深水井注泡沫隔离液井口环空圈闭压力计算研究

Calculation of Wellhead Annular Pressure Build-up for Foam Spacer Injection in Deepwater Wells

深水油气井由于水下井口特殊结构,B、C环空压力圈闭压力无法通过井口释放,注泡沫隔离液可有效降低深水井环空圈闭压力,目前尚未有注泡沫隔离液的理论模型和实验研究,无法指导现场开展注泡沫隔离液。基于气体、液体状态方程,考虑套管径向变形影响,建立了深水井注泡沫隔离液环空圈闭压力计算模型,通过室内试验测定了流体热物性参数,基于室内试验和理论分析的方法,分析了深水井注泡沫隔离液时最佳气液比。通过分析可知,环空流体热膨胀系数和压缩系数随温度、压力发生改变,环空气体体积增加时,环空圈闭压力降低,当气液比达到5%时,环空圈闭压力趋于稳定。该分析结果对现场实施深水井注泡沫隔离液环空圈闭压力防治具有理论指导意义。

The B and C annulus trapped pressure cannot be released through the wellhead due to the special structure of the underwater wellhead.Foam spacer can effectively reduce Annular Pressure Build-up(APB)in deep water wells.At present,there is no research on the theoretical model and experimental verification of foam spacer,and hard to guide the site foam spacer injection operation.Based on the equation of state of gas and liquid,considering the influence of radial deformation of casing,the calculation model of APB is established.The thermos-physical parameters of the fluid were measured by laboratory test.The best gas-liquid ratio of foam spacer injection in deepwater wells was analyzed by laboratory test and theoretical analysis.It can be seen from the analysis that the thermal expansion coefficient and compression coefficient of annulus fluid change with the temperature and pressure.When the volume of annulus gas increases,the annulus trapped pressure decreases.The pressure tends to be stable when the gas volume ratio in annular reaches 5%.The analysis results have theoretical guiding for the prevention and control of annular trapped pressure in deep water wells.