抽油泵漏失系数的概念与计算方法修正

DOI :10. 16082/j . cn ki . issn . 1001-4578. 2004. 03. 005

　　石　油　机　械

CHINA PETROLEUM M ACHINERY 2004年　第32卷　第3期 设计计算

　　　　　　·13·

抽油泵漏失系数的概念与计算方法修正

杨海滨　张　琪

(石油大学(华东) 石油工程学院)

　　摘要　有杆抽油系统中抽油泵容积效率的计算一般由柱塞行程损失系数、泵筒的充满系数、

漏失系数和抽汲液体的体积效应系数等4部分构成。从分析抽汲液体的损失排量角度分析了各系数的含义, 并指出传统漏失系数的概念与计算方法存在的问题。一般认为, 抽油泵的漏失系数为其理论排量和漏失量的差值与理论排量之比, 按此概念进行计算会得出不同的容积效率。鉴于此, 给出了漏失系数相应的概念与修正的计算方法, 并得出以下结论:(1) 泵漏失系数是进入泵筒内的液量和泵筒内液体漏失量之差与进入泵筒内液量之比; (2) 传统算法所计算的漏失系数大于修正方法所计算的漏失系数; (3) 各损失排量分别计算有助于泵效分析; (4) 现场应用中, 分析泵效应考虑油管的漏失。

　　关键词　抽油泵　容积效率　漏失系数　概念　计算方法　修正

理论排量之比, 即

引　　　言

抽油泵的漏失是影响抽油泵容积效率的主要因素之一。在油藏条件不变的情况下, 抽油泵在井下工作期间, 泵效是逐步下降的, 主要原因就是泵的漏失。因此, 正确理解泵的漏失概念有着十分重要的意义。

通过计算抽油泵的损失排量会有助于分析各因素影响泵效的程度。泵效在整个机采系统效率中占有重要的比重, 准确地计算泵效, 也有助于对机采系统效率的理解。

η=

Q T -ΔQ

Q T

(2)

　　考虑到泵效影响因素, 则有

η=ηβηλl ηB

(3)

式中　η——考虑抽油杆柱和油管柱弹性伸缩后的λ—柱塞冲程与光杆冲程之比, 表示杆、管弹性伸缩对泵效的影响;

　β———进入泵内液体体积与柱塞让出的泵内体积之比, 表示泵的充满程度;

　η——泵漏失对泵效影响的漏失系数; l —　ηB ———原油到达地面后的体积与其进入泵内的体积之比。

　　下面对各部分损失排量进行计算。损失排量主要包括柱塞行程损失、泵筒充满程度、泵漏失和液体体积系数影响4个部分[2]。

1. 柱塞行程损失

　　由于柱塞冲程S p 小于悬点冲程S , 理论排量的定义是Q T =1440f p Sn (f p 为柱塞截面积, m ; n 为冲次, 1/min ) , 从而形成由于行程损失减少的排量, 所减少的值ΔQ 1为

2

抽油泵损失排量的计算

生产现场中所定义的泵效是泵的实际排量Q 与其理论排量Q T 的比值[1], 用η表示, 即

η=

Q T

(1)

　　这实际上是泵的容积效率概念。泵的容积效率η是泵的理论排量Q T 和泵的损失排量ΔQ 之差与

杨海滨, 教授级高级工程师, 生于1959年, 1982年2月毕业于大庆石油学院, 后获南京理工大学工学硕士学位, 现为石油大学(华

东) 在读博士生, 在江苏油田科技处从事科技管理工作。地址:(225009) 江苏省扬州市文汇西路1号。电话:(0514) 7760155。E -mail :yanghb @joeco . com . cn 。

(收稿日期:2003-05-26; 修改稿收到日期:2003-07-12)

ΔQ 1=1440f p n (S -S p )

p

根据定义, ηλ, 于是

S

ΔQ 1=(1-η) Q T λ

的量并非是理论排量的(1-η倍, 而是进入泵筒l ) 内液体的(1-ηl ) 倍。进入泵筒内的液体排量应是

(4)

