Design of Hot Water Tracer Systems to Prevent Hydrate Formation in Gas Gathering Lines

This paper is a follow-up to a similar paper, presented at the C.I.M.Petroleum and Natural Gas Division's Annual Technical Meeting in Calgary in1962, on the method for transporting wet natural gases utilizing hot watertracing. In this paper, this new approach in gas gathering is examined in lightof two years' operating history, with special emphasis on the heat transferbetween pipes and the soil. Solutions for the steady-rate heat transfer fromsingle pipes and parallel buried pipes are presented in the paper. Practical soil conductivities were calculated, using these equations, fromsix months of test data. It was found that the over-all thermal conductivity inthe Wildcat Hills field varies only between 0.4 and 0.65 Btu/(hr.) (sq. ft.)(°F/ft.), in spite of the wide variety of soil types. Based on the experience gained from the operation of the Wildcat Hillstracer system, and from heat transfer studies, a suggested design procedure ispresented in the paper. Introduction Natural gases form hydrates in the presence of free water at temperatures higher than the freezing point of water. The temperature of hydrate formationis a function of the pressure and the composition of the gas. One way to prevent hydrate formation is to maintain the gas temperature above the hydrate formation temperature. A tracer system can be defined as a means of hydratecontrol by heating gas gathering lines with hot water lines. The application ofthis method to gas gathering systems was proposed by Mr. T. Nitescu, president of Canadian Fina Oil Limited. The basic principle of the tracer system is thatby maintaining the soil around the gas pipe at or above the temperature of thegas, there would be no heat loss from the gas to the soil. The soil around the gas line is heated by a hot water line or, as generally referred to in this paper, the "tracer line."