定向钻进钻头运行轨迹调控

在定向钻孔施工中,结合地层促斜规律进行跟踪设计,控制钻头运行轨迹十分重要。实践证明,在具层理的二叠系地层中定向钻进,当钻孔定向弯曲方向相逆于岩层倾向(α=65°～80°),常规稳斜孔段自然弯曲表现为增斜;当钻孔定向弯曲方向相顺于岩层倾向(α=45°～65°),常规稳斜孔段自然弯曲表现为降斜,其顶角变化率均为1°～3°/100m。同时,钻孔方位也发生漂移,其方位漂移率为10°～30°/100m。因此在调整增斜孔段的终点方位和顶角时,要为稳斜孔段预留提前量。在定向造斜时,造斜钻具的工作角(β)决定着钻孔轴线的空间位置变化,理论计算的β值经过修正后才能作为造斜器在孔内的装置工作角(ω_0)。

HOW TO ADJUST AND CONTROL MOVING TRACES OF BITS IN CONSTRUCTION OF DIRECTED HOLES

In the course of construction of directed holes,effective controls on movingtraces of the bits by the means of immediately revising the drilling designs accordingto deflection-promoting regulations in strata to be drilled can not too overvalued. Drilling practices suggest that when drilling projects are performed upon the well-bedded strata of Permian age,amount of the natural inclination from the intervalneeding to be guided to a desired dip tends to increase if the direction of the drilling isopposite to the dip(α=65°-80°)of the strata and,conversely,to decrease ifidentical to the dip(α=45°- 65°).No matter whether increase or decrease,thezenithal angles of drilling holes can not exceed a limit of 1°-3°per 100m.At thesame time,their azimuthal angles also move about from 10°-30° per 100m.For thisreason,proper adjustment of these two angles at the lower end of the guided intervalwith increased inclination will call for planing certain angles of advance for it beforedrill construction.On the other hand,working angle(β)of a deflection-making bitas well decides,to a large extent,the spatial variation of the hole's axis.So thevalue of β,obtained by theoretically calculating,is not revised until it can be servedas the working angle at which the whipstock is positioned inside the hole.