Horizontal Drilling with Dual Channel Drill Pipe

摘要

Drilling of long horizontal wells is subjected to challenges, such as hole cleaning, drill string torque and drag, and challenges related to the Equivalent Circulating Density (ECD). Where the window for the downhole pressure is small, the length of the open hole section is limited by the dynamic ECD. The result is that several liners or casing strings may be required to reach the target depth. The Reelwell Drilling Method provides a new solution for above mentioned challenges, incorporating a dual drill string, 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, however, differs in that the downhole pressure gradient is managed instead of the pressure at one depth in the well. In addition, this new method of ECD control provides efficient hole cleaning at low flow rates, and enables torque and drag reduction due to buoyancy of the drill string.