关键词: 温度, 压力, 保温油管, 生产井, 海洋

Abstract:

Adoption of insulated tubing on the upper part of offshore production strings is an effective method to increase temperature of produced liquids and prevent wellbores from wax deposition. A scientific design for a proper depth of insulated tubing requires accurately predicting the temperature profile of offshore production wellbores. When produced liquids were regarded as a gas-liquid two-phase flow, equations for its mass conservation, momentum conservation and energy conservation could be, respectively, deduced. These equations integrate effects of temperature and pressure on thermophysical properties of oils, gases and formation waters as well as the effect of deviation angle on heat transfer and pressure drop with the internal heat resource caused by mechanical energy loss of an electric submersible pump. A numerical simulation method suitable for a coupling solution to temperature and pressure fields of offshore production wellbores was established using staggered grids and the fully-implicit finite-volume discrete technique, and this method offered a guarantee to make the solution of the model stable and convergent. The established model was applied to analyze temperatures of an offshore production wellbore and design the depth of its insulated tubing. The result shows that the prediction of the model is of high accuracy with a fractional error of 0.46%, and the designed depth of insulated tubing can effectively increase the temperature of oil fluids and prevent the wellbore from wax deposition.

Key words: temperature, pressure, insulated tubing, production well, offshore