用于压裂液的胶囊破胶剂性能评价

文章编号:1000-2634(2002)06-0068-03用于压裂液的胶囊破胶剂性能评价Ξ吴敏1,叶艳2(1.西南油气田分公司天然气研究院,四川泸州646002;2.西南石油学院研究生院)摘要:胶囊破胶剂是近年发展起来的一种新型破胶技术。

它是以一种或多种常用的破胶剂为囊心,表面裹上一层防水的囊衣材料而形成的微小胶囊,具有延缓释放破胶剂的特点,在压裂作业中可高浓度使用而不影响其它流变性能。

简述了胶囊破胶剂技术的现状、类别、特点,并选用国内外的部分胶囊破胶剂样品进行了室内性能评价实验。

关键词:胶囊破胶剂;压裂液;破胶剂;释放中图分类号:TE357.12 文献标识码:A 自50年代以来,水力压裂技术在油气增产作业中应用日益广泛。

压裂液中的胶凝剂用来提高液体粘度,控制流体滤失,携带支撑剂。

在完成造缝、控滤及携砂后,则要求聚合物降解,迅速彻底地返排出液体,恢复油气生产。

如聚合物降解不好,就会产生明显的伤害,降低油气产量。

在不同的储层条件下,聚合物具有不同的降解方式。

一般在地层温度>93℃时,聚合物可自行降解;54～93℃时可用氧化物类破胶剂;<54℃时可用酸或酶作破胶剂[1]。

常用的破胶剂包括过硫酸盐,酶类,酸,KMnO4等。

这些常规破胶剂随压裂液泵入,遇热即开始发挥作用,随时间延长而不断破胶。

其降解聚合物速度与破胶剂用量成正比。

如果在泵入时加入太多破胶剂,压裂液就会过早降解,使油层受到入井流体严重的穿透伤害;如果用量过少,则破胶不彻底,在裂缝层表面与中心形成滤饼,对油层造成残渣和滞留体伤害,降低导流能力。

为解决这个矛盾,发展起一种新型的延迟释放破胶技术,即在常规破胶剂外包裹上一层防水囊衣材料,形成胶囊破胶剂。

它可在保证高浓度破胶剂的条件下又不改变流体的流变特性。

90年代以来,胶囊破胶剂在各国不同区块、数百井次的现场应用中,取得了良好的增产效果。

1　类别及特点大量文献调研表明,胶囊破胶剂种类繁多。

按其所针对的压裂液类型,主要可分为三类。

1.1　用于水基压裂液的胶囊破胶剂压裂液中的胶凝剂包括胍胶及其衍生物,纤维素衍生物;交联剂可以是锆、钛、锑、铝、硼。

破胶剂主体通常为过硫酸铵,过硫酸钠,生物纤维素酶,碳酸钠,过氧化物,酸等。

这也是目前用途最广、研究最多的一类胶囊破胶剂。

1.2　用于交联酸冻胶的胶囊破胶剂[2]酸为常用水溶性酸,交联剂常用含2个碳以上有机钛或锆。

破胶剂主体常为氟化物,磷酸盐,硫酸盐及聚羧酸盐化合物等。

1.3　用于油基压裂液的胶囊破胶剂在20～65℃油基压裂液中使用,以CaO和Ca(OH)2为破胶剂主体,油溶性材料作囊衣,聚合物应包含聚烯烃或聚烯烃-醋酸乙烯共聚物。

2　国内外发展及现状胶囊破胶剂是以一种或多种常用的破胶剂为主体,通过一定的生产工艺,在表面裹上一层物理、机械性能良好的囊衣材料而形成的微小胶囊。

具有隔水耐温作用的囊衣使破胶剂在随压裂液泵入初期不发挥作用,压裂施工完后,流体滤失压力下降,裂缝闭合,在充填层内产生极高的点对点的压力,从而使囊衣破碎,释放出破胶剂来。

