Summary Modern-day oil exploration pushes operators into harsher and more-difficult drilling environments in the search for hydrocarbon reserves. Eastern Canada is one of those environments where deep water and the need to penetrate through thick salt sheets greatly increases difficulties faced by drillers. This paper describes a case history of deepwater subsalt drilling and examines the requirements for success. This paper also details the challenges using seismic data, of prewell planning for dealing with high pore-pressures and variable fracture gradients. Experience shows that prewell engineering differs considerably from conditions actually encountered that require rapid adjustments based on actual well data. In the case reported here, a fluid influx occurred at a depth where planning indicated a significantly lower pore-pressure. This influx directly led to losing a bottomhole assembly (BHA), sidetracking, and a re-evaluation of the well data and pore-pressure regimes possible at that depth. This paper also highlights the need for flexible well designs able to respond to unanticipated drilling hazards and wellbore problems. In the case history reported here, the 11¾-in. casing was set 511 m higher than originally planned because of pore-pressure increases. This decision had a significant effect later in the well construction program, requiring the use of expandable casing not originally in the well program. This paper illustrates on-the-fly modification of drilling designs to rapidly deploy unplanned equipment, the use of unconventional borehole sizes, and the use of newer technology such as rotary-steerable assemblies for side-track kickoff. The paper will also discuss the optimized use of hole openers and expandable casing and the potential effects of expandable casing on subsequent hole-opener use. These dynamic modifications and immediate implementation of lessons learned allowed successful drilling to a record depth for eastern Canada. Introduction The Weymouth A-45 well is located approximately 160 miles south by southeast from Halifax, Nova Scotia, Canada, in the deepwater area of the Scotian Shelf. Prewell seismic analysis identified the presence of a subsalt anomaly, the 1507-m-thick Argo salt sequence. This sequence presented a potential major drilling challenge and also a significant problem in prewell pore-pressure and fracture gradient planning. The well incorporated a complex well design using concentric hole openers and an unconventional casing designed to successfully complete the well. The well design was planned in response to the challenges posed by the 1685-m deepwater environment and the thick salt deposit, as well as their combined effect on overburden and fracture pressure. The impact of these factors combined with limited drilling-pressure margins (based on expected pore-pressure increases) required a more complex borehole and casing design. Despite the potential hazards and complex well design, the drilling program allowed for flexibility in the decision processes and in well design changes not only to deal with problems encountered, but also, to extend drilling successes. Flexibility was particularly important when drilling through the salt body with a point-the-bit rotary-steerable system. Although the rotary-steerable system was not planned for use below the salt, the success of the system in the shallower parts of the well led to its subsequent use below the salt and highlighted the flexibility of rotary-steerable technology. Planning and Design Three seismic lines and six offset wells were provided to perform an initial analysis of the Weymouth Prospect in August 2002. These data were processed using the Sperry Drilling Services formation-pressure estimation model to generate overburden, pore-pressure, and fracture-pressure predictions. The six offset wells (H-100 Shubenacadie, H-98 Evangeline, H-38 Glenelg, J-48 Glenelg, N-49 Glenelg, and M-41 Tantallon) showed two different pore-pressure regimes unrelated to water depth. H-100 and M-41 were both deepwater wells.

TX 75083-3836, U.S.A., fax 1.972.952.9435. AbstractModern day oil exploration pushes operators into harsher and more difficult drilling environments in the search for hydrocarbon reserves. Eastern Canada is one of those environments where deepwater and the need to penetrate through thick salt sheets greatly increase the difficulty faced by drillers. This paper describes a case history of deepwater, sub-salt drilling and examines the requirements for success. This paper also details the challenges, using seismic data, of pre-well planning for dealing with high pore pressures and variable fracture gradients. Experience shows that pre-well engineering differs considerably from conditions actually encountered, conditions that require rapid adjustments based on actual well data. In the case reported here, a fluid influx occurred at a depth where planning had indicated a significantly lower pore pressure. This influx directly led to losing a BHA, sidetracking, and a re-evaluation of the well data and pore pressure regimes possible at that depth. This paper also highlights the need for flexible well designs able to respond to unanticipated drilling hazards and wellbore problems. In the case history reported here, the 11¾in. casing was set 511m higher than originally planned due to pore pressure increases. This decision had a significant effect later in the well construction program, requiring the use of expandable casing, not originally in the well program.This paper illustrates on-the-fly modification of drilling designs to rapidly deploy unplanned equipment, the use of unconventional borehole sizes, and the use of newer technology such as rotary steerable assemblies for side-track kick-off. The paper will also discuss the optimised use of hole openers and expandable casing and the potential effects of expandable casing on subsequent hole opener use. These dynamic modifications and immediate implementation of lessons learned allowed successful drilling to a record depth for Eastern Canada.

When the operator embarked on an intermittent 5 well exploration, appraisal and development campaign offshore Norway between 2009 and 2012 using the West Alpha there were many challenges. The rig contract was part of a multi company consortium, the well program was varied, a 3 rd generation semi submersible rig was being used and all inclusive operating rates were high at around $1,000,000 per day.Following and expanding upon the management principles previously employed 1 , the lead operator identified an opportunity to leverage the consortium program and develop a strong relationship with the service companies, in particular the rig contractor.Health, Safety, Security and Environment (HSSE) was a key driver and over 1000 rig days were delivered without a Lost Time Incident (LTI). The lead operator was able to harmonise and standardise procedures used on every well, regardless of who operated the rig. This enabled a much clearer and more consistent message to be delivered to the work environment. This paper will outline the management process taken by the operator and contractor that enabled the following performance to be delivered: 1000 days LTI free rig operations. Record setting drilling performance with improvements up to 40%. No damage to the environment. This paper will also describe how the principles have been transferred to other parts of the operators & contractors organisations.

Optimizing well control processes are critical in high-temperature/high-pressure (HPHT) drilling operations so they do not encounter high cost overruns and compromise safety. The key to success is recognizing and mitigating challenges and associated risks early to adequately optimize drilling operations. This leads to a more effective drilling operation with reduced risk, increased safety margins and increased probability of successfully achieving the well's objectives.This case describes an integrated work process that has been implemented, incorporating pre-drill and real-time pore pressure prediction with proactive equivalent circulating density (ECD) management during well planning and drilling operations. This work process is especially important for optimizing drilling fluid properties to retain the drilling parameters within a safe operating mud window identified by real-time pore pressure and wellbore stability prediction. Operating in this safe window enables reduction in wellbore instability, formation damage, hole cleaning inefficiencies and poor drilling performance, resulting in improved safety margins, reduced risk, improved drilling performance and reduction in non-productive-time (NPT).Several recent examples from Suncor Energy Norge HPHT wells are presented to illustrate the success of utilizing this integrated approach, resulting in drilling HPHT wells with no formation pressure-related NPT. The process begins with identifying pressure-related challenges in the pre-drill planning phase, optimizing the drilling process by validating, defining and maintain the drilling parameters within the safe operational window through an integration of proactive real-time pore pressure prediction and ECD management using all available LWD measurements: acoustic, gamma, resistivity, density, formation pressure while drilling, imaging, ECD, and temperature. Analysis is performed on mud logging data such as gas, the drilling exponent, cuttings and borehole caving and surface drilling data. Finally, lessons learned are captured that will further improve drilling efficiency and best practices in upcoming drilling campaigns. IntroductionRisk mitigation is a key element when it comes to drilling HPHT wells, and safe and predictable operations are paramount in that respect.

No abstract