Preparation method of organic rheology modifying agent for full-oil-based drilling fluid

The invention discloses a preparation method of an organic rheology modifying agent for full-oil-based drilling fluid. The preparation method comprises the following steps: 1) reacting polybasic fatty acid or ester of the polybasic fatty acid with hydroxyalkyl-substituted amine at 130 to 150 DEG C, wherein the hydroxyalkyl-substituted amine reacts with half of the carboxyl groups or carboxylic esters of the polybasic fatty acid or the ester of the polybasic fatty acid based on the rate of charge; and 2) reacting the reaction product in step 1) with organic polyamine at 150 to 170 DEG C, wherein the organic polyamine completely reacts with the amidation-free carboxyl or carboxylic ester in step 1) based on the rate of discharge. The organic rheology modifying agent prepared by the preparation method disclosed by the invention is in a gel structure with a certain strength, and can effectively improve the suspension property and thixotropy of the oil-based drilling fluid, thus the drilling liquid which is high in shear thinning performance and yield value, low in gel strength and low in plastic viscosity can be generated.