另外,囊衣的溶解、分解,液体的渗透及温度等因素也是破胶剂释放的原因。

胶囊破胶剂的用量通常可达常规破胶剂的8～第24卷　第6期 西南石油学院学报 Vol.24　No.6 2002年　12月 Journal of S outhwest Petroleum Institute Dec　2002Ξ收稿日期:2002-02-28作者简介:吴敏(1971-),女(汉族),四川南充人,工程师,学士,主要从事油气井开发生产中油田化学剂的研究与应用工作。

10倍[3]。

从1989年4季度首次在现场使用胶囊破胶剂以来,延迟破胶技术曾在包括加利福尼亚,新墨西哥,西德克萨斯等地区的几百口油气井中使用,与常规破胶剂相比,排液率增加,需要抽汲的井大为减少,累计产量和初始产量都明显增加[1,4,5,6]。

国内初期胶囊破胶剂是用于水基聚合物压裂液的双层微囊破胶剂,可使支撑剂充填层的渗透率从35%提高到49%。

1995年,新疆石油管理局又研制了一种三层球体式胶囊破胶剂,所用的囊衣材料在4～8h内能自行溶解于油,对地层不会造成二次伤害。

近年,总公司石油勘探开发科学研究院研制开发了NBA-101胶囊破胶剂[7]。

它是在过硫酸盐材料表面包裹一层或多层特制的高分子薄膜而形成的20～40目微粒。

3　室内性能测试3.1　实验内容与方法为了对胶囊破胶剂的性能、特点有更直观的认识,尤其是对它们释放有效成分的能力、室内评价方法及它对压裂液性能的影响有更充分的了解,我们选取了2种胶囊破胶剂样品,进行室内性能评价实验。

2种样品分别为国外公司的A剂和国内的B 剂。

实验内容包括胶囊破胶剂的破碎方法、破碎条件、囊心有效组分含量测试、破胶剂释放率及在压裂液中的性能等。

实验方法参照有关标准进行。

3.2　胶囊破胶剂的破碎方法与条件胶囊破胶剂在室温、常压条件下放置,外层胶囊不破碎,破胶剂有效组分包裹在囊衣中不发挥破胶作用。

当地层裂缝闭合产生压力和撞击,或温度升高,则导致外层囊衣不同程度的破碎而释放出破胶剂来。

这也是胶囊破胶剂能高浓度使用而不影响流变等性能的重要原因。

我们目前的室内条件难以完全模拟地层情况,在探索大量实验方法的基础上,决定采用两种方法使胶囊破胶剂破碎释放。

一种是将样品装入压制机(Compactor)内,加载不同压力,保持一定时间使其破碎。

推荐模拟裂缝闭合压力为40MPa。

另一种方法是将样品在一定温度下的蒸馏水中放置不同的时间,使其逐渐释放。

因为胶囊破胶剂A、B是适用于中温地层的胶囊破胶剂,选定的考察温度为70℃。

据资料介绍,A、B两种胶囊破胶剂的囊心组分均为过硫酸盐,因此我们采用了碘量法分析释放出的破胶剂含量。

3.3　有效含量的测试称取2.00g破胶剂样品,装入压制机内,分别对样品加载10、20、30、35、40MPa的不同压力,保持3min;将压制后得到的内容物配成1%溶液静置30 min;用碘量法测定不同压力下的过硫酸盐含量;以压力为横坐标,释放出的过硫酸盐含量为纵坐标作图,当含量随压力变化达到稳定时的对应值即为胶囊破胶剂有效含量。

