Alkyl cyclic anhydride based emulsifiers for oil based mud

A wellbore fluid, comprising:

• an oleaginous continuous phase;
• a non-oleaginous discontinuous phase;
• and
• an emulsifier stabilizing the non-oleaginous discontinuous phase in the oleaginous continuous phase, wherein the emulsifier is the product of a reaction between an alkyl cyclic anhydride and a polar reactant, wherein the polar reactant is one or more selected from a group consisting of alkyl amine and polyamine;
• wherein the polar reactant is one or more polyamines selected from a group consisting of ethylene diamine, diethylene triamine, triethylene tetramine, tetraethylene pentamine, 1,4-aminobutane, 1,3-diaminobutane, hexamethylene diamine, 3 (n-isopropyl-amino)propyl amine, N,N′-diethyl-1,3-propanediamine, hexapropylene heptamine, penta(1-methyl propylene) hexamine, tetrabutylenepentamine, hexa-(1,1-dimethylethylene) heptamine, di(1-methylbutylene)triamine, pentaamylhexamine, piperidine, piperizine, morpholine, and thiomorpholine.