收稿日期:2007-05-28
作者简介:熊昕东(1973-),西南石油大学博士后流动站、中石化西南分公司博士后工作站在站博士后,专业方向:油气田开发。地址:
(618000)四川德阳龙泉山北路298号西南分公司工程技术研究院,电话:0838-*******,E -mail:xxds wp i@https://www.doczj.com/doc/033504600.html,
开采工艺
新场气田上沙溪庙气藏水锁效应研究
熊昕东
1,2
,王世泽2,张国东2,赵金洲3,汤 勇
3
(1中石化西南油气分公司博士后工作站2中石化西南油气分公司工程技术研究院3西南石油大学)
熊昕东等.新场气田上沙溪庙气藏水锁效应研究.钻采工艺,2007,30(4):95-97
摘 要:低渗砂岩气藏特殊的地质特性造成开发过程中普遍存在较强的水锁效应,是导致气井产能下降,储量难以得到有效动用的重要影响因素。为此,在大量的实验基础上,对新场上沙溪庙气藏水锁伤害机理、水锁对开发造成的影响以及水锁解除方法进行了研究
,认为水锁效应将导致压裂液滤失带启动压力增加,气相渗透率降低,当滤失带流动需要克服的启动压力从0.94M Pa 上升到7.15MPa 时,压裂液返排率从80%下降到40%,对储层造
成极大的伤害,是新场J s 21、J s 23
气藏储量难动用的主要原因之一。优化低伤害压裂液,并全程混氮加强返排,是新
场上沙气藏压裂开发过程中克服水锁效应的重要手段。
关键词:低渗气藏;水锁效应;水锁解除;开发对策;新场气田
中图分类号:TE 311 文献标识码:A 文章编号:1006-768X (2007)04-0095-03
勘探开发实践证实,低渗气藏由于低孔低渗特点,流体流动通道窄、渗流阻力大、液固界面及液气界面表面张力大,水锁效应明显增强,导致气井产能下降,严重影响到储量的有效开发。系统研究低渗气藏水锁伤害机理,寻找有针对性的开发对策,对低渗气藏的开发有明显的指导意义。
一、水锁伤害机理分析
储层喉道细、储渗相关性差,粒间孔隙、孔喉分
布的不均匀状态导致由于钻井液、完井液、固井液、压井液、酸化压裂液以及井筒生产积液等外来流体侵入储层后产生水锁效应,造成较大的启动压力梯度、近井地带储层的含水饱和度增加、气相渗透率降低、气井产能下降。另一方面,当地层的压降梯度超
过地层原始平衡水恢复流动所需的启动压差,会使近井地层一部分平衡共存水以分相渗流和蒸发态方式流入井筒形成井底积液,而井底积液则在井筒回压、储层岩石润湿性和毛细管压力作用下,会向生产层组中、低渗层的微毛细管孔道反向渗吸,形成反向渗吸水锁伤害,对低渗低产气井,这一现象尤为严重[1]
。
图1是低渗透气井产生水锁的机理结构示意图。水锁伤害产生的初步条件是该气井具有一个较低的残余原始含水饱和度,并且在一般毛管压力条件下该气井的原始含水饱和度小于多孔介质中的残余油条件下的含水饱和度。气井不产水或产水较少,干燥,致密,受成岩作用,易产生较低的残余油饱和度。
初始条件 溢满水相流体 用气解除水锁
图1 水锁效应孔隙比例机理图
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在干燥的条件下,由于多孔介质中原先就存在
低原始水饱和度,渗流剖面的大多数区域为气体流动,从而使气体的原始相对渗透率较高。但是由于修井(如钻井泥浆滤失,完井液,压井液等)作业后的流体的滤失,导致近井地带储层产生高含水饱和度以及流动临界含气饱和度。此时,若接着通过对该气井进行压降试井,其含水饱和度将减少到束缚水饱和度,而不是降低到很低的原始含水饱和度。若束缚水饱和度远远大于原始水饱和度,则该渗流剖面上的气体流动就会受到较大限制,气体的相对渗透率也会相应降低。
二、新场上沙气藏水锁伤害实验研究
1.水锁效应实验测试
本次实验主要采用长岩心驱替实验来进行测试
。反渗吸水锁启动压差实验的评价手段主要是通
过不同阶段长岩心气驱水压力和气相渗透率的变化来作定性和定量的评价,其中流速和压差是一种评
价手段。实验表明,新场上沙气藏J s 21、J s 23
气层,随着气井近井地层岩心中反渗吸水锁量的增加,使其恢复流动所需的启动压差也相应提高(图2)。
图2 常规岩样启动压差与水锁量的关系
图3 水锁后采出气量与渗透率关系(0.1HP V )
为了实验模拟反向水锁机理,气驱水过程在长
岩心出口端注少量地层水形成近井带的水锁状态。运用稳定法分别对实验中束缚水存在条件下不同水
锁强度(0.1、0.2、0.3HP V )气驱水过程气相渗透率进行了测试(图3)。在束缚水存在条件下,测得气相有效渗透率随气体累积产出量的增加而得到恢复,当产出气量较少时,气相有效渗透率较小,反映了水锁堵塞的影响。
