The survey accuracy requirements are dictated by the following:
The geological target should be as large as possible to minimize costs (directional drilling and surveying), considering the expected survey uncertainties.
2. Collision avoidance
The survey accuracy is defined by the separation factor (SF): the ratio between the 3D centre to centre well distance and this distance minus the inter-boundary distance between the envelopes of the borehole position uncertainty. For SF < 2.5 it is recommended to perform a full 3D proximity analysis. For SF < 1.5 it is . . .