[收稿日期]2010 10 02[基金项目]国家科技支撑计划项目(2006BAB03B03)。

[作者简介]叶礼友(1982 ),男,2005年中国石油大学(华东)毕业,博士生,现主要从事低渗气藏渗流理论及工程应用研究工作。

可动水饱和度作为低渗砂岩气藏储层评价参数的论证叶礼友 (中国科学院渗流流体力学研究所,河北廊坊065007)高树生,熊 伟,胡志明,郭和坤(中国石油勘探开发研究院廊坊分院,河北廊坊065007)[摘要]由于低渗砂岩气藏高含水饱和度、易产水且产水量对于气藏的开发效果影响很大,使得采用常规储层评价方法评价低渗砂岩气藏时出现较大偏差,因此寻求能表征储层产水特征的新评价参数是低渗砂岩气藏储层评价的前提。

通过室内大量岩心核磁共振测试的可动水饱和度及其与对应储层物性孔隙度、渗透率及含水饱和度之间的关系对比分析表明,低渗砂岩储层的可动水饱和度与储层孔隙度、渗透率及原始含水饱和度之间都没有很好的对应关系,可动水饱和度是由储层的微观孔隙结构决定的,与孔、渗同属一个层次的储层固有属性;而可动水饱和度测试结果与对应储层的气井产水特征分析表明,储层可动水饱和度与对应气井产水特征具有很好的对应关系,可动水饱和度可以有效表征低渗砂岩储层的产水特征。

因而,可动水饱和度作为低渗砂岩气藏储层的评价参数是可行而且有效的。

[关键词]低渗砂岩气藏;可动水饱和度;核磁共振;储层评价[中图分类号]T E122[文献标识码]A [文章编号]1000 9752(2011)01 0057 03储层评价是低渗砂岩气藏开发的重中之重,甜点 的确定才能保证气藏开发的经济性和有效性[1,2]。

由于低渗砂岩气藏低渗、高含水饱和度、易产水且产水量对于气藏的开发效果影响很大,使得采用常规储层评价方法来评价低渗砂岩气藏出现较大偏差,因而寻求能表征储层产水特征的新评价参数是低渗砂岩气藏储层评价的前提。

为此,通过室内核磁共振结合离心的方法测试了大量四川盆地须家河组低渗砂岩气藏储层岩心的可动水饱和度,分析了可动水饱和度与岩心物性及对应气井产水特征之间的关系,论证了可动水饱和度作为低渗砂岩气藏储层评价参数的必要性和可行性。

1 可动水饱和度低渗砂岩气藏储层中的原始含水饱和度一般较高,原生水包含束缚水和可动水。

束缚水吸附于岩石表面和赋存于微细孔喉内,在生产开发过程中无法运移;而可动水赋存在较大一些的孔喉或孔隙中,在生产过程中可以运移并部分产出,对气井产能影响很大。

核磁共振技术已广泛应用在油气田储层参数的研究中[3~6]。

应用核磁共振技术结合离心技术可测量岩心可动水饱和度。

首先,根据油气藏完全成藏理论,运用核磁共振技术结合离心的方法来确定试验岩心的T 2截止值。

将不同离心力离心后的核磁含水饱和度与原始含水饱和度对比后,确定300psi (2 068M Pa)是须家河组低渗砂岩储层原始含水饱和度对应的离心力。

由300psi 离心后对应的核磁共振T 2谱线结合饱和水状态的T 2谱线,计算得到的T 2值即为该岩心所代表的储层的T 2截止值。

图1中的二条谱线分别是岩心饱和水状态和300psi 离心后对应的T 2弛豫时间谱,离心后的T 2谱线与横轴包围的面积代表岩心原始含水饱和度的信息,饱和状态T 2谱线与离心后的T 2谱线之间的面积代表原始含气饱和度信息,其中虚线段为T 2截止值标定线,其右侧与离心后的T 2谱线包围的面积就是岩心的可动!57!石油天然气学报(江汉石油学院学报) 2011年1月 第33卷 第1期Journal of Oil and Gas Technology (J JPI) Jan 2011 Vol 33 No 1水信息,由此可计算出试验岩心可动水饱和度。

