Preparation And Characterization Of Organoclays For Oil-based Drilling Fluids

In this work,the rheological properties and r mechanism of organo-montmorillonite(OMt),organo-palygorskite(OPal)and organo-sepiolite(OSep)in oil-based drilling fluids were studied.The influences of clay mineral structure,chemical composition,and the interaction with organic modifiers were also investigated.OMt formed a “house of cards” network structure in oil by dispersion,swelling and exfoliation.The gel formation and strength are deeply influenced by the surfactants' nature,loading level and aging temperature,which finally control the rheological properties of oil-based drilling fluids.Organic cations intercalated into the interlayer space by cation exchange,increasing the basal spacing.Organic surfactants with greater lipophilicity,the larger size and more loading level,which led to the larger basal spacing and better lipophilicity of OMt,resulted in excellent rheological properties of oil-based drilling fluids.Temperature rising firstly promoted the swelling and/or exfoliation ability,but the rheological properties declined above 180°C.The thermal stability of OMt in oil-based drilling fluids was affected by both the desorption and thermal decomposition of organic modifiers.Organic modifiers were adsorbed on the surface of palygorskite and sepiolite by cation exchange and physical adsorption,thereby improving the compatibility between OPal(OSep)and oil.OPal and OSep formed a disordered three-dimensional network structure by dispersing their nanofibers or bundles.The insertion of organic molecules into the channels or surface grooves significantly improved the rheological properties and thermal stability of OPal(OSep)in oil-based drilling fluids.The compounds of OMt and OPal(or OSep)with the mass ratio of 1:1 exhibited greater rheological properties and thermal stability than individual organoclay in oil-based drilling fluids.The exfoliated OMt nanosheets and the dispersed OPal(OSep)nanofibers formed a stronger network structure,improving the rheological and thermal stability of oil-based drilling fluid.