The Bentley Oil Field is a heavy oil field located on the East Shetland Platform in the UK Northern North Sea, 8 kilometres (5.0 mi) southeast of the Bressay Field (operator: Statoil), 15 kilometres (9.3 mi) east of the Kraken Field (operator: EnQuest) and 20 kilometres (12 mi) north-northeast of the Bruce Field (operator: BP).
The Bentley Field, located on the UK continental shelf in block 9/3b in 110 m of water, contains approximately 900 MMstb in-place of heavy (10 to 12 oAPI) viscous (1500 cP) crude. The field is four-way dip closed at uppermost Palaeocene, lowermost Eocene, Dornoch sandstone level, and covers an area of about 16 km by 5 km at a depth of around 1.1 km TVDss. The reservoir is high porosity (33%), net to gross pay (90%) and with ultra-high apparent horizontal permeabilities approaching 50 Darcies based on flow-test measurements, but consistent with unconsolidated sand. 
The field was discovered in 1977 with the Amoco 9/3-1 vertical exploration well, which discovered an 81 ft oil column in high quality Dornoch sandstone. The field was subsequently licensed to Conoco who appraised it with two further vertical wells (9/3-2A and 9/3-4) in the 1980s. These confirmed the presence of a large accumulation, estimated at that time to be similar to today’s figure at around 900 MMstb in-place. Attempts to gas-lift the 9/3-1 well failed due to the viscous nature of the Bentley crude, whilst an attempt to flow 9/3-2A using a downhole pump failed due to mechanical reasons.
With two failed tests and an oil price below $20/bbl Conoco relinquished the license in the mid 1990s.
There was no further activity on the block until 2003 when Xcite applied for, and were awarded, a Promote License on the block during the UK 21st Licensing Round. This was the first licensing round in which Promote Licences had been awarded and represented an important initiative from the UK licensing authorities to encourage small and new-start companies to acquire and promote acreage. The license was converted to a Traditional License in 2005 prior to Xcite’s first appraisal well (9/03b-5) in 2008.
This well was a vertical appraisal well, drilled at the end of 2007 and successfully flow-tested in January 2008. This was followed two more wells drilled November 2010 (9/03b-6 and 9/03b-6Z) to identify reservoir structure and characterise reservoir properties. The resultant flow-test delivered a surface constrained, final stabilised rate of 2,900 stb/day.
In August 2012 a successful extended well test was performed to gather more data on the reservoir properties and water cut by using the jack-upRowan Norway. In October 2012 after 60 days, Xcite Energy announced the successful conclusion of the extended well test, with the 9/3b-7 and 7Z wells successfully suspended for future use as production wells. 
The Bentley crude oil produced during the extended well test was stored on a floating storage unitScott Spirit, and was sold to BP as per the off take agreement. 
The recoverable reserves are estimated at 267 million barrels (42.4×106 m3) of heavy oil (API 10-12) and total oil in place is in excess of 880 million barrels (140×106 m3).
Since 2013 Xcite Energy Resources has been working with and signed memorandums of understanding with a number of industry partners to do pre-FEED/assurance engineering prior to arranging financing. The industry partners include AMEC, ARUP, Teekay Shipping, AIBEL AS, Baker Hughes and China Oilfield Services Limited. The company has also signed a collaboration agreement with Statoil and Shell in May 2014 to make available and share field-specific technical and operational information for the evaluation of potential synergies and collaboration between the Bentley and Bressay Fields, and another collaboration agreement in October 2014 with EnQuest and Statoil in order to evaluate the potential utilisation of common gas import infrastructure between the Kraken, Bentley and Bressay fields.
In October 2015 the Bentley license was reviewed in order to ascertain the appropriate field determination boundary for agreement with the OGA and the boundary of the Bentley oil field has been accepted subject to formal FDP approval.
Xcite announced in February 2016 that they had successfully completed a technical review of the first phase of the Bentley field development with the Oil and Gas Authority to ensure that the plan meets the OGA's policy objectives of maximising the economic benefit to the UK of its oil and gas resources. At the same time the company announced that they anticipate submitting a field development plan to the OGA in 2016.
The Bentley field is planned with a phased development. The first phase development, with a 5-year drilling programme, and focused on the northern area of the field will be followed by a second phase, which will focus on the western and south areas of the Bentley field. As the Bentley development will be short of fuel gas for meeting its power generation and process heat requirements, the first phase development plans is to include a 10 km 6" pipeline from a tie-in to the Kraken field for fuel gas import.