2 可动水饱和度是储层的固有属性测试了四川盆地须家河组低渗砂岩储层64块岩样的可动水饱和度,岩样孔隙度分布在3 65%~15 2%之间,渗透率分布在(0 0005~1 286)∀10-3 m 2之间,原始含水饱和度分布在27 16%~87 36%之间。

测试结果表明,可动水饱和度分布在5 08%~13 87%之间,且可动水饱和度与孔隙度、渗透率和原始含水饱和度都没有很好的对应关系,如图2~4所示。

孔隙度低的岩心可动水饱和度可能很高,而孔隙度高的岩心可动水饱和度可能很低。

这是由于所测孔隙度为有效孔隙度,其主要表征储层有效孔隙所占的比例,不能很好地表征孔隙之间的连通性,而可动水饱和度受到孔隙大小及连通性的影响;渗透率低的岩心可动水饱和度可能较高,而渗透率高的岩心可动水饱和度可能较低,这是由于尽管渗透率受孔隙大小及连通性的影响,但不同大小孔喉分布比例的岩心可能具有相同的渗透率,而可动水饱和度受不同大小孔喉分布比例影响大,小孔喉占的比例越高,可动水饱和度越低;可动水饱和度与原始含水饱和度没有很好的对应关系是由于原始含水饱和度不仅受到微观孔喉分布的影响,还受到成藏动力的影响。

图1 可动水饱和度核磁共振测试计算示意图 图2 可动水饱和度与孔隙度关系图3 可动水饱和度与渗透率关系 图4 可动水饱和度与原始含水饱和度关系可动水饱和度与孔隙度、渗透率及原始含水饱和度无对应关系,表明可动水饱和度是受储层微观孔隙结构决定的,与孔、渗同属一个层次的低渗储层固有属性,在储层评价中这一属性需要考虑。

!58! 石油天然气学报(江汉石油学院学报)2011年1月图5 可动水饱和度与气井产水特征的关系3 可动水饱和度可有效预测气井产水特征分析同一口井所取岩心的可动水饱和度平均值与对应的气井产水特征发现,可动水饱和度与气井产水具有明显的正相关关系(图5)。

可动水饱和度越大,气井产水量越大。

可动水饱和度低于6%的气井不产水,可动水饱和度介于6%~8%的气井产少量水,可动水饱和度介于8%~11%的气井大量产水,可动水饱和度大于11%的气井严重产水(如可动水饱和度大于11%的3口气井水淹,无法生产)。

