The Alma (formerly Argyll/Ardmore) Field, Blocks 30/24 and 30/25a, UK North Sea

2020 ◽  
Vol 52 (1) ◽  
pp. 360-370 ◽  
Author(s):  
Longxun Tang ◽  
Jon G. Gluyas ◽  
Stuart Jones ◽  
Bernard Besly

AbstractThe Alma Field (formerly Argyll and then Ardmore) is located within Blocks 30/24 and 30/25 on the western margin of the Central Graben. Hamilton drilled the first discovery well 30/24-1 in 1969 and the field, named ‘Argyll’, became the first UK offshore oilfield when production commenced in 1975. Oil was produced from the Devonian Buchan Formation, Permian Rotliegend and Zechstein groups, and Jurassic Fulmar Formation from 1976 until 1992, when the field was abandoned for economic reasons. In 2002, Tuscan Energy and Acorn Oil & Gas redeveloped the field and renamed it as ‘Ardmore’. A further 5 MMbbl were produced until 2005, when the field was again abandoned due to commercial considerations. In 2011, EnQuest was awarded the licence to redevelop the field and renamed it as ‘Alma’. The field came on stream in October 2015 and has produced oil at an average c. 6000 bopd since start-up.Total ultimate recovery was expected to be about 100 MMbbl. As of end 2005, the field had produced 72.6 MMbbl as Argyll and 5 MMbbl as Ardmore. A further 4.3 MMbbl has been produced from the Alma Field to September 2017 (which includes about 0.5 MMbbl from a long-reach well drilled into the Duncan/Galia Field immediately west of Alma). In January 2020 EnQuest announced that the Alma Field would cease production early. The total production from the three phases of field development will be about 85 MMbbl of oil.

2020 ◽  
Vol 52 (1) ◽  
pp. 606-616 ◽  
Author(s):  
Simon Wright ◽  
James Bramald ◽  
David Brett ◽  
Scott Dingwall ◽  
John Horsburgh ◽  
...  

AbstractThe Stella Field is located in UKCS Block 30/6a, c. 230 km SE of Aberdeen. Stella Field is a four-way, dip-closed and salt-cored dome with a 600 ft gas-condensate column underlain by a 250 ft oil column within the 5–30 ft thick Paleocene Andrew Sandstone Member. Oil is also present in the underlying chalk reservoirs of the Danian Ekofisk and Maastrichtian Tor formations. Following the discovery of the field in 1979 there have been three phases of appraisal followed by the recent development, with first oil in February 2017.The field development has been challenging as the 38-year gap between discovery and first oil illustrates. Principal challenges have included structural undulations and radial faulting combined with a thin primary reservoir, variation in hydrocarbon, compartmentalization and depletion relating to producing fields. These issues have been reviewed following the latest drilling results and ideas on the petroleum geology updated.Block 30/6a, containing the Stella Field, was originally awarded to Shell/Esso in the first Licensing Round in 1964 as part of multi-block licence P011. The current Stella P.011 licence holders are Ithaca Energy (UK) Limited (operator) with 54.66%, Dyas UK Limited with 25.34% and Petrofac GSA Limited with 20%.


2003 ◽  
Vol 20 (1) ◽  
pp. 691-698
Author(s):  
M. J. Sarginson

AbstractThe Clipper Gas Field is a moderate-sized faulted anticlinal trap located in Blocks 48/19a, 48/19c and 48/20a within the Sole Pit area of the southern North Sea Gas Basin. The reservoir is formed by the Lower Permian Leman Sandstone Formation, lying between truncated Westphalian Coal Measures and the Upper Permian evaporitic Zechstein Group which form source and seal respectively. Reservoir permeability is very low, mainly as a result of compaction and diagenesis which accompanied deep burial of the Sole Pit Trough, a sub basin within the main gas basin. The Leman Sandstone Formation is on average about 715 ft thick, laterally heterogeneous and zoned vertically with the best reservoir properties located in the middle of the formation. Porosity is fair with a field average of 11.1%. Matrix permeability, however, is less than one millidarcy on average. Well productivity depends on intersecting open natural fractures or permeable streaks within aeolian dune slipface sandstones. Field development started in 1988. 24 development wells have been drilled to date. Expected recoverable reserves are 753 BCF.


