The key to the stable performance of water-based drilling fluid at high temperature is related to the dispersion state of core colloidal particles,but the influence of the dispersion state of colloidal particles is very complicated.For the core components of water-based drilling fluid,the shear stress-strain temperature curve of bentonite colloid was obtained through high-temperature and high-pressure rheological testing,and the particle size distribution of colloidal particles was tested after different temperature effects.The dispersion,flocculation,and aggregation states and formation mechanisms of clay mineral colloidal particles were analyzed within the temperature range of room temperature to 220℃.In addition,the high temperature stability mechanism of porous fibrous clay mineral colloid rich in magnesium was revealed from a microscopic perspective by means of SEM test and clay mineral layer structure analysis.At the same time,based on a comprehensive analysis of the changes in rheological properties and filtration loss before and after high-temperature hot rolling,the interaction mechanism between bentonite/composite clay minerals and polymer based treatment agents at high temperatures is revealed from the perspectives of clay mineral structure characteristics,polymer chain breakage,adsorption characteristics,etc.Combined with experimental results,it is clear that low concentration bentonite/sepiolite composite colloids have significant high-temperature stability advantages,which provides theoretical support for the construction of ultra-high temperature water-based drilling fluid.
High temperatureWater-based drilling fluidMicro-analysisClay colloidDispersed state
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