Horizontal Drilling With Dual-Channel Drillpipe

Abstract

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 184683, “Horizontal Drilling With Dual-Channel Drillpipe,” by O.M. Vestavik and J. Thorogood, Reelwell; E. Bourdelet, Total; and B. Schmalhorst and J.P. Roed, DEA Deutsche Erdoel, prepared for the 2017 SPE/IADC Drilling Conference and Exhibition, The Hague, The Netherlands, 14–16 March. The paper has not been peer reviewed. A new drilling method provides a solution for challenges encountered in drilling of long horizontal wells, incorporating a dual drillstring with a separate channel for the return fluid from the well. This arrangement enables managed-gradient drilling (i.e., to drill with a constant downhole pressure gradient that can be controlled to be nearly independent of the flow rate). The solution is similar to managed-pressure drilling (MPD) but differs in that the downhole pressure gradient is managed instead of the pressure at one depth in the well. Introduction The technology for drilling and completion of long horizontal sections has improved significantly in recent years. However, challenges such as hole c leaning, equivalent-circulating-density (ECD) control, and torque-and-drag reduction still exist. ECD is linked to hole cleaning and is often a limiting factor. Long-reach horizontal wells can also be limited by the torque and drag of the drillstring. The dual-drillstring configuration has specifically been developed to provide solutions to these challenges, as follows: Hole cleaning: Drill cuttings are removed from the bottom of the hole through a separate flow channel inside the drillstring. ECD control: Managed-gradient drilling creates a constant downhole pressure gradient independent of the flow rate. Torque and drag: A heavy-over-light fluid solution reduces torque and drag through buoyancy. Fig. 1 presents a schematic of the drilling-fluid flow for this arrangement. The dual drillstring allows drilling mud to be pumped down the annulus inside the drillpipe, with the return flow up the concentric inner pipe. The system can be installed on a standard drilling rig. A topdrive adapter connects the rig’s topdrive to the top of the dual drillstring. The adapter contains a swivel that allows for pumping mud into the drillpipe annulus and for the return flow from the inner pipe to be directed back to the surface mud system. The lower end of the dual drillstring connects to a standard bottomhole assembly (BHA) by means of an inner-pipe valve, which contains entrance ports for the return fluid and isolates the well during pipe connections.