1440f p S p n β或ηλβQ T , 式(7) 的漏失系数应修正为

ηβQ T -ΔQ 3λ

η(13) l =ηβQ T λ　　则式(8) 因漏失而损失的排量ΔQ 3修正为

ΔQ 3=ηβ(1-ηQ T λl )

(14)

　　漏失部分的排量并未变为实际排量, 受液体体积系数影响的排量应该是1440f p S p n β-ΔQ 3, 于

是

Q ′=ηβQ T -(1-ηηβQ T λl ) λ

　　ΔQ 4=Q ′-Q , 则式(10) 修正为

ΔQ 4=ηλβηl (1-ηB ) Q T

4

　　2. 泵筒的充满程度

由于上冲程时进入泵筒的液体体积V y 小于上冲程活塞让出的体积V p , 于是有充满系数β,

V y

β=(5)

V p

　　因液体充满程度的影响而减少的排量为ΔQ 2。泵筒内所减少的液体体积正是进入泵筒内的气体体积V g , V g =V p -V y , 则ΔQ 2=1440f p S p n (1-β), 于是

ΔQ 2=η(1-β)Q T (6) λ　　3. 泵的漏失影响

由于泵的漏失所减少的排量为ΔQ 3, 根据参考文献[2]的定义,

ηl =

则

Q T -ΔQ 3

Q T

ΔQ 3=(1-ηQ T l )

(7) (8)

(15)

　　ΔQ =

∑ΔQ i

i =1

, 把式(4) 、(6) 、(14) 和

(15) 代入后得

ΔQ =[(1-η) +η(1-β)+λλ

ηβ(1-η+ηβη1-η]Q T λl ) λl (B )

　　将式(16) 代入式(2) 得

η=1-[(1-η) +η(1-β)λλ

+ηβ(1-η+ηβη1-η]λl ) λl (B )

　　化简后, η=ηβη3) 相符。λl ηB , 与式(

下面, 将两种漏失系数的算法进行比较。首先令参考文献[2]中所定义的漏失系数为

′ηl , 修正后的漏失系数为ηl , 则有

′

ηl =

(16)

4. 液体体积系数影响

由于液体体积系数B l 的影响, 使得地面实际排量Q 小于泵筒实际排量Q ′, 根据定义,

ηB ==(9)

B l Q ' 　　泵筒内的实际排量为进入泵筒内的液量减去泵

的漏失量, 则有Q ' =S p n β-(1-ηQ T =(ηβ+ηQ T l ) λl -1) 　　根据式(9) , Q =η, 于是B Q ′

Q =(ηβ+ηηλl -1) B Q T

　　因液体体积系数的影响而损失的排量ΔQ 4=Q ′-Q , 则有

ΔQ 4=(ηλβ+ηl -1) (1-ηB ) Q T

(10)

Q T -ΔQ 3

Q T

(17) (18)

ηl =

ηβQ T -ΔQ 3λ

ηβQ T λ

　　式(17) 和式(18) 分别除以Q T 和ηβQ T , λ得

′

ηl =1-

　　总的排量损失, 亦即理论排量与实际排量之差

ΔQ 有

4

ΔQ 3ΔQ 3

, ηl =1-ηλβQ T Q T

　　ΔQ =

∑ΔQ l

i =1

=(1-ηβηQ T (11) l -ηλB -ηl ηB +ηB )

　　把式(11) 代入式(2) 有

η=η(12) l +ηl βηB +ηl ηB -ηB 　　显然, 式(12) 与式(3) 不符。经研究发现,

如果按式(3) 计算泵效, 泵的漏失系数需要重新定义。

∵　　　ηλ

ΔQ 3ΔQ 3ΔQ 3ΔQ 3

∴　　　1-Q T ηβQ T Q T ηβQ T λλ　　因此, ηl ′>ηl 。这说明, 传统算法的漏失系数大于修正后算法的漏失系数, 而所算的漏失量前者小于后者。

