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在水平井钻井中，进行水平井造斜段实钻井眼轨迹中靶情况判别和待钻井眼轨迹的设计是非常复杂而又至关重要的问题，它们相互影响，并直接关系着水平井钻井的成败。文中揭示了实钻井眼轨迹和待钻井眼轨迹间的相互关系。首先通过实钻井眼轨迹数据和井下钻具的造斜能力来判别实钻井眼轨迹与原设计井眼轨迹的偏离情况，然后根据偏离的情况来修正待钻井段的井眼轨迹设计，并对待钻井段造斜钻具组合进行判别：当未发生偏离时，不改变原钻具组合，继续钻进；当实钻井眼与原设计轨迹发生偏离时，利用实钻中正在使用的造斜钻具另加一套稳斜钻具可准确钻达水平段的入靶点。这样可充分保证在钻达水平段入靶点时的垂深、水平位移都能达到原设计要求，为水平段在产层内准确钻进打下良好的基础。

UNDRILLED BOREHOLE TRAJECTORY DESIGN OF THE DEFLECTING INTERVAL IN A HORIZO NTAL WELL AND ITS APPLICATION

In the drilling of horizontal well,it is a very complex and most important problem to judge the conformability of the drilled borehole trajectory of the deflecting interval in a horizontal well with the actual situation and to design the undrilled borehole trajectory.They influence each other,being directly relaed to the success or failure of drilling horizontal well.The interrelation between the drilled borehole trajectory and the undrilled one is revealed in the paper.Firstly,the deviation of the drilled borehole trajectory from the original design one can be distinguished in light of the data of drilled borehole trajectory and the deflecting capacity of downhole drilling tools,then,on the basis of the deviation,the borehole trajectory design of the undrilled interval may be corrected and the deflecting drilling tool assembly for undrilled interval can be distinguished as follows:when the deviation doesn't happen,the original drilling tool assembly is unalterable,the drilling being continuous;while the deviation of the drilled borehole from the original design trajectory happens,through attaching a set of maintain angle drilling tools to the existent deflecting ones in drilling,the entry target point of the horizontal interval may be accurately reached,which may fully ensure that the vertical depth and horizontal displacement of the horizontal interval can all fulfill the requirements of the original design so as to set up a good basis for accurately drilling of the horizontal interval in the payzone.