Abstract
The efficient exploitation of hydrocarbon resources is strongly dependent on the drillers’ ability to position wells accurately. This is particularly challenging for smaller targets and on long reach or horizontal wells. Conventional wireline VSP’s can provide valuable assistance but such operations require either the drill string to be removed from the hole or the pumping of the geophone tool through the drill string. Both of these methods add time to the well construction. In long sections of open hole wireline operations may present risks, in the form of sticking and potential fishing operations, which prevent VSP surveys being acquired in lookahead mode. Ideally, VSP data would be acquired at several stages of the drilling process to enable corrective action to be taken to assist accurate bit placement. The costs in terms of rig time alone generally make this option prohibitive.
Ongoing developments for cost effective exploitation of mature and pressure-depleted reservoirs have led to wider applications for coiled tubing drilling. The combination of a seismic tool with the coiled tubing drill string therefore provides an ideal configuration to reduce drilling costs and optimise well placement. This paper discusses the conventional methods available for geosteering of the bit, the additional benefits of incorporating a seismic tool into the drill string and describes the development of a seismic while drilling tool (SMWD) for coiled tubing drilling.
