限流压裂曲线分析及压开层位的判定计算冯明生 方宏长中国石油天然气集团公司石油勘探开发科学研究院前 言在层间存在应力差的情况下,对多油层进行压裂,一般选择投球压裂或者限流压裂方式,其压开的层位一般要根据压后的井温或产液剖面进行判定,但费用高、判定不及时、易产生影响的因素较多,且不可能对每口井进行测试。

有很多学者曾对压裂曲线进行了分析,但集中于裂缝参数的解释,若能通过对多层压裂曲线进行分析来判断压开的层位,不仅有经济意义,而且具实际意义。

作者利用孔眼摩阻公式已解释了投球压裂曲线[1],建立了相应的关系式,可以判定投球是否压开新层以及压开的层位。

在此基础上,笔者对限流压裂曲线进行解释,并应用于鄯善等油田。

基本公式及参数下述公式参数的敏感性分析以及对曲线分析的假设已在文献[1]中进行了论述,这里不赘述。

孔眼摩阻P m=(22.88q2ρ)/(d p4a2)(1)q=Q/n p(2) 对鄯善油田有P m=28.7(Q/n p)2(3)n p=5.357(Q/P m1/2)(4) 停泵后的瞬时压降落差为p L=p j-p isi=p f+P m+P e(5) 当p f=0时,由(5)式有P m=p L-P e=p j-p isi-P e(6) 利用(4)式和(6)式就可以计算畅通的孔数(n p)。

用孔眼摩阻公式分析限流压裂在常规排量下,限流压裂布孔要求射孔总数一般不超过20左右,破裂压力高的地层布孔数相对较多,破裂压力低的地层布孔数相对较少。

可以利用(4)式和(6)式处理限流压裂的压降落差,如果计算的n p值等于射孔数,表明所有的层位被压开,如果n p值小于射孔数,则表明有的层没有压开,可对层间的布孔进行匹配组合,使之与n p值相等。

如有A、B、C三个层,其布孔分别是5个、3个、7个,若计算得n p值为10则表明B、C两层被压开,而A层没有压开,如果出现多种组合就应该综合其它因素进行考虑。

在限流压裂中,可在前置液中进行停泵,计算n p 数,如果压开程度差,则可投适当少量的球封堵畅通孔眼来改善层间布孔,以达到压开各层的目的,也可以就地改成投球压裂设计,其投球数等于n p值,或比n p值多1～2个球,这一设想是切实而且可行的。

用孔眼摩阻值分析限流压裂的砂堵。

设有A、B两油层,按限流压裂进行布孔,其布孔数分别为n A、n B,施工示意图见图1。

假设A层先砂堵,在A层砂堵过程中,其进液量逐渐减少,可忽略不计,直至完全砂堵,而对于B层,其进液量是逐渐增多的,其摩阻是逐渐增加的,所以井底压力急剧上升的增值就是B层孔眼摩阻增值。

即p m f=p2-p1=P m2-P m1(7)在第2点时孔眼摩阻值为P m2=28.7(Q2/n p2)2(8)在第1点时孔眼摩阻值为P m1=28.7(Q1/n p1)(9)施工完成后瞬时停泵时P m3=28.7(Q3/n p3)2(10)98 石　油　勘　探　与　开　发 1999年8月 PETRO LE UM EXP LORATI ON AND DE VE LOP ME NT V ol.26N o.4 图1　压裂施工示意图利用(10)式求出n p3,由于n p3=n p2,再由(7)式、(8)式、(9)式联立,计算出n p1,如果n p1-n p2=n A ,表明砂堵的是A 层,如果n p1-n p2=n B ,表明砂堵的是B 层。

对于多层限流压裂,应用上述方法不仅可以判断压开的层位,而且可以判断多次砂堵层位。

应用实例本文提出的方法已在吐哈油田S13218井、S10213井、S10216井、S7212井和S7214井等多口井得到了验证,现举2例。

1　S7214井压力监测曲线见图2,射孔情况见表1。

施工完停泵时,p L 为5.82MPa ,Q 为4.82m 3/min ,P e 为2.2MPa ,P m 为3.62MPa ,计算得n p 为14。

图2　S7214井压裂监测曲线表1　S7214井射孔情况表层位深度(m )厚度(m )孔数S3.12918.0～2932.414.48S3.22952.7～2961.79.06S4.13017.0～3031.014.08 从曲线上看施工完成前有砂堵显示,p m f 为2MPa ,Q 为4.82m 3/min ,由(7)式解得n p 为22。

两个n p 之差为6,表明S3.2层施工过程中砂堵,其余的层均被压开。

由图3可见,S3.1、S3.2、S4.1这3个层温度异常幅度很大,说明都被压开。

这表明计算结果与井温测试结果相吻合。

图3　S7214井压裂后井温图2　鄯12217井射孔及产液剖面测定情况见表2。

表2　鄯12217井射孔及产液剖面表层位深度(m )孔数产液深度(m )液量(m 3/d )S2.33009.5～3014.073009.5～3014.4530S3.23045.7～3056.5173045.7～3055.9321 从剖面情况看,两层都被压开,监测曲线见图4。

