Patent ID: 6842699

Claim:
A method of recovery of hydrocarbons from a reservoir in a subterranean earth formation, the method comprising: (a) drilling a first borehole into the reservoir; (b) obtaining information about a position of the first borehole at least within the reservoir, (c) drilling a second borehole in proximity to the first borehole using a directional drilling device; (d) making a measurement with a Gyro-MWD tool in the second borehole at a first rotational position; (e) rotating the Gyro-MWD tool a plurality of discrete angles encompassing the first rotational position and taking additional measurements thereat, giving a plurality of additional measurements; (f) determining a bias in measurements made by said Gyro-MWD tool from said measurements at said first rotational position and said plurality of discrete angles; (g) determining from said measurements and said determined bias a position and orientation of the second wellbore; and (h) controlling the directional drilling device in response to the obtained information about the location of the first borehole and the determined position and orientation of the second wellbore so as to maintain a desired relation between the position of the first borehole and the position of the second borehole.