Study On Interaction Mechanism Of Correlative Phases At Cement/Formation Interface

Along with the secondary development of old oilfield in eastern China and the faster step of exploration and development of oil and gas field in western China and offshore, the isolation system invalidation of cement-formation interface becoming more and more serious, due to the influences of the objective factors (geological structure etc.) and the human factors. Depend on what we have known, our country and even the world development mainly has the following two big problems: First, interlayer channeling after the oilfield put on production can cause waterflood, and then the water ratio is too high. The second, oil and water emitting from casing after cementing can usually cause great hider danger. The origin of these problems is the isolation system invalidation of cement-formation interface.In order to solve the above problem, the physical and mathematical models verified was established, which based on deep study for the curing kinetic mechanism, and combined other test means. It provides a theoretical support and technical guidance for the quality improvement of cement-formation interface.The main content of the thesis is summarized as follows:In chapter one, the purpose and significance of thesis topic selection were introduced firstly, including hydration process and products of cement slurry, the structural characteristics of mud cake, the activity potentiality of blast furnace slag and the technology of Mud To Cement (MTC) and Mud cake To Agglomerated cake (MTA). The others such as research approach, technical route, research content and innovative points were introduced secondly.Basic principles of reaction kinetics and test method were mainly introduced in the second chapter. Solid-state reaction kinetics was introduced, and kinetic principle was illustrated, based on curing characteristics of cement-formation interface. Using Arrhenius theorem and its applicability, physical significance of kinetic triplet, including activation energy, pre exponential factor and reaction model, was explained. In order to determine kinetic parameters, advantages and disadvantages of non-model method and model fitting method were discussed, and the dynamic method and isothermal method were proposed. Then, in view of the importance of sample preparation, three methods of experimental simulation, including shaft imitating into ground, mud cake formatting method and interface simulating method, were put forward. Finally, for test meanings, experimental instrument, test condition and test steps of differential scanning calorimetry (DSC) were described, and the other test meanings were briefly presented, such as environmental scanning electron microscope (ESEM), X-ray energy dispersive analysis (EDX), X-ray diffraction (XRD), differential thermal analysis (DTA), thermogravimetry (TG), and so on.According to the basic principle of reaction kinetics, the interaction mechanism of mud cake interface system between cement slurry and Nayang/universal drilling fluid was elaborated in the third chapter. Firstly, using laboratory experiment, g-grade well cement slurry was prepared, and the density, theology and well building ability of Nayang fluid were measured, and the rheology of universal drilling fluid was adjusted. Then, the curing characteristics of these two systems were analyzed with dynamic method and isothermal method. Curing process temperatures such as initial curing temperature, isothermal curing temperature and post treatment temperature were determined with T-βextrapolation method, and two types of apparent activation energy were solved with Kissinger method and Ozawa method. Meanwhile, the reaction order of mud cake solidification was determined. As the reaction order of the second system was approximate to 1, the curing reaction was judged by simple reaction, and the second system wasn't analyzed with isothermal method. Combining with the methods of XRD, TG/DTA, ESEM and EDX, hydration reaction course of oil well cement and kinetic diffusion of interface system were analyzed, and the curing kinetic process of this two mud cake system were summarized.In fourth chapter, the interaction mechanism of mud cake interface system between MTC cementing fluid and Nanyang/universal drilling fluid was elaborated. Firstly, the technology of mud transformed to be cement slurry was briefly introduced, and the activator formula was adjusted on the basis activator research of predecessors, and the MTC cementing fluid was self prepared. Then, the curing process was illustrated using the same procedure with the third chapter. We can know the solidification and cementment of interface between MTC cementing fluid and mud cake of universal drilling fluid was accordance with Prout-Tompkins curing model, compared with three interface systems front narrated, which was deeper exploration for the kinetic model research.The MTA cementing technology is different from the MTC technology, and the interface system curing kinetics of the MTA was expounded. First, the scientific conception of the MTA was introduced, and the reaction mechanism of mud cake modifier (MCM) and formatting agent of agglomerated cake (FAA) was interpreted. Then, the curing process of MTA cement-formation interface was analyzed with dynamic method and isothermal method. A problem worthy to be pointed out is that there were two exothermic peaks slightly overlapped on the DSC curve of MTA interface system. Meanwhile, the solidification and cementment of MTA interface system was accordance with Kamal compound curing model. Finally, the interaction relationship among interface incidence phases was analyzed, and the physical model and mathematical model were built and verified with indoor strength experiment. Meanwhile, some new discussion in the further study and technology improvement of interaction mechanism at cement-formation interface was described.Finally, research results of this thesis were summarized systematically. There are four innovative points in the research process as follows:1. Basic principle of reaction kinetics was introduced, and the interaction mechanism of cement-formation interface was illustrated, and chemical reaction kinetic models were established, and the physical models and mathematics models were built for the mud cake interface systems including g-grade oil well cement slurry and Nanyang/universal drilling fluid, MTC cementing fluid and Nanyang/universal drilling fluid, and MTA cement-formation interface.2. The application range of chemical reaction kinetics was extended, and the MTA cementing technology theory was perfected from the perspective of physical chemistry,.