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吐哈盆地致密砂岩气藏醇基压裂酸化技术与应用

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盆地 致密 砂岩 气藏醇基压裂 酸化 技术 应用
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  基金项目:中国石油天然气股份有限公司科研项目(编号:2009D-1503-08)。作者简介:安耀清,1970年生,高级工程师,博士研究生;主要从事压裂酸化工艺技术及现场管理工作。地址:(100088)北京市朝阳区东湖渠屏翠西路8号安东石油技术(集团)有限公司井下工程事业部。电话:13810745241。E-mail:13909958086@163.com吐哈盆地致密砂岩气藏醇基压裂酸化技术与应用安耀清1吴明江2杨建委2段 萍2张勇国21.中国地质大学(北京)2.中国石油吐哈油田公司井下技术作业公司安耀清等.吐哈盆地致密砂岩气藏醇基压裂酸化技术与应用.天然气工业,2011,31(11):68-70.摘要针对吐哈盆地巴喀和红台两个致密砂岩气藏常规的压裂液、酸化液水敏、水锁伤害严重,对储层的二次伤害大的实际情况,开展了醇基压裂液、酸化液技术研究。室内岩心实验定量分析了储层水敏、水锁伤害程度,确定了压裂液及酸液中甲醇及各添加剂的最佳浓度和加量,建立了既能防水锁水敏伤害、又能实现深部酸化的多氢酸+醇酸化液体系,给出了酸液体系中各酸型的推荐使用浓度,并最终研制出了适合该区致密砂岩气藏储层改造的醇基压裂、酸化液体系,其性能指标优于常规压裂、酸化液体系。现场20口井的试验应用取得了显著的增产效果,说明自主研制的醇基压裂液、醇酸酸液在该区具有很好的适应性。关键词吐哈盆地致密砂岩气藏压裂(岩石)水锁伤害醇基压裂液醇基酸化液DOI:10.3787/j.issn.1000-0976.2011.11.0171 储层改造难点分析吐哈盆地中国石油吐哈油田公司开发的致密砂岩气藏储层岩性致密、渗透性差、孔喉细小、毛细管压力高、水锁伤害严重;同时储层黏土含量高,水敏性强,黏土水化膨胀伤害严重。在巴喀致密气藏的前期压裂酸化中,因常规水基压裂液的水锁和水敏伤害而严重影响压裂效果,有些井甚至出现反效。因此,该类致密砂岩气藏压裂酸化改造中的储层保护难度大,要求压裂液在具备黏温性能稳定、低滤失、低摩阻、低残渣、易返排、携砂性好等多种优良性能的基础上,具有更强的防水锁、防水敏性能。2 储层水敏、水锁伤害分析与评价2.1 水敏伤害分析与评价柯21井X射线衍射全岩分析实验测定表明,储层岩石中黏土矿物含量为26.8%~27.1%,黏土中绝大部分为伊利石,含量在88%~92%之间,其次为伊蒙混层矿物。岩心样品水敏试验结果表明:使用蒸馏水测得的岩心渗透率为模拟地层水测得的岩心渗透率的48.8%,因此储层段水敏程度为中等偏强。2.2 水锁伤害分析与评价低孔低渗储层中的少量水相通常占据小孔隙角隅,油气位于孔隙中间部位。当外来液相侵入后,会在孔隙喉道中形成液相堵塞,其液—气或液—油弯曲界面上存在着毛细管压力,产生毛细管自吸效应,使得孔隙结构含水量急增,大大减少了储层油气通道的数量。形成水锁伤害[1-2]。研究结果表明[3],水锁伤害是低渗透储层最主要的伤害形式,损害率一般为70%~90%,特别是当储层渗透率很低或原始含水饱和度低于外来液体入侵形成的束缚水饱和度时[4],水锁效应会更加严重(图1)。本文参考文献[5]提出了预测水锁严重程度(APTi)的评价标准:当APTi>1.0,水锁效应不明显;当0.8<APTi<1.0,有潜在水锁效应;当APTi<0.8,水锁效应明显。通过对KXX井岩样进行水锁损害评价,其结果表明:最大、最小水锁指数分别为0.61和0.01,表明10块岩样均发生了严重水锁损害。3 醇基压裂液配方研制与试验评价3.1 醇类优选及浓度确定室内对不同比例的醇类进行了表面张力测定,从测定结果可知,随着醇浓度的升高,表面张力下降,表·86·天然气工业2011年11月图1水锁伤害分析示意图明醇类的加入具有良好的降低表面张力的作用;相同浓度下,乙醇的表面张力明显低于甲醇,但是考虑到甲醇的成本较低,因此,首先选用甲醇作为醇基压裂液的溶剂。另外,从测定结果还可看出,当醇浓度在30%以上时,表面张力下降趋缓,因此筛选醇浓度应小于30%。通过实验研究了中国石油吐哈油田公司常用羟丙基胍胶在不同甲醇浓度水溶液中的增稠性能。实验结果表明:当稠化剂浓度不变时(羟丙基瓜胶浓度为0.4%),甲醇浓度从0上升到20%,基液黏度上升,甲醇浓度上升到30%时,基液黏度下降为27mPa·s,配伍性变差。因此,甲醇浓度为20%时,羟丙基瓜胶在醇水溶液中具有最好的配伍性和增稠性,因此筛选最佳甲醇浓度为20%。3.2 醇基压裂液配方研制针对储层实际特点,通过实验优选了各添加剂类型及加量,形成了适合吐哈油田致密砂岩气藏的压裂液配方如下。基液:0.4%瓜胶+0.3%杀菌剂+0.5%黏土稳定剂+0.5%助排剂+0.3%Na2CO3+20%甲醇+2%KCl。交联剂:B∶A=10∶3,配方连续剪切90min之后,黏度保持在80mPa·s以上,可以满足施工要求。3.3 醇基压裂液性能实验评价室内对研制的醇基压裂液性能进行实验评价,结果表明:①醇基压裂液的表面张力低于26mN/m,低于水基压裂液;②防膨率在80%以上,优于水基压裂液;③残渣含量为462mg/L,低于550mg/L的行业标准;④用K2X井岩心实验醇基压裂液的伤害率在23.65%~27.7%之间,而水基压裂液的伤害率在32.1%~36.8%之间,可见醇基压裂液伤害率比常规压裂液降低幅度约1/3(图2);⑤甲醇的加入有利于降图2常规压裂液和醇基压裂液伤害率对比图低压裂液的表面张力和黏度,从而有利于压裂液施后的返排,降低了压裂液对储层的伤害。4 醇酸酸化液配方研究与试验评价4.1 酸化酸型及浓度选择针对吐哈盆地致密气藏酸化改造特点,利用巴喀油田K2X井(3 140m)储层的岩粉与不同浓度的盐酸、土酸、氟硼酸、多氢酸和3类醇酸进行了溶蚀实验,通过实验确定适用于该储层的酸型及浓度。