Emulsifier for synthetic-based mud, process for preparation, and drilling method

A process for preparing an invert wellbore fluid, comprising the steps of:

• (A) making an emulsifier composition, comprising the steps of:
• (1) reacting a polyalkyleneamine having from 4 to 30 carbon atoms, at least one secondary amine group, and at least two primary amine groups, with a monocarboxylic acid having from 4 to 30 carbon atoms or an acyl halide or hydrocarbyl ester thereof, to form a first reaction product comprising a polyalkyleneamidoamine derivative of the polyalkyleneamine;
• (2) reacting the first reaction product from step (1) with a dicarboxylic acid selected from maleic acid, fumaric acid, maleic anhydride, and combinations thereof to form a second reaction product an acid-substituted amidoamine;
• and
• (3) heat treating the maleated amidoamine from step (2) at a temperature and for a time sufficient to form a heat treatment product comprising an isomer of the acid-substituted amidoamine, wherein the heat treatment product has an acid number less than an acid number of the second reaction product,
• wherein the heat treatment product from step (3) comprises iso-amidoamine compound (II) or a mixture of iso-amidoamine compound (II) with acid-substituted amidoamine compound (I) and/or formyl-substituted amidoamine compound (III), according to the formulae:
• wherein each R1 is a C4 to C30 hydrocarbyl;
• R2, R3, R5, and R6 are each independently selected from H, C to C4 alkyl, C1 to C4 alkoxyalkyl, and C1 to C4 hydroxyalkyl;
• n and m are independently integers from 1 to 10;
• and y is an integer from 1 to 5;
• and
• wherein molar proportions of compounds (I), (II), and (III), are optionally 0-90:10-100:0-60 based on the total moles of compounds (I), (II), and (III), present in the emulsifier composition;
• and
• (B) formulating the emulsifier composition in an emulsifying amount in an invert wellbore fluid further comprising an oleaginous external phase, a non-oleaginous internal phase, one or more rheology additives, and one or more wetting additives, wherein the one or more wetting additives comprise a hydrocarbyl ethoxylate having the formula RO—(CH2CH2O)nH wherein R is a C5-22 hydrocarbyl group and n is an integer in the range of 2 to 30.

A process for making an emulsifier composition, comprising the steps of:

• (1) reacting a polyalkyleneamine having from 4 to 30 carbon atoms, at least one secondary amine group, and at least two primary amine groups, with a monocarboxylic acid having from 4 to 30 carbon atoms or an acyl halide or hydrocarbyl ester thereof, to form a first reaction product comprising a polyalkyleneamidoamine derivative of the polyalkyleneamine;
• (2) reacting the first reaction product from step (1) with a dicarboxylic acid selected from maleic acid, fumaric acid, maleic anhydride, and combinations thereof to form a second reaction product an acid-substituted amidoamine;
• and
• (3) heat treating the maleated amidoamine from step (2) at a temperature and for a time sufficient to form a heat treatment product comprising an isomer of the acid-substituted amidoamine, wherein the heat treatment product has an acid number less than an acid number of the second reaction product,
• wherein the heat treatment in step (3) is controlled wherein the heat treatment product has an acid number less than 35 mg KOH/gram, an amine number less than 10 mg KOH/gram, and a viscosity of less than 800 centipoise at 50° C. when measured at a dilution of 50 wt % in an IO1618 base oil.