2.水锁效应对压裂开发的影响
相渗曲线表明,束缚水饱和度(70%)远远大于原始含水饱和度(50%)。而两者差值越大,不利的相对渗透率效应也就越明显,水相圈闭渗透率造成
损害的可能性就越大[2]
。除了对井底积液严重的井采用适当的排水采气工艺外,应积极寻找其它多种解除水锁的方法、技术,有效提高气井产能。
图4 新场J s 21压裂液返排率与滤失带启动压力关系
压裂是解除水锁的一个重要手段,但是压裂过程中本身也伴随着水锁伤害现象。通过长岩心驱替实验发现,随着气井近井地层岩心中反渗吸水锁量的增加,使其恢复流动所需的启动压差也相应提高,以J s 21
为例,孔隙度取10.8%,储层厚度22m ,压裂液500m 3,压裂缝长200m ,滤失半径0.6m 计算,当返排率从80%下降到40%时,气体通过滤失带流
动需要克服的启动压力从0.94MPa 上升到7.15MPa (图4),而启动压力的增加,反过来使压裂液返排率降低,对储层造成极大的伤害。因此,通过低伤害压裂液技术和改善压裂工艺中的返排技术,可以降低压裂过程中的水锁伤害,提高压裂见效水平和储量的动用程度。
三、开发技术对策
1.气井水锁解除机理
在气井中,沿径向方向上解除水锁伤害,通常要
经过两个阶段:①气井生产过程中蒸发解除水锁。在气井生产过程中,由于天然气的抽提蒸发效应,可使部分地层水蒸发为气态而被采出。天然气中含气态地层水量随着地层压力的下降而增加,因此在低渗气井生产过程中,含水的岩石孔隙中完全饱和有
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压缩性流动的气体将引发蒸发现象,通过气体的萃取抽提作用蒸发掉近井地层的水,降低了含水饱和度,恢复了近井地层的气体渗透率,达到了解除水锁伤害的目的,从而可提高低渗气井的产能。对于不产地层水的气井,这一机理是有效的。②气井生产过程中气驱解除水锁伤害的机理。气井在生产过程中水锁伤害解除的另一机理是利用产出的天然气的有效压能,驱替近井地层的水,降低近井地层的含水饱和度,恢复近井地层的气体渗透率,达到解除水锁伤害的目的,从而提高低渗气井的产能。
2.新场上沙气藏水锁解除技术
目前国内外采用的低渗气藏水锁解除方法主要有:水力压裂、注混相溶剂、预热地层、添加表面活性剂、注气吞吐等[3]。结合新场气田上沙气藏的开发地质、生产动态特征及现场试验,主要采用的开发对策是采用大型水力压裂,优化低伤害压裂液,并全程混氮加强返排工艺。
将混气压裂液在高压下挤入地层,可起到隔离、降滤失和助排作用,且返排效果明显。氮气具有储能性质,压裂过程中加入液氮的基本目的就是充分利用氮气的压缩势能,克服水锁效应,增大压裂液的返排率[4]。混气压裂先后经历前置液混注氮气、携砂液混注氮气和顶替液混注氮气三个过程。前置液及先期泵注的携砂液在裂缝中的暴露时间长,滤失量大,距离井筒远,应将这一部分压裂液的混气量增大,提高氮气的降滤失、助排作用(为提高混注氮气的降滤失能力,可以考虑在前置液增加发泡剂);而在缝口附近不宜将氮气量提高,防止砂沉不连续或干扰砂子的沉降,使裂缝得不到有效支撑。建议混注氮气量按照泵注压裂液的次序线性递减或台阶性递减,这既能保证返排时氮气的连续性,又可保证填砂的有效性。值得注意的是顶替液混注氮气时,必须准确计算混气液量,以免顶替过量,将携砂液送入地层过深,造成裂缝闭合,渗流能力降低,影响压裂效果。
在新场上沙气藏难动用储量开发中,近期实施的压裂气井全部采用了全程混氮并纤维防砂技术,现场应用效果显著。根据实验数据,计算优化混注氮量为7%～9%,混氮方式为按照泵注压裂液的次序线性递减混氮,至缝口处降至零。
四、现场实例分析
通过采用低伤害压裂工艺技术、大型压裂工艺技术和高效返排工艺技术,在新场J s
2
1、J s
2
3气藏难动用储量压裂开发试验井取得实质性进展,施工成
功率100%,压后12h平均返排率达到70%以上,压后单层平均无阻流量5×104m3/d,如川孝487-1井加入陶粒70m3,压后在16.5MPa下测试产量: 5.2621×104m3/d,川孝470-1井输气产量达到: 1.567×104m3/d、川孝492D井测试产量达到2×104m3/d左右。
五、结论与认识
(1)新场上沙气藏开发过程中,由于凝析水、地层水以及外来水侵入气层,将产生水锁伤害,严重影响气体相对渗透率;
(2)低渗砂岩气藏压裂液滤失将导致滤失带启动压力增加,压裂液返排困难,对储层造成极大伤
害,这也是新场J s