实验结果见图1。

图1　胶囊破胶剂有效含量从图1可见,加载压力的大小对胶囊破胶剂的破碎释放影响很大。

随着压力的增加,释放出的过硫酸盐含量明显升高。

当压力达到30MPa时,释放含量基本趋于稳定。

实验结果表明,胶囊破胶剂A、B的有效含量分别为85.90%和76.20%。

3.4　释放率的测试取1.00g胶囊破胶剂与20.00g陶粒混合,装入压制机,加载压力40MPa,测定通过挤压破碎释放的破胶剂含量。

通过式(1)计算出胶囊破胶剂释放率。

R=(η2/η1)×100(1)式中R—胶囊破胶剂释放率,%η1—胶囊破胶剂有效含量,%η2—胶囊破胶剂挤压破碎释放的含量,%经分析测定,A、B通过挤压破碎释放的过硫酸铵含量分别为66.19%和52.33%。

根据实验结果,A、B剂的释放率分别为77.05%和68.67%。

3.5　温度对破碎释放的影响将胶囊破胶剂分别加入到室温(20℃)和70℃蒸馏水中,取样,分析测定10～120min所释放出的过硫酸盐含量。

实验结果见表1。

96第6期 吴敏等:　用于压裂液的胶囊破胶剂性能评价表1　温度对胶囊破胶剂释放的影响(常压)时间/min 过硫酸盐含量/%A20℃ 70℃ B20℃ 70℃100.500.58　0.550.6530 1.428.30 2.6217.9160 2.2015.38 4.0026.1590 4.1537.74 6.8542.181205.4646.32　9.2354.15从表1来看,温度对胶囊破胶剂有效组分的释放影响明显。

在室温下释放量很低,当温度为70℃时,释放速度明显加快,破胶剂中的有效组分在120min 时可释放约50%。

另外,在一定温度下,随着时间的延长,胶囊破胶剂破碎释放出的过硫酸盐含量增加,这与囊衣的耐水性也有关。

耐水性越好,囊衣壁越厚,释放出的量随时间上升的趋势越小。

3.6　对压裂液性能的影响将A 、B 两种胶囊破胶剂分别加入到HP G Ο有机硼压裂液体系的配方中,用Fann50旋转粘度计测试它们在常压,70℃,170s -1下的抗剪切性能,并与加入过硫酸盐常规破胶剂的压裂液对比。

实验结果见图2。

图2　胶囊破胶剂对压裂液性能的影响从图2可见,加入常规过硫酸盐破胶剂的压裂液,其表观粘度在30min 内迅速从328.4mPa ・s 下降为约20mPa ・s ;而使用胶囊破胶剂时,即使其加量增加4倍,它所在的压裂液粘度下降仍很平缓,剪切120min 后,A 、B 破胶剂的压裂液体系表观粘度均在150mPa ・s 以上。

因此现场施工过程中,胶囊破胶剂可高浓度使用,或与常规破胶剂配合使用。

与常规破胶剂相比,在室温下配制压裂液的过程中,胶囊破胶剂基本不发挥作用。

施工结束后,受裂缝闭合应力和温度等多重作用,胶囊破胶剂将迅速释放出破胶剂,既可保证压裂液的充分破胶水化,减少对地层的伤害,又不会在配液泵注时影响压裂液的流变和携砂能力。

