低温调堵剂凝胶的流变特性

大庆石油学院学报
第32卷第3期2008年6月J OU RNAL OF DAQ IN G PETROL EUM INSTITU TE Vol.32No.3J un.2008
收稿日期:2007210218;审稿人:卢祥国;编辑:任志平
基金项目:国家科技攻关项目(2003BA613-07-05)
作者简介:张继红(1969-),女,博士,副教授,主要从事油气田开发与提高采收率方面的研究.
低温调堵剂凝胶的流变特性
张继红1,王亚楠1,赵提财1,于海明1,刘明君2
(1.大庆石油学院提高油气采收率教育部重点实验室,黑龙江大庆　163318;　2.大庆油田有限责任公司第九采油
厂,黑龙江大庆　163853)
摘　要:采用RS600流变仪PP20防滑锥板测量系统,通过流变特性实验,研究低温调堵剂凝胶的黏弹特性、屈服应
力特性和蠕变回复特性.实验结果表明,低温调堵剂凝胶为黏弹性体,其弹性特征强于黏性特征,损耗角始终低于45°;低
温调堵剂凝胶表现出较强的屈服应力特征,屈服应力变大,达到屈服点后存在应变变软,其屈服应力随主剂质量分数的
增大而增大,说明主剂质量分数大的调堵剂凝胶自身的材料胶结强度较大.调堵剂凝胶体系具有蠕变-回复特性,在定
应力和相同加载时间下测得调堵剂凝胶的柔量与主剂质量分数有关,主剂质量分数小时,柔量大,调堵剂凝胶容易变形.
关　键　词:调堵剂;凝胶;流变性;屈服应力;蠕变回复
中图分类号:TE243 文献标识码:A 文章编号:100021891(2008)0320034203
由于油藏具有非均质性,导致注入水沿高渗透层或大孔道“窜流”,使得各层储量动用程度差,油田含水率上升速度快,油田水驱采收率和注水利用率降低,必须采用高强度的调堵剂对油藏的高渗透层或大孔道进行有效调堵,以提高油田的水驱采收率[1].低温凝胶类调堵剂在高渗透、大孔道油藏中具有良好的注入特性,能够被顺利地运移到预定封堵位置,堵[2].调堵剂的封堵强度综合反应高强度调堵剂调堵能力,具体表现为调堵剂自身的材料强度和调堵剂凝胶与岩心孔隙基质表面的黏结强度[3].通过低温调堵剂凝胶的黏弹特性、屈服应力特性和蠕变回复特性实验,研究低温调堵剂凝胶自身的材料强度.
1　实验材料和方法
低温调堵剂凝胶是对扶余油田低温(低于30℃
)大孔道油藏研制的淀粉接枝聚合物凝胶,其溶液体系主要由淀粉接枝聚合物(主剂)、有机交联剂、引发剂、缓聚剂组成.将成胶后的调堵剂体系简称为低温调堵剂凝胶.低温调堵剂溶液成胶后,形成具有黏弹性的凝胶态材料.
使用德国HAA KE 公司RS600流变仪,采用转子Sensor 为PP20的防滑锥板测量系统,测量低温调堵剂凝胶的黏性、弹性、屈服应力特性及蠕图1　凝胶的黏弹特性曲线
变-回复特性[4].
2　调堵剂凝胶影响因素
2.1　黏弹特性
调堵剂凝胶体系的黏弹特性实验条件为30℃、振荡
频率f 为0.10～10.00Hz ,在剪切应力τ为1Pa 时,不
同频率下调堵剂凝胶的黏弹特性曲线见图1,其中G ′为
储能模量,G ″为耗能模量.由图1可以看出,振荡频率低
时,储能模量比耗能模量大10倍左右;随着频率增大,储
能模量和耗能模量呈上升趋势,但储能模量比耗能模量上升的幅值小,储能模量上升约60%,耗能模量上升约20%,说明在一定频率范围内,调堵剂凝胶为黏弹性流体,且其流变特性主要以弹性为主.
在线性黏弹性理论中,应力与应变之间的损耗角(也称为相位角)δ也是表示物料黏弹性的参数,δ在
本质上是与储能模量和耗能模量有关的量,其正切等于储能模量与耗能模量的比值,即tan δ=G ″/G ′[5].