2
1、J s
2
3储量难动用的重要原因之一;
(3)采用大型水力压裂技术、低伤害压裂液技术,并全程混氮加强返排工艺,对新场上沙气藏是有效的开发对策,其中,优化混氮量为7%～9%,混氮方式采用线性混氮;
(4)低渗砂岩气藏的水锁伤害特征具有普遍性,本次研究对于国内外同类气藏的开发具有借鉴意义。
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Research I nstitute of L iaohe O ilfield Company,Xingl ongtai D is2 trict,Panjin City124010,L iaoning Pr ovince,P.R.China Tel: 86-427-7803884 E-mail:l onghua3138@https://www.doczj.com/doc/033504600.html, M EASURE AN D MO N I T I O R I NG TECHN I QUES O F RE M A I N I NG O I L SATURAT I O N I N W ATERFLOOD D E2 VE LO P M ENT RESERVO I R AN D I TS APPL I CAT I O N CHAO Hongzhou,WANG Chiyu,L I U Feng,ZHAO J ian2 bin and DONG Ping(Natural Gas Depart m ent,CNPC Tari m O il2 field Company),D PT30(4),2007:84-87
Abstract:I n China,most waterfl ooding oil reservoir is ex2 p l oited overly,the integrated water content rati o is high,but the recovery rati o is l ow,new ly increased and residual reserves is not available.Undergr ound remaining oil has a great potential t o in2 crease exp l oitable reserve and recovery rati o.This paper briefly in2 tr oduced the f or m ing conditi ons,distributi on,influencing fact or and research method of re maining oil.The key technique t o study remaining oil is confir m ing its oil saturati on.So,this paper intr o2 duced s ome l ogging technol ogies of re maining oil saturati on in the open hole well and cased hole,such as Neutr on L ifeti m e Logging (NLL),Carbon-Oxygen(C/O)Spectral Logging and resistivity l og etc.,and analyzed the influence of s ome para meters such as por osity,cementati on index,for mati on water,te mperature and p ressure on A rchie for mula,and put for ward the method t o eli m i2 nate the influence of high salinity f or mati on https://www.doczj.com/doc/033504600.html,pared and analyzed the measure and monit oring means t o re maining oil satu2 rati on,this paper expounded the actuality and devel op ing trend of remaining oil saturati on l ogging technol ogy.
