Preparation And Properties Of Micro Nano Plugging Materials For Water Based Drilling Fluid

The problems of small pore throat diameter and strong water sensitivity in low permeability reservoirs improve the difficulty of oil and gas exploitation,and the deterioration of wellbore stability caused by shale hydration is the key to the difficulty of exploitation.In order to improve the stability of the borehole wall,the main chain monomer and adsorption monomer were polymerized by emulsion polymerization method,and the micro-nano plugging material was prepared.The structure of the product was determined by IR,Raman and NMR spectra.The thermal stability of the product was tested by thermogravimetric differential thermal analysis.The particle size of the product was determined by particle size distribution.The inhibitory effect of the product on the hydration and dispersion of clay was tested by clay expansion experiment and mud ball immersion experiment,and its mechanism was explored.The effect of the product on the rheological properties and filtration loss of drilling fluid was tested.Finally,the sealing performance of the product on micro and nano pore was investigated by membrane plugging experiment.The concrete results are as follows:（1）No.1 plugging material:the plugging material prepared by emulsion polymerization method has been verified by characterization that the structure is consistent with the design,the thermal decomposition temperature is 320℃,the particle size distribution is between 297.5～691nm,D₅₀ is 453 nm,D₉₀ is 630 nm,belongs to micro nano level,and the oil dissolution rate is up to 99.9%.The clay swelling experiment and mud ball immersion experiment proved that the plugging material could adsorb clay and inhibit the hydration of clay effectively.The water-based drilling fluid test showed that the FL_HTHP could be controlled at about 10 m L under the conditions of 100～130℃,less than 2 times of aging and 1.5 wt%of plugging material.The filtration membrane plugging experiment proved that it took 35 min to completely filtrate 100 m L aqueous solution of 1.5 wt%plugging material using 0.45μm filter membrane as filtering medium.It has been proved that this material is suitable for plugging the pores in the diameter range of 0.45～5μm,and through comparative experiments,the plugging effect of this material is far better than that of several mesh calcium carbonate.（2）No.2 plugging material:the plugging material prepared by emulsion polymerization method has been verified by characterization that the structure is consistent with the design,the thermal decomposition temperature is 295℃,the particle size distribution is 390.6～2775.2 nm,D₅₀is 572 nm,D₉₀ is 1798 nm,belongs to micro nano level,and the oil dissolution rate is as high as 99.8%.The clay swelling experiment and mud ball immersion experiment proved that the plugging material could adsorb clay and inhibit the hydration of clay effectively.The water-based drilling fluid test confirmed that the plugging material was aged less than 2 times at100～130℃,and the plugging material was used at 1.5 wt%with FL_HTHP≤10 m L.The filtration membrane plugging experiment proved that it took35.4 min to completely filtrate 100 m L aqueous solution of 1.5 wt%plugging material using 0.45μm filter membrane as filtering medium.It has been proved that this material is suitable for plugging the pores in the diameter range of 0.45～10μm,and through comparative experiments,the plugging effect of this material is far better than that of several mesh calcium carbonate.