4　结　论(1)胶囊破胶剂是以常规破胶剂为主体,表面裹上一层防水囊衣材料而形成的微小胶囊。

它具有既可高浓度使用破胶剂又不改变流体流变性能的特点。

(2)胶囊破胶剂在压力和温度的作用下会释放出其中包裹的有效组分。

随压力和温度的上升,释放的量增加;常温常压下则基本不起破胶作用。

(3)与常规破胶剂相比,加入胶囊破胶剂的压裂液抗剪切能力明显提高;同时,因其在压裂液中的高用量,可实现更迅速、更彻底地破胶。

参考文献:[1]　Parker M A ,Laramay S B.properties and application ofdelayed -release breakers[C].SPE 24300,1992.[2]　Joel L Boles ,Arthur S ,Metcalf ,Jeffrey C .Coatedbreaker for crosslinked acid[P].US :5497830,1995-4-6.[3]　DOWELL Co.Fracturing Materials Manual[R ].Decem 2ber 1993.[4]　Janet Gulbls ,K lng M T ,Hawklns Q W ,Brannon H D ,et al.Encapsulated breaker for aqueous polymeric fluids [J ].SPE Production Engineering ,February 1992.[5]　Joe Small ,Mike Wallace ,Steve Van Howe.Improvingfracture conductivities with a delayed breaker system :A case history[C].SPE 21497,1991.[6]　朱海峰,盛杰,化得元.水基聚合物压裂液双层微囊破胶剂[P].CN :1099786A ,1995.[7]　赵忠扬.优质植物胶水基压裂液系列研究与应用[J ].石油与天然气化工.1997,26(3):185-187.(编辑　朱和平)7西南石油学院学报 2002年F L UIDL I XiaoΟming(S outhwest Petroleum Institute,Nanchong Sichuan637001,China),PU XiaoΟlin.JOU RNAL O F S OU T HW ES T PET ROL EU M IN S TI TU T E,V OL.24, N O.6,53-56,2002(ISS N1000-2634,IN CHIN ES E)A new kind of lowΟdensity system,which is called recy2 clable microΟfoam drilligfluid,has been put forward recently both domestic and overseas.It has overcome most disadvantages of conventional foam system such as bad pumping and oneΟoff use that may lead to lots of waste of agents and serious environ2 mental pollution.Based on the theoretic analysis of formations and stability of the microΟfoam system,a physical chemistry model has been put forward in this paper.By a lot of experi2 ments on the basis of the formation,stability and application conditions,a system that can accord with the hypothetical con2 ditions has been obtained finally.The system has many advan2 tages such as high stability,adjustable density(range from0.5～0.9g/cm3),low filtrate and good ability to resist salt,calci2 um and temperature.K ey w ords:foam drilling fluid;microΟfoam;stability;mi2 crostructure;macroΟcapacitySYNTHESIS OF A N OVE L GEMINI SURFACTANT HAN TieΟzhu(S outhwest Petroleum Institute,Nanchong Sichuan637001,China),HU XingΟqi,L IO FuΟmei.JOU R2 NAL O F S OU T HW ES T PET ROL EU M IN S TI TU T E,V OL. 24,N O.6,57-59,2002(ISS N1000-2634,IN CHIN ES E)G emini surfactant is a new type of surfactant,which is made up of two identical amphiphilic moieties covalently con2 nected to the level of the head group by a spacer group.As a re2 sult,the separation between the polar head groups within G em2 ini surfactants is strongly decreased when they aggregate and furthermore the surface activity is greatly pared with general surfactants,introduction of G emini surfactants is a breakthrough in concept.Therefore G emini surfactants were re2 puted as a new generation of surfactants.An easy synthesis method of a novel G emini surfactant is reviewed by the alka2 nization of tertiary amine and the proton transfer reaction be2 tween multiple isocyanate and reagent containing active hydro2 gen.The structure is analyzed by IR test and surfaceΟactive property is determined.Results show that the surfactant has u2 nique structure and possess excellent surfaceΟactive properties.K ey w ords:surfactant;gemini;spacer group;high sur2 face activityLAB ORAT OR Y STU DY ON INTERFACIA L RHE OLOGICA L PR OPERT Y OF POLYMER/SURFACTANT DISPLACE2 MENT SYSTEMYE ZhongΟbin(S outhwest Petroleum Institute,Nanchong Sichuan637001,China),SHI LeiΟting,Y AN G JianΟjun,et al.JOU RNAL O F S OU T HW ES T PET ROL EU M IN S TI2TU T E,V OL.24,N O.6,60-63,2002(ISS N1000-2634, IN CHIN ES E)By means of deepΟchannel viscous traction interfacial vis2 cometer and improved measuring method,the surface viscosity of polymer/surfactant dual system and the interfacial viscosity between polymer/surfactant and simulation