| 摘要 |
Apparatus for curving a vertical borehole laterally towards the horizontal by anchoring a diverter downhole in the bore-hole near the formation to be produced. A special cantaloupe shaped drilling mill is attached to the end of a rigid drill string to form an opening through the casing wall in proximity of the formation to be produced. Then a special concave cutting device enlarges the opening into a window of a size to accommodate a flexible drill string that subsequently is attached to the rigid drill string. A bit attached to the flexible drill string is extended through the window where it drills a curved borehole towards the horizontal and continues laterally through the formation. The flexible drill string has a central fluid passageway and is formed of resilient material which surrounds an inner spring member to form a flexible, longitudinally extending, torque transferring drilling string. The opposed ends of the spring member each abutt a coupling member which enables the flexible tool string to be connected into any drill string. The spring is tight wrapped and transmits torque produced by the rig into a drill bit.
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