In the exploration and production (E&P) industry attempts at reducing the cost of the well construction by applying various well architecture slim designs has attracted attention from operators for decades. The recent industry downturn has further contributed to a renewed focus on this strategy. In this study we present a slim well design application within the FortunaCo project (a Joint Venture between OneLNG and Ophir), which aims at developing the Fortuna and Viscata fields in Deepwater offshore Equatorial Guinea. An advanced static nonlinear Finite Element engine is used in this process, which considers contact and friction; can handle large deformations and is therefore suitable to carry out buckling analysis. The top hole structural robustness is analyzed using this engine in the event of a worst case axial load, which for this study is assumed to be:The Conductor Pipe (CP) able to take its own weight only,The upper section of the surface casing (inside the CP) free of cement,The full buoyant weight of the Horizontal Christmas tree and Subsea Blowout Preventer applied onto the well. This paper demonstrates that the selected numerical model is suitable to estimate critical buckling loads and identify post-buckled modes exerted on surface structural casings. Furthermore, it is shown that the visualization capabilities and speed of the engine allow the operator to optimize the design iteratively in an efficient manner. We conclude that the selected methodology is suitable for the operator to validate a slim well design for a Deepwater development application at concept phase for minimal cost with the necessary level of confidence.

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Shallow oil reservoirs, commonly associated with heavy oil, require massive completion programs. The reason for these huge completion programs is due to the need for larger hole sizes compared with standard borehole developments. The commercial feasibility of these developments relies on repetitive and predictable drilling performance in large hole sizes and high-angle curvatures to reach very soft formations. One such development is the Mariner field in the UK sector of the North Sea, which was discovered 30 years ago. This field, located 140 km east of the Shetland Islands in 110m water depths, is the largest new field development in the UKCS. Two targeted reservoirs contain heavy oil in shallow unconsolidated sands in the Maureen and Heimdal formations. Field objectives included the following:100+ well targets at the rate of ± 12 wells per yearTimely well delivery scheduleTechnology application to lower Drilling &Well operations sanctioned cost by at least 25% The construction program for the Mariner field required the 20-in. casing shoe to be set at a shallow true vertical depth subsea (TVDSS) of ±750m, at inclinations between 35 and 55°, and build rates of 3 to 5°/30m in the ultra-soft formations with an unconfined compressive strength (UCS) of < 1000 psi. Although the advancements made in rotary steerable system (RSS) technologies are capable of generating 15 to 18°/30m dogleg severity (DLS) output, these technologies have historically been confined to small hole sizes extending from 5⅞ in. to 9½ in. This paper describes the development of the world’s first RSS bottom hole assembly (BHA) design, capable of delivering repetitive and predictable performance to drill large hole sections to high inclinations in shallow, ultra-soft formations.

In deepwater and other challenging environments, operators often have to drill through ‘problem zones.’ These zones could be rubble zones, tar zones, or just unstable pressure zones. In the past, operators often had to drill through these areas, lose drillstrings, and drill a sidetrack, hoping that they might be able to avoid these areas the second time. But with the advancement of steerable drilling liner systems, we now have a solution in place to tackle the toughest drilling challenges. With much of the equipment coming from field-proven technologies, the next generation of steerable liner systems is increasingly proving to be the answer to reducing nonproductive time. This technology will allow operators to drill well sections directionally with the liner string as part of their normal drilling operations and case off that section all in one trip. This paper highlights these steerable liner systems and illustrates their ability to outperform conventional casing while drilling systems.