气井是否产水的临界值为6%。

这表明可动水饱和度能表征低渗砂岩气藏储层的产水特征,可有效预测气井产水情况。

可动水饱和度作为储层的固有属性,且能有效表征低渗砂岩气藏产水特征,故应作为低渗砂岩气藏储层评价参数。

这一新参数的使用将储层产水特征这一低渗砂岩气藏重要评价信息纳入到评价方法中,使得评价方法更有针对性和准确性。

4 结 论 1)低渗砂岩气藏开发效果受气藏产水量影响很大,常规储层评价方法不适用于低渗砂岩气藏,需寻求能够表征储层产水特征的新储层评价参数。

2)可动水饱和度是与孔隙度和渗透率同属一个层次的低渗砂岩气藏储层的固有属性,且能有效表征低渗砂岩储层产水特征,应作为低渗砂岩气藏储层评价参数。

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effect of different microb es in differ ent culture media and inves tigating the degradation efficien cy of cru de oil,the surface tens ion ofm edia,viscosity of sample and relative content variation of saturated hydrocarb on,arom atic h ydrocarbon,non hydrocarb on and asphalt The r esult sh ows that th e bacteria u sed in the ex perim ent could degrade the crude oil T he cru de oils treated by bacteria w ere an alyz edw ith gas chromatograph(GC),then the resu lts of GC sh ow that the relative percent contents of crude oils changed a lot,approximatelysaturated hydrocarbon content were increas ed,aromatic h ydrocarbon,n on h yd rocarb on an d asphalt w ere lik ely rais ed or r educed un derdifferent condition s In con sideration of the variety of degradation efficien cy,su rface tension of medium,vis cosity and relatively compon ents conten t,microbial degradation improves the pr op erties of the crude oil greatly T he effect of Bjbios w ith No 1M ediu m is optimalon degrading cru de oil in this experimen tKey words:cru de oil;microbial degradation;surface ten sion;oil componen t;Qigequ an Oilfield53Volcanism and Halite Genesis in Shahejie Form ation of Paleaogene in Dongpu D epressionXUE Guo g ang,GAO Jia n zhen (First A uthor s A d dr ess:T he4th Oil Pr od uction P lant,Zhongy uan Oilf ie ld Comp any,SI N OP EC, Puy ang457001,China)Abstract:By studying volcanic and s aline rocks in Don gpu Dep ress ion,it w as found out th at th ey had features of equ itime and heteropic facies,alth ough volcan ic rocks w er e distributed in the south,w hile saline rocks w er e distributed in the n orth Based on the analysis of tectonic evolu tional character s in Dongpu Depres sion,it w as considered that volcanism w as caused continu ou sly in the Paleaogene basin, it indu ced lake w ater saline,dense lake w ater sun k onto the lake bottom and created hot brine w ith hig h den sity H eavy geothermal brin e flow ed from th e south to north,deposited in the north low lying lak e bottom as th e temperatu re fallin g dow n,and formed s alin e rock by chem ical sedim entation T herefore heavy geothermal b rine is the main mechanism of saline rocks in Dongpu DepressionKey words:Don gpu Dep ress ion;S hahejie Form ation;volcanism;brine;saline rock57Demonstration of Mobile Water Saturation as Evaluation Parameter of Low Permeability Sandstone Gas Reservoir YE Li yo u,GAO S hu sheng,XIO NG Wei,HU Zhi ming,GUO H e kun (First A uthor s A d dr ess:Institute of Porous Flow and Fluid M ech anics,T he Chinese Ac ade my of S cience s,L ang f an g065007,H ebe i,China)Abstract:Conventional res ervoir evaluation method w as unavailable for low permeability s and ston e gas res ervoirs,as th ey w ere easy to produ ce w ater and th e influence of w ater production to developm ent effect w as great S o,d eterm ining a new reser voir evaluation param e ter w hich could characterize w ater production of low permeability res ervoirs w as the first step for reservoir evaluation M obile w ater satu ration of great nu mber of core samples w as measu red by n uclear magnetic resonance(NM R),an d the relation ship betw een mobile w ater saturation and phys ical p roperty of cores and w ater p rodu ction of the cor resp ondin g gas w ells w as analyzed Th e resu lts s how that there is no good relationsh ip betw een mobile w ater s aturation and porosity,permeability an d original w ater s aturation M obile w ater satu ration is an intrins ic property of th e r eservoirs con trolled by the micr o pore structu re of reser voirs,w hich is on the sam e level w ith porosity and permeab ility;m ovable w ater s aturation and the w ater production of corresponding gas w ells have a good relationsh ip T his indicates that m obile w ater s aturation can