参考文献 11
何培,冯连勇,TOM Wilber.马塞勒斯页岩气藏单井产量递减规律及可采储量预测[J].新疆石油地质,2015,36(2):249-252.HE Pei,FENG Lianyong,TOM Wilber.Production decline rule and recoverable reserves prediction of Marcellus shale gas well in a production unit,Pennsylvania,US[J].Xinjiang Petroleum Geol⁃ ogy,2015,36(2):249-252.
目录contents

    摘要

    随着中国页岩气工业的发展和大量页岩气井的投产,如何有效地预测页岩气井的产量和可采储量已成为油气藏工程的重要课题,也是页岩气资源的生产和管理部门极为关心的问题。由于页岩气是以吸附状态和自由状态分别储存于超致密页岩基质和次生裂缝系统中,而页岩气井在钻井、完井、测井和压裂过程中受到泥浆的多次污染。因此,投产后的页岩气井表现出明显的独立性、差异性和复杂性。再者,由于页岩气井以降压解吸和能量消耗式开采,具有投产即进入递减的特征,因此,产量递减法已成为首选的评价方法。基于陈元千等提出的广义单峰周期预测模型,经简化后得到预测页岩气井产量和可采储量的泛指数递减模型。该模型的递减指数 m 为 0~1。当 m=1时为著名的指数递减模型;当m=0.5时可得具有实用价值的0.5型泛指数递减模型。对于具体的非常规气井,在实际预测中,需要利用生产数据通过线性迭代试差法,确定acm值。根据美国宾州Marcellus页岩气藏两口页岩气井生产数据,利用泛指数递减模型,对页岩气井的产量和可采储量进行预测。结果表明,建立的泛指数递减模型是实用有效的。

    Abstract

    With the advancement in China’s shale gas industry and the large-scale production of shale gas wells,how to effectively forecast the production rate and recoverable reserves of shale gas wells and has become a crucial subject of oil and gas reservoir engineering. It is also a matter of great concern to shale gas production and management departments. As shale gas is stored in the ultra-tight shale matrix and the secondary fracture system in the adsorption state and the free gas state,respectively,it can be polluted by mud during the drilling,completion,logging,and fracturing. Therefore,the shale gas wells that have been put into production show obvious independence,diversity,and complexity. More importantly,shale gas wells are brought into production by desorption after pressure drops and energy consumption featured by the decreasing production at the moment it starts. Consequently,the production decline method has become the first choice for evaluation. In this paper,the generalized single peak cycle model proposed by Chen Yuanqian et al.is simplified into a pan exponential decline model(PEDM)that can forecast the production rate and recoverable reserves of shale gas wells. The decline exponent m ranges from 0 to 1. At m=1,it is the famous exponential decline model. At m=0.5,it is the 0.5-PEDM of practical value. For specific unconventional shale gas wells,it is necessary to use production data to determine the values of ac,and m by linear iterative trial and error method in actual forecasting. The application of production data from two wells in the Marcellus shale gas reservoir,Pennsylvania,the US,elicits the effectiveness of the PEDM in forecasting the production rate and recoverable reserves of shale gas wells.

  • 非常规页岩气藏由超致密的基质和次生裂缝组成。页岩气分别以吸附状态和自由状态储存于这两种介质中。页岩气的产量及其递减的快慢除与基质的吸附气含量和次生裂缝发育程度有关外,还与水平井的钻井、完井和压裂效果有关。页岩气井的开采表现为定容、封闭、消耗式和投产即进入递减的特点。因此,利用线性递减模型[1-2]、广义递减模型[3] 和幂函数递减模型[4] 预测页岩气井产量和可采储量均取得了较好效果。为此,基于广义单峰周期预测模型[5],建立预测页岩气井产量和可采储量的泛指数递减模型,并介绍该模型的派生、无因次产量曲线和模型的求解方法。

  • 1 泛指数递减模型的建立

  • 在广义翁氏模型[6]、威布尔模型[7]、陈-郝模型[5] 和瑞利模型[8] 的基础上,陈元千等建立了广义单峰周期预测模型[5],其中产量、峰值产量、峰值出现时间和可采储量计算式分别为:

  • q=atbe-tm/c
    (1)
  • qpeak =abc2.718m1/m
    (2)
  • tpeak =bcm1/m
    (3)
  • GR=ac(b+1)/mmΓb+1m
    (4)
  • 由(1)式—(4)式可以看出,广义单峰周期预测模型有 abcm 四个常数。其中常数 a 控制峰值的高低,a 值愈大峰值产量愈高,反之愈低。常数 b 控制峰位,b 值愈大,峰位距纵轴愈远,反之愈近。常数c控制峰值后产量递减的快慢,c值愈大产量递减愈慢,反之愈快。时间指数 m用于判别模型的类别:当m=1时可得广义翁氏模型;当m=2时可得陈-郝模型;当m=b+1时可得威布尔模型;当m=2且b=1 时可得瑞利模型。对于广义单峰周期预测模型,当 b=0时即得投产进入递减的泛指数递减模型。

  • 泛指数递减模型的产量和可采储量计算公式分别为:

  • q=ae-tm/c
    (5)
  • GR=ac1/mmΓ1m
    (6)
  • 由(6)式可见,GRac1/m 均成正比,与 m 成反比。

  • 在(6)式中的 Γ(1/m)值可查伽马函数表或由相关经验公式[9] 求得,相关经验公式为:

  • Γ1m=Γ(Z+1)=2.507(Z+2)Z+0.5eZ+2×1.0864Z+1+1
    (7)
  • 其中:

  • Z=1-mm
    (8)
  • 由(5)式对时间求导得:

  • dqdt=-mqct1-m
    (9)
  • Arps定义的递减率[10] 为:

  • D=-dqqdt
    (10)
  • 将(9)式代入(10)式得泛指数递减模型的递减率为:

  • D=mct1-m
    (11)
  • 由(11)式可以看出,泛指数递减模型的递减率与 m 成正比,与 c 成反比。当 t=0 时,初始递减率趋近于无穷大。

  • 2 泛指数递减模型的派生

  • m=0.5 时,Γ(1/m)=1.0,由(5)式、(6)式和 (11)式可得具有实用价值的 0.5 型泛指数递减模型,其产量、可采储量和递减率计算式分别为:

  • q=ae-t0.5/c
    (12)
  • GR=2ac2
    (13)
  • D=0.5ct0.5
    (14)
  • m=1时,Γ(1/m)=1.0,由(5)式、(6)式和(11) 式可得著名的指数递减模型,其产量、可采储量和递减率计算式分别为:

  • q=ae-t/c
    (15)
  • GR=ac
    (16)
  • D=1c
    (17)
  • 3 泛指数递减模型的无因次关系

  • 为了建立泛指数递减模型的无因次产量曲线,首先将(5)式改写为:

  • q=ae-cm-1(t/c)m
    (18)
  • 泛指数递减模型的无因次产量和无因次时间分别为:

  • qD=qq0
    (19)
  • tD=tc
    (20)
  • 将(19)式和(20)式代入(18)式,且由(15)式可以看出,当 t=0 时,q = a = q0,由此得泛指数递减模型的无因次产量与无因次时间之间的关系式为:

  • qD=e-cm-1tDm
    (21)
  • 由(21)式可以看出:当m=0时,qD为常数;当m= 1时,qD=etDqD为指数递减。当取c=5时,由(21)式求得不同 m值时 qDtD的无因次关系(图1);当 m= 0.5时,由(21)式求得不同 c值时 qDtD的无因次关系(图2)。由图1 和图2 可以看出,m 值比 c 值对 qD 的影响明显。

  • 图1 c=5时泛指数递减模型qDtD的关系

  • Fig.1 The qD-tD curves of PEDM,c=5

  • 4 泛指数递减模型的求解方法

  • 由(5)式可以看出,泛指数递减模型是带有acm 三个常数的非线性递减模型,需根据实际生产数据,利用线性迭代试差法进行求解。为此,首先将(5)式等号两端同时取自然对数得:

