Study On Temperature-induced Self-Diverting Fracturing Fluid

In this dissertation,a novel temperature-induced self-diverting fracturing fluid was developed.Furthermore,self-diverting fracturing technology was proposed based on it.At room temperature,this fracturing fluid has good injectivity.Without adding other materials,this fracturing fluid will transform to gel with the heating function of formation.The fracture will be blocked effectively,subsequent liquid diverted automatically,which resulting in new fractures formed.The gelling,gel-breaking temperature and time of the self-diverting fracturing fluid can be controlled precisely.Therefore,the fracture can be repeatedly blocked and diverted through optimization design in once fracturing operation.After operation,the gel will be broken down by the heating function of formation,and the fracture capacity can be restored.Finally,multi-fracutres can be formed in once fracturing operation.It can be used as an excellent temporary plugging agent,but also has the function of fracturing fluid(opening the formation and carrying proppant),and it is matched with the conventional fracturing fluid system.Consequently,self-diverting technology could be realized the function of fracturing and diverting simultaneously.The self-diverting fracturing technology not only provide new direction for divering (plugging) fracturing,refracturing technology etc,but also the greater significance lies in solving the problems of increasing stimulated reservoir volume technology,such as high requirements for tools and materials,limited by reservoir property,complex in process,high cost etc.The main research works are as follow:(1)The dissertation reviewed the technologies and theories that could enhance stimulated reservoir volume,as also the current temporary plugging agent materials.The supramolecular chemistry theory and the supramolecular gel materials were also reviewed.After analyzed the restiriction of current technology and materials,we proposed the significance of research self-diverting fracturing technology,and definited the work of this dissertation.(2)Based on the principle of host-guest chemistry and supramolecular chemistry,the multi-component gel systems were constructed by the synergistic action of various noncovalent interactions.After studying the influence of guest molecular and salts on the gelation temperature of the system,the method of control gelation temperature was obtained.Nextly,we construed five kinds of gel system.After tested,two kinds of gel system were selected.This provided the precondition for the research of self-diverting fracturing techonology.Finally,the FT-IR,XRD and SEM measurements were used to characterize the gel system construction and the gelation mechanism was proposed.(3)The rheological property,compatibilities,suitabilities of this two kind self-diverting fracturing fluid were tested in detail to identify the application condition.The temporary plugging ability,diverting ability,filtration resistance,proppant carrying capacity of the two self-diverting fracturing fluids were tested systematically.(4)Based on the features and advantages of the two self-diverting fracturing fluid,the processes of self-diverting fracturing technology were concrete analysed,and three kinds of feasible process plans were proposed.