Key words:re maining oil,research method,oil saturati on, Carbon-Oxygen(C/O)Spectral Logging,Neutr on L ifeti m e Log2 ging(NLL),resistivity l og
CHAO Hongzhou(engineer),born in1972,graduated fr om the Che m ical Engineering Depart m ent in Xi’an Shiyou I nstitute, is engaged in the manage ment of gr ound engineering technol ogy. Add:Natural Gas Depart m ent,CNPC Tari m O ilfield Company, Korla841000,Xinjiang,P.R.C. Tel:86-996-2175342 E-mail:chaohz@https://www.doczj.com/doc/033504600.html,
RESEARCH O N CO RRE LAT I V I T Y O F D I FFERENT W E LL-T Y PE’S D R I L L I NG CO ST I N O I L F I E LD D EVE L2 O P M ENT
X I E Danfeng1,CHEN W u1,CHE N Jun1,ZHONG Shuiqing1,2,ZHAO M ao1,2,ZHANG Yuanze2,WANG Q ianl ong3 and CHEN Huail ong4(1.Engineering Technique I nstitute,Shan2 dong University of Technol ogy;https://www.doczj.com/doc/033504600.html,PC Sichuan Petr oleu m;3. Changqing O ilfield D rilling Co.;4.Research I nstitute of Petr ole2 u m Exp l orati on and Devel opment),D PT30(4),2007:88-90 Abstract:W hen p r oducing oil-gas res ources,the vertical well,directi onal well,horiz ontal well or extended reach well are drilled.D ifferent well-type corres ponds t o different drilling cost, and results in different econom ic benefit.Therefore,it is i m portant t o dope out drilling cost accurately.However,not all kinds of well -type’s drilling cost are easy t o survey,such as the drilling cost of horizontal well and extended reach well is difficult t o dope out because of their high technol ogical difficulties,comp lex drilling situati ons and excessive random fact ors.The paper utilized rank-related-coefficient and regressi on analysis methods in statistics t o analyze different well-types’drilling cost data of5oilfields,de2 ter m ined the rank correlativity a mong different well-type’s unit drilling cost,and i m itated the relati on curve of well-type and unit drilling cost,finally obtained the conclusi on that the cost permeter of vertical well,directi onal well,horiz ontal well and extended reach well have assu med e0.4202rising.It p r ovided a shortcut f or survey drilling cost.
Key words:directi onal well,horiz ontal well,extended reach well,drill f ootage,drilling cost,trend fitting
X I E Danfeng(fe m ale),graduated fr om the M anage ment Sci2 ence and Engineering Depart m ent in South west Petr oleu m Univer2 sity in2006,now she is a lecturer of Engineering Techniques I n2 stitute,Shandong University of Technol ogy.Add:Engineering Technique I nstitute,Shandong University of Technol ogy,Zibo City 255012,Shandong Pr ovince,P.R.China Mobile Phone: 138******** E-mail:xuan19810108@https://www.doczj.com/doc/033504600.html,
PRESSURE D R O P M ECHAN I S M O F ENHANC I NG W ATER I NJECT I O N TECHNOLO GY W I TH HYD R O PH O2 B I C I T Y NAN OM ETER S i O2
D I Q i n feng1,G U Chunyuan1,SH I L iyi1and F ANG Hai p2 ing2(1.Shanghai University;2.Shanghai I nstitute of App lied Physics,Chinese Acade my of Sciences),D PT30(4),2007:91 -94
Abstract:According t o the new sli ppage effect on nanopat2 terned interfaces,the p ressure dr op mechanis m s of enhancing water injecti on technol ogy w ith hydr ophobicity nanometer Si O2were put for ward.W hen hydr ophobicity nanoparticleswere ads orbed on sur2 face of por ous walls,nanoparticles layer was f or med instead of hy2 drated layer.W ettability of pore wall then beca me str ongly hydr o2 phobicity fr om hydr ophilicity,and sli p effects on nanoparticles lay2 er happened,it decreases the fl ow resistance obvi ously and makes fluid vel ocity obvi ously faster.Experi m ents of changing wettability of por ous walls were done,and the facts that por ous walls surface were abs orbed by nanoparticles was validated under SE M.The re2 sults of fl ow experi m ent show water-phase per meability were in2 creased about47percent averagely after treat m ent by nanofluid.
