Research on the influence of production fluctuation of high-production gas well on service security of tubing string

Abstract

The production of high temperature and high pressure gas wells fluctuates with time, which makes the pressure in the string fluctuate obviously and affects the service security of tubing string. In this paper, a pressure fluctuation model of the complete production process (including well opening, production and shut-in) is established, which is suitable for the multiphase flow of gas well. The pressure fluctuation in the tubing string is simulated. Influence of different well depth and average production on the fluctuating pressure of gas well are analyzed. According to the research results, if the well opening time top is 50 s, a transient pressure fluctuation is generated at wellhead and drops gradually. After the production starts, a pressure fluctuation will occur at wellhead 10~15 s after top, which is small and attenuates quickly. Pressure increases quickly in the shut-in moment and reaches the peak at tsh. Although pressure increases gradually with the well depth, fluctuation flattens out. The hysteresis phenomenon in appearance of pressure wave becomes more and more obvious with the well depth. The greater the production of gas well, the greater the pressure fluctuation in tubing string during well opening and production, but the value may not be very high. During well shut-in, the greater the production, the greater the pressure fluctuation and the value. Amplitude, angular frequency and value of phase are in direct proportion to pressure fluctuation degree and valve radix is in inverse proportion to pressure, which means that the greater the valve radix, the smaller the pressure.