1. A computer-implemented method of modeling a wellbore fluid that comprises a base fluid and one or more fluid additives, the method comprising: identifying a target viscosity profile of the wellbore fluid; determining an initial set of values of the fluid additives that are based at least in part on the target viscosity profile; determining, with one or more non-linear predictive models, a computed viscosity profile of the wellbore fluid and a computed set of values of the fluid additives based, at least in part, on the initial set of values of the fluid additives; comparing at least one of the computed viscosity profile or the computed set of values with a specified criteria of the wellbore fluid; and preparing, based on the comparison, an output comprising at least one of the computed viscosity profile or the computed set of values.