川西积液水平井井筒压力及液位预测

摘要

The technical key to drainage technology optimization and drainage parameter determination is to predict accurately the borehole pressure and liquid level of liquid-loading horizontal wells. The pressure balance model of tubing and tubing-casing annulus in liquid-loading horizontal well was developed based on the U-shape pipe principle by using fluid statics and dynamics equations. In this model, the tubing pressure drop is derived from the flowing gas above the liquid level and the two-phase flowing below the liquid level, and the two-phase liquid holdup is basically obtained from the drift model. The tubing-casing annulus pressure drop is derived from the static gas column pressure above the liquid level and the static liquid column pressure below the liquid level. The tubing pressure and the tubing-casing annulus pressure are equal at downhole connecting points. However, two liquid level parameters cannot be solved only by using one balance equation. To deal with this problem, the liquid level in tubing-casing annulus was measured by virtue of ground echometer, and then the liquid level and pressure in tubing were solved by means of the model. Case study indicates that by virtue of this method, the borehole pressure and liquid loading level in liquid-loading horizontal wells in West Sichuan Gasfield can be predicted accurately, and its prediction time efficiency is superior to that of traditional manometry. The influential factors were also analyzed. And it is indicated that the liquid level in tubing is generally higher than that in annulus, and the decrease of tubing-casing pressure difference can reflect indirectly the reduction of liquid loading volume in tubing.%正确预测积液水平井井筒压力与液位是优选排液工艺、制定排液参数的技术关键.基于U型管原理,结合流体静力学与动力学方程,建立了积液水平井油管与油套环空压力平衡模型.模型中油管压降来源于液位以上流动气体与液位以下的两相流动,其两相流持液率基于漂移模型得到;油套环空压降则来源于液位以上的静气柱压力和液位以下的静液柱压力;油管与油套环空压力在井下连通点处相等;模型计算采用了先借助地面回声仪获得油套环空中的液位,再利用模型求解油管液位及压力的方法.川西气田什邡6-1HF水平井的模型预测压力与实际测压数据的误差为3.75%,表明该方法能够正确预测川西气田积液水平井的井筒压力与积液液位,且预测时效优于传统的测压方法.影响因素分析表明,油管液位通常高于环空液位,油套压差的减少能够间接反映油管积液量的减少,为类似油田的开发提供技术指导.