Determination of appropriate kick tolerance to safely drill a narrow margin well can be challenging. A conventional approach using conservative assumptions and a single bubble model can lead to premature deployment of contingency casing strings or render some scenarios un-drillable. Uncertainties in pressures and depths in HPHT wells make a robust design that can handle all possible scenarios especially challenging. This paper will examine a strategy for challenging these assumptions and presents a robust methodology for safely managing ultra-low kick tolerance and large subsurface uncertainties by taking advantage of MPD influx management techniques and multi-phase modelling. The key elements defining the well control envelope include formation strength, resolution of influx detection, realistic shut-in times, safety margin and method of influx control (circulating response with MPD vs non-circulating response with BOP). This kick tolerance strategy will be implemented for a lengthy HPHT campaign in the UK North Sea. The strategy is designed to enable drilling the reservoir sections to TD and achieving all well objectives where applying a more conventional approach may require contingency casing to be deployed and key well evaluation objectives to be regretted. In addition, the well control strategy will take advantage of MPD influx management to control potential influxes within very small volumes while continuing to circulate.

Managed Pressure Drilling (MPD) is an increasingly common technique in narrow margin HPHT wells. However, MPD is sometimes viewed as a 'bolt-on' technology, only added after much of the planning work has been carried out and all other alternatives have been exhausted. By this stage key aspects of the well design are already fixed and major benefits of MPD can therefore be missed. The decision to use MPD should be made at the earliest stage of well planning, not on the basis of having no remaining alternatives, but by understanding the value that MPD can bring to the project. By doing this, MPD can be fully integrated into the well design, rig specification, procedures and training. This paper describes how an early commitment to integrate MPD into an HPHT drilling operation can make MPD more than just an enabling tool, and turn it into a performance tool that offers significant operational benefits.

The Shearwater field is a deep, high-pressure, high-temperature (HPHT) reservoir located in the UK Central Graben of the North Sea. The current drilling campaign represents the first round of well re-entries into the field following a campaign of slot recoveries to facilitate sidetrack development opportunities.A high level of reservoir depletion (Ͼ 8000 psi) has resulted in significant changes to the drilling envelope that has added complexity to the drilling practices required to successfully exploit the remaining reserves.Managed Pressure Drilling (MPD) Technology was pursued as an enabling technology to navigate within some very narrow margins in the first well of the redevelopment campaign. MPD was implemented in conjunction with drill-in liner and wellbore strengthening technologies to successfully deliver this first well and prove the techniques required to prolong field life.To promote successful implementation of MPD in the target zone, the technology was employed in the previous hole section to gain experience with the equipment and procedures where pressure control was less critical.MPD was used to control bottom hole pressure to manage background gas and facilitate changes to equivalent mud weight. It was further used to minimise the effects of loss/gain mechanisms and enable drilling through a tight margin between pore and fracture pressure while reducing the risk of borehole instability and losses. The technology was also used to determine appropriate mud weights for tripping and provide trip margin to avoid swabbing while tripping. In addition, MPD was used to facilitate cementing in tight margins. This paper will highlight the multiple uses of MPD throughout the start-up of this current drilling campaign and key learnings enabling successful implementation of a new technology on the rig. Shearwater OverviewShearwater is a HPHT gas condensate field discovered in 1988 and located in the UK Central Graben of the North Sea. Primary production is from the Fulmar -a sandstone reservoir with virgin pressure of 15,400 psi and temperatures Ͼ 360°F. MPD Objectives by Hole Section ¼؆ Hole Section to Top Cromer KnollMPD was not planned as a requirement for this hole section. The primary objective for MPD in the 12 ¼Љ hole was to gain experience and shakedown the equipment, rig-up configuration and procedures on a rig using MPD for the first time.Although not a primary objective, MPD could also provide enhanced kick detection capability in the event of higher than expected pressures (especially through the Hod Mass Flows -discrete layers of hard, low porosity chalk interbedded with marls within the Hod formation and commonly associated with high background gas levels while drilling), loss detection capability in the event of lower than expected pressures and the ability to test the drilling window through dynamic pore pressure and FIT/LOT tests.MPD could also be used to allow a lower mud weight to facilitate identification of the pressure ramp in the Tor and promote faster rates of penetration through the chal...

To safely plan and execute MPD Influx Control operations, the limits of the primary barrier envelope must be communicated and understood. These safe operating limits have historically been represented with an MPD Operations Matrix. More recently, the development of the Influx Management Envelope (IME) has provided a means of communicating the primary barrier limits with improved accuracy and clarity. However, the generation of the IME currently requires performing a series of complex well control simulations with specialist engineering support. Because drilling operations are dynamic in nature, a practical method to generate the IME boundaries at the wellsite is required so that changes to mud weight, flowrate, surface and bottom hole circulating temperatures, trajectory, and bit depth can be accounted for, and the IME kept up to date. This paper describes the development of a novel tool to quickly and automatically generate IMEs at the wellsite without the need for sophisticated modelling software and specialist personnel. The single bubble derivation that was originally presented by Culen et al was analysed further to obtain a more accurate and explicit relationship rather than an implicit one, which forms the basis for the calculations. The IME can be updated based on any well parameter changes, which allows field engineers to maintain an up to date and accurate IME throughout MPD operations.

The benefits of Managed Pressure Drilling are well understood in the drilling industry, but until now, they have never been integrated into a Jack-Up rig. For a UK North Sea HPHT campaign, the Drilling Contractor, Operator and MPD Service Provider collaborated for what is believed to be the World's first fully integrated, permanently installed MPD system for a Jack-Up, capable of drilling the most challenging narrow-margin HPHT wells. Overcoming the perceived complexity and cost of MPD are common obstacles. Integrating MPD systems into jack-up rigs addresses both challenges by simplifying logistics planning and operations and reducing costs. Putting MPD at the heart of the rig's drilling system offers a wealth of advantages to both the Operator and Drilling Contractor and provides ‘MPD on demand’ for all operations undertaken from the rig.