含H2S天然气井溢流过程动态模拟

考虑H₂S在井筒中的相态变化,建立了含H₂S气井井筒动态溢流模型,同时采用有限差分法对模型进行求解,结合四川某含H₂S天然气井现场数据模拟含H₂S天然气井溢流过程,并将模拟结果与不含H₂S气井进行对比分析。研究结果表明：随着温度和压力的降低,H₂S在上部地层井段发生相变并直接引起气体体积的膨胀。含气率的突增使钻井液池增量迅速增加,且在相同的溢流时间内,关井时刻钻井液池增量增加更明显。含H₂S气井井筒内气体膨胀更迅速,导致环空压力下降更快,环空流型转化更加迅速。此外,井底压力下降更快,关井套压迅速增加,进一步加剧了溢流程度。因此,含H₂S气井井喷预警时间急剧缩短,井控难度和井喷危险大大增加。

Dynamic simulation of overflow process inH2S-containing natural gas well

Considering the change of phase state of H₂S in wellbore, the dynamic overflow model of H₂S-containing gas well is established. The model was solved using the finite difference method at the same time the Matlab program, combined with field data to simulate the overflow process of a H₂S-containing natural gas well in Sichuan. The simulation results were compared with H₂S-free gas well. Results show that: With the decrease of temperature and pressure,H₂S changes phase in the upper stratum and directly causes expansion of gas volume. The sudden increase of gas void fraction causes the rapid increase of pit gain, and the increase of pit gain is more obvious at the time of shut-in in the same overflow time. The gas expansion in the wellbore of H₂S-containing gas well is faster, resulting in faster reduction of annular pressure and faster transformation of annular flow pattern. In addition, the bottom hole pressure decreases faster and the shut-in casing pressure increases rapidly, which further aggravates the overflow degree. Therefore, the warning time of H₂S gas well blowout is shortened sharply, and the difficulty of well control and blowout danger are increased greatly.