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Collaborating Authors
Abstract Fifty years after the first jackup drilled its first well for Standard Oil Company of Texas in the Gulf of Mexico, jackup drilling operations commenced for the first time in the treacherous sea conditions on the Grand Banks of Newfoundland. This paper addresses the risk management solutions, the boundary pushing technology, and the stakeholder cooperation that helped ensure jackup drilling operations on the Grand Banks could be performed without compromising safety and environmental protection. Recommendations are presented for continuing jackup activities in the region. Introduction The first well offshsore Newfoundland was spudded in 1966 utilizing a drillship. During the 1970's several drillships and semi-submersibles were active on the Grand Banks and the Labrador Shelf. The Hibernia discovery well was drilled in 1979 by a drillship and later that year a semi-submersible reentered the same well and conducted drill stem testing. Over 170 exploration-appraisal wells and 80 development wells have been drilled offshore Newfoundland all of which were drilled by either floating units or drilling installations mounted on a concrete platform. In 1996, the concept of jack-up drilling operations was proposed as an alternative way forward. The metocean operating conditions were determined to be within the capacity of new harsh environment jack-up designs. However, the iceberg and sea ice conditions on the Grand Banks required further deliberation. An ice statistical analysis and subsequently a risk assessment were conducted to quantify whether the proposed jackup concept was an acceptable one. The following rationale was then presented to the oil and gas community to promote jackup drilling operations as a feasible and desirable alternative.The jackup structure evolved quite substantially since drilling commenced offshore Newfoundland in the early 1970's. Non productive time in jackup drilling opertions is generally considered to be 10%-14% less than semisubmersible drilling operations. If one gives consideration to the anchor pattern of moored floating units during drilling operations, the footprint and hence an iceberg exclusion zone is approximately 10 times the area occupied by an elevated jackup. Jackup acceptance criteria have been standardized so as to guide industry and regulatory regimes with respect to site specific assessments. There is huge potential for mobilization and equipment certification cost savings by utilizing harsh environment jackups that are present in Atlantic Canada rather than importing floating drilling units from the international arena. The results of a risk assessment have ultimately demonstrated the feasibility of the jack-up drilling operation in the region. Upon completion of an independent study commissioned by Canada-Newfoundland regulatory authorities, an environmental impact study by an operator, the regulatory approval process for the drilling program, and a declaration that the ice free season had begun; a jackup was mobilized to Newfoundland waters to begin its first drilling operation on the Grand Banks. There were several lessons learned during the two years of seasonal jackup drilling activity in the region and the ultimate objective of this paper is to share those lessons with the oil and gas community.
Extending the drilling season beyond the open water period in the Arctic is the primary driver behind a new jackup concept designed to operate in light ice conditions. The defining feature of the Arctic jackup is its telescopic leg that protects the drillstring from ice loads and is adjustable for depths down to approximately 50 m. Developed at the University of Stavanger in Norway as part of a graduate thesis and presented in a technical paper at the 2014 Arctic Offshore Technology Conference in Houston, the hull of the jackup is ship-shaped and borrows from icebreaker technology to withstand hits from drift ice as it is transported to an Arctic drilling location. The design of the Arctic jackup's other supporting legs are also unique and key to enabling the system to remain in ice conditions for more than a month after the open water season has ended. The design seeks to provide operators with an extra 30 to 40 days on the back end of the season--enough time, the designers say, to drill and test a new well in the same season.
Extending the drilling season beyond the open water period in the Arctic is the primary driver behind a new jackup concept designed to operate in light ice conditions. The defining feature of the Arctic jackup is its telescopic leg that protects the drillstring from ice loads and is adjustable for depths down to approximately 50 m. Developed at the University of Stavanger in Norway as part of a graduate thesis and presented in a technical paper at the 2014 Arctic Offshore Technology Conference in Houston, the hull of the jackup is ship-shaped and borrows from icebreaker technology to withstand hits from drift ice as it is transported to an Arctic drilling location. The design of the Arctic jackup's other supporting legs are also unique and key to enabling the system to remain in ice conditions for more than a month after the open water season has ended. The design seeks to provide operators with an extra 30 to 40 days on the back end of the season--enough time, the designers say, to drill and test a new well in the same season.
Predicting the Penetration Resistance of Plain Tubular Jack-Up Legs
Irvine, J. (Cathie Associates Ltd.) | Torres, I. (Cathie Associates Ltd.) | Cathie, D. (Cathie Associates Ltd.) | Raymackers, S. (Geosea NV, Zwijndrecht) | Morris, C. (Geosea NV, Zwijndrecht) | Ezzamel, A. (Vattenfall) | Osborne, J. (Vattenfall)
Abstract The existing SNAME and ISO guidelines for jack-up operations detail methods for predicting the penetration resistance of jack-up spud can footings but not for plain tubular legs. This paper summarises the site conditions at a predominantly stiff clay site, details the penetration assessment methodology developed after reviewing previous jack-up performance and presents a comparison of the predicted and actual penetration data. Introduction Vattenfall recently developed the Kentish Flats Extension project located in British waters on the south side of the Thames Estuary, approximately 10km north of the Kent coastline in a water depth of 4- 5m LAT (Lowest Astronomical Tide). The project comprised the installation of 15 wind turbines generators immediately adjacent to the existing Kentish Flats offshore wind farm. The geology at the Kentish Flats Extension is considered challenging for jack-ups as it comprises a layer of very soft to soft silty clay overlying stiff to very stiff fissured London Clay. There are also several large infilled paleochannels running through the region with the potential for significant soil variability. The original Kentish Flats wind farm was constructed using conventional jack-ups and there were several issues during construction including an extremely large predicted penetration range, deep penetration of spud legs, and leg extraction difficulties. The construction activities for the Extension wind Farm were to be undertaken by the "Neptune", a jack-up vessel with plain tubular legs and no spud can footing. As a result of the previous experience, a project team comprising Vattenfall, Geosea and Cathie Associates was appointed to review site conditions and available leg penetration data, and undertake a detailed assessment of predicted jack-up leg penetrations for the jack-up vessel "Neptune" prior to installation works. General industry practice is to use a pile design method such as the API-2GEO method to predict penetration, however, there is little published data to support this. Therefore, several different methods were assessed for potential use. The penetration assessment methods were initially applied to the geotechnical survey jack-up ("Deep Diver") to determine the most appropriate method, and then the preferred method was used to predict the "Neptune" leg penetrations. The predictions were then compared with actual penetrations experienced in the field.
SPE Member Abstract The object of the paper is to illustrate how a non-cantilevered jackup unit can make its drilling package more useful to reach unreachable wells of multi-well drilling platforms. Introduction For any platform with water depth suitable to available jackups, there are three alternatives.Tender assisted drilling package. Cantilever type jackup. Slot type jackup with a. cantilever conversion b. skidbase and 'skiddable' drilling package. The tender option requires an assistance from a floating crane (derrick barge). The derrick barge operation is justifiable to deep water operation where jackup units are not suitable. Day rate on a derrick barge in some area where it is not readily available tends to be very high. Unpredictable delays due to weather or uncertain operational complications can make the situation worse. Experienced platform owners have selected this option in the past when Cantilever type jackup units (second option) are either expensive or not suitable. Cantilever jackup rig is a better option if it has enough leg length to meet water depth, air gap and expected penetration. However, all well locations must be within the reach of the cantilever. P. 603