Hybrid Rotary Steerable System Delivers Higher Build Rates and Smoother Holes

Abstract

Young Technology Showcase Every drilling engineer’s dream would be to deliver more complex well profiles and smoother, more consistent boreholes in less time—ideally in a single run—eliminating the need to trip out of hole. The problem is that conventional positive displacement motors (PDMs) and rotary steerable systems (RSS) both exhibit limitations in different drilling scenarios. Industry Challenges and Needs Downhole motors, for example, are capable of delivering reliable, very high dogleg well profiles. However, because the drillpipe alternates between rotating and sliding, rates of penetration (ROPs) are low and hole quality is tortuous, increasing the potential for stuck pipe. On the other hand, fully rotating RSS deliver smoother wellbores at higher ROPs than PDMs, reducing drilling time by as much as 50%. However, the maximum build rate of a typical RSS is only 6 to 8 deg/100 ft, and much lower while drilling soft formations, enlarged holes, or hard interbedded stringers at high angles to the wellbore. For well profiles with high build rates, an RSS may be used for the vertical and lateral sections while motors must be used between the kickoff and landing points. This requires at least three bottomhole assemblies (BHAs) and multiple trips out of hole. To reduce risks while saving rig time and costs, drillers would prefer the hole quality and performance of an RSS combined with the high dogleg capability and steering assurance of a PDM. To meet operators’ growing needs both in unconventional shales and difficult formations, Schlumberger developed the PowerDrive Archer high build-rate RSS. In a single run, the technology can deliver well profiles previously possible only with motors. By improving borehole quality and reducing tortuosity, it minimizes the risk of stuck pipe and facilitates the deployment of casing, sleeves, and completion equipment (Fig. 1). It can perform openhole sidetracks and drill deeper before kickoff than other RSS, maximizing reservoir exposure and increasing potential production. Description, Development, and Deployment The high build-rate RSS represents a breakthrough in steering control. The RSS has been in use since the late 1990s. However, it could not deliver the 8-to-12-deg/100-ft build rates necessary for typical well profiles in unconventional shale plays. Due initially to rapid increases in shale drilling, Schlumberger began development in 2007 of a new RSS aimed at roughly doubling the maximum build rate of previous tools.