Technical and engineering work streams are largely complete and it is expected that the field will commence operation approximately three years after FDP approval from the UK Government. FDP submission is currently pending commercial and funding discussions which are ongoing as of May 2016. The company announced in their 2015 third quarter results that technical and commercial due diligence on the Bentley field had been completed by a potential field development partner, but that they remained very actively engaged with a wide range of parties in order to maximise the opportunity to secure the required funding. Separately, the that the company has committed a significant amount of time to a technical review of the Bentley field development concept with the United Kingdom Oil and Gas Authority.
In late May 2016 Xcite Energy announced that they had reached agreement on the principal commercial terms for the development funding of the first phase of the Bentley project, but that they require a partner to join the development group. Separately, the company is running a tender process to select an EPCIC contractor for the MOPU and FSO and to finalise a drilling rig contract.
Statoil at the drawing board to save costs on Bressay
The Norwegian State-owned company Statoil and its partner, the Royal Dutch Shell (Shell), are considering all options in order to reduce costs for the development of the heavy crude oil offshore project, Bressay, in the UK North Sea.
In November 2013, while Statoil and Shell were expected to make the final investment decision, they in fact stepped back from that phase in the light of the first experiences acquired by the junior company Xcite Energy Resources Limited (Xcite or XER) from the similar field Bentley only eight kilometers away from Bressay.
Located 160 kilometers from the Shetland Islands, these heavy crude oil fields are concentrated together with Statoil Marinerand Enquest Kraken in the middle of the North Sea along the boarder with the Norwegian territorial waters.
In Bressay,Statoil and Shell are sharing the working interests in such a way:
– Statoil 81.625% is the operator
– Shell 18.375%
Discovered in 1976 for Bressay and in 1977 for Bentley, these fields were left undeveloped because of the challenging conditions of these 10 to 12 degree API heavy crude oil fields and associated sour gas.
Among these heavy crude oil projects of this area of the North Sea, Bressay is recognized as one of the most challenging for which Statoil and Shell mobilized all the lost advanced technologies.
As a result, when Statoil and Shell decided to stop Bressay development on its first concept, the project was estimated to cost between $6 and $7 billion capital expenditure.
Statoil and Shell to phase up Bressay development
With Mariner and Bressay, Statoil would have originated the largest projects in the UK North Sea.
But the first solutions tested by Xcite on the neighboring Bentley fields motivated Statoil and Shell to rethink their concept for Bressay.
With 257 millions barrels of recoverable crude oil (2P), Bentley is very similar to Bressay estimated to hold between 200 and 300 million barrels of recoverable reserves of crude oil.
Because of the nature of heavy crude oil in these fields, the production process developed by the companies is rather complex in order to optimize the recovery rate of these fields.
Typically these projects will require:
– Chemicals and diluents injection
– Risers and flowlines heating
– Oil and gas separation
– Water treatment
The accumulation of all these processes have a direct impact on the weight of the topsides and the definition of the structure to support them.
In Bressay, Statoil was considering a single large platform, similar to Mariner, while in BentleyXcite is combining a Sevan-type floating storage and offloading (FSO) vessel together with an Arup steel frame platform for production.
These differences in the concept are mostly related to the different methods of extracting the crude oil at the down hole.
In addition, the designed selected by Xcite provides all the flexibility to develop the field in phases, whereas the FSO remains all along the full development while the production unit can be adapted or even replaced at any time to the production goals and constraints.
With this new concept and costs revised downward, Statoil and Shell are expecting to sanction the Bressay phase-1 project in UK North Sea by 2016.
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Tags: 10 to 12 degree API heavy crude oil fields and associated sour gas, Arup steel frame platform for production, Bressay phase-1 project, Bressay platform, capital expenditure, Chemicals and diluents injection, Demulsifier, field Bentley and Bressay field, Final Investment Decision, FSO vessel, heavy crude oil fields, heavy crude oil offshore project Bressay in the UK North Sea, junior company Xcite Energy Resources Limited or XER, Norwegian State-owned company Statoil, Norwegian territorial waters, Oil and gas separation, recoverable crude oil (2P), recoverable reserves of crude oil, Risers and flowlines heating, Royal-Dutch Shell (Shell), Sevan-type floating storage and offloading (FSO) vessel in Bentley, Shetland Islands, Statoil Mariner and Enquest Kraken, topsides, water treatment
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