Technology Update: Conductor Anchor Node Optimizes Efficiency of Riserless Deepwater Exploration Drilling

Abstract

Technology Update The conductor anchor node (CAN) technology was introduced as part of the architecture for Centrica’s Ivory deepwater exploration well in the Norwegian Sea to optimize efficient operations for the well’s riserless section. The CAN (Fig. 1), developed by NeoDrill, is a large steel cylinder that is open at the bottom with an open guide pipe in its center. The device sets into the seabed, working similarly to a suction anchor, and carries and secures a well’s conductor (top-hole casing). The CAN is set in place by a dynamically positioned (DP) installation vessel before the drilling rig arrives. The technology is designed to save rig time and expense, simplify logistics and rig operations, and expedite well startup (https://www.spe.org/en/jpt/jpt-article-detail/?art=2641). With the CAN, seabed marker buoys and DP transponders were preinstalled by a construction vessel in June 2014. The spud location was prepared for an efficient startup when the drillship arrived in October of that year. A pilot hole was drilled 50 m off-set from the preinstalled CAN to investigate for shallow hazards and record useful drilling parameters to determine soil strength. The interpreted soil strength information was used for selecting the optimum conductor length for jetting it in and landing in the CAN. The conductor jetting method was chosen to optimize the dual-derrick rig operations. All the riserless activities using the dual derricks were optimized to reduce the rig time and maximize the parallel-activities advantages. Well Design and Challenges The overall strategy for the well was to perform as much work as possible before rig arrival, to reduce exposure to weather and optimize operations in the riserless sections of the well. NeoDrill was contracted for preinstalling the CAN to facilitate safe jetting operations and reduce the conductor string length, which is made possible for jetted or cemented conductors by the high axial load-bearing capacity of the CAN system. Conductor analysis concluded that a 50-m CAN-supported conductor would suffice, compared with the 80- to 100-m length required for a conventional conductor. Conductor jetting is the quickest installation option, as it does not require cementing operations, tripping for a new drilling bottomhole assembly (BHA), and drillout. The conductor jetting operation was performed using a special conductor running and drillout tool, the Dril-Quip Cam Activated Drill Ahead Tool (CADA tool), which allows each new section to be drilled without tripping for a new BHA. The CAN allows the conductor to be landed safely without waiting for soil to consolidate (soak) before the CADA tool is released for drilling to resume. Thus, the risks of the conductor and wellhead housing sinking after the tool’s release are mitigated.