Wax is typically defined as the high molecular weight paraffins which become insoluble in crude due either to the loss of light ends and/or a decrease in the temperature of the crude.
Wax consists of straight-chain, branched or cyclic paraffins with carbon numbers typically ranging between C15 and C70+. The melting point of the wax increases with increasing carbon number, while the solubility in crude oil decreases with increasing carbon number.
Source: API RP 17A, Design and Operation of Subsea Production Systems—General Requirements and Recommendations, Fourth Edition, Reaffirmed 2011. Global Standards