2020 ◽  
Vol 52 (1) ◽  
pp. 664-678 ◽  
Author(s):  
M. Camm ◽  
L. E. Armstrong ◽  
A. Patel

AbstractThe Lower Cretaceous Britannia Field development is one of the largest and most significant undertaken on the UK Continental Shelf. Production started in 1998 via 17 pre-drilled development wells and was followed by a decade of intensive drilling, whereby a further 40 wells were added. In 2000 Britannia's plateau production of 800 MMscfgd supplied 8% of the UK's domestic gas requirements.As the field has matured, so too has its development strategy. Initial near-field development drilling targeting optimal reservoir thickness was followed by extended reach wells into the stratigraphic pinchout region. In 2014 a further strategy shift was made, moving from infill drilling to a long-term compression project to maximize existing production. During its 20-year history the Britannia Platform has undergone numerous changes. In addition to compression, production from five satellite fields has been routed through the facility: Caledonia (2003), Callanish and Brodgar (2008), Enochdhu (2015) and Alder (2016). A new field, Finlaggan, is due to be brought through Britannia's facilities in 2020, helping to maximize value from the asset for years to come.As Britannia marks 20 years of production it has produced c. 600 MMboe – surpassing the original ultimate recoverable estimate of c. 570 MMboe – and is still going strong today.


2020 ◽  
Vol 52 (1) ◽  
pp. 189-202 ◽  
Author(s):  
J. A. Hook

AbstractThe Hewett Field has been in production for some 50 years. Unusually for a Southern North Sea field in the UK Sector, there has been production from several different reservoirs and almost entirely from intervals younger than the principal Leman Sandstone Formation (LSF) reservoir in the basin. Some of these reservoirs are particular to the Hewett area. This reflects the location of the field at the basin margin bound by the Dowsing Fault Zone, which has influenced structural evolution, deposition and the migration of hydrocarbons. The principal reservoirs are the Permo-Triassic Hewett Sandstone (Lower Bunter), Triassic Bunter Sandstone Formation (BSF) (Upper Bunter) and Permian Zechsteinkalk Formation. There has also been minor production from the Permian Plattendolomit Formation and the LSF. Sour gas is present in the BSF only. Several phases of field development are recognized, ultimately comprising three wellhead platforms with production from 35 wells. Gas is exported onshore to Bacton, where the sour gas was also processed. Peak production was in 1976 and c. 3.5 tcf of gas has been recovered. Hewett has also provided the hub for six satellite fields which have produced a further 0.9 tcf of gas. It is expected that the asset will cease production in 2020.


Geophysics ◽  
2002 ◽  
Vol 67 (2) ◽  
pp. 379-390 ◽  
Author(s):  
William L. Soroka ◽  
Thomas J. Fitch ◽  
Kirk H. Van Sickle ◽  
Philip D. North

Amplitude variation with offset (AVO) analysis was successfully performed on a 3‐D prestack seismic volume. Important conclusions were that AVO results could improve field development and production, that 3‐D AVO results were more useful than 2‐D AVO results, and that reliable AVO results could be generated on land. The AVO results were used to help develop an infill drilling program to increase production. AVO information lowered the risk of finding hydrocarbons by helping to identify seismic events that had a higher probability of being gas‐saturated sands. The 3‐D seismic survey covered known gas zones and potential new reserves. The AVO calibration work showed that positive AVO gas responses (classes 2 and 3) were observed for 90% of the zones associated with known production. One 15‐ft‐thick gas reservoir below seismic resolution did not give a positive AVO anomaly. A well drilled to an untested zone displaying a positive AVO anomaly encountered commercial quantities of gas. Production from this new zone at the initial flow rate increased the total production rate in this 25‐year‐old field by >50%. The AVO method was shown to be applicable onshore and to provide useful results in more consolidated geologic environments with classes 2 and 3 AVO responses. For the successful use of AVO, greater effort and extra care in acquisition and processing were needed than in a normal seismic program.


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