Eliminating Rig Time from MWD Surveying

Abstract

Directional surveys are taken while drilling a well to enable well placement and to avoid hitting other wells. This requirement is becoming increasingly important as reservoirs become more complex to reach and fields become ever more crowded. Taking directional surveys either before, during or post connection takes time, waiting for surveys to be pumped up takes longer and may need to be repeated if a critical survey cannot be taken first time which is a particular problem in shallow hole offshore operations. This paper outlines an industry first technology that will effectively eliminate surveying time, a definitive continuous survey will be available to the directional driller at all times, eliminating the need to take and wait for a survey before making the next directional drilling decision. Continuous 6 axis surveys are cutting edge replacement for the static six axis Measurement While Drilling (MWD) surveys which have been used as the primary surveying tool worldwide for decades. The three magnetometers and Inclinometers provide an accurate inclination and azimuth when the drillstring is stationary. Continuous six axis MWD surveying could be described as a static survey captured continuously while drilling a stand allowing for accurate inclination and azimuth at all times. The directional driller will know where they are definitively at all time, eliminating the requirement for surveying time, enabling efficient decision making while eliminating the need for additional pump cycles, their associated wash outs and the directional difficulties that stem from that. Field test examples of this continuous 6 axis MWD surveying will be shown with comparisons between other MWD systems these will be analyzed to establish consistency and accuracy. An error model for the continuous six axis survey will be discussed in some detail, as it is inherently different to a normal static MWD survey and comparison will be made to other error models. The time savings involved with continuous six axis surveys will also be shown, with a discussion on the associated benefits to the directional driller from reduced pump cycles. Directional surveying is generally seen as a must have on a rig, however the associated rig time is considerable. This unique and world first method will discuss how continuous six axis survey are made, the accuracy modelled and so how the industry can eliminate rig time associated with MWD surveying.