Locating a downhole reference member for subsequent drilling operations

摘要

The method provides a means of setting an apparatus in a cased wellbore to act as a marker and orienting locator for all subsequent drilling operations where the apparatus is not required to withstand compression, tension and torque of well operations. In a preferred application a reference member is lowered into a borehole on a pipe string, once the preferred depth is attained an orienting member is oriented and set within the reference member to assist with the aligning of the reference member. The reference member is then set and the pipe string is disconnected and retrieved. In a preferred embodiment the apparatus includes a reference member (10) having upper and lower slips (12, 14), an orientation member (Figure 2a, ref.16), upper and lower cones (18, 20) having cooperating wedge surfaces (60, 62) and a rachet member (22) where the rachet member allows the cones to move apart upon setting in order to maintain the slips in an expanded position. The well reference apparatus and method have particular application in the drilling of multiple lateral boreholes an existing cased well and the apparatus may further include a plurality of mills and a whipstock (Figures 10-16). Numerous embodiments of the invention are disclosed.