An advanced rig control system that was provided to a major international land drilling contractor streamlines the ergonomic tasks that are routinely performed by a driller. The system employs joystick controls from a specially designed console with touch-screen displays that eliminate conventional SCR and drawworks control panels. Signals are routed though industrial grade computers and robust programmable logic controllers (PLC) to integrate data and control to simplify the correct operation of the rig. An electronic automatic driller is used to optimize drill line payout with up to four selectable constraints chosen by the driller and/or drilling engineer.
Maintenance of the software can be achieved from a remote command station via a telephone or satellite connection. The PLC and user interface software code can be monitored and modified if necessary. Using a data logger that records and transmits PLC parameters, the system designers can verify that the driller is using the system as intended.
While this remote connectivity provides high system reliability, it can increase operating risk unless proper procedures are followed. This paper identifies the risk factors and recommends specific policies to mitigate these risks. Specific examples are cited where the software on a working rig was modified from a remote site.
Introduction
Recent advances in rig control systems are now available for land rigs and retrofit units. Employing sophisticated information and control techniques, systems were developed to simplify the presentation of data to the driller alongside ergonomically designed control devices. These systems offer many desirable attributes, such as touch-screen operation and "Activity-Based Controls." The use of touch-screens allow the driller or assistant driller to easily press a screen ‘button’ located conveniently near his field of view to control the new robotic machines on the drill floor1. "Activity-Based Controls" employ a technique of displaying only the information needed for a specific task and modifying the display automatically when the task changes. (Fig. 3).
The workstation is designed for comfort and functionality. The positioning of the touch-screen displays was analyzed to ensure maximum visibility of the drill floor and vee door while still within the peripheral view of the operator. To reduce operator fatigue, there is minimal arm extension needed to reach the panels and discrete controls. The conventional brake handle is replaced with a single joystick that controls the drawworks as simply as an air tugger: pull back to hoist and push forward to lower. A second joystick controls the catheads. Several discrete push buttons are provided for emergency shut downs as well as a range override for the electronic automatic driller. The touch screens replace the myriad of control devices and gauges found on today's conventional rigs, but the hydraulic weight indicator provides a familiar read out of hookload and weight on bit. (Fig. 1 and 2).
The touch screen monitors are driven by industrial grade, rack-mounted computers located in a safe area, and additional client servers can be provided in a trailer or quarters for remote monitoring of displays and alarms as desired. The controls are networked to provide a serial connection between the various devices and sensors to minimize the cable requirements. (Fig. 5) Data is collected in a digital acquisition unit (DAQ). Drawworks computations are made in a PLC that include throttle commands and semi-automatic braking commands for block positioning2 and auto-drilling3. The Electronic Driller™4,5 allows the driller to establish boundary conditions to control line payout: rate of penetration, weight on bit, differential torque, and/or differential pressure. The complete package, known as the Varco Integrated Control and Information System (V-ICIS SE™4), provides supervisory control of specific drilling equipment via their PLCs and an industrial Ethernet communications protocol.
