预防气体水合物堵塞的深水油气井测试安全阀下入位置研究

深水油气井测试过程中，容易发生气体水合物堵塞井下安全阀的问题，为避免出现该问题，研究了安全阀合理下入位置的确定方法。利用气体水合物相平衡微观试验装置，在室内模拟了地层水矿化度下多组分气体水合物在水中的相变过程，得到了温度和压力对气体水合物相平衡的影响规律；分析了气体组分、水深、地温梯度和井口压力对生成气体水合物的影响，预测了气体水合物的生成区域，从安全和成本2方面考虑给出了安全阀最小下入深度的确定方法。研究发现，气体组分、水深、地温梯度、井口压力均会影响安全阀的下入位置，产出气中乙烷、丙烷和丁烷含量增加更易生成气体水合物；同时，水深越深，地温梯度越小，井口压力越大，生成气体水合物的区域越大，安全阀需要下入到更深的位置。研究认为，上述研究成果可为深水油气井测试中安全阀下入位置的确定提供参考。 

The Setting Depth of the Testing Safety Valve in Deepwater Oil and Gas Wells for Gas Hydrate Blockage Prevention

During the testing of deep water oil and gas wells, gas hydrate is prone to block downhole safety valves. To prevent it from happening, a method for determining the reasonable setting depth of safety valve was studied. The gas hydrate phase of equilibrium micro-test device was used to simulate the phase transition process of multi-component gas hydrates under various formation water salinities in the laboratory and to obtain the influencing law of temperature and pressure on the phase equilibrium of gas hydrate. The effects of gas composition, water depth, the geothermal gradient and wellhead pressure on the formation of gas hydrate were analyzed to predict the formation area of gas hydrate, and the method in determining the minimum setting depth of safety valve was obtained from the aspects of safety and cost. Studies suggest that all the factors including gas composition, water depth, geothermal gradient, and wellhead pressure could affect the setting depth of safety valve, and the increased contents of ethane, propane and butane in the produced gas are more likely to form gas hydrates. In addition, the setting depth of the safety valve will be further lower as deeper water depth, smaller geothermal gradient, higher wellhead pressure, and larger gas hydrate formation area. The results of this study could provide a reference for determining the setting depth of test safety valve in deep water oil and gas wells.