图4　S12217井压裂监测曲线第一次砂堵p m f =p 2-p 1=12.5MPa Q 2=Q 1=4.9m 3/min设砂堵前两层都被压开,则n p1=24。

由P m2=28.7(Q 2/n p2)2P m1=28.7(Q 1/n p1)209 石油勘探与开发・油田开发 V ol.26N o.4　解得n p1为7。

砂堵前24孔是畅通的,砂堵后7孔是畅通的,17孔变成了死孔眼,而这种孔数的分布与层的孔数匹配得十分吻合,表明S3.2层已砂堵,显然S2.3后砂堵。

施工完停泵时p L =p j -p isi =3.7MPa由于砂堵,裂缝内不再有大量液体流动,裂缝摩阻可忽略,即P e =0,则P m =3.7MPa ,因此n p =5.357(Q/P m1/2)=7虽然两层都砂堵了,但S2.3层在S3.2层已砂堵时接近砂堵,此后才完全砂堵,其进液能力仍然优于S3.2层,所以停泵计算的是7孔而不是24孔。

前后两次计算结果一致,既与层间布孔吻合,也与产液剖面测试结果一致,这表明分析符合实际情况。

应用本文方法对文献[2]中美国D J 盆地1口限流压裂井资料进行多次砂堵分析判断,前后吻合得很好,与井的各层布孔匹配得很好,也与文献报道压开层数相吻合,说明该方法也可适用于其他油田。

结 论限流压裂的瞬时压降落差表现为压开层位的畅通孔眼的摩阻值,其压降落差幅度越大,压开的层位越少,反之则越多。

压裂曲线压力突然上升,说明有层位在压裂过程中砂堵,压力上升幅度表现为其它压开层的孔眼摩阻的增值。

利用本文给出的关于限流压裂瞬时压降落差以及砂堵时的关系式进行分析计算,可以判断限流压开的层位及其砂堵的层位,实例应用表明该方法简单、可靠,具有自我验证性。

这种方法不仅可以进行压后分析,也可以用在压裂过程中进行实时分析,及时反馈多层压裂剖面信息,实时地修改不符合地层实际情况的压裂设计。

符　号　注　释P m ———孔眼摩阻值,MPa ;q ———单孔流量,m 3/min ;ρ———液体密度,g/cm 3;d p ———孔眼直径,cm ;a ———孔流量系数;Q ———总注入流量,m 3/min ;n p ———畅通孔数;p L ———瞬时停泵时的压降落差,MPa ;p j ———瞬时停泵时的瞬时起始压力,MPa ;p isi ———瞬时停泵时的关井压力,MPa ;P f ———管道摩阻,MPa ;P e ———裂缝延伸摩阻,MPa ;p m f ———投球或砂堵造成的压力上升增值,MPa 。

下标:1,2,3———曲线上的3个点。

参　考　文　献1　冯明生.投球压裂曲线分析及压开层位的判定计算.大庆石油地质与开发,1999,18(2).2Dcramer D.The application of lim ited 2entry techniques in massive hydraulictreatments.Bjtitan CO SPE 16189.第一作者简介　冯明生,男,33岁,工程师,从事压裂、防砂、气库运行机制、油田开发和剩余油分布及挖潜的研究工作。