既然泵效的概念是建立在现场应用基础上, 那么泵效的计算就有必要考虑产出液在举升过程中油管的漏失, 尤其是一些老井油管漏失是一种较常见的现象。分析泵效时, 把油管漏失归咎于泵显然是不合理的。现假定油管的漏失系数为ηlt , 其定义为, 进入油管的液体排量和油管漏失量ΔQ 5之差

漏失系数概念与计算方法的修正

由于抽油泵的漏失减少了理论排量, 而所漏失

与进入油管液体排量之比, 即

ηlt =

ηλβηl ηB Q T -ΔQ 5

ηλβηl ηB Q T

(19)

到说明。

现以理论计算的泵效值作为计算依据, 并认为

修正后泵无漏失。那么, 修井前泵的漏失量ΔQ 3=13. 42t /d 。

(20)

如果根据式(17) 进行漏失系数计算

′

η=0. 5908l =32. 8

　　而以修正后的漏失系数计算式(18) 进行计算η=0. 4517l =0. 82×0. 91×32. 8　　修井前的实际产液量为10. 3t /d 。根据计算, ηλ与ηB 未变, 分别为ηλ=0. 82, ηB =0. 97, β值因沉没度发生变化, 计算得β=0. 89。根据这3个参数及修正前后的两个漏失系数计算所得的修井前的泵效分别为0. 4182和0. 3197。显然, 修正后的漏失系数计算结果更接近实际值。

　　那么, 式(3) 可以修正为

η=ηβηλl ηB ηlt

　　需要说明的是, 在现场很难确定油管的漏失状况, 之所以提出油管漏失系数的概念, 主要目的是进一步完善泵效的理论概念; 此外, 由井口到计量站的漏失也未考虑, 如果现场管理比较完善, 这部

分漏失可以忽略。

实　例　分　析

江苏油田的C2-3号油井, 工作1a 后因泵漏失、泵效下降, 进行修井作业, 作业前后泵效分别为31. 5%和71. 8%,泵径为44mm , 泵挂深度为

1210m , 作业前后沉没度发生较小变化, 分别为410m 和348m , 油管无漏失, 该井作业前后的产液量分别为10. 3m 3/d 和23. 5m 3/d , 含水62%,冲程为2. 5m , 冲次为6min -1, 油管直径为62mm , 采用直径为19mm 的15NiMo 单级抽油杆, 作业前后均进行油管锚定且锚定可靠, 该油区饱和压力较低, 该油井地面生产油气比为16, 溶解系数为3. 81m 3/(m 3·M Pa ) , 计算中取声波在抽油杆中传播速度为4968m /s 。下面对该井的泵效及漏失进行计算分析。

根据美国石油学会推荐的有杆抽油系统设计计算方法标准API RP11L 计算冲程损失系数ηλ, 经计算并查表后得η0. 82, 计算中忽略余隙。λ=根据参考文献[1]中(3-94) 式, 求得泵充满系数β=0. 91。

经计算得该井的理论排量Q T =32. 8m /d 。在泵无漏失的条件下, 泵的容积效率应该是η=0. 724。计算结果与现场实测修井后的结果基本相符, 说明修井后泵基本无漏失, 现场示功图也得

3

结　　　论

(1) 泵漏失系数是进入泵筒内的液量和泵筒内

液体漏失量之差与进入泵筒内液量之比。

(2) 传统算法所计算的漏失系数大于修正后的方法所计算的漏失系数, 经实例分析得到验证。

(3) 各损失排量分别计算有助于泵效分析。(4) 现场应用中, 分析泵效应考虑油管的漏失。定义油管漏失系数为, 进入油管的液体排量和油管漏失排量之差与进入油管液体排量之比。

参　考　文　献

1　张　琪. 采油工程原理与设计. 山东东营:石油大学出

版社, 2000:134

2　沈迪成, 艾万诚, 盛曾顺等. 抽油泵. 北京:石油工业

出版社, 1994:195～204

(本文编辑　王志权

)

　科学开发石油资源, 创造绿色动力世界　

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