油层含油性判别分析

文章编号:1000-2634(2004)01-0013-03
油层含油性判别分析Ξ
唐洪
(西南石油学院资源与环境学院,四川南充637001)
摘要:大安寨油组是川中油田的主力产油层,油气多产于碳酸盐岩地层,开采时间较长,不少井产量下降,甚至枯竭,因而研究大安寨油井含油特征、预测产能是十分必要的。

根据试油井段的产能分析,将储层分为干层、低产层和高产层三类;应用测井、地质及试油试采资料,归纳出不同类型产层的定性特征;并建立起判别产层的模型,形成一套选取产层和预测产能的方法。

关键词:产能预测;含油特征;大安寨
中图分类号:TE122.112 文献标识码:A
引　言
川中地区大安寨组是川中油田的主力产油层,
也是四川盆地主要的陆相产油层系,在多年钻探成
果的基础上,前人对川中大安寨油气产层已做了大量工作,如储层特征,油气分布特征等。

但由于大安寨油气多产于碳酸盐岩地层,开采时间较长,不少井产量下降,甚至枯竭,且大安寨是多层油气藏,因而研究大安寨油井含油特征、预测产量是十分必要的。

本文应用测井、地质及试油试采资料,归纳出不同类型产层的定性特征;并建立起判别产层的模型,形成一套选取产层和预测产能的方法。

大安寨时期川中位于四川盆地的中间地带;随着湖泊的扩张、
退缩。

该区形成了介屑滩,黑色页岩夹薄层泥灰岩以及介壳灰岩与黑色页岩互层的连续沉积。

大安寨油藏储集岩为介屑灰岩,厚10～40m,主要产油区域中,一般单层厚1～3m,物性甚差,普遍见微小裂缝。

1　测井曲线特征
通过对67口井104个试油层段的产能进行分析,可将大安寨储集层分为干层,低产层,高产层。

其中,低产层为产能低于1t/(D・m)层段,而高产层段则大于1t/(D・m)。

对各类层段的双侧向、声波时差曲线研究、对比发现,不同类型的层段的测井曲线特征是不同的。

1.1　干层
干层的测井曲线可分为两类(见图1)。

图1　干层测井曲线特征
(1)深、浅侧向较低(金华地区的小于200Ω・m,
第26卷　第1期 西南石油学院学报 Vol.26　No.1　2004年　2月 Journal of S outhwest Petroleum Institute Feb　2004　Ξ收稿日期:2003-03-28
作者简介:唐洪(1973-),女(汉族),四川中江人,在读博士,从事开发地质、石油地质教学和科研工作。

八角地区可达300Ω・m ,幅度小,正、负均有;声波时
差较高,多大于190μs/m。

图2　低产层测井曲线特征
(2)深侧向远大于浅侧向,深侧向一般为200～
300Ω・m ;声波时差低于
190μs/m 。

1.2　低产层
低产层测井曲线特征为:层段内双侧向和声波时差曲线较平直,电阻率值一般在100～200Ω・m ,有的也可高达400～500Ω・m ,幅度差小,多小于50Ω・m 。

声波时差小于160μs/m (见图2)。

1.3　高产层
高产层测井曲线也可分为两类(见图3)。

(1)电阻率值高,深测向均大于1000Ω・m ,正幅差,其值集中于200～300Ω・m ,有的可达1000Ω・m ;声波时差较低,为160～170μs/m 。

(2)深、浅测向值较低,在500Ω・m 左右,幅差值多为50～100Ω・m ;声波时差为160～170μs/m ,且呈锯齿状。

2　定量判别和产能预测
2.1　两组判别分析
利用两个母体(A ,B )的P 个判别变量构成一个适合的综合判别指标,这个判别指标即判别函数,记作Y =Y (X 1,X 2,…,X P ),A ,B 两类中的每个样品(设A 有i 个,B 有j 个样品)均可分析出X 1,
X 2,…,X P 值,代入判别函数中就可求出一个判别
值Y i (A ),Y j (B ),用Y (A )、Y (B )分别表示
Y i (A )、Y j (B )的平均数,通过判别分析的方法,可
以求出一个介于Y (A )和Y (B )之间的判别指标
Y C ,若Y (A )≥Y (B ),则代判别样品中其判别样
品的判别值Y ≥Y C ,就判别它属于A ;当Y <Y C 是就判别其属于B 。

