MPD enables drillers to navigate through narrow drilling windows to reach designed target depths. After a hole section is drilled, pressure management is still required to pull drill strings out and run and cement liners. Conventional cementing programs and procedures may not be practical for a challenging hole section that has been drilled by MPD. Elaborate wellbore pressure management is required to ensure safe and efficient cementing operations. The same closed loop circulation system utilized for drilling is used to manage the wellbore pressure during cement operations. The technique of pressure management during liner cement jobs was utilized repeatedly by a major client in one of the most challenging HPHT campaigns in the North Sea. This paper provides an insight into the technique as well as information on the procedures, challenges and lessons learned pertinent to these operations. Various cases studies describing the setup, planning and execution of operations, simulation vs measured data will be compared. Drilling wells in complex environments with century-old technology is difficult at best and unsafe at worst. From drilling through narrow pore-pressure/fracture-pressure gradient windows to mitigating kicks and differential sticking, managed pressure drilling (MPD) succeeds when conventional techniques are likely to fail. MPD entails the use of specialized equipment to control wellbore pressure profiles more precisely than is possible with conventional drilling methods. MPD enables drillers to navigate through narrow drilling windows to reach designed target depths. After a hole section is drilled, pressure management is still required to pull drill strings out and run and cement liners. Conventional cementing programs and procedures may not be practical for a challenging hole section that has been drilled by MPD. Elaborate wellbore pressure management is required to ensure safe and efficient cementing operations. The same closed loop circulation system utilized for drilling is used to manage the wellbore pressure during cement operations. A case study describing the setup, planning and execution of operations, and simulation is presented in this paper.

This paper reviews the recently concluded successful application of a Managed Pressure Drilling (MPD) system on a High-Pressure High-Temperature (HPHT) well with Narrow Mud Weight Window (NMWW) in the UK sector in the Central North Sea. Well-A was drilled with the Constant Bottom Hole Pressure (CBHP) version of MPD with a mud weight statically underbalanced and dynamically close to formation pore pressure. Whilst drilling the 12-1/2" section of the well with statically under-balanced mud weight, to minimize the overbalance across the open hole, an influx was detected by the MPD system as a result of drilling into a pressure ramp. The MPD system allowed surface back pressure to be applied and the primary barrier of the well re-established, resulting in a minimal influx volume of 0.06 m3 and the ability to circulate the influx out by keeping the Stand Pipe Pressure (SPP) constant while adjusting Surface Back Pressure (SBP) through the MPD chokes in less than 4 hours with a single circulation. After reaching the 12-1/2" section TD, only ~0.025sg (175 psi) Equivalent Mud Weight (EMW) window was available to displace the well and pull out of hole (POOH) the bottom hole assembly (BHA) therefore, 3 × LCM pills of different concentrations were pumped and squeezed into the formation with SBP to enhance the NMWW to 0.035sg EMW (245 psi) deemed necessary to kill the well and retrieve BHA. MPD allowed efficient cement squeeze operations to be performed in order to cement the fractured/weak zones which sufficiently strengthened the well bore to continue drilling. A series of Dynamic Pore Pressure and Formation Integrity Tests (DPPT and DFIT) were performed to evaluate the formation strength post remedial work and to define the updated MMW. Despite the challenges, the MPD system enabled the delivery of a conventionally un-drillable well to target depth (TD) without any unplanned increase/decrease in mud weight or any costly contingency architecture operations, whilst decreasing the amount of NPT (Non Productive Time) and ILT (Invisible Lost Time) incurred. This paper discusses the planning, design, and execution of MPD operations on the Infill Well-A, the results achieved, and lessons learned that recommend using the technology both as an enabler and performance enhancer.

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.

A long-term suspended subsea exploration well within a producing gas reservoir needed to be decommissioned after 21 years. During a pre-decommissioning diving campaign, bubbles confirmed as reservoir gas were observed to be percolating from the well bore through a hard silt / cement debris plug inside the wellhead. A pressure study established that the reservoir may have re-charged to 2,200 psi. An alternative pressure controlled well re-entry method was required to safely re-enter, tie-back the well to surface with 16-in. high pressure riser, install BOP while preventing gas from reaching the rig floor from seabed. Two existing cement plugs would then be drilled out under controlled conditions due to the potential for high-pressure gas beneath the plugs. Casing integrity evaluation and cement bond logging would be carried out to establish the path of gas ingress into the wellbore. Remedial work would be conducted, and permanent abandonment barriers installed in the well. Casings and wellheads would then be recovered from a depth below the seabed. A customized managed pressure drilling (MPD) system was designed using a rotating control device (RCD) and modified drilling chokes. A pioneering plan was developed to meet the specific well re-entry requirements of the percolating suspended well to account for the potential for virgin reservoir pressure at seabed and the wellhead silt plug preventing deployment of BOP test tools. A hazard and operability study (HAZOP) was conducted with key personnel, which supported development of well-specific operating procedures and decision matrices. Successful deployment included MPD system calibration, well behavior fingerprinting, and training of rig personnel at the well site. The combination of experienced personnel, innovative MPD equipment, specific procedures, team interactions and risk analyses were key to safely completing this well re-entry and decommissioning scope. The strategy enabled drilling out of two cement plugs with potential high-pressure gas trapped beneath them. Both cement plugs, 356ft and 669ft long, were drilled without any well-control or plugged-choke events. Throughout the process, the well was monitored using MPD equipment, which included an RCD on top of rig's BOP, modular drilling chokes and multiple pressure gauges and sensors installed at critical points. Additionally, temporary modifications were made to the rig and new lines of communication between the rig crew and the MPD team were established to ensure all pressures were correctly interpreted and the decision matrix was correctly applied. An effective close partnership developed between the equipment service provider, well operator and drilling contractor was a key enabler to deliver this very challenging novel implementation of MPD technology within eight weeks. The MPD approach was estimated to have saved 9 days of rig time, when compared to alternative coiled tubing-based solutions. This paper describes the first MPD-assisted well re-entry for well decommissioning in the UK North Sea sector. The novel application of existing technology can help operators to cost effectively re-enter and decommission troublesome legacy wells without harm to people, environment or assets. This new approach resulted in the safe unconventional re-entry and decommissioning of a potentially live gas well.

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.