在实验过程中,对调堵剂凝胶施加一个按正弦时间函数变化的振荡剪切应力τ:
τ=τ0sin (ω
t ),(1)式中:τ0为振荡剪切应力的幅值;ω为振荡角频率,ω=2
πf .测量相关时间的应变γ为γ=γ0sin (ω
t -δ),(2)式中:γ0为振荡剪切应变的幅值.
令|G 3|=τ0/γ0,G 3为绝对动态模量,G
′=|G 3|co s δ,G ″=|G 3|sin δ,δ=arctan (G ″/G ′).δ=0°时为纯弹性固体;δ=90°时为纯黏性流体;0°<δ<90°时为黏弹性体[6].
在凝胶的黏弹性测量过程中,若储能模量比耗能模量大,则δ低于45°,凝胶表现出的弹性特征强于其黏性特征;反之,若储能模量比耗能模量小,则δ高于45°,凝胶表现出的黏性特征强于其弹性特征
.图2　调堵剂凝胶损耗角随振荡频率的变化曲线 在不同频率下振荡剪切过程中调堵剂凝胶δ的变化见图
2.由图2可以看出,在一定频率范围内,δ随着频率的增大而
增大,但增加的幅值不大,且δ始终低于45°,说明该调堵剂凝
胶为弹性大、黏性小的黏弹性体.该凝胶体系的弹性较大、韧
性较强,在与地层岩石孔隙介质相胶结时强度大,在没有外力
破坏的情况下其胶结强度长久不变.
2.2　屈服应力特性
屈服应力是样品“坚固强度”的一种表征,与样品成分、均
质性、凝胶状态等有关系[4].调堵剂凝胶的屈服应力测量采
用的是CS 应力扫描,
在屈服应力测量过程中,控制剪切速率
图3　不同主剂质量分数凝胶屈服应力测量曲线为0.3s -1,控制测量时间为180s ,测量温度为30℃,测定剪
切应力的变化.
不同主剂质量分数下调堵剂凝胶的屈服应力测量曲线见
图3,其中σ为屈服应力,t 为时间.由图3可以看出,在相同
时间内,随着主剂质量分数增加,调堵剂凝胶所受到的剪切应
力增加,应力与时间的关系曲线呈逐渐上升趋势.当测量时
间约为100s 时,曲线上升到峰值;然后曲线下降,当下降到
一定程度后又趋于平稳.根据应力与时间关系曲线中的峰值
转矩,确定调堵剂凝胶样品的屈服应力.同时,得出该调堵剂
的屈服应力特征:①屈服应变比金属大得多,主要原因是材料
本身黏弹性的作用;②过屈服点后,有一应力下降不大,即应
表1　不同主剂质量分数凝胶的屈服应力w (主剂)/%σ/Pa
733508363496195变变软.
同一剪切速率( γ=0.3s -1)、不同主剂质量分数下的屈
服应力变化见表1.由表1可以看出,主剂质量分数越大,调堵剂凝胶的屈服应力越大,说明调堵剂凝胶自身的材料胶结
强度会更大、更坚固.
2.3　蠕变-回复特性
蠕变-回复显示一定应力下样品黏性和弹性的时间响应,凝胶的蠕变-回复特性采用CS 流变方法进行测量,在测量过程中设定恒定应力,测定与时间相关的应变γ(t ):
第3期 张继红等:低温调堵剂凝胶的流变特性
γ(t )=J (t )τ,(3)
式中:J (t )为柔量,是与时间相关的物质常数,类似于稳态流动试验中的黏度.该参数表明样品的柔性,在给定应力下,样品的柔量越高,样品就越容易变形[7].只要为实验样品设定的实验条件能够确保应力/应变关系处于线性黏弹性区域,柔量就与所施加的应力无关[8].
调堵剂凝胶的蠕变-回复应变曲线见图4.由图4可以看出,当设定应力τ为1kPa ,蠕变、回复时间为300s 时,一旦给调堵剂凝胶体系施加应力,应变就会增加,但随着时间的增加,应变增加量逐渐减少,表示有蠕变现象;在施加应力后期,应变随时间几乎不再增加,说明这时即使延长加载时间,调堵剂凝胶也不会再发生蠕变现象.卸载后调堵剂凝胶可基本恢复加载前的状态,表明对调堵剂凝胶所加应力在弹性极限应力范围内.
