# Greater Markham Area gas fields

The Greater Markham Area gas fields are natural gas reservoirs and gas production facilities that straddled, or are close to, the UK and Netherlands median line of the southern North Sea. The UK field production facilities, which export gas to the Netherlands, began operation in 1992.

## The fields

The Greater Markham Area gas fields are located in UK Blocks 49/4, 49/5, 49/9 and 49/10 and in Netherlands Blocks J3 and J6 of the southern North Sea. The fields are named: Markham, Windermere, Chiswick, Grove, Stamford and Kew.

### Markham

The Markham gas field was discovered by Ultramar in July 1984 with well 49/05-2. It is a lower Permian Leman/Slochteren sandstone, sourced from Carboniferous coal measures and is overlaid with Permian Silverpit claystone. It is a sweet gas with 83 % methane and a gas/condensate ratio of 9 barrels per million standard cubic feet (9 bbl/MMSCF) or 52.2 m$^3$/10$^6$ m$^3$. Recoverable reserves were estimated to be 700 Billion cubic feet (BCF) or 19.8 x 10$^9$ m$^3$. Ownership of the gas was established by the UK/Netherlands Markham Treaty as 37.40 % UK and 62.60 % Netherlands.
The original licensee for Markham was a joint venture comprising Ultramar Exploration Ltd (89.50 %), DNO Offshore Ltd (8.00 %) and Ranger Oil (UK) Ltd (2.5 %.). Ownership passed to CH$_4$ Energy Ltd in 2003, Venture Production acquired ownership in 2006. Ownership eventually passed to Centrica, then in 2017 to Spirit Energy a joint venture of Centrica plc and Bayerngas Norge AS.

### Windermere

The UK Windermere gas field produced gas to Markham and hence to the Netherlands. Windermere is a Rotliegend-Leman sandstone discovered in 1989 by well 49/09b-2 by Mobil (who named the field Avalon) and had an estimated gas in place of 104 BCF or 2.8 x 10$^6$ m$^3$.

### Chiswick, Grove and Kew

The Chiswick and Kew are both Carboniferous fields Chiswick has gas in place of 687 BCF or 19.45 x 10$^6$ m$^3$ and Kew 85 BCF or 2.41 x 10$^6$ m$^3$.

## Development

The Greater Markham Area gas fields were developed in stages. Markham and Windermere gas fields were the first to be developed in 1994 and 1996. Gas was produced by two offshore installations, detailed in the table.
Offshore platforms Markham and Windermere :
| Installation | Markham ST-1 | Windermere |
| Blocks | 49/5a and 49/10b (UK), J3b and J6 (NL) | 49/9b |
| Coordinates | 53° 50.527’ N 02° 52.059’ E | 53° 49.937’ N 02° 46.364’ E |
| Owner | Spirit Energy | Ineos UK SNS Ltd |
| Type | Normally unattended | Normally unattended |
| Water depth, metres | 31 | 35 |
| Installation date | 1994 | November 1996 |
| Jacket type | Fixed steel | Fixed steel |
| Jacket legs | 4 | 3 |
| Jacket piles | 4 | 3 |
| Jacket weight, tonnes | 888 | 382 |
| Topsides dimensions, metres | 26.3m x 22m | 30m x 30m |
| Topsides weight, tonnes | 1,300 | 452 |
| Wellheads | 6 | 2 |
| Export to | Markham J6-A | Markham ST-1 |
| Production start | November 1992 | April 1997 |
The Chiswick, Grove, Kew and Stamford gas fields were developed over the period 2006-2014 by four offshore installations, detailed in the table.
Offshore installations Chiswick, Grove, Kew and Stanford :
| Installation | Chiswick | Grove | Kew | Stamford |
| Blocks | 49/4a | 49/10a | 49/4c | 49/10c |
| Coordinates | 53.939967 2.7740533 | 53.858778 2.886000 | 53.954935 2.784486 | 53.804192 2.836928 |
| Owner | Spirit | Spirit | Spirit | Spirit |
| Type | Platform | Platform | Subsea wellheads | Subsea wellheads |
| Water depth, metres | 40 | 30 | 41 | 34 |
| Installation date | 2006 | 2006 | 2014 | 2009 |
| Jacket type | Fixed steel | Fixed steel | – | – |
| Jacket legs | | | – | – |
| Jacket piles | | | – | – |
| Jacket weight, tonnes | 650 | 500 | – | – |
| Topsides weight, tonnes | 350 | 480 | – | – |
| Wellheads | | | 1 | 1 |
| Export to | Markham J6-A | Markham J6-A | Chiswick | Markham J6-A |
| Production start | 2006 | 2006 | 2014 | 2009 |
In addition to the platforms and subsea wells there were also gas and methanol pipelines and umbilicals in the Greater Markham area.
Pipelines and Umbilicals :
| From – To | Country | Fluid | Diameter, inches | Length, km | Pipeline number |
| Markham ST-1 – Median line | UK | Gas | 12 | 2.35 | PL992 |
| Median line – J6A | Netherlands | Gas | 12 | 3.13 | PL992 |
| J6A – Median line | Netherlands | Methanol | 2 | 3.127 | PL993 |
| Median line – Markham ST-1 | UK | Methanol | 2 | 2.347 | PL993 |
| Windermere – Markham ST-1 | UK | Gas | 8 | 6.8 | PL1273 |
| Markham ST-1 – Windermere | UK | Methanol | 2 | 6.8 | PL1273.1-3 |
| Chiswick – J6A | UK, Netherlands | Gas | 10 | 18.3 | PL2353 |
| J6A – Chiswick | UK, Netherlands | Methanol | 1.5 | 18.3 | PL2354 |
| Grove – J6A | UK, Netherlands | Gas | 10 | 13.4 | PL2319 |
| J6A – Grove | UK, Netherlands | Methanol | 2 | 13.4 | PL2320 |
| Stamford – J6A | UK, Netherlands | Gas | 6 | 7.5 | PL2367 |
| J6A – Stamford | UK, Netherlands | Methanol | | 7.5 | PLU2368 |
| Kew – Chiswick | UK | Gas | 6 | 3.1 | PL2974 |
| Chiswick – Kew | UK | Methanol | | 3.1 | PLU2975 |

## Production

Gas production from Greater Markham Area fields is shown in the table and the graphs.
Gas Production :
| Field | Production start | Peak flow, mcm/y | Peak year | Production ceased | Cumulative production to 2020 (mcm) |
| Markham | November 1992 | 933 | 1995 | April 2016 | 7,877 |
| Windermere | April 1997 | 438 | 1998 | April 2016 | 2217 |
| Chiswick | 2007 | 569 | 2009 | – | 6915 |
| Grove | 2007 | 636 | 2010 | – | 3873 |
| Kew | 2014 | 175 | 2014 | – | 1053 |
| Stamford | 2009 | 132 | 2009 | 2013 | 165 |
The production profile, in mcm/y, of the Markham field was as shown.
The production profile, in mcm/y, of the Windermere field was as shown.
The production profile, in mcm/y, of the Chiswick field was:
The production profile, in mcm/y, of the Grove field was:
The production profile, in mcm/y, of the Kew field was:
The production profile, in mcm/y, of the Stamford field was:

## Decommissioning

Spirit Energy submitted a Markham ST-1 decommissioning Programme to the Oil and as Authority in 2018. Ineos Oil & Gas UK submitted a Windermere decommissioning Programme to the Oil and as Authority in 2018. Decommissioning activities entailed plugging and abandonment of the wells and removal of all structures above the seabed. The Markham topsides were taken to Lerwick Shetland for dismantling.