  • 图2 m=0.5时泛指数递减模型qDtD的关系

  • Fig.2 The qD-tDcurves of PEDM,m=0.5

  • lnq=lna-1ctm
    (22)
  • 若设:

  • α=lna
    (23)
  • c=1β
    (24)
  • 则得:

  • lnq=α-βtm
    (25)
  • 再利用(25)式进行线性迭代试差法求解。当m 值为 0~1 时,可按步长为 0.05 给定不同的 m 值,求得相关系数最高直线的m值,即为欲求的正确m值,并由(25)式进行线性回归,确定直线的截距α、斜率 β 和相关系数 R2。最后,由(23)式和(24)式分别确定ac值。

  • 5 应用实例

  • 将美国宾州 Marcellus页岩气藏的 M1和 M2井投产后的产量递减数据[11] 绘于图3,利用线性迭代试差法,由(25)式求得两口井的最佳直线关系并绘于图4。由图4的线性回归求得:M1井的 m 值为 0.5,α值为 6.460 6,β值为 0.280 5,相关系数为 0.990 0;M2 井的 m 值为 0.5,α值为 5.837 3,β值为 0.277 9,相关系数为 0.994 0。由(23)式和(24)式分别求得两口井的ac值:M1井的ac值分别为639.44和3.57; M2井的 a c 值分别为 342.85 和 3.60。将两口井的 acm 值分别代入(5)式,得 M1和 M2井的产量预测公式分别为:

  • 图3 M1和M2qt的关系

  • Fig.3 The q-t curves of M1 and M2 wells

  • 图4 M1和M2井的lnqt m最佳的直线关系

  • Fig.4 The optimal linear lnq-t m relations of M1 and M2 wells

  • q=639.44×e-t0.5/3.57
    (26)
  • q=342.85×e-t0.5/3.60
    (27)
  • 由(26)式和(27)式分别预测两口井的理论产量并绘于图3。由图3可以看出,预测曲线与实际数据符合得很好。

  • 将 M1和 M2井的 mc值分别代入(11)式,将预测得到的两口井的递减率绘于图5。由图5可见,两口井的递减率随时间的变化基本一致,这与两口井的mc值均基本相同有关。

  • 图5 M1和M2井的Dt的关系

  • Fig.5 The D-t relations of M1 and M2 wells

  • 将 M1和 M2井的 m 值代入(7)式,可得两口井的完全伽马函数,Γ(1/m)=Γ(2)=1.0。将2口井的完全伽马函数值以及acm值分别代入(6)式,可得M1 和M2井的可采储量分别为:

  • GR=639.44×3.571/0.50.5×1.0=16299×104=1.6299×108m3
    (28)
  • GR=342.85×3.601/0.50.5×1.0=8887×104=0.8887×108m3
    (29)
  • 6 结论

  • 通过对广义单峰周期预测模型的简化,得到预测页岩气井投产即进入递减的泛指数递减模型。该模型适用性较强,可对不同页岩气井的产量、可采储量和递减率进行预测。泛指数递减模型的递减指数为 0~1。随着 m值的增加,产量的递减率增加,随着 c 值的增加,产量的递减率减小。由 m=0.5 和 m=1可分别得到 0.5型的泛指数递减模型和著名的指数递减模型。由于 M1和 M2井的 mc 值均基本相同,因而两口井的递减率几乎是重合的。实例应用结果表明,所建立的泛指数递减模型是实用有效的。

  • 符号解释

  • a——广义单峰周期预测模型和泛指数递减模型的产量常数,104m3/mon;

  • b——广义单峰周期预测模型的峰位指数,dim;

  • c——广义单峰周期预测模型和泛指数递减模型的时间常数,mon;

  • D——递减率,mon-1

  • GR——页岩气井可采储量,104m3

  • m——泛指数递减模型的时间指数,dim;

  • q——页岩气井产量,104m3/mon;

