Fingerboard

Key Takeaways

• The derrickman's position at the monkey board during tripping is one of the most physically demanding and hazardous jobs on a drilling rig: the monkey board is typically 80-100 feet above the rig floor on a land rig and higher on a semi-submersible, reached by climbing the derrick ladder or riding a personnel basket; the derrickman works alone at this elevation, often in cold, wet, or windy conditions, catching and racking stands of drill pipe that weigh 1,000-3,000 pounds; the safety systems protecting the derrickman include a retractable lifeline tethered to the derrick structure, a stabbing board (a movable platform that positions the derrickman close to the pipe without requiring them to lean over), and a belly buster or body belt that keeps the derrickman secured when reaching for pipe in the fingerboard; falls from the monkey board are one of the leading causes of fatal accidents in drilling operations, which is the primary driver behind the industry's investment in automated pipe-handling systems that eliminate the derrickman's need to work at height.
• Fingerboard capacity determines the maximum stand-back capacity of the rig, which is a critical factor in well planning for deep wells where the total drill string length requires multiple trips: a fingerboard that can hold 200 stands of 90-foot stands has a setback capacity of 18,000 feet of drill pipe, which is sufficient for most conventional wells; ultra-deep wells (15,000-25,000 feet measured depth) may require drill pipe that cannot all be racked in the fingerboard at once, requiring a strategic management plan where some drill pipe is laid down on the pipe deck and the remaining fingerboard space is used for the drill collars and heavyweight pipe that go in the bottom hole assembly; the derrick structure's load capacity also limits how much pipe weight can be racked at a given elevation, with the bending moment from a full fingerboard of heavy-weight pipe potentially exceeding the structural rating of the mast if the setback design is not verified against the rig's load chart.
• The transition from kelly-drive rigs to top-drive rigs changed fingerboard management because top drives can drill with longer stands (triples instead of doubles), which reduces the number of connections made and broken during tripping and therefore reduces both the time spent at the fingerboard and the total number of stand-setting operations the derrickman must perform; a double is two joints of drill pipe (approximately 60 feet), while a triple is three joints (approximately 90 feet); a 10,000-foot drill string requires 167 trips into the fingerboard for doubles but only 111 for triples, a 33% reduction in derrickman operations per trip; on ultra-deep wells, some rigs are designed to drill with fourbles (four joints, 120 feet), further reducing the number of connections and fingerboard operations, though fourbles require a taller derrick and more robust pipe-handling equipment to manage the additional pipe weight hanging in the mast.
• Automated pipe-handling systems (variously called iron roughnecks with pipe-racking arms, automated pipe handling, or robotic derricks) are being deployed on new-build offshore rigs and some onshore drilling contractors to eliminate the derrickman from the monkey board: these systems use a combination of a floor-level iron roughneck (which makes and breaks connections at the rotary table), a vertical pipe-racking arm at the fingerboard level (which receives stands from the elevator and places them in the fingerboard slots), and a control system that tracks the location of each stand in the fingerboard to retrieve the correct pipe during trip-in; the control system's pipe tracking is a significant improvement over the derrickman's mental map, because it provides a digital record of exactly which stand is in which fingerboard slot, allowing the driller to verify that pipe is being run back in the hole in the correct order; the safety benefits of removing personnel from height are clear, but the systems require rigorous maintenance because a mechanical failure at the fingerboard level during a trip can cause a stand to swing free in the derrick, a potentially catastrophic event.
• The fingerboard arrangement for a directional well with a complex bottom hole assembly (BHA) must account for the fact that the BHA components (drill collars, measurement-while-drilling tools, rotary steerable systems, downhole motors) cannot be racked in the fingerboard like standard drill pipe because they are heavier, stiffer, and often contain sensitive electronics; BHA components are typically racked in a dedicated area of the fingerboard with wider slots or in a separate stabbing board arrangement at a lower level of the derrick, with their position tracked carefully because their order of assembly in the BHA during trip-in must follow a specific sequence determined by the directional plan; running a BHA component in the wrong order can require pulling the drill string back out (another trip) to correct the assembly, at a cost of many hours of rig time.