盐岩地层井眼缩径控制技术新方法研究

A NEW APPROACH FOR CONTROLLING TIGHT HOLE IN SALT FORMATION

防止盐岩卡钻传统的措施是采用饱和盐水泥浆 ,阻止盐岩溶解 ,加大泥浆密度 ,减缓盐岩向井眼方向的流动 ,防止缩径。但这种以提高泥浆密度为前提的盐层钻井在高温、高地应力区域 ,不能从根本上解决盐岩层卡钻的问题 ,因为实际钻井中泥浆密度不能无限制地增大 ,否则其他岩性层段易产生复杂情况 ,并且影响钻速。提出了解决这类问题的新方法 ,采用适当密度的欠饱和盐水泥浆 ,通过调整氯根 (Na Cl浓度 ) ,让欠饱和盐水泥浆能满足井眼截面的盐溶解速率与盐层的缩径率平衡 ,从而达到防止盐岩卡钻的目的 ,并在实际钻中得到较为有效的应用。

The conventional approach to avoid stuck in salt formation is to use high density saturated brine mud. This approach may be effectual in some low in situ stress and low temperature salt formation, but can not prevent from tight hole in high in situ stress and high temperature salt formation. In addition, it is impractical to increase mud weight too much in drilling practice because mud lost may be induced in weak sand. A new way is presented to control tight hole in high in situ stress and high temperature salt formation by low density unsaturated brine mud. The salt solution rate can be controlled by adjusting content. If the balance between salt solution rate and hole shrinkage rate is established, stuck can be avoided successfully. The technique is used successfully in field.