摘要
泥页岩中含有水敏性黏土矿物,当与钻井液接触时,泥页岩与钻井液相互作用,泥页岩水化不仅改变了井眼周围的应力分布,使得泥页岩地层的井壁失稳问题比常规恒定弹性参数的应力失稳问题复杂得多,井壁坍塌周期预测更是难上加难。认为若要预测井壁坍塌周期必须建立井壁稳定性与钻井液浸泡时间的定量关系,落脚点就在于岩石力学参数,通过室内实验建立岩石力学参数随钻井液浸泡时间的变化关系,建立坍塌压力随时间的变化关系,进而得到垮塌宽度随钻井液浸泡时间的变化关系。认为当井壁垮塌宽度增加到不再明显变化时为一个周期,这时井壁应力重新达到平衡。从结果出发,避免了复杂的力学—化学耦合过程,从而达到能较为准确预测井壁坍塌周期的目的。
In mud shale, there are large amounts of water-sensible clay minerals. When in contact with drilling fluid, the mud shale interacts with drilling fluid each other, which may lead to swelling due to hydration. This alters the stress distribution near borehole. And one problem of borehole instability in mud shale becomes more serious than that of stress instability in conventional constant elastic parameters. So, it's more difficult to predict borehole collapse cycle. Our study deems to establish a quantitative correlation between borehole stability and change of drilling- fluid soaking- time. To make rock mechanical parameters clear is very important in this correlation. So, through some experiments, the first relationship that these parameters changes with soaking time is established; and then, the second one that collapse pressure varies with time is set up; at last, the third one that collapse width changes with soak time may be gained. It's demonstrated that one cycle should be no obvious change that the width increases. At this time,borehole stress reaches a balance again. This procedure avoids a complicated mechanical and chemical match, and finally can realize an aim to predict the collapse cycle very accurately.
出处
《天然气技术与经济》
2016年第5期32-35,82,共4页
Natural Gas Technology and Economy
关键词
页岩储层
井壁稳定性
垮塌宽度
坍塌周期
shale reservoirs
borehole stability
collapse width
collapse cycle