反之,若Y (B )≥Y (A ),则代
判别样品中其判别样品的判别值Y ≥Y C ,就判别
它属于B ;当Y <Y C 是就判别其属于A 。

求取判别指标的准则是使两组新变量的均值之差为最大,且各组组内离差平方和为最小。

2.2　干层与产层的判别
对已知的产层段和干层段进行两组判别分析,建立判别函数如下:
Y =1.5946×10
-4
×R td +2.067×10-4×
R tl -4.6147×10-3×
ΔT Y (A )=-0.6335　Y (B )=-0.8744Y C =-0.7368
式中:Y (A )、Y (B )—分别为产层、干层Y 的平均值;Y C —综合判别指标;R td 、R tl —深、浅测向电阻率值;ΔT —深波时差。

41西南石油学院学报 2004年
经回判验证(见表1),误判率为21.5%。

表1　产层与干层段的判别结果
产 层 段
井号R td R tlΔT判别值回判
金132********.0-0.778B
金44370240175-0.4A
金46280180187.5-0.632A
金47650600187-0.699A
角29800850172.5-0.7834B
金1112501400152.5-0.6352A
金23550520200-0.647A
角853********.5-0.4928A
干 层 段
金20180180177.5-0.7533B
角34340260195-0.7919B
角82700270162.5-1.012B
金33280200165-0.6754A
金267580215-0.9637B
金883428230-1.05B
2.3　高产层与低产层的判别
Y=-3.9745×10-4×R td+9.984×10-5×
R tl-2.5967×10-3×ΔT-0.049533×X
Y(A)=-0.652 Y(B)=-0.825
Y c=-0.748
式中:Y(A)、Y(B)—分别为高产层、低产层Y的平均值;Y C—综合判别指标;R td、R tl—深、浅测向电阻率值;ΔT—声波时差;X—(1/(((X3-156)/464)2)×X1))1/2。

经回判(见表2),对高产层段的判别完全正确,低产层中有3层误判为高产层,其误判率为15%。

2.4　产能预测
对连续的射孔试油层段作产能与测井参数的相关关系研究表明:根据产能分类以后,高产层段的产能与电阻率、声波时差呈正相关;低产层段的产能与电阻率、声波时差均呈负相关关系。

用回归分析的方法建立起高、低产层的产能预测公式如下:
高产层的产能预测公式
Y=X-0.1.055×3.458
X=(0.6/(((ΔT-156)/464)2.5×R td))0.4
低产层的产能预测公式
Y=X0.1897×0.4347
X=1/(R t d×ΔT)×105
式中:Y—产能;R td—深测向电阻率;ΔT—声波时差。

对单层连续射孔层段进行检验(见表3),产能的误差为0.2t/D・m左右。

表2　高产层与低产层段的判别结果
高 产 层 段
井号R td R tlΔT X判别值回判
金10190200175 1.77-0.5977A
金132402251870.97-0.6066A
金37550540170 1.41-0.676A
金44370240175 1.27-0.6404A
金46280180187.50.88-0.6238A
金476506001870.59-0.7133A
金483203001900.76-0.6283A
角29800850172.50.99-0.7301A
明186********.88.32-0.7648A
低 产 层 段
金1112501400152.5 3.75-0.9388B
金235505202000.45-0.7083A
金2911501250182.50.52-0.832B
金30510400172.5 1.25-0.6726A
角81540189153.5 6.66-0.923B
角853********.5 1.25-0.6099A
角8812505501850.45-0.9446B
角891200400187.50.43-0.9408B
角9215001500165.0 1.33-0.9408B
表3　产能预测检验结果
井号属性干层判别结果产层判别结果预测产能实际产能
金10高产-0.7359产层-0.5976高产 1.348 1.27
金37高产-0.5852产层-0.676高产 1.53 1.81
金48高产-0.7637干层
金29低产-0.4504产层-0.8319低产0.55580.25
金30低产-0.6320产层-0.6726高产
金81低产-0.5808产层-0.9230低产0.76180.57
角88低产-0.5407产层-0.9446低产0.50960.31
误判率 14.2%　14.2%
3　结　论
(1)大安寨储集层可按产能分为干层、低产层、高产层三类:它们分别有不同的测井曲线特征。

(2)大安寨组的干层、高产层、低产层可以通过以上模型中的判别函数进行判别,并对产层进行产能预测。

参考文献:
[1]　邓良全.用测井资料对四川碳酸盐岩的老井选层[J].
西南石油学院学报.1992,14(2):30-37.
(编辑　罗先碧)
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第1期 唐洪:　油层含油性判别分析　
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