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季刊,2016年6月创刊
主管:教育部
主办:中国石油大学(北京)
   清华大学出版社有限公司
出版:清华大学出版社有限公司
编辑:《石油科学通报》编辑部
主编:陈勉
地址:北京市海淀区学院路20号院
   902信箱中国石油大学期刊社
邮编:100083
电话:010-82377349
         010-89734040
E-mail:bops@vip.163.com
     本刊导读
Unconsolidated sandstone formations display specific mechanical deformation behavior in their stimulation or injection,  
which is distinct from that of tight formations upon hydraulic fracturing. In this regard, the mechanical mechanisms must be  
revealed to interpret the macro and micro-scale deformation, therefore providing theoretical guidance for field practices. Given the
characteristics of an unconsolidated sandstone formation such as soft texture, great plasticity, and high permeability, this article  
brings in soil mechanics to introduce the formation stimulation and injection augmentation technique known as microfracturing, then  
delves into the dilation and microfracture initiation mechanisms during microfracturing in such a type of formation. Based on the  
microfracturing mechanisms, assessment methods of microfracturing efficiency, including laboratory experiments, analytical solu
tions, and numerical approaches, are discussed, and summarized on their necessity as well as advantages and disadvantages. Based  
on the mechanical mechanisms and the calculation methods, the applications of microfracturing in the stimulation of ultra-heavy oil  
formation, plugging-removal in wellbores and artificial interference of the geostress field, are discussed with respect to the detailed  
approaches and successful case studies. Finally, the automatic evaluation technique of microfracturing efficiency is proposed using  
ultra-heavy oil formation stimulation as an example. It is found that microfracturing is a complex mechanism that combines the  
theories and techniques of poroelasticity, plasticity, and fracture mechanics. It demonstrates various functionalities in different  
engineering scenarios, but generally shows a series of features of the process from dilation to microfracture initiation. It is believed  
that the analysis of its stimulation efficiency in realistic practices must consider multiscale effects and use multiple numerical  
approaches. Microfracturing in an ultra-heavy oil formation is mainly characterized by the microfracture generation surrounding the  
wellbores and the porosity dilation in between the dual wells, which lead to an enhanced effect of thermal convection and subse
quently a fast interwell hydraulic communication. Microfracturing in the plug removal of a wellbore results in a back flush of the  
sand grains, interwell porosity dilation and flow recovery through microfractures, which would extend the efficiency of the removal  
attempt. Moreover, microfracturing can also provide a means of artificial geostress field interference for the near wellbore, interwell,  
and inter-stage or inter-cluster regions, which favorites the predesigned fracturing goal. Future investigation shall be dedicated to  
improving the automatic implementation of the microfracturing technique, and to further developing an intelligent decision making  
and control approach when applying the technique, eventually reducing the need for man-made work efforts.


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