塔里木盆地北部油田水特征离子及意义
文章编号:0253 9985(2000)04 0372-02
塔里木盆地北部油田水特征离子及意义
周晓芬
(西北石油局规划设计研究院中心实验室,新疆乌鲁木齐830011)
摘要:塔里木盆地北部西达里亚、塔河1号及塔河3,4号油田的油田水具有相近的离子组成,其可溶物质主要成分与海水一致,表明其主要为海相成因。油田水中不同的离子组成及浓度指示特定的地质意义:HCO -3与地层密度具有良好的正相关关系,地层时代愈老,直线斜率愈大;SO 42-,Ca 2+,Mg 2+浓度的差异预示油田水的不同来源; -含量不受地层岩性影响,而由原油物性决定, -含量高,则原油物性就好;Br -浓度大于350mg/L 的油田水则是凝析油的特征。
关键词:油田水;特征离子;地质意义;塔北油田作者简介:周晓芬,女,38岁,工程师,化学中图分类号:TE133 文献标识码:A
油田水化学成分及含量的变化与地层的成因、储集性能和油气性质密切相关。塔里木盆地北部经过长期的油气勘探,积累了丰富的油田水资料。在该地区,油田水产层较多,主要为奥陶系、石炭系、三叠系及上第三系中新统苏维依组。不同油田的油田水特征差异明显,利用这些区别,可有效解决诸多地质疑点。
1 油田水成分
塔里木盆地北部油田的油田水以CaCl 2水型为主,矿化度为200 103
mg/L 左右。西达里亚、塔
河1号、塔河3号及塔河4号的油田水有着相近的离子组成及含量(表1),推测它们来自同一水源,
表1 塔北油田水主要离子含量平均值/mg L -1
Table.1 Average value of major ionic contents of oilfield water in North T arim Basin
油田Cl -(Na ++K +)Ca 2+Mg 2+SO 42-HCO -3I -Br -塔河3,4号(O 1)111 10349 6 10318 9 103244523225811 7361塔河3,4号(C 1)125 10366 5 10311 5 1035114411524 289 3塔河1号(T)130 10
3
69 6 103
10 8 103
12103121384 5227塔河2号(T)
136 10374 1039 1 103
20721871784 2233雅克拉(K 1)65 9 103
36 8 1032 7 10
3
759
16985327 8120
西达里亚(T)134 10372 4 10310 7 10312832611284 1257巴楚(C 2)
48 103
48 103
2 1 103
466
2350
853
27 8
119
收稿日期:2000 03 06
与现代海水离子浓度具有较好的可比性(表2),因
此,它们可能源自同一海相成因的地表水。
表2 塔北油田水与现代海水离子浓度对比表Table2 Comparison of ionic concentration between oilfield water
in North Tarim and sea water
类型HCO -3SO 42-Cl -Ca 2+Mg 2+Na +现代海水0 417 6855 041 153 6930 62油田水0 0840 1661 205 600 0732 30河水
58 5
11 2
2 8
15
4 1
6 3
2 特征离子
2 1 HCO 3-油田水中的HCO 3-
来源于成岩过程中有机质
分解的C O 2:
H 2O+C O 2 H 2C O 3(1)
H 2CO 3 HC O -3+H +(2)HC O -3+H + 2H ++CO 3
2-(3)
pH 值为5时(1)式成立,pH 值为6 3时(2)式
成立,pH 值为10 3时(3)式成立。由此可以看出
HC O 3-含量与溶液中H +浓度密切相关。塔北油田
第21卷 第4期
石油与天然气地质
OI L &GAS GEOLOGY
2000年12月
水的pH 值普遍在5~6之间(巴什托构造的某些井在7左右),有利于HCO -3存在。统计结果表明:塔河油田水HCO 3-与密度有良好的线性关系,时代愈老,线性关系的斜率愈大(图1,2,3)
。
图1 塔河油田石炭系地层水HCO 3-与密度比值的关系Fi g.1 Relati onship bet ween HC O -3of formation water and
rock density in Carboniferous T ahe
Oilfield
图2 塔河油田奥陶系地层水HCO 3-与密度比值的关系Fig.2 Relationship betwee HCO -3of Tertiary formatin
water and the specific value rock density in T ahe
Oilfields
图3 塔河油田三叠系地层水HCO 3-与密度比值的关系Fig.3 Relationship between HCO -3of formation water and
rock density in Ordovician Tahe Oilfield
2 2 Ca 2+,Mg 2+,SO 4
2-
塔北不同区块的油田水其Ca 2+,Ma 2+,SO 42-浓度存在明显差异:巴什托麦6、麦4、麦10井,巴参1井及塔河3号、4号S46等井石炭系油田水的SO 4
2-
浓度比塔北其它区块高一个数量级左右。雅
克拉构造上的YK 1、沙参2、沙7井SO 4
2-
浓度最
低,一般在100mg/L 左右。另外,(Ca 2+
+Mg 2+
)与SO 42-浓度在不同的层位具有不同的关系(图4),据此可以较好区分塔北各油田的油田水。
2 3
-
油田水中的 -主要来源于海藻及其它海相有机物,浓度的高低反应了该地层古代海水中海藻及其它海相有机物的丰度。塔北油田的油田水中,巴什托油气田石炭系的 -含量最高,一般在16mg/L 至50mg/L 之间;雅克拉油田下白垩统的 -含量次之,在10mg/L 至15mg/L 之间;其它地区较低。统计结果表明:塔北油田 -
含量与地层岩性无关,而与原油性质关系密切,原油密度小 -
含量就高。
图4 塔北地层水SO 42-浓度与Ca 2+,Mg 2+浓度关系Fig.4 Concen trating relationship between SO 2-4
Ca 2+and Mg 2+of formation water in North Tarim Basin
1!塔河奥陶系;2!塔河石炭系;3!塔河三叠系;
4!塔北下白垩统;5!巴楚石炭系
2 4 Br -塔北油田水中,Br -浓度大于350mg/L 的钻井有T402井、TK104井、S22井、S32井、DK10井及沙
