In 2000, two unplanned disconnects of the Lower Marine Riser Package (LMRP) occurred on deepwater rigs in the Gulf of Mexico. Both were attributed to human error. The IADC Deepwater Well Control Task Force reconvened to study this problem and investigate preventative measures. The results of this study were presented to the Minerals Management Service (MMS) in July 2000. The report includes recommendations regarding the Primary Control System for prevention of unplanned disconnects as well as guidelines concerning back-up systems to maintain or regain wellbore security. The back-up systems studied include 1) intervention by Remote Operated Vehicle (ROV); 2) deadman systems/autoshear systems; and 3) acoustic control systems. Introduction The occurrence of two unplanned LMRP disconnects within a matter of weeks resulted in a request by the MMS to reconvene the IADC Deepwater Well Control Task Force (Task Force) in March 2000. The cause of both incidents was determined to be human error. Therefore, the Task Force focused first on short- and long-term preventative measures, followed by an evaluation of existing back-up systems which could assist in maintaining or recovering control of the well in the event of an unplanned disconnect. Objectives. The Task Force established the following specific objectives:To formulate recommendations to the MMS and industry on guidelines dealing with the prevention of inadvertent disconnection of the LMRP and other similar occurrences which would undermine the integrity of the wellbore. The Primary Control System was identified as the focus.To formulate recommendations to the MMS and industry on guidelines dealing with back-up systems to maintain or regain wellbore security. These back-up systems were initially identified as ROV intervention, acoustic control systems, interlock functions, and deadman systems/autoshear systems. Five subcommittees were formed to study the areas of prevention, ROV intervention, interlock functions, deadman/autoshear, and acoustic control systems. Each subcommittee included representatives from operators, drilling contractors and service companies, who worked at a rapid pace to return comprehensive reports on all options. Eventually interlocks were included in the category of Prevention Improvement Measures, leaving ROV intervention, deadman/autoshear systems, and acoustic controls as the mitigation system options considered. After completing their analysis of preventative measures and mitigation systems, Task Force members ranked the alternatives and concluded that Prevention Improvement Measures provided the first line of defense against unplanned disconnects (Table 1). Recommendations After numerous meetings among subcommittee members and six Task Force meetings throughout the spring and summer of 2000, the following recommendations were presented to the MMS:All practical Prevention Improvement Measures be applied to floating rig operations in the OCS at a deliberate pace (Table 2).One of more of the mitigation system options should be applied as determined most appropriate by the Operator and Rig Contractor for the specific rig and well characteristics (Tables 3, 4, 5). Prevention Improvement Measures. The investigation of preventative measures covers alternatives for all types of systems on both new and older rigs. It is expected that sufficient means of reducing the probability of an unplanned disconnect can be applied to all rigs within a reasonable time.

This paper was prepared for presentation at the 1999 SPE/IADC Drilling Conference, Amsterdam, The Netherlands, 9-11 March 1999.