oil have been mea2 sured.Results show that the rheological property of surface lay2 er of polymer/surfactant fluids system is quite different from that of interfacial layer between polymer/surfactant and simula2 tion oil.The new parameter,dimensionless interfacial viscosity proposed in this paper,can describe the interfacial rheological property better,because it is free from the influence of bulk vis2 cosity.Polymer concentration influences interfacial rheological property remarkably,while polymer concentration located in the two sides of its critical associating concentration,the ten2 dencies of dimensionless surface viscosity and dimensionless in2 terfacial viscosity with surfactant concentration are inconsistent.K ey w ords:interfacial viscosity;combination chemical flooding;enhanced oil recovery;hydrophobical associating poly2 mer;polymer;surfactantSTU DY OF E LASTICIT Y IN OI L DISPLACEMENT PR O2 CESS B Y HPAMZHU Y angΟwen(Shengli Oilfield Co,Ltd,Dongying Shangdong257000,China),ZHAN G Y iΟgen,L IU Kun,et al.JOU RNAL O F S OU T HW ES T PET ROL EU M IN S TI2 TU T E,V OL.24,N O.6,64-67,2002(ISS N1000-2634, IN CHIN ES E)When hydrolyzed polyacrylamide(HPAM)solution flows in porous medium,it will exhibit elasticity and enhanced valid viscosity if velocity reaches a critical value.But we do not have the same opinion about its valid distances of elasticity and how much contribution to oil displacement efficiency when it is flow2 ing from injection well to producing well under changeable ve2 locity.In this paper,the effect of injecting velocity on the elas2 ticity of conventional HPAM has been studied.The oil dis place2 ment efficiency of HPAM is compared with nonΟelastic Xanthan gum and glycerin,and the maximum distance of elasticity of the polymer solution flowing in the reservoir has been decided.K ey w ords:hydrolyzed polyacrylamide;elasticity;critical velocity;oil displacement efficiencyPERFORMANCE EVA L UATION OF ENCAPSU LATE D BREAKER IN FRACTURING F L UIDSWU Min(Natural G as Research Institute of S outhwest Oil and G as Branch,Luzhou Sichuan646002,China),YIE Y an. JOU RNAL O F S OU T HW ES T PET ROL EU M IN S TI TU T E, V OL.24,N O.6,68-70,2002(ISS N1000-2634,IN CHI2 N ES E)An encapsulated breaker is composed of particles that are coated with a waterproof coating,which can reduce releasingⅤNo6 Journal of S outhwest Petroleum Instituterate of the breaker.The encapsulated breaker can be used in fracturing treatment at higher concentrations and has littleinflu2 ence on viscosities of fracturing boratory study on per2 formance of the encapsulated breaker has been conducted by comparing with other products from abroad and home,which has indicated a method and results of rheological properties of the fracturing fluid.K ey w ords:encapsulated breaker;fracturing fluid;break2 er;releaseSTU DY ON PH OT OCATA LYTIC OXIDATION DEGRADA2 TION OF PHEN OL IN AQUE OUS SOL UTIONCHEN Ji(S outhwest Petroleum Institute,Nanchong Sichuan637001,China),RAO XiaoΟtong,ZHAO Bo,et al. JOU RNAL O F S OU T HW ES T PET ROL EU M IN S TI TU T E, V OL.24,N O.6,71-73,2002(ISS N1000-2634,IN CHI2 N ES E)A new TiO2ΟAg compound catalyst that is made by solΟgel method has been introduced.When treating water sample con2 taining phenol by the catalyst,the conditions of the photo2 catalytic oxidation degradation,influential factors and degrada2 tion rate have been studied.Experimental results show that the catalyst has a fairly good activity of catalytic oxidation to phenol in aqueous solution under sunlight.Under the conditions of hav2 ing air flow through,p H=4.0,concentration of phenol is5 mg/L and treating time is3hours,the removal rate of phenol can reach about98%.For the catalyst,its performance is sta2 ble,easy to settle down and separate and it is reusable by high temperature activation.S o it is able to reduce costs of water treatment effectively.K ey w ords:photocatalytic oxidation;titanium dioxide; phenol;wastewater treatmentONE APPR OACH OF HARNESSING REFINING WASTE A L KA L I L IGU OR CONTAINING ORG ANIC SU LFIDESGUO ChuanΟmei(S outhwest Petroleum Institute,Nan2 chong Sichuan637001,China),TAN G XiaoΟdong,Sun G ang, et al.JOU RNAL O F S OU T HW ES T PET ROL EU M IN S TI2 TU T E,V OL.24,N O.6,74-77,2002(ISS N1000-2634, IN CHIN ES E)The process of acidization of waste alkali liquor and airstrip has been put forward in this paper.Part of compressed air (9.5%)used by recovery apparatus is taken into the stripping tower of waste alkali liquor as stripping air and the stripped H2S、RHS go along with air to recover sulfur in the recovering sulfur tower,which not only saves the energy consumption of air stripping apparatus,but also fully recovers resources of sulfur and decreases environmental pollution caused by waste alkali containing organic sulfides in oil refining.This approach is of great significance for our refinery in processing the Middle East crude oil with high content of sulfur and harnessing waste alkali liguor containing sulfur.The optimum experimental conditions are as follows:vitriol(98%)84ml/L,p H=4.5～5.5,strip2 ping temperature90℃,stripping time2.5h.After the airstrip, the waste alkali liguor can be used to produce sodium sulfate or be directly discharged after dilution in engineering workshop. The total content of sulfur in discharge water is<1mg/L、p H =7,which reaches the first degree of G B8987-1996.K ey w ords:waste alkali liquor containing organic sulfides; acidizationΟairstrip method;comprehensive utilization;process; environment protectionREASEARCH OF OI L FI LE LD GR OUN D WATER IN JEC2 TION SYSTEM PR OGRAMMING TECHNIQIUEL IAN G GuangΟchuan(S outhwest Petroleum Institute, Nanchong Sichuan637001,China),ZHAO JinΟzhou, ZHEN YunΟping,et al.JOU RNAL O F S OU T HW ES T PET ROL EU M IN S TI TU T E,V OL.24,N O.6,78-81,84, 2002(ISS N1000-2634,IN CHIN ES E)The ground water injection system is the important part of oil field flooding system,its programming influences the invest2 ment and running cost of total system.The programming method of the ground flooding system was studied in this paper and the total optimization problem was separated two parts,the programming of water injection branch line and that of water injection trunk line.In the programming of water injection branch line,a mathematical model aimed at system investment and reliability was proposed,the resolve method of this model was also provided.In view of the features of water injection trunk line,the optimization of trunk line and the minimum in2 vestment was reached through optimization of pump station po2 sition,defining the alignment of main trunk line and the inter2 section point of trunk line and branch line under the situation of meeting the demand of water injection technology.K ey w ords:Ground water injection system;MultiΟobjec2 tion programming;ReliabilityF LOW LAW ON STRATIFIE D LAMINAR F LOW IN PIPEHE ChengΟcai(S outhwest Petroleum Institute,Nanchong Sichuan637001,China).JOU RNAL O F S OU T HW ES T PET ROL EU M IN S TI TU T E,V OL.24,N O.6,82-84,2002 (ISS N1000-2634,IN CHIN ES E)In the paper,twoΟphase stratified laminar flow law in pipe was established with fluid mechanics NΟS equations.The cou2 pling conditions of the two phase interface was set up the fluid mechanics analysis of the two phase laminar interaction and the mathematics equations of the two phase stratified flow and the flow law was obtained the transportation of hight viscidity fluid easily comes true by the application of the stratified flow princi2 ple.K ey w ords:flow in pipe;stratified flow;mathematical model;pressure drop.ⅥAbstract 2002。