The Law's Research Of Hydration Of Class G Oil Well Cement Under High Temperature

Based on foundational theory and researching results of Portland cement, hydration process, composition of hydration products, morphology and microstructure of hydration products in hardening cement paste, thickening property, rheological behavior, and strength property of Jiahua Class G Oilwell Cement are studied systematically and intensively for the range of temperature from 25℃ to 200℃. Nature laws of hydration and some main properties which are affected by temperature, additives and added amount of additives are analyzed and evaluated in detail. The nature relationships between hydration process and main properties are revealed. Acting mechanism of temperature and additives is explained. So critical temperature of strength decline, optimum amount of sand added to cement slurry, rule of properly controlling slurry properties and properly choosing additives are determined for Jiahua Class G Oilwell Cement. For deep well cementing, provided a foundation for optimization and designing appropriate cement slurry composition based on Jiahua Class G Oilwell cement.In process and laws of hydration, morphology and microstructure of hardening cement paste, hydration process, hydration products, morphology and microstructure are tested and analyzed for Jihua Class G cement by using DSC, XRD and SEM based on analyzing and summarizing researching achievements of cement clinkers and portland cement. Conclusions such as hydration rate and hydration process can be accelerated with the increase of temperature, and at higher temperatures there are the trend to overlap the exothermic peaks of C3A, C3S and C,S one another are given. And revealed the nature and characteristics of the changes of main hydration products which vary with temperature and silica sand. When temperatures exceed 110℃ there are a lot of C,SH products for pure cement slurry and when added some silica sand to cement slurry there are products C,S6H5 below 150℃ and products C6S6H above 150℃. Varying characteristics of morphology, microstructure and binding form of hydration products in hardening cement paste are given. Revealed relations among acting characteristics of silica sand, changing characteristics of porosity and conditions such astemperature, additives etc. Hydration kinetic model and reaction formulas of Class G cement for 25-200C temperature range are established. Nature of the influence of temperature, silica sand and its amount on hydration process, hydration products and microstructure is presented.In cement engineering properties, thickening time and rheological behavior of cement slurries, growth and change of strength for cementstone are tested and analyzed by using High-Temperature-Pressure-Consistometer, High-Temperature-Pressure-Rheometer, Static Gel Strength Analyzer etc. based on introducing and analyzing the types and action mechanism of tetardant which usually used in oil field. ConclusionL in licated that Hauschel-Bulkely model can be more exactly used to describe the rheological behavior of cement slurry. Foundational method and mathematics calculation formulas have been established, which can be used to analyze and determine the rheology parameters. Analytical method and calculation formulas for laminar axial flow of cement slurry in pipe and eccentric annuli have been given. And provided a foundation for designing hydraulic parameters of cementing jobs. Conclusions such as: cement slurry thickening time decreases with the increase of temperature by the multinomial form with third or second power, rheology parameters have different varying tendency with the increase of temperature, etc. have been presented. The influencing law and action of additives on thickening time and rheology parameters have been analyzed. The nature relation between slurry properties and the action mechanism of additives have been revealed. Critical temperatures which the strength begins to decline have been determined to be 110℃ and 150℃ respectively. Reasonable amounts of silica sand which will be added to cement slurry to enhance the...