气田污水处理回注系统腐蚀机理与防护对策研究 精品.docx

气田污水处理回注系统腐蚀机理与防护对策研究 精品.docx

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气田污水处理回注系统腐蚀机理与防护对策研究精品

长庆油田分公司

科技攻关项目

汇报材料

气田污水处理回注系统腐蚀机理

与防护对策研究

2007年12月

气田污水处理回注系统腐蚀机理与防护对策研究

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2007年12月

目录

前言·······················································································································1

第一章靖边气田污水处理系统存在的主要故障·················································2

1靖边气田回注污水的处理工艺及现状···························································2

1.1净化厂回注污水的处理工艺及现状··························································2

1.2北二区、南二区回注污水的处理工艺及现状············································3

2污水的处理系统存在的主要故障···································································4

2.1污水处理和回注系统存在严重的腐蚀现象··············································4

2.2污水处理和回注系统存在严重的结垢现象··············································6

2.3污水中微生物的大量繁殖··········································································6

2.4污水处理系统出水水质不合格··································································6

3小结···················································································································6

第二章气田污水处理系统回注污水的腐蚀机理及影响因素分析·····················8

1气田采气工艺特点及污水的水质特点···························································8

1.1采气工艺流程······························································································8

1.2第一采气厂天然气气体组成······································································8

1.3气田污水的组成性质分析··········································································8

1.3.1水质分析···································································································8

1.3.2污水处理系统出水（回注污水）中悬浮物粒径分布·····························10

2第二净化厂回注污水管线附着物组成分析·················································11

3腐蚀倾向的判断·····························································································12

4污水处理系统腐蚀因素及腐蚀机理·····························································12

4.1H2S和CO2的腐蚀作用···············································································12

4.1.1硫化氢腐蚀·····························································································12

4.1.2二氧化碳的腐蚀·····················································································14

4.2溶解氧的腐蚀作用····················································································15

4.3细菌的腐蚀作用························································································15

4.4溶解氧引起的腐蚀····················································································16

5气田污水处理及回注污水的腐蚀影响因素的研究·····································17

5.1矿化度对不含醇污水的腐蚀影响····························································17

5.2pH值对不含醇污水的腐蚀影响······························································18

5.3H2S含量对不含醇污水的腐蚀影响··························································19

5.4CO2含量对不含醇污水的腐蚀影响·························································21

5.5四种回注污水的腐蚀规律研究································································21

6小结·················································································································23

第三章第一采气厂污水处理及回注系统腐蚀控制方法及耐蚀金属材料、缓蚀

剂的的选择与性能评价···········································································24

第一部分控制腐蚀的方法···················································································24

1控制腐蚀的关键环节·····················································································24

2腐蚀的控制技术·····························································································25

2.1合理的设计································································································25

2.2正确选用金属材料····················································································25

2.3改变腐蚀环境····························································································25

2.4电化学保护································································································26

2.5用耐腐蚀非金属材料代替金属材料························································26

2.6采用耐腐蚀覆盖层····················································································26

2.7使用化学药剂····························································································27

3小结·················································································································27

第二部分气田污水处理及回注系统耐蚀金属材料的选择与性能评价···········27

1气田回注系统耐腐蚀材质的选择·································································27

1.1超高强度油井管························································································27

1.2高压套管····································································································28

1.3防腐蚀套管····························································································28

1.4特殊螺纹油井管························································································28

1.5连续管········································································································28

1.6膨胀管········································································································29

1.7抗CO2腐蚀油井管·····················································································29

1.8不锈钢系列································································································29

2气田回注污水耐腐蚀材质的性能评价·························································30

3小结·················································································································30

第三部分缓蚀剂的筛选及性能评价···································································31

1缓蚀剂的选择及作用机理·············································································31

2缓蚀剂的筛选及性能评价·············································································32

2.1静态挂片缓蚀试验····················································································32

2.2静态酸性缓蚀试验····················································································33

2.3动态挂片缓蚀试验····················································································34

2.4缓蚀剂加药量与缓蚀率的关系································································34

2.5缓蚀剂不同温度下的缓蚀性能································································34

2.6模拟现场动态腐蚀试验············································································35

3细菌腐蚀的控制·····························································································36

3.1油田细菌腐蚀的危害················································································36

3.2杀菌剂评价方法························································································36

3.2.1镜检法·····································································································36

3.2.2标准平皿计数法·····················································································36

3.2.3液体稀释法·····························································································36

3.3杀菌剂WT-809的杀菌效果······································································37

4缓蚀剂、杀菌剂的配伍性能···········································································37

5小结·················································································································38

第四章气田回注污水处理系统的防腐处理方法和工艺流程研究···················39

1气田回注污水处理系统防腐处理方法的确定·············································39

2气田回注污水处理系统工艺流程的确定·····················································40

第五章结论···········································································································41

前言

随着靖边气田的逐步开发，局部区块开始产出地层水，气田污水总量在逐渐增大，不含醇污水量也越来越大，造成目前的污水处理工艺和处理能力已不能满足生产需要，严重影响了气田的正常生产和富水区中的储量动用，增加了气田生产组织难度。

