Abstract
Movement of cuttings produced while drilling is not a new issue to the drilling industry. We do however see the overall depth of wells, as well as their inclusion of extended horizontal runs ever increasing. We find the risk of differential sticking, excessive loss of pressure, and general stuck pipe situations compounded with every foot deeper we drill. The circulating sub has been a long relied upon tool in the drilling world that has aided in the acceleration of cuttings along the annulus towards the surface. When activated they can reduce build-up of debris and cuttings on the low side of the drill string through horizontal runs and in deep and ultra-deep drilling applications by increasing annular velocities. The downside to these tools has always been the constraints of the technology. Various systems for engaging and disengaging circulating subs have been designed over the years, improving on particular points such as actuation, or split flow design, but these designs have consistently relied on fishing out a drop ball or dart to deactivate, or dropping additional balls to cycle the tool. This takes costly time to pump the balls down the string and limits the total number of cycles before the tool must be pulled and serviced, potentially interrupting the run. Service companies have long been searching for a simpler, more efficient method of circulating to the annulus without the lost time and complicated cycling methods required by current technology.
Utilizing a new cycling mechanism design and an open bore (to allow for potential fishing of MWD components), drillers can now cycle an infinite number of times without regard for the tool needing to be pulled due to maximum cycling count being reached. The tool is cycled using a single drop ball and changes in flow rate alone. The tool can be launched with the ball in place, alleviating the need to pump a ball down at all, or the ball can be launched from surface during the run if fishing through the ID is required prior to activating the circulation sub.
This paper details how the development of a step change in circulating technology is assisting a major service company in reducing downtime during the use of the circulating tools in hole. This design has proven easier to operate and has reduced the overall time lost struggling with current tool designs. Supporting case studies are included to detail the increase in efficiency and reduction in costs.