地址:北京市910信箱油气田开发研究所,邮政编码100083。

收稿日期　1998209214(编辑　陈志宏　郭海莉)《石油勘探与开发》1999年第5期部分文章预告吐鲁番坳陷含油气系统罗红军等………………………………………………………………………………………塔西南群苦恰克构造带油气运移与聚集张春明等……………………………………………………………………焉耆盆地三叠系—侏罗系含油气系统吴富强等………………………………………………………………………塔里木盆地巴楚地区构造样式与演化傅建奎等………………………………………………………………………准噶尔盆地侏罗系沉积构造与油气分布刘银河…………………………………………………………………………四川盆地寒武系—震旦系含气系统成藏特征及有利勘探区块戴鸿鸣等……………………………………………松辽盆地东部断陷盆地群层序地层学研究胡玉双等…………………………………………………………………安徽淮南地区上元古界至下古生界风暴岩特征及其沉积环境意义周进高等………………………………………碎屑岩天然气储集层次生孔隙形成的三种成因机理陈丽华等………………………………………………………苏北盆地溪桥含氦天然气田地质特征及含氦天然气勘探前景郭念发等……………………………………………大张坨凝析气藏循环注气开发方案研究崔立宏等……………………………………………………………………特低渗透油田裂缝发育区剩余油分布及调整技术熊维亮等…………………………………………………………低渗透油田地应力、裂缝系统与油田开发张莉等………………………………………………………………………确定地层原油粘度的经验方法苏继红等………………………………………………………………………………国际经营中油田开发方案编制的原则和思路杨雪雁 (1)9 1999年8月 冯明生等:限流压裂曲线分析及压开层位的判定计算 flooding.Before and after injection the combination system the NMR pictures were taken.In NMR picture a rich oil region was seen which indicates that this alkaline/sur factant is effective.Subject heading: Alkaline,Sur factant,C ombination drive,Inter facial tension,Enhanced oil recovery,Nuclear magnetic res onanceAnalysis of limited entry fracture curve and judgement of opened or screen2out zones.Feng,M ingsheng;et al.(Research Institute of Petroleum Exploration and Development,C NPC,Beijing100083,P. R.China).Shiyou Kantan Yu Kaifa1999,26(4),89291.Fracturing curves im ply much in formation about formation,but multi2zone fracturing curve is rarely discussed at present.With the per foration friction pressure equation,this paper analyses tw o im portant parts of the limited entry fracture pressure curve one of which is the instantaneous shut2in pressure drop,and the other is the sudden step2like pressure rise resulted in by the screen2out for the limited2entry,and new equations have been built up with which we can judge which zones are fractured up or not,and which zones are screened2out for the limited entry.This method has been proved by in formation of ten wells,its results very much fit to that of well tem perature testing,production section measurement and per foration distribution on the section.This method is economical,prom pt,sim ple and reliable.Subject heading:Limited entry fracturing,Curve,Friction loss,Decision,Layer locationThe application of interw ell tracer method in oilfield production. Zhao,G uoyu(Research Institute of Oilfield Chemistry T echnique, Zhongyuan Petroleum Exploraton Bureau,Henan457001,P.R. China).Shiyou Kantan Yu Kaifa1999,26(4),92295.F or a water flooding oilfield,interwell tracer method as a im portant oil reserv oir engineering means,has gained rapid development and extensive application in recent years.I t can feedback many reserv oir in formations such as heterogeneity of oil2bearing formations,distribution and flowing features of injection water etc..S ince1994,it has been under g one the experiment and application in m ore than80well groups of Zhongyuan oil field,and obtained better application efficiency.I ts operational technology,m onitoring technique and method of numerical analysis are successively developed and com pleted.This method has been applied mainly in following aspects:①combined with the result of data of well logging to determine the water production zone and determine the type and am ount of plugging agent used;②to identify the large passageways and to certify the sealing property of a fault;③to guide the making of a profile adjustment and water plugging program and④predict the recovery factor of the oil reserv oir.Interwell tracer technique gives a very g ood result of application in Zhongyuan oil field.An im portant guiding effect is developed in the determination of com prehensive block adjustment.A summarization of the experience and recognition in the technical process recognizes that interwell tracer method can als o be applied to determine the type,am ount of agents used in tertiary production and operational parameters can be used to evaluate the result of oil displacement.Thus it gives a technical reservation for the tertiary recovery which will be applied in Zhongyuan oil field.Subject heading:Interwell tracer,Output curve,Numerical analysis, Zhongyuan oil field,ApplicationLogging technology of geophysically absorbed light hydrocarbons and its petroleum geological significance.Li,G uangzhi;et al. (Petroleum G eochemical Prospecting Center,C NSPC,Anhui230022, P.R.China).Shiyou Kantan Yu Kaifa1999,26(4),96299,102. S ome of the light hydrocarbons migrated from the oil and gas reserv oirs well certainly be abs orbed by the s oil substrate during migration and leaves s ome migrating traces with significant characteristics behind them.Thus the evaluation and prediction of the hydrocarbon potentials below can be made by means of analyzing the characteristics of the geophysical abs orbed light hydrocarbons.A com plete consideration of the change of the state of occurrence and content of different com ponents in light hydrocarbons during the drilling and sam pling process,wetness of light hydrocarbons(W h),balancing point of light hydrocarbons (B h),characteristics of light hydrocarbons(C h),contents of C22C4, C52C7,C1/nC4,iC4/nC4,iC5/nC5,C2/(C1+C2+C3+C4+C5),C3/ (C1+C2+C3+C4+C5),nC4/(C1+C2+C3+C4+C5),etc.11 items of parameters are used to predict oil/gas beds and identify the type of oil/gas beds,evaluated the quality of reserv oir beds and determine the upper and lower limits of oil/gas reserv oir beds.Results of application shows that the physically abs orbed light hydrocarbon logging technique is rapid,accurate and economic and has a very g ood forecast in application.Subject heading:Logging,G eophysical abs orbed light hydrocarbons,Oil and gas formation,Evaluation,Prediction]71[ V ol.26　N o.4 ABSTRACT 。