Study On Ultra-high Density High Temperature Drilling Fluid And Rheology Control Mechanism

Recent years, in company with the exploration and exploitation of deep oil and gas fields, the complex formations in high temperature and high pressure condition were often drilled through. There was a dire need to solve the problem that how to regulate the rheology of ultra-high density drilling fluid under HTHP and develop ultra-high density high temperature drilling fluid systems.Based on the investigating and surveying of both here and abroad literary, the rheology control mechanism of ultra-high density drilling fluid was studied and the ultra-high density high temperature drilling fluid formula with good rheology was developed by experiments. First of all, the influence laws of temperature, pH value and bentonite content on the rheology and the particle size distribution of bentonite slurry were researched. The reasonable particle size graduation of barite was obtained by researching the influence laws of the properties particle size graduation and area property of weight additive particles on the drilling fluid rheology. The relationship between free water phase and rheology of drilling fluid and the factors of free water phase were studied. The influence of several kinds of main additives used in ultra-high density drilling fluid on rheology was surveyed by experiments. On the basic of knowledge of rheology control mechanism of ultra-high density drilling fluid, the ultra-high density fresh-water drilling fluid formulation and the ultra-high density formate drilling fluid formulation were developed by experimentally studying the compatibility of main additives and weight additives. Evaluation results show that they both have preferable rheology, temperature-tolerant and stability and can essentially satisfy the demand of rig site utilization.