基于核磁共振技术研究页岩自发渗吸过程  

NMR Study on Shale Spontaneous Imbibition

作　　者：蒙冕模 葛洪魁[1,2] 纪文明[1,2] 高启超[1,2] 任凯[1,2] 

机构地区：[1]油气资源与探测国家重点实验室中国石油大学,北京102249 [2]中国石油大学,北京102249

出　　处：《特种油气藏》2015年第5期137-140,158,共4页Special Oil & Gas Reservoirs

基　　金：国家"973"课题"致密储层人工缝网形成与重复压裂改造控制机理"(2015CB250903);国家自然科学基金重大项目课题"多重耦合下的页岩油气安全优质钻井理论"(51490652)

摘　　要：页岩储层水力压裂初期形成水锁,导致压裂液返排率低,关井一段时间后水锁自动解除。运用低磁场核磁共振技术,研究压裂液在页岩自发渗吸过程中的分布特征。结果表明:砂岩和火山岩T2谱均存在3个峰,随自发渗吸时间的增加,核磁信号振幅均匀增加,表明砂岩和火山岩自发渗吸过程中,所有孔隙均匀吸水;但页岩T2谱具有双峰特征,且自发渗吸过程中核磁信号振幅增加具有不对称特征,右峰(大孔隙和裂缝)在自发渗吸初期被迅速充满,随自发渗吸时间的增加,左峰的左翼振幅逐渐重合,表明液体优先充满微孔隙,右翼振幅逐渐增加,稍大孔隙逐渐被液体充填,且右翼整体向右移动,表明页岩中出现了大量的新孔隙,新增孔隙是吸水膨胀产生的微裂缝。Water- block is frequently generated in the early stage of hydraulic fracturing in shale reservoirs,which leads to low flowback ratio of fracturing fluid,and it will automatically release after shut- in for a certain time. In order to determine the reason of this phenomenon,low magnetic- field intensity NMR was used to identify the fracturing fluid distribution in the spontaneous imbibition of shale reservoir. Research indicates that there are 3 peaks in the T2 spectrums of both sandstone and volcanic samples. The amplitudes of NMR signals increase evenly with the time of spontaneous imbibition,which shows that all the pores of sandstone and volcanic samples absorb water evenly during the spontaneous imbibition. The T2 spectrums of shale sampleshavefeature of double peaks and the amplitudes of NMR signals increase asymmetrically during the spontaneous imbibition. The right peak( large pores and cracks) is rapidly filled in the early stage of spontaneous imbibition. The left- wing amplitudes of left- peak gradually overlap in the spontaneous imbibition process,which demonstrates that micropores werepreferentially filled by fluid. The amplitudes of right- wing gradually increase and relatively large pores were filled by fluid. In addition,the right- wing moves to the right integrally,which manifests that there are a lot of new pores in shale samples,and these new pores are microcracks resulted from imbibition and swelling.

关 键 词：自发渗吸 核磁共振 页岩 水力压裂 

分 类 号：TE357.1[石油与天然气工程—油气田开发工程]