Enhancing Well Control Through Managed Pressure Drilling

摘要

In addition to enhancing drilling safety and performance, MPD offers new options for well control.Because MPD allows rapid changes in bottom hole pressure, the response to an unwanted influx duringMPD operations is not necessarily to shut-in and weight-up. Instead, the required overbalance can beregained dynamically to stop an influx, as well as circulate it from the wellbore. This fundamentaldifference from conventional drilling allows components of the primary barrier envelope to be usedwithout having to activate secondary well control equipment, as the MPD system is designed to handleinfluxes to a maximum size. Most commonly in MPD operations, this can be achieved by closing an MPDchoke, while circulation is maintained. The advent of dual gradient drilling offers further variation indynamic well control practices.MPD is a deviation from traditional drilling practices and the technique is relatively new to industry.MPD systems are designed to detect and control influxes of a certain size, however, many MPD operationsrevert quickly to conventional shut in procedures when confronted with an influx regardless of the size.Effectively, all influxes are treated as kicks.Inconsistent definitions and misunderstandings of MPD systems’ equipment and capabilities amplifythe problem of determining when dynamic operations are appropriate. The switch from influx managementwith the MPD system to conventional well control is governed procedurally through the definitionof operational decision points based on influx indicators and surface backpressure during drilling.Quantification of manageable influx size is not standard. The onus is on the operator to define thesedecision points such that influxes are safely managed by the MPD system, while the rig handles kicks.Further, the use of MPD equipment can also be used to limit the resultant size of an influx that has becomea kick, demonstrating that MPD equipment can ultimately enhance drilling safety, in most cases.In this paper, differentiation between appropriate MPD operations using the primary and secondarybarrier envelopes is proposed. The work explores the key factors that must be considered in determiningwhen the appropriate initial response to any influx is dynamic or conventional. A common understandingthroughout industry of the safety related aspects of MPD may lead to the use of such systems on everyrig, defining the new normal.