A new two-dimensional transient forecast model of wellbore temperature based on precise time step integration method

Abstract

Dramatic temperature changes in the wellbore can lead to the severe deformation and breakage of the wellbore string, packer seal malfunction, and other operational accidents. A new two-dimensional (2D) transient forecast model of the wellbore temperature is established to provide accurate temperature parameters for the precision mechanical analysis of the wellbore string and the safety evaluation of well integrity. Furthermore, a precise time step integration scheme of the forecast model using the precise time step integration method of a one-point subdomain is proposed. A solution method for the 2D transient forecast model of the wellbore temperature is proposed by combining the precise time step integration method. Finally, a case study focused on a high-temperature deep gas well with a transient wellbore temperature is presented by comparing the calculation results of the different models and solution methods. The sensitivity analysis of the wellbore temperature is performed as well. The results indicate that the forecast model in this paper has higher accuracy than the existing two-dimensional transient model. By contrast analysis of the finite difference method and the solution method that combines the precise time step integration method, the solution method has the advantages of better convergence and faster calculation speed. The major sensitive parameters that affect the stability time of wellbore temperature are ranked as follows: gas production rate, tubing size, specific heat, temperature gradient, gas relative density, and thermal conductivity. The work presented can provide a theoretical foundation and technological basis for the transient forecast of the wellbore temperature, which is critical for well completion design and wellbore safety evaluation.