Method for preparation of biomimetic polymer for stabilizing wellbore and drilling fluid

摘要

The present invention provides a biomimetic polymer for stabilizing wellbore, a method for preparation of the biomimetic polymer, and a drilling fluid. The polymer contains carboxymethyl chitosan that serves as a backbone and dopamine-derived groups grafted on the backbone. The polymer provided in the present invention can improve the strength of shale in the wellbore, seal the shale pores and reduce the filter loss of drilling fluid, and thereby attains an effect of stabilizing the wellbore in shale formation in drilling process.

主权项

1. A method for preparation of a polymer containing constitutional units represented by formula III, comprising:
(1) reacting polymer containing constitutional units represented by formula III with an unsaturated carboxylic acid represented by general formula R4CH═CHCOOH in a graft copolymerization reaction; (2) condensing the polymer obtained in (1) with dopamine and/or dopamine hydrochloride; wherein, R′ and R″ are H or —CH2COOR3′ independently, and R′ and R″ are not H at the same time; R3′ is H or an alkali metal; and R4 is H or C1-C10 alkyl; wherein in (1), conditions of the graft copolymerization reaction include: reaction temperature is 50-90° C. and reaction time is 1-10 h; calculated in hydroxyl in the polymer containing the constitutional units represented by formula III, the molar ratio of the polymer containing the constitutional units represented by formula III to the unsaturated carboxylic acid is 1:0.1-4, wherein the weight average molecular weight of the polymer is 50,000-100,000 g/mol.