超临界二氧化碳钻井流体携岩特性实验

An experimental study on carrying cuttings features for supercritical carbon dioxide drilling fluid

超临界二氧化碳钻井流体已在油田二次开发的侧钻井中成功应用。应用Angel模型计算了超临界二氧化碳钻井流体在不同状态下携岩最低返速,绘制了二氧化碳钻井流体在不同温度下携岩需要的最低返速与压力关系曲线。根据相似性原理,设计开发了超临界二氧化碳钻井流体循环模拟实验装置。通过实验揭示了携岩能力随井斜角变化规律,即井斜角为0°～36°携岩最容易;井斜角为36°～54°携岩开始变得困难;井斜角为54°～72°携岩最困难;井斜角为72°～90°携岩变得相对容易;在40°C和8.5MPa条件下完成携岩所需最低携岩返速为0.637～1.019m/s。随着井筒内压力增加,所需的最低携岩返速减少,即携岩能力逐渐增加。随着井筒内温度增加,所需的最低携岩返速逐渐增加,即携岩能力逐渐降低。实验结果与Angel理论模型的计算结果基本相符。

The supercritical CO2 drilling fluid has been successfully applied to lateral drilling in the secondary development of oilfields.The minimum up-hole velocity of carrying cuttings for the supercritical CO2 drilling fluid under various conditions was calculated with the Angel model,and a correlation curve of the minimum up-hole velocity and pressure required by carrying cuttings of the supercritical CO2 drilling fluid at different temperatures was drawn.On the basis of the similarity principle,an experimental device for circulating simulation of the supercritical CO2 drilling fluid was designed and developed.Experiments revealed a variation trend of the carrying cuttings capability with the change of the deviation angle,i.e.the deviation section with the angle between 0°～36° was the easiest for carrying cuttings,the one between 36°～54° became somewhat difficult,the one between 54°～72° was the most difficult,and the one between 72°～90° became relatively easy again.The minimum up-hole velocity required by carrying cuttings under the conditions of 40°C and 8.5MPa ranged between 0.637～1.019m/s.Moreover,the minimum up-hole velocity required by carrying cuttings decreased with the increase of borehole pressure,namely the carrying cuttings capability was gradually increasing.On the contrary,the minimum up-hole velocity required by carrying cuttings increased gradually with the increase of borehole temperature,namely the carrying cuttings capability was gradually decreasing.These experimental results were basically consistent with the calculated outcome by the Angel theoretical model.