参2井,最高可达900mg/L;另外,B r -
/总矿物大于
0 15 的井有T402井、沙参2井、TK10井、麦4井、沙32井、沙22井、DK10井、沙38井、麦10井、麦6井、沙29井及YK1井等。上述这些井的原油多为凝析油。因此在塔北油田可以将Br -浓度大于350mg/L,Br -/总矿物大于0 15 作为凝析油的判识指标。
3 结论
(1)塔北油田水主要来自于海相水;
(2)油田水中HCO -3浓度与地层密度正相关;(3)不同油田水的Ca 2+
,Mg 2+
与SO 42-
相对浓
度具有显著差异。
(4)Br -浓度可作为判识凝析油的一个指标。
373
第4期 周晓芬:塔里木盆地北部油田水特征离子及意义
CHARACTERISTIC IO NS OF OILFIELD WATER IN NORTHERN
TARIM BAS IN AND ITS S IGNIFICANCE
Zhou Xiaofen
(Central Laboratory o f Plannin g and Designing Institute,Northwest Bureau o f Petroleum,CNPC,U rumqi,Xing j iang) Abstract:The oilfield water in xidaliyia,Tahe 1,Tahe 3and Tahe 4Oilfields in Northern Tarim Basin has similar ionic composition,and the principal compositions of soluble materials are consistent with sea water,suggesting its marine ori gin.The different ionic compositions and concentration indicate different geological features.HC O-3has positive coher ence with the strata density,the concentration differences of SO2-4,Ca2+,Mg2+indicate different origin of the water. The content of I-is determined by physical features of crude oil but not lithologic feature,and bears negative coherence with the density of crude oil.When c oncentration of Br-in oilfield water is more than350mg/L,the oil would be con densate oil.
Key Words:oilfield water;characteristic ion;geological significance;North Tarim Oilfield
(上接第365页)
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ANALYS IS OF PETROLEUM S YSTEM IN NANPU SAG
Liu Yunhua1 Zhou Haimin2 Xiong Baoxian3 Li Yonglin3 He Huiqiang2
(1.Changsha Institute o f Geotectonics,Chinese Academy of Sciences,Changsha,H unan;
2.China Unive rsity o f Geosciences,Wuhan,Hubei;
3.China University o f Geosciences,Beijing)
Abstract:According to oil source rock correlation,there are two petroleum systems in Nanpu Depression.One is Shahe jie Formation petroleum syste m,the other one is Dongying Formation petroleum syste m.The source rocks of Sha 3mem ber of the first system began oil generation in the late stage of Dongiyng Formation,and formed self generation self reservoiring oil pools;the source rocks of the system began secondary oil generation in late Minghuazhen Formation,and formed Tertiary secondary oil pools.As for the second syste m,the source rocks of the third member of Dongying Forma tion in the south side of Gaoliu Fault started oil generation in the late stage of Minghuazhen Formation,and formed self generation self reservoiring oil pools of Dongiyng Formation and Tertiary secondary oil pools,but no hydrocarbon pools could be found in the north side of the faults.So it is suggested that hydrocarbon exploration should aimed at the petroleum syste m of Shahejie Formation in Gaoshangpu and Liuzan areas of the sag,and the Dongying Formation petroleum system in Beipu and Laoyemiao areas.
Key Words:petroleum system;cri tical moment;hydrocarbon pool;Nanpu Sag
374石油与天然气地质 第21卷