固井水泥浆不同凝固状态时的气体窜流实验

Gas Channeling Experiment of Cement Slurry in Different Solidification State

针对气体窜流问题,设计和开展了水泥浆不同凝固状态的气体窜流实验,观察了气体窜流现象,测量了气体窜流压力,分析了气体窜流形态及窜流路径,研究了气体窜流规律。研究表明,当水泥浆凝固时间较短(120 min和180 min)时,气体窜流压力较小(低于0.05 MPa),气体主要从水泥浆内部缓慢窜出,窜流通道尺寸总体较小但由下而上逐渐变大;当凝固时间增至200 min和220 min后,气体窜流压力增大至0.15 MPa和0.20 MPa,气体主要从内部突然大量猛烈窜出,窜流通道呈"糖葫芦"形和"裂缝"形且尺寸较大;凝固时间增至240 min后,窜流压力进一步增大至0.22 MPa,此时气体不能从水泥浆内部窜流,只能从水泥浆和井壁之间的胶结界面处窜出。建议针对水泥浆的不同凝固状态采用不同的策略来进行防窜设计。

Experiment on the gas channeling in different setting states of cement slurry was designed and conducted to deal with gas channeling. In the experiment, the gas channeling was observed, the gas channeling pressure measured, the form and path of gas channeling analyzed, and the pattern of gas channeling studied. The study results have shown that when the cement slurry sets in a short time(120 min and 180 min), the gas channeling pressure is low(<0.05 MPa), the gas channels slowly through the interior of the cement slurry, and the diameter of the channel is small but increases from the bottom to the top of the cement column. When the cement slurry sets in a longer time, say, 200 min and 220 min, the gas channeling pressure is increased to 0.15 MPa and 0.20 MPa,the gas channels abruptly in a high flow rate through the interior of the cement slurry, and the channel is in a shape of “serial bubbles” and “fractures” with big sizes. When the cement slurry sets in 240 min, the gas channeling pressure is increased to 0.22 MPa, and the gas can no longer channel through the interior of the cement slurry, it can only channel through the interface between the cement slurry and the borehole wall. It is thus recommended that anti-channeling measures should be designed in according with different setting states of the cement slurry.