Oligomeric betanine type foam drainage agent and preparation method

The invention relates to an oligomeric betanine type foam drainage agent for foam drainage gas recovery in the later period of oil and gas well development and a preparation method. The agent can improve the foaming performance and stability of a foaming agent in electrolytes and hydrocarbons. The technical scheme is as follows: the chemical name of the foam drainage agent is N,N,N''-alkyl sodium diethyletriaminepentaacetate named NDDTP; firstly, sodium hydroxide and an isopropyl alcohol aqueous solution are added to a three-neck bottle, and the solution is stirred for dissolution; then diethylenetriaminepentaacetic acid is added, the mixture reacts at the temperature of 65-75 DEG C for 15 min, and an intermediate product,namely, sodium diethylenetriaminepentaacetate, is obtained; then a bromoalkanol solution is added to the intermediate product solution while stirring, and the mixture reacts at the temperature of 75-85 DEG C for 6-8 h; finally, a coarse product is obtained through distillation of a reaction liquid, and a solid product is obtained through desalinzation with ethanol and recrystallization with acetone. A foam drainage solution is prepared through compound of the foam drainage agent and ethylene glycol, has good foaming performance and foam stability and is used for increasing gas recovery ratio.