深水钻井气体沿井筒上升的膨胀规律

Expansion Characteristics of Uprising Gas along Wellbore in Deepwater Drilling

深水钻井井筒温度场与陆地钻井井筒温度场不同,而气体沿井筒上升的膨胀规律与温度密切相关,为了更好地进行深水钻井井控,需要求出深水钻井井筒温度场,并在此基础上分析深水钻井过程中气体沿井筒上升的膨胀规律。根据能量守恒定律和真实气体状态方程建立了深水钻井井筒温度场和气体膨胀计算模型,并利用所建立的模型分析了深水钻井时气体沿井筒上升的膨胀规律:气侵发生在井底时,循环期间的气体膨胀明显大于非循环期间的气体膨胀,井深越深两种工况的差别越明显;无论是循环期间还是非循环期间,钻井液密度越小,气体膨胀越明显;气侵发生在隔水管底部时,非循环期间的气体膨胀大于循环期间的气体膨胀,与气侵发生在井底情况相反;气侵速度一定,溢流到达某井深时,非循环期间的溢流体积比循环期间的大。

The temperature field of deepwater drilling is different with that of onshore, and the gas ex- pansion is related to temperature field. In order to control well flow in deepwater drilling,it is necessary to calculate the temperature field along wellbore in order to analyze the gas expansion. According to energy conservation and real gas equation of state, a deepwater drilling borehole temperature and gas expansion model was established. This model was used to analyze the gas expansion along wellbore. The result shows that when kicks occurred at bottom hole, the gas expansion rate in circulation is higher than that of non-circulation. The difference is increasing with the increase of welldepth. Whether it is circulating or not, the lower the mud density,the more evident the gas expansion is. When kicks occurred at the bottom of riser, the gas expansion rate in circulation is smaller than that of non-circulation. If the gas kick rate is constant, the overflow volume in circulation is smaller than that in non-circulation at certain depth.