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.
Highlights
There are abundant natural gas resources of onshore deep layer in China
As gas well is filled with high-pressure natural gas mixed fluid, the action of wellhead valve or production fluctuation may force a change in the flow pattern of natural gas near the wellhead, creating a fluctuating pressure that is transmitted in tubing string
A pressure fluctuation model of the complete production process is established, which is suitable for the multiphase flow of gas well
Summary
There are abundant natural gas resources of onshore deep layer in China. According to the 4th evaluation results of oil and gas resources of China National Petroleum Corporation (CNPC), the quantity of resources in ultra-deep formation of onshore is 42% of the total quantity of conventional natural gas resources. With the development of these high-temperature, high-pressure and high-production oil and gas wells, the difficulty of oil and gas exploration is increasing, which puts forward higher requirements for wellbore integrity (Zhang et al, 2017a, 2018, 2019). During exploitation of high-temperature, high-pressure and high-production gas wells, fluid flow rate in tubing string is high. Obvious fluctuation amplitude and large pressure value will threaten the service security of tubing string and cause serious wellbore integrity problems (Zhang et al, 2013, 2017b), which may have big impact on field operation safety. It is very important to study the transient flow process and pressure fluctuation in tubing string during the complete production process of gas well to ensure the wellbore integrity and safe production of gas well (Zhang et al, 2020b)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
