The surveyed position accuracy degrades when one approaches the magnetic and geographical poles. Both magnetic and gyroscopic tools are affected. We have analyzed the accuracy of several magnetic and gyroscopic services in a number of representative synthetic wellbores. Locations representative for the North Sea and the Barents Sea are chosen. The results show that an increase in horizontal target dimension by a factor of 2 is necessary when moving from 60°N to 75°N, to maintain the same hitting probability.Examples of areas which may be affected by these findings, are: target design, well planning, surveying programs and practices, anti-collision criteria, and the ability to drill relief wells.

Introducing new control functionality on the drilling rig has an effect on handling of machinery and controls and on the overlying work process both on the rig and for off-site support. New operational procedures taking these factors into account are therefore required to ensure safe and efficient application of such new technology.This paper presents a new method for developing operational procedures for the driller when applying a system for automatic safeguarding and optimization of pump and pipe control in drilling operations. This method has been developed and subsequently applied through a lengthy study. A laboratory test environment has been used for this purpose, containing an advanced drilling simulator with the safeguarding and optimization functionality integrated.The method applied consists of three phases, all performed in the laboratory test environment. Initially, the measurable effect of use of the system on the driller's performance was evaluated in detail, using a set of test cases and a series of test-personnel from a drilling contractor. Subsequently the ability to drill a well section with incorporated incidents and exceptions was studied. Finally, operational procedures were developed in cooperation with the test-personnel, again using the test environment for testing and checking of procedures.In this development process the focus has been on varying system modes and on handling of system and drilling process exceptions, while taking into account the effect of human factors and the wider organizational context of work conduct.The authors believe that the method described is a suitable way to develop procedures for application of new control functionality on the drilling rig, and would recommend that such studies should be performed for new technologies to be applied in control of drilling operations.