土酸溶蚀率在6.0%~14.0%之间,建议土酸酸化时选择氢氟酸浓度为1.5%~2%;氟硼酸溶蚀率在9.0%~12.0%之间,建议氟硼酸酸化时选择氟硼酸浓度为8.0%~12.0%;多氢酸溶蚀率在15.0%~17.0%之间,比盐酸、土酸、氟硼酸溶蚀率高,建议多氢酸酸化时选择SA602浓度为6%,SA702浓度为5.0%~7.0%;该区土酸+醇酸液可溶物较低,醇酸溶蚀率在8.74%~9.12%之间;氟硼酸+醇酸液溶蚀率在4.61%~6.42%之间;多氢酸+醇酸液体系溶蚀率在14.08%~15.45%之间,其中加入甲醇的酸液体系溶蚀效果好于乙醇和异丙醇,因此对吐哈盆地低渗致密气藏建议采用多氢酸+醇酸化体系,醇类型优先考虑甲醇。4.2 配方酸液的配伍性评价与醇浓度确定实验室在配方酸液中分别加入不同浓度的甲醇,在室温和90℃温度下静置6h,观察酸液反应后的变化情况,以考察配方酸液与甲醇的配伍性。实验结果表明:无论在常温还是90℃恒温6h后,配方中不加入甲醇的酸液体系所含沉淀较其他4种不同百分浓度甲醇酸液体系明显增多;加入15%左右甲醇的酸液体系所含沉淀较其他4种不同百分浓度甲醇酸液体系少,说明醇类的加入能够有效减少沉淀物的产生,改善酸液体系整体配伍性。酸液配伍性实验中甲醇表现出了良好的配伍性和抑垢性,实验表明:加入15%左右甲醇的酸液体系配伍性最好,因此推荐使用浓度为15%的甲醇。·96·第31卷第11期                  开 发 工 程             4.3 配方酸液岩心酸化效果实验评价实验选用K2X井岩心,酸化效果实验结果见表1。岩心酸化流动效果评价实验结果表明:采用加入醇类的多氢酸酸液体系处理岩心后,其最终渗透率为基准渗透率的3~5倍,取得了很好的渗透率增幅效果。5 应用情况与效果评价醇基压裂酸化工艺技术现场应用20井次,施工成功率100%,有效率87%,施工最高压力92.6MPa,施工最高砂比50%,平均砂比32.5%,最大入井液量826.3m3,最大加砂量66.6m3,最大入地层酸液量120m3,甲醇最高浓度20%。最大增气量55 000m3/d,平均增气量21 000m3/d,最大增油量50t/d,平均增油量6.1t/d,醇基压裂酸化效果统计见表2。其中柯23井于2010年1月24日对井段3 991.0~3 999.0m进行射孔后无显示,采用常规黏土酸酸化后在3mm油嘴条件下稳产气2 494m3/d,产油1.8m3/d;后于3月6日对该井段采用羧甲基压裂液进行加砂压裂,入井总液量457.6m3,共加砂50.1m3,压后累计返排出液281.4m3,返排率59%,在3mm油嘴条件下测气产量为176m3/d,见油花,压裂出现反效;后于4月23日采用醇基酸化液进行酸化改造,入井酸量120m3,甲醇浓度15%,酸化后自喷返排出液172.3m3,返排率143.6%,在3mm油嘴条件下测得稳定气产量为11 600m3/d,油产量2.1m3/d,醇基酸化液取得了显著的增产效果。表1注酸过程中渗透率演变统计结果表序号 岩心编号 酸型K/Ko基液 正驱前置液 正驱处理液 后置液 基液酸化效果 备注1 K2X-1-3 土酸 1.00  0.31  6.57  8.27  20.76 有效 岩心有出砂现象2 K2X-1-3 多氢酸 1.00  0.30  0.37  2.00  1.65 有效3 K2X-3-1 多氢酸醇酸 1.00  1.28  3.94  18.00  21.00 有效4 K2X-1-1 氟硼酸醇酸 1.00  0.78  1.56  0.94  1.75 有效表2致密砂岩气藏醇基压裂酸化效果统计表井号 措施内容措施前产量日产气/104 m3日产油/t措施后产量日产气/104 m3日产油/t日增气量/104 m3日增油量/t累计增量气/104 m3油/t一次返排率红台206 醇基压裂 0.1000  1.500  50.0  1.4  50.0  151.1  2 418.9  90.0%红台2-46醇基压裂 1.0000  6.500  5.5  5.5  5.5  9.5   6.7  46.9%柯23 醇基酸化 0.0180  1.160  2.1  1.2  2.1  42.2  397.0  143.6%6 结论与认识1)吐哈盆地中国石油吐哈油田公司开发的致密砂岩气藏存在较严重的水锁和水敏伤害,大大影响压裂增产效果。2)自主研制的醇基压裂液体系,具有残渣含量低、表面张力低、破胶液黏度低、储层伤害率低、防膨效果好等特点,具有显著的防水锁、防水敏伤害的作用,能够满足上述致密砂岩气藏的压裂需求。3)醇基酸液性能研究表明,甲醇与酸液各种添加剂有良好的配伍性,醇酸具有很好的解除水锁、促进残酸返排、降低二次伤害等作用。4)醇基压裂酸化技术通过在上述致密砂岩气藏20井次的现场应用,取得了显著的增产效果,说明自主研制的醇基压裂液、醇酸酸液对该区致密砂岩气藏具有很好的适应性。参考文献[1]赖南君,叶仲斌,刘向君,等.低渗透致密砂岩气藏水锁损害室内研究[J].天然气工业,2005,25(4):125.[2]尚万宁,张耀刚,李治,等.气井储层水锁效应解除措施应用[J].天然气工业,2008,28(5):89-90.[3]唐海,吕渐江,吕栋梁,等.致密低渗气藏水锁影响因素研究[J].西南石油大学学报:自然科学版,2009,31(4):91-94.[4]曾伟,陈舒,向海洋.异常低含水饱和度储层的水锁损害[J].天然气工业,2010,30(7):42-44.[5]朱国华,徐建军,李琴,等.砂岩气藏水锁效应实验研究[J].天然气勘探与开发,2003,26(1):34-35.