不同主剂质量分数调堵剂凝胶的蠕变-回复柔量曲线见图5.由图5可以看出,加载后各主剂质量分数下的调堵剂凝胶的柔量不断增大,但增加的幅度逐渐减小;τ为1kPa 时,加载50s 后柔量与时间的对应关系曲线基本为水平线,说明柔量不再增加.另外,主剂质量分数越小,在同一加载时间内,调堵剂凝胶的柔量越大,即调堵剂溶液中主剂质量分数越少,其成胶后的调堵剂凝胶在定应力下就越容易变形.因此,为防止变形应尽量选择主剂质量分数较高的调堵剂
.
图4　凝胶的蠕变-
回复应变曲线图5　不同单体质量分数凝胶的蠕变-回复柔量曲线
3　结论
(1)在一定频率范围内,低温调堵剂凝胶的储能模量大于耗能模量,且损耗角始终低于45°,说明该调堵剂凝胶为黏弹性流体,且其弹性特征强于黏性特征.
(2)低温调堵剂凝胶表现出较强的屈服应力特征,主剂质量分数越大,调堵剂凝胶的屈服应力越大,说明主剂质量分数大的调堵剂凝胶其自身材料胶结强度大.
(3)调堵剂凝胶体系存在蠕变-回复现象,并且在同一加载时间内,调堵剂凝胶的柔量随主剂质量分数的减小而增大,说明主剂质量分数小的调堵剂凝胶在定应力下容易变形.
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K ey w ords:Lamadian oilfield;wettability;reservoir nat ure;water driven oil;infill well
Solution to the unsteady flow problem in anisotropic triple2porosity reservoir with impermeable top and bot2 tom boundaries and a partially penetrating vertical w ell based on the source f unction approach/2008,32(3): 29-33
WAN G Hai2tao,ZHAN G Lie2hui
(S t ate Key L aboratory of Oil an d Gas Reservoi rs Geolog y and ex ploitation,S out h W est Pet roleum U2 ni versit y,Cheng d u610500,Chi na)
Abstract:In order to solve t he unsteady flow problem in anisot ropic t riple2poro sity reservoir wit h t he im2 permeable top and bottom boundaries and a partially penet rating vertical well,firstly,we used“Point Source”and“Line Source”approach to obtain t he point source solution in a infinite3D reservoir,t hen u2 tilized t he“mirror image”p rinciple and Poisson summation equation to obtain t he point source solution in a3D reservoir wit h t he impermeable top and bottom boundaries,t hen integrate t he continuous point source solution along t he penet rating formation to obtain t he solution of t he concerning problem under u2 niform2flux idealization.Then we utilized t he conclusion about“Efficient average pressure point”which was derived by Gringarten and Ramey to obtain t he solution of an infinite2conductivity line source in con2 cerning conditions.Finally he utilized t he Stehfest numerical inversion and program design to draw typi2 cal curves,and analyzed t he factors which affect t he shape of t he typical curves such as storativity, t ransfer coefficient,t he penet rating ratio,and vertical anisot ropy degree.The result s help people to un2 derstand t he flow mechanism of t his type of reservoir and also can be employed for well test and p roduc2 tivity research and so on.It p rovides t heoretical basis for people to reasonably develop reservoir.
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(1.Key L aboratory f or Enhanci ng Oil/Gas Recovery of M i nist ry of Ed ucation,D aqi n g Pet roleum
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DEN G Song2sheng1,YAN G Li2yun1,DON G Jian2wei1,L I Zhao2jie1,Q IN Wei2
(1.De pt.of M ilit ary Oil S u p pl y Engi neeri ng,L EU,Chongqi ng400016,Chi na;2.S out hw est S y n2 t hetic Pharm aceutical Cor p.L t d.,Chongqi ng401147,Chi na)
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K ey w ords:fire;buried pipeline;unstable temperat ure field;finite difference;grid division
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DA I Jiang1,2,L I Zi2feng1,L IU Guo2zhi2,YU Zhen2dong2
(1.M echanical Engi neeri ng College,Yans han Universit y,Qi nhuang dao,Hebei066004,Chi na;2. Oil Testi n g Com p any of D aqi n g Oil f iel d Cor p.L t d.,D aqi ng,Heilong j i ang163412,Chi na) Abstract:A technology of fract uring two-layers wit h single st ring running means t hat it can fract ure two layers,and finish flowing back and t he production testing after f ract uring wit hout p ulling st ring. Wit h t he reasonable design of st ring struct ure and downhole tools,t he p ressure monitoring and well temperat ure measuring can be finished,and a complete set of technology is formed t hat contains two-。