Key words:hydr ophobicity nanometer Si O2,sli ppage effect, wettability,water injecti on
D I Q i n feng,is a doct or and p r ofess or,his research direc2 ti on:engineering mechanics,string dynam ics and app licati on, and
E OR technique.Add:M echanics I nstitute,Shanghai Univer2 sity,149Yanchang Road,Shanghai City200072,P.R.China Tel:86-21-56333256 E-mail:qinfengd@https://www.doczj.com/doc/033504600.html, STU DY O N W ATER LOCK EFFECT I N X I NCHANG SHANGSHA GAS RESERVO I R
X I O NG X i n dong1,2,WANG Shize2,Z HANG Guodong2, ZHAO J inzhou3and T ANG Yong3(1.Post-Doct orWorkstati on of South west Petr oleu m B ranch,Sinopec;2.Engineering Technol ogy Research I nstitute,South west Petr oleu m B ranch,Sinopec;3. South west Petr oleu m University),D PT30(4),2007:95-97 Abstract:Special geol ogic characteristics of l ow per meability gas reservoirs caused relatively str ong water l ock effect,which re2 duced the rate of single gas well and effected the devel opment of reserves.I n this paper,based on a l ot of experi m ents,water l ock mechanis m,affecti ons t o exp l oitati on,and the ways t o release wa2 ter l ock da mage were studied.W ater l ock would enlarge threshold p ressure and reduce the per meability of gas phase.W hen thresh2 old p ressure r ose fr om0.94MPa t o7.15MPa,the fl ow back rate of fracture liquid would decrease fr om80%t o40%which da maged for mati on greatly.Technol ogy of fracture fluid op ti m izati on and ni2 tr ogen pu mp ing at one ti m e were effective t o release water l ock in XinChang gas field.
Key words:l ow per meability gas reservoirs,water l ock effect,release water l ock damage,devel opment strategy,Xin2 chang gas field
X I O NG X i n dong,born in1973,is engaged in the research on oil/gas field devel opment in the Post-Doct or Workstati on of South west B ranch,Sinopec.Add:298North Longquanshan Road,Deyang City618000,Sichuan Pr ovince,P.R.China Tel:86-838-8941039 E-mail:xxds wp i@https://www.doczj.com/doc/033504600.html, ANALY S I S O F EFFECT O F CE M ENT SHEATH O N CAS I NG M ECHAN I CAL PR O PERT Y I N O I L-GAS W E LL L IM aohua1,XU Shouyu1and N I U W eidong2(1.College of Geo-res ources and I nfor mati on,China University of Petr oleu m (East China);2.Shengli O ilfield Bohai No.2D rilling Co.), D PT30(4),2007:98-101
Abstract:The article established the model of t w o di m ensi on p lane axis sy mmetry and p lane strain,and utilized Ansys finite el2 ement s oft w are t o analyze the def or mati on feature of casing under the effect of ce ment sheath.The analysis results indicate,the earth stress act on ce ment sheath in p r oducti on,the maxi m u m stress f or m on in wall of casing.Under the unifor m l oad,casing
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Vol.30No.4July2007DR I L L I N G&PRODUCTI O N TECHNOLOGY