  • q0——当t=0时的初始理论产量,104m3/mon;

  • qD——无因次产量,dim;

  • qpeak——广义单峰周期预测模型的峰值产量,104m3/mon;

  • R2 ——相关系数,dim;

  • t——生产时间,mon;

  • tD——无因次时间,dim;

  • tpeak——广义单峰周期预测模型峰值出现的时间,mon;

  • Z——完全伽马函数的变量;

  • αβ——泛指数递减模型最佳直线的截距和斜率;

  • Γ(Z+1)——完全伽马函数。

  • 参考文献

    • [1] 陈元千,周翠.线性递减类型的建立、对比与应用[J].石油学报,2015,36(8):983-987.CHEN Yuanqian,ZHOU Cui.Establishment,comparison and ap⁃ plication of the linear decline type[J].Acta Petrolei Sinica,2015,36(8):983-987.

    • [2] 陈元千,齐亚东,傅礼兵,等.井控页岩气可动地质储量和可采储量的评价方法[J].油气地质与采收率,2018,25(4):73-78.CHEN Yuanqian,QI Yadong,FU Libing,et al.Methods for esti⁃ mating well-controlled movable in-place and recoverable re⁃ serves of shale gas[J].Petroleum Geology and Recovery Efficien⁃ cy,2018,25(4):73-78.

    • [3] 陈元千,唐玮.广义递减模型的建立及应用[J].石油学报,2016,37(11):1 410-1 413.CHEN Yuanqian,TANG Wei.Establishment and application of generalized decline model[J].Acta Petrolei Sinica,2016,37(11):1 410-1 413.

    • [4] 陈元千,傅礼兵.幂函数递减模型的建立、对比与应用[J].油气地质与采收率,2019,26(6):87-91.CHEN Yuanqian,FU Libing.Establishment,comparison and ap⁃ plication of power function decline model[J].Petroleum Geology and Recovery Efficiency,2019,26(6):87-91.

    • [5] 陈元千,郝明强.多峰预测模型的建立与应用[J].新疆石油地质,2013,34(3):296-299.CHEN Yuanqian,HAO Mingqiang.Establishment and application of the multi⁃peak forecasting model[J].Xinjiang Petroleum Geolo⁃ gy,2013,34(3):296-299.

    • [6] 陈元千.对翁氏预测模型的推导及应用[J].天然气工业,1996,16(2):22-26,102.CHEN Yuanqian.Derivation and application of Weng’s predica⁃ tion model[J].Natural Gas Industry,1996,16(2):22-26,102.

    • [7] 陈元千,胡建国.预测油气田产量和储量的Weibull模型(为纪念克拉玛依油田勘探开发40周年而作)[J].新疆石油地质,1995,16(3):250-255,287.CHEN Yuanqian,HU Jianguo.Weibull model for predicting out⁃ put and reserve in an oil and gas field[J].Xinjiang Petroleum Ge⁃ ology,1995,16(3):250-255,287.

    • [8] 陈元千.瑞利模型的完善推导与应用[J].油气地质与采收率,2004,11(4):39-41.CHEN Yuanqian.The perfect derivation of Rayleigh model and its application[J].Petroleum Geology and Recovery Efficiency,2004,11(4):39-41.

    • [9] LANCZOS C A.Precision approximation of gamma function[J].Journal of the Society for Industrial and Applied Mathematics:Se⁃ ries B,Numerical Analysis,1964:1 186-1 196.

    • [10] ARPS J J.Analysis of decline curves,Trans[J].AIME,1945,160:228-247.

    • [11] 何培,冯连勇,TOM Wilber.马塞勒斯页岩气藏单井产量递减规律及可采储量预测[J].新疆石油地质,2015,36(2):249-252.HE Pei,FENG Lianyong,TOM Wilber.Production decline rule and recoverable reserves prediction of Marcellus shale gas well in a production unit,Pennsylvania,US[J].Xinjiang Petroleum Geol⁃ ogy,2015,36(2):249-252.

  • 参考文献

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