1 petroleum region of wessex basin topic: petroleum region ... · in and around kimmeridge bay...

1 Petroleum Region of Wessex Basin

Topic: Petroleum Region of Wessex Basin

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Petroleum Region of Wessex Basin

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Petroleum Region of Wessex Basin

The natural design of Wessex basin constitutes a part of a larger intracratonic basin system that

claims a large area of the southern England region, the English Channel and northern France.

Underlain by pre-Variscan basement, the research says that the origin of the Wessex basin was in

the Permo-Trias rifting that is responsible to affect most of the north Western Europe. There

were further phases of extension underwent by the basin during the Jurassic, before it underwent

a modification due to uplift and tilting that occurred in the late Cretaceous and subsequent

Alpine inversion events during the Tertiary (Gao, 2013).

The Wessex basin is subdivided into various component parts which are represented by

somewhat a series of paleohighs and sub-basins. The northern and southern margins of the main

are od the basin are the 'Pewsey fault System' and the 'Central Channel High' respectively. The

Purbeck-Isle of Wight Disturbance, and the underlying Mesozoic Purbeck-Isle of Wight Fault

system are separated effectively by the Portland Wight Basin from intra-basinal highs of the

South Dorset Shelf and (Wood, 2011).


There are more intra-basinal structural elements in the Wessex basin area which include:

• The South Dorset Basin (Winterbourne Kingston Through). It is bounded by 2 E-W

trending extensional faults, within the South Dorset Shelf.

• The Wardour and Ports down Fault Systems: it represents an important intra-basinal

growth fault sets, in front of and to reverse reactivation in the Tertiary.


• The Watch-Cothelstone-Hatch Fault System: it transects the basin majorly in subsurface,

trending NNW-SSE

Petroleum System of Wessex Basin


The Wessex Basin is a system of connected Mesozoic basins that span to cross southern

England, the English Channel and the Northern are of France. The areas of the Wessex Basin

claims more than 20,000 square kilometers of southern England, primarily within the counties of

Dorset and Hampshire. It further extends into offshore English Channel (Law, 2010). It is

therefore known as a significant petroleum province consisting of a fairly complete sequence of

Permian to Cretaceous sediments. In this region there are source rocks for petroleum generation,

seals (or caprocks) to keep oil accumulations in place and reservoir rocks in which oil may

accumulate. The complex tectonic history of the basin has facilitated the burial of source rocks

into this zone to enhance oil generation. It is also responsible to form structures (traps) for oil

accumulation in this region (Law, 2010).


The basin that contains Wytch Farm is the largest onshore oilfield of western Europe as well as

larger than most of the offshore fields in UK. There are other two much smaller fields (Wareham

and Kimmeridge) which also produce oil in the region,. Additionally there is a series of oil


seepages which are known in outcrops on the Dorset coast. There is also an ongoing exploration

to search for new prospects in the basin (Gąsiewicz and Słowakiewicz, 2014).

There formation of the basin underwent four distinct phases.

Phase 1. Permo-Triassic: it was a period of continental desert sedimentation, in the beginning

simultaneously with rifting and igneous activity.

Phase 2. There was a shallow marine sedimentation in the Jurassic in the ending of the period

that led to occurring of continental deposition. The sediments were influenced by syn-

sedimentary extensional faulting trending east-west, and caused a down-thrown of Southern

Dorset to the south.


Phase 3. In ate Cr after stability and marine chalk sedimentation more faulting, eastwards tilting

and erosion occurred. Followed by Tectonic inversion that