随着开发规模的扩大及富水区块的全面开发，产水井、产水量会不断增加，产水井的合理开发和污水拉运、处理之间的矛盾将更加突出。

靖边气田的主力气层为下古奥陶系马家沟组，该产层在局部区块产出地层水。

通过长期动态监测，结合静态分析，认为目前整个气田范围内存在北二区、陕5井区、陕93井区和陕181井区四个产水区，另外还有32个产水井点。

目前水体面积738.05km2，投产井中有48口产出地层水，占靖边气田投产井总数的20.48%，所产污水约占气田污水总量的60%以上。

目前采气一厂建成的气田污水（设计）处理能力为700m3/d，分为含醇污水处理和不含醇污水处理两种工艺，其中气田含醇污水设计处理能力300m3/d，气田不含醇污水设计处理能力400m3/d。

含醇污水处理系统包括污水预处理、甲醇回收、污水回灌等处理单元，第一采气厂含醇污水处理装置主要建在三座天然气净化厂内，其中甲醇再生装置是含醇污水处理的关键设备，目前共有4套装置。

不含醇污水处理系统主要建在靖边气田两个较大的富水区，即南二区和北二区。

产出污水，连同生产污水、检修污水、循环水排污水等经过处理后，回注地下，由于天然气产出污水中溶解有高浓度的CO2、H2S等腐蚀性气体，而且常含有大量的矿物质、悬浮物、机械性杂质及乳化油、烃类气体等。

使污水具有较强腐蚀性和较易结垢倾向性。

靖边气田污水的水质特点决定了其对金属设备和管线具有很强的腐蚀性。

使污水处理和回注系统长时间存在腐蚀、细菌滋生、出水固悬物超标等问题，导致污水处理及回注系统管线及油套管多处腐蚀穿孔，影响了生产的正常进行。

为解决这一长期存在的问题，经过大量的实验室研究，并根据我们对同类系统研究和处理的经验，确定出了适宜的污水处理方案和配套的化学助剂。

第一章靖边气田污水处理系统存在的主要故障

靖边气田含油含醇污水由于吸收天然气中的CO2、H2S等组分而显酸性，而且常含有大量的矿物质、悬浮物、机械性杂质及乳化油等，再加上在天然气开采过程中为了减缓腐蚀及防止水合物的生成，人们在井筒和地面管线中定期注入一定量的组成较为复杂的化学药剂和甲醇，这就使得采出污水成为一个含醇、含盐、含油、含大量机械杂质、呈酸性的具有较强腐蚀性和较易结垢的复杂且稳定的体系。

根据结垢理论分析和预测，这种水系统在常温常压下已有结垢趋势存在，在甲醇回收过程中，随着温度的增加，其结垢趋势将进一步增加。

所以气田含油含醇污水在高温下有严重的结垢趋势存在，在甲醇回收处理过程中会产生大量结垢，从而使甲醇回收装置中换热器管程和精馏塔陶瓷波纹板填料中产生严重的结垢堵塞，同时水中大量的机杂和乳化油的沉积会进一步加剧管程和精馏塔陶瓷波纹板填料堵塞，影响甲醇回收装置处理效率和处理能力。

另外，由于气田污水矿化度和Cl-离子含量很高、且pH值较低，同时还溶解有一定量的CO2、H2S等腐蚀性气体和大量的乳化油存在，使这种气田含醇污水对管线和设备等具有很强的腐蚀性。

1.靖边气田回注污水的处理工艺及现状

1.1净化厂回注污水的处理工艺及现状

净化厂的回注污水主要包括生产污水、检修污水、循环水排污、锅炉房排污、甲醇回收单元塔底水及生活污水；生活污水、生产污水和检修污水经核桃壳过滤器处理，循环水排污、锅炉房排污及甲醇回收单元塔底水（又称混合污水）经纤维球过滤器处理；处理后的各种污水在调节罐混合，然后由回注泵回注到地层。

图1第一净化厂回注污水处理工艺流程

图2第二净化厂回注污水处理工艺流程

1.2北二区、南二区回注污水的处理工艺及现状

北二区共有产水井数21口，目前正常生产产水井数18口，井筒积液井数3口。

随着井网的不断完善，2004年后该井区水气比降低并趋于稳定，平均日产气量3.5863×104m3，平均日产水量9.891m3，累计产气10.0079×108m3，累计产水18.664×108m3。

北二区在运行过程中，日均处理水量84m3，回注压力为9.80Mpa。

其污水回注处理工艺流程为：

来水大罐沉淀组合过滤器回注地层。

南二区共有产水井数14口，目前正常生产产水井数9口，井筒积液井数5口。

到2003年后该井区内井网逐渐完善，产水气井增多，水气比趋于稳定，目前平均日产气量3.3674×104m3，平均日产水量6.732m3，累计产气量8.8378×108m3，累计产水量7.090×104m3。

南二区在运行过程中，日均处理水量245m3，回注压力为9.30MPa。

其污水回注处理工艺流程为：

来水大罐沉淀组合过滤器回注地层。

第一净化厂的污水处理单元及处理量见表1。

表1第一采气厂气田污水处理系统建设情况

污水预处理

甲醇再生装置

污水回灌

备注

投产

日期

设计能力（m3/d）

投产

日期

设计能力（m3/d）

投产

日期

设计能力（m3/d）

一净

2000

150

1997

100

1997

240

含醇

污水处理

2000

50

二净