Study on computing method of bottom-hole flow pressure of gas well with abnormal high pressure and high-productivity

Bottom-hole flow pressure（BHFP）of the gas well with abnormal high pressure and extra-high production is essential to the gas well dynamic analysis and management. According to wellhead pressure behavior of the gas well with high pressure and high production, based on mass conservation, momentum conservation and energy conservation, pressure-temperature coupling model for unsteady heat-transfer was established, and BHFP calculation software for gas well with abnormal high pressure and extra-high production were developed with considering the heat-transfer through the production process and the flowing behavior in the wellbore. The comparison results of BHFP obtained by calculation and field test showed that for BHFP calculation of extra-high production gas well, the applicability of conventional empirical calculation equations of friction resistance coefficient, such as Colebrook, Jain and Chen, are poor and the BHFP calculated by those equations is always abnormal. In other words, with the increase of production, the BHFP gained by those equations is increases and sometimes is even higher than the formation pressure. The abnormalities of BHFP could be eliminated by estimating the fluid flow region according to the Reynolds number and then choose the appropriate formula for calculating friction factor. For the extra-high production gas well, the high productivity and fast flowing rate causing that the calculated BHFP with considering the kinetic energy is about 0.2~0.6 MPa higher than that without considering kinetic energy. Thus, kinetic energy must be considered in the BHFP calculation process of the extra-high pressure gas well. The BHFP calculated by the new model was highly fitted with the measured value and the new model has better applicability.