Heat transfer can be of importance in the design of multiphase petroleum flowlines. However, heat transfer data for gas-liquid flows are available only for small-diameter pipes at low pressures. Moreover, existing prediction methods are largely nor suited to petroleum pipeline conditions due to implicit use Of simplistic two-phase flow models. In this work heat transfer estimation methods are derived for nonboiling gas-liquid flow in pipes of high Prandtl number liquids, such as crude oil. The methods are readily evaluated for engineering applications and are applicable to all flow regimes, except those with low liquid holdup. Comparison is made with literature data. Accuracies of +/-33 percent are obtained in general. The methods explicitly couple with arbitrary prediction methods for two-phase flow pressure drop and liquid holdup. This explicit coupling makes plausible the hypothesis that predictions will be robust at conditions well beyond the range of the existing experimental data.