Study On Properties Of Nano-SiO₂ And BaSO₄ In Oil-Based Drilling Fluid

With the increasing depth of drilling,the performance requirements for drilling fluids are also increasing.In order to maintain a stable and sustainable development,we must continue to develop new technologies.The development of modern nanotechnology provides a possibility for solving the drilling problems that are currently facing.Because of the surface effect and small size effect of nano-materials,it has the characteristics of high dispersion stability and low dosage,which is in line with the development trend of low solid phase of drilling fluid.At the same time,excellent rheological and lubricity of nanometer materials,can have a huge development potential in improving the drilling fluid.In this paper,the nanomaterials were introduced into the grouting materials of the drilling fluid.The weighting agents and bentonite were modified to study their rheological properties,lubricity and sealing properties in liquid paraffin,and their properties in drilling fluid were evaluated.The main contents and results are as follows:?1?Study on preparation and properties of nano-SiO₂ oil-based drilling fluid base slurryAccording to the literature research,in order to improve the dispersion stability of bentonite in drilling fluid,it is usually modified with organic ions and simple metal ions.We tried this modification method,but the dispersion of organic bentonite in the liquid paraffin is still poor.Therefore,the nano-SiO₂?DNS-2?,which is similar to the properties of bentonite,has been selected to replace the bentonite.Configure new "clay",and study the dispersion stability,rheological property,lubricity and sealing property of "clay" base pulp with different proportions.The results show that the addition of SiO₂ increases the overall dispersion stability,reduces the viscosity of the low temperature region,improves the lubricity,the filtration loss and the sealing property.When the total amount of "clay" is 2%,the ratio of organic bentonite to DNS-2 is 1:1,it shows the best results.?2?Preparation of oil-soluble BaSO₄@SiO₂ nanoparticles and investment of their properties in liquid paraffinThe BaSO₄@SiO₂ nanoparticles were prepared by simple and environmentally friendly methods.The effects of temperature,reactant concentration,water/alcohol ratio and dropping speed on the morphology of nanoparticles were investigated.The morphology,structure and chemical composition of the samples were characterized by transmission electron microscopy?TEM?,X-ray powder diffraction?XRD?and Fourier transform infrared spectroscopy?FT-IR?.Under the optimum conditions,as-prepared BaSO₄@SiO₂ were nearly with an average diameter of 30 nm,the silica shell thick:ness was about 5nm.The core-shell structure was modified by Octadecyltrimethoxysilane and the BaSO₄@SiO₂ nanoparticles with better oil solubility were obtained.The rheological properties and lubricity of BaSO₄@SiO₂ nanoparticles which were studied by means of six-speed rotational viscometer and friction wear testing machine in liquid paraffin.The results show that the synthesized oil-soluble BaSO₄@SiO₂ nanoparticles have the characteristics of improving the dispersion stability,the rheology and lubrication.In addition,due to the accumulation of particles between different particle size can increase the unit density,we envision the inclusion of oil-soluble BaSO₄@SiO₂ nanoparticles with micron barium sulfate,and test the performance of micro-nano compound weighting agent in drilling fluid.It has been proved that the compound weighting agent has the characteristics of increasing the effective density and improving the overall rheology and lubricity.In combination with different proportions of rheology and lubricity,when the micron weighting agent:nano-weighting agent = 9:1?mass fraction?,the overall nature is the best.3)Evaluation of oil-soluble nanometer brium sulfate in oil-based drilling fluidSelect the optimal proportion of micro-nano compound weighting agent?micron weighting agent:nano-weighting agent mass ratio of 9:1?,and add it to the best match "clay"?the mass ratio of organic bentonite to DNS-2 nano-silica is 1:1?.A basic oil-based drilling fluid was installed and tested for rheology,lubricity,filtration and sealing in oil-based drilling fluids.Compared with the commercial oil-based drilling fluid,it is found that the experimental preparation of oil-based drilling fluid has a great advantage in lubricity and viscosity stability.