Emulsion stabilizing agents

A water-in-oil subterranean treatment fluid, comprising an aqueous phase, an oil phase and from 0.3 to 5.0 g/100 ml of an emulsion stabilizing agent, which is a polyamide obtained by reacting in a first step:

• a) one mole of a polyamine having n amino groups with exchangeable hydrogens, wherein n is an integer ranging from 3 to 5;
• b) from n/2 to n−0.8 moles of a C6-C30 saturated or unsaturated aliphatic monocarboxylic acid or an ester thereof or mixtures thereof;
• to obtain an aminoamide characterized by a saponification number below 30 mgKOH/g;
• and, subsequently, in a second step, reacting the aminoamide with:
• c) from 0.4 to 1.1 moles of a C4-C6 unsaturated dicarboxylic acid or with the corresponding anhydride for each mole of remaining amino groups bearing exchangeable hydrogens;
• to obtain the polyamide;
• with the proviso that during or after the second step the reaction mass is heated at temperature ranging from 130 to 200° C. until at least 30 by weight (wt %) of the emulsion stabilizing agent has a molecular weight higher than 1700 Da, as determined by organic gel permeation chromatography calibrated with polyethylene glycol standards;
• wherein said emulsion stabilizing agent of which at least 30 wt % has a molecular weight higher than 1700 Da has a total recovery in a shale recovery test higher than an emulsion stabilizing agent prepared identically except for not being heated to the temperature ranging from 130 to 200° C.