Study On High Density White Oil Base Drilling Fluid

In recent years,with the increase in demand for oil and energy,people gradually shift the focus from exploring shallow layers to deep layers,from land to ocean.At the same time,development of ultra-deep drilling technology has provided technical support for mining deep formations.The increase of depth brings a series of problems,including high temperature,high pressure,wall collapse and so on.In order to solve these problems,the research and application of high density of oil-based drilling fluids is particularly important.Study of weighting agents is important to high-density drilling fluid.The modification On the barite surface,which can turn the hydrophilic surface to oleophobic surface,will make weighting materials disperse better in oil-based drilling fluids.In this paper,sodium dodecyl benzene sulfonate and sodium dodecyl trimethyl ammonium bromide were used to modified natural barite by orthogonal experiment to study the effects of various factors on the modification.The most Good modification conditions were confirmed and composite modified barite is prepared to use in oil-based drilling fluids.Cooperation of different size weighting material can reduce the internal friction of the solid particles,while improving the drilling fluid rheology and reduce setting of weighting materials.Experimental results showed that the use of a single size barite for drilling fluids unable to achieve optimal results;Alfred equation calculated the proportion of differen size barite.So Alfred equation were proved feasible on weighting oil-based fluid.On the basis of the four size barite,the best ratio of combination were determined to be used in further experiments.On the basis of the different size barite combination,Through experiments for optimizing the type and amount of the treatment agents,the formulation of high density white-oil-based drilling fluid system is determined as follows: #5 white oil + 4% emulsifier JHMUL-2 + 2% CaO + 2% organic clay FBGEL-1 + 2.5% fluid loss additive?HIFLO + HIROL?+ barite + CaCl₂ solution?wt20%?+3% blocking agent?talc?,oil-water ratio of 8: 2.The evaluation results show that this system has good resistance to water-pollution and clay-pollution,good performance on setting stability,lubricity,inhibition properties,temperature resistance,reservoir protection performance and compatibility with the composite modified barite properties.