effectively characterize the w ater production of low permeability sandstone gas reservoirs Th us,mobile wa ter s aturation u sed as th e evaluation param eters in low permeability sandstone gas res ervoirs is feasible and effectiveKey words:low perm eability san dstone gas r eservoir;m ob ile w ater saturation;n uclear magnetic r esonance;reservoir evaluation60The Application of Fuzzy Mathematic Method in C omprehensive Evaluation for the Low Permeability Reservoirs of C han gqing OilfieldWEI Yi,ZHAO Guo xi,ZHOU We n ge,H AN Fa jun,LI Ta o (A uth or s A dd ress:S tate K ey L abora tory f or E xp lor ation and De v elop ment of L ow p erme ability Oil and Gas Fields;Ex tr a low Per meability Re se rv oir s E xp lor ation and De ve lop ment P ilot Base, Ch angqing Oilf ield Comp any,X i an710078,S haanx i,Ch ina)Abstract:An integrated m ethod w as provided for comprehen sive evaluation of the multiple factors affecting low permeab ility reser voirs in L Wellb lock of G Oilfield in Changqing,by us ing fu zzy mathematic methods,th e s tu dy was b as ed on17parameters,the reservoirs w ere in tegrally evaluated,13param eters w er e chosen as the main factors for the com preh ens ive evalu ation in cons ideration of the result of corr e lation analysis Fuzzy math ematic methods w ere applied by using S PS S s oftw are for the comprehensive evaluation an d the prediction of H reservoir of G Oilfield Five larges t contributin g factors for reser voir characteriz ation was determined,and th e res ervoirs w ere su bdivided in to3types Th e m ethod is reliable in the prediction of favorable reservoirs,an d the classification results ar e proved to be consis tent w ith th e outcome of in dividu al w ell production rate with a coincidence rate over90% T he method of the comp rehensive evaluation using fuzzy m athematics is determined as an effective and desirable w ay for development of H res ervoir in G OilfieldKey words:low permeability;comprehen sive r eservoir evaluation;fuzzy m athematics;factor an aly sis;cluster analy sis;m ultiple compar is on63F orw ard Num erical Filtering of Low Frequency Electrom agnetic Field R espo ns e Ba sed o n F ast C osine T ra nsform F iltering A lg orithm XU Zhen ping,H U We n bao (Fir st A uth or s A d dr ess:College of Geop hysics and S p ace I nf ormation,China Univ er sity of G eosc i ences,Wu han430074,H ubei,China;K ey L abor atory of E xp lor ation T ec hnologies f or Oil and G as Resourc es(Yang tze Univ er sity), M inistr y of Ed ucation,Jing z hou434023,H ubei,China)Abstract:T he theoretical derivation method of fas t Hankel transform w as u sed to d erive the filter coefficients and algorithm of fast cosin e transform,an d the fast cosine tran sform filter coefficients w ere obtain ed,an d the cosine filter coefficien ts w ere us ed to calculate the high os cillation integrals and to redu ce the computation time,im prove th e accu racy of the calculation,It is applied for forw ard numerical calcu lation of low frequ ency electromagnetic field response of cylindrical coordinate and for an alyz ing the errors of the cos ine filtering algorithm of low frequency electromagnetic field resp on se an d the high precision frequen cy resp on se is obtain edKey words:fas t cos ine tran sform;fast H ankel transform;filterin g coefficient;electrom agnetic fields res pon se w ith cylindrical coordinates 68Seismic Sedimentary Study on Deepw ater Submarine Fan ReservoirsQI Yu,LIU Zhen,SUN Li c hun,LI Ya n,LIU Li na (Fir st A uth or s Ad d ress:Facu lty of Geoscie nces,China Univ er sity of P etr ole um;S tate K ey L aboratory f or P etrole um R esou rce s and P rospe cting,Ch ina Unive rsity of P etroleu m,B eij ing102249,China) Abstract:Seis mic sedimen tology had special advantages in depositional s ystems res earch In order to depict the depositional s ystem of submarine fan reservoirs more accurately,s eism ic s edimentary study was carried out by using strata s lice and frequ ency division interpr e tation of s ubmarine fan chann el Based on sequence stratigraphic fram ew ork,a series of strata slices w ere prepar ed T hose s trata slices#。