Disclosed is a method for introducing additives into formation fluid from an oil and gas well in or moving through equipment and systems located downstream from the oil and gas well. The method is practiced using pellets having a density sufficient to suspend the pellet at an interface of two phases of fluid within the Downstream Equipment. The pellets are prepared from a pellet matrix, such as an ethoxylated wax, and, optionally, a weighting agent as well as an additive. By varying the amount of weighting agent, the density of the pellet can be varied to suspend it at a desired point for a time sufficient to deliver the additive to the desired point within the Downstream Equipment. The method of the invention may also be used with Refinery Equipment such as a fuel distribution system or a waste water treatment system.