井筒中天然气水合物生成条件预测及应用

PREDICTION OF GAS HYDRATE FORMATION CONDITIONS IN WELLBORE

吴志良

Wu Zhiliang

西北大学, 地质学系, 西安, 710069 2. 中国石油化工股份有限公司, 华东分公司采油厂, 江苏, 泰州, 225300

Geology Department of Northwest University, Xi'an, Shaanxi 710069, China 2. Oil Production Plant of East China Petroleum Bureau, SINOPEC, Taizhou, Jiangsu 225300, China

天然气水合物生成条件的预测方法主要有经验公式法、相平衡法及统计热力学法。其中相平衡法不适用非烃含量较高的气田(松辽盆地腰英台气田CO2含量达22%,此法不适用);统计热力学法涉及参数较多,不便于实际应用。该文首先探讨了气井井筒压力温度的计算方法及地层热力学参数的选取,在此基础上以腰英台气田YS1井实测数据为例,采用2种经验公式法计算了井筒中水合物生成的压力温度条件。根据井筒中不同深度的压力温度分布及形成水合物的压力温度条件,可预测不同流量下井筒是否会形成水合物,从而在生产时必须确定一个最低流量值;在新井测试时,可根据不同产量和井口压力温度预测井筒是否会形成水合物,从而能预先制定测试方案和措施,避免因水合物形成冰堵影响气井的测试。

Empirical formula,phase equilibrium and statistical thermodynamics are major prediction methods for gas hydrate formation conditions.Among them,the phase equilibrium method is not applicable in gas field with higher content of non-hydrocarbon(e.g.content of CO2 in Yaoyingtai Gas Field is up to 22%,so the method is not applicable),and the statistical thermodynamics involves many parameters,so it is not convenient to be used in practice.The methods for calculating wellbore pressure and temperature and selection of formation thermodynamic parameters of gas well were discussed at first.Based on the discussion and taking the measured data of well YS1 in Yaoyingtai Gas Field as example,two empirical formula methods were used to calculate the pressure and temperature under which the gas hydrate was formed in wellbore.On basis of distribution of pressure and temperature at different depth of wellbore and formation conditions of gas hydrate,it can be predicted whether hydrate is formed in wellbore at different flow rates so as to determine a minimum flow rate during production.For new well test,it can be predicted whether hydrate is formed in wellbore according to different production rate and wellhead pressure and temperature so as to formulate testing program and countermeasures in advance and avoid influence of ice barrier caused by hydrate formation on gas well test.

https://doi.org/10.11781/sysydz200803315