(修改回稿日期2011-09-10 编辑韩晓渝)·07·天然气工业2011年11月Abstract:Through an in-depth investigation,the origin,background,feature,applicable scope,and some errors caused during theapplication of the single-point test are discussed in detail.The single-point method originated from the binomial and exponential flowequations,and the coefficients of its constants(such as Ad,nand C,which are equal to 1)are obtained from the average Ad,n ofthe multiple rate flow after flow test,so the single-point test is a statistical method for empirical testing.That is why the single-pointtest is incoherent with geological properties of production zones,fluid properties,and environmental properties.So the gas wel de-liverability derived from the single-point test method is only approximate values,and this method should only be used when there areno multiple rate wel testing data,which can be used to estimate the gas wel deliverability in order to prevent massive gas from beingvented to the air.Instead of adopting the unreliable data from the single-point test method,the gas field development and engineeringdesign need accurate and reliable data which can be only obtained by the multi-point open flow potential test at the early period of theinitial pilot field development.Keywords:gas wel,deliverability,wel test,single-point test,binomial equations,exponential equations,empirical relationship,a-daptabilityDOI:10.3787/j.issn.1000-0976.2011.11.015Sun Zhidao,senior engineer,born in 1934,is mainly engaged in oil and gas field development research.Add:Room 702,Unit 4,Block.2Building No.20,Mail Box 910,Xueyuan Rd.,Beijing 100086,P.R.ChinaTel:+86-10-8359 3274  E-mail:cxbbj@sina.comFactors affectingthe productivityof fractured horizontal wels consideringwelbore pressure lossJiangBiwu1,Cui Yong1,Mu Xiangjing2,Han Zhihua3,Xia Yanxu3,TangLongxun4(1.CNPC Overseas Exploration and Development Co.,Ltd.,Beijing100034,China;2.Oil TeachingandResearch Section,Naval UniversityofEngineering,Tianjin 300450,China;3.LangfangBranch ofTele-Communication &Power EngineeringCompany,China Petroleum Pipe Bureau,CNPC,Langfang,Hebei065000,China;4.Southwest Petroeum University,Chengdu,Sichuan610050,China)NATUR.GAS IND.VOLUME31,ISSUE11,pp.66-67,11/25/2011.(ISSN1000-0976;In Chinese)Abstract:An ideal state for a fractured horizontal gas wel is generaly regarded as the case without considering the pressure loss atthe horizontal sections of horizontal wels.The productivity of such gas wels is simply the summation of the productivities at eachfracture,which is obviously impractical.Therefore,the corresponding equations are deduced and in combination with such a case ofa certain gas reservoir in Middle East.This case study analyzes how the factors,including fracture position,welbore radius,andfracture half length,influence the productivity of the fractured gas wels.The results show that the gas production rate at the endfracture is higher than that at the middle fracture.The longer fractures are not always the better,so there is an optimal value of frac-ture length for the maximum productivity.In addition,the influence caused by the welbore radius is limited on the productivity offractured horizontal wels.The above conclusions provide guidance about the stimulation of practical gas wels.Keywords:horizontal wel,fracturing,productivity,pressure loss,affecting factorDOI:10.3787/j.issn.1000-0976.2011.11.016JiangBiwu,senior engineer;born in 1976,is mainly engaged in oil and gas field development.Add:International Investment Building,No.6,North Fuchengmen Rd.,Xicheng District,Beijing 100034,P.R.ChinaMobile:+86-13488717579  E-mail:hunterbwj@163.comAlcohol-based fracturingand acidizingfluids for the tight gas reservoirs in the Tuha BasinAn Yaoqing1,2,Wu Mingjiang2,YangJianwei 2,Duan Ping2,ZhangYongguo2(1.China UniversityofGeosciences,Beijing100088,China;2.Downhole Services Operation Company,TuhaOilfield Company,PetroChina,Shanshan,Xinjiang838200,China)NATUR.GAS IND.VOLUME31,ISSUE11,pp.68-70,11/25/2011.(ISSN1000-0976;In Chinese)Abstract:Baka and Hongtai,two tight gas reservoirs in the Tuha Oilfield,show characteristics of serious water sensitivity and waterblock damage as wel as great secondary damage to the reservoirs if the regular fracturing and acidizing fluids are used.Therefore,a·521·Natural Gas Industry,Vol.31,Issue 11,2011study is conducted on the alcohol-based fracturing and acidizing fluids.Through the core sample tests,aquantitative analysis is car-ried out of the damage degree of water sensitivity and water block damage to the reservoirs,on this basis,the optimal concentrationand dosage of alcohol and each additives are determined in fracturing and acidizing fluids,thus the specific acidizing fluid system withmulti-hydrogen and alcohol is obtained not onlyto prevent serious water sensitivity and water lock damage but to achieve deepacidization.In addition,the recommendable concentration is also provided for each acid in the system of acidizing fluids.Moreover,the system of alcohol-based fracturing and acidizing fluids is thus designed applicable for the stimulation of Tuha tight gas reservoirsand shows a better performance than the regular ones.With this fluid system applied in 20wels,a significant increase of wel pro-ductivity is achieved as a result.This indicates that the new alcohol-based fracturing and acidizing fluids designed independently haveexcelent adaptabilityin this study area.Keywords:Tuha Basin,tight sand gas reservoir,fracturing,water-block damage,damage,alcohol-based fracturing and acidizingfluidsDOI:10.3787/j.issn.1000-0976.2011.11.017An Yaoqing,senior engineer,born in 1970,holds a Ph.D degree and is mainly engaged in fracturing and acidizing technology andmanagement.Add:Department of Downhole Engineering,AnDong Petroleum Technology(Group)Co.,Ltd.,No.8,Pingcuixi Rd.,Donghu-qu,Chaoyang District,Beijing 100088,P.R.ChinaTel:+86-13810745241  E-mail:13909958086@163.comA new type of hydraulic liner release controlerChen Yushu(Downhole Services Company,ChuanqingDrillingEngineeringCo.,Ltd.,CNPC,Chengdu,Sichuan610051,China)NATUR.GAS IND.VOLUME31,ISSUE11,pp.71-73,11/25/2011.(ISSN1000-0976;In Chinese)Abstract:In liner cementing,backout rotation is often used to release the liner and the suspension weight is used to determine wheth-er the liner has been released already or not.But in the cases of deep wels,ultradeep wels,directional wels,and horizontal wels,backout release often fails and the suspension weight change cannot correctly reflect the release.Therefore,this study is conductedto solve that problem.Based on the analysis of the technical defects of the conventional method,a hydraulic latch type release controlsystem is developed and the release can be identified by the hydraulic pressure change,which is easy to be observed.This systemconsists of latch device and latch control mechanism,connected between the running string and the liner.It is run in the hole togeth-er with the liner hanger.By bal dropping,hydraulic hanging and pressure pumping-up,the latch retracts to release the liner.Thenhold the pressure and pul up the string to unset the stinger and release the pressure.If an obvious pressure change is observed,itshows that the liner has been successfuly released.This new type of hydraulic liner release controler eliminates the need of backoutrotation in complicated welbores,easy to operate,safe and reliable.And the process of weighting the string during the previousrunningin becomes unecessary,resulting in cost reduction.This new development improves the liner release process and the linerhanging cementing quality.Keywords:deep wel,directional wel,horizontal shale gas wel,hydraulic liner release,hydraulic pressure,controler,cementingqualityDOI:10.3787/j.issn.1000-0976.2011.11.018Chen Yushu,engineer,born in 1954,graduated in driling technology from Southwest Petroleum Institute in 1990.He is now en-gaged in development and promotion of downhole tools for petroleum industry.Add:No.6,Ruifeng Lane,North Sec.4,2nd Circle Rd.,Chenghua District,Chengdu,Sichuan 610051,P.R.ChinaMobile:+86-15982438306  E-mail:chenyushu136@163.comDrilingfluid technologyfor a high ROP in drilingdeepwels through clastic rocks,western Sichuan BasinZhangJun,PengShangping,YangFei,Yu Zhigang,He Zhiqiang(Sichuan Renzhi Oilfield Technical Service Co.,Ltd.,Mianyang,Sichuan621000,China)·621·Natural Gas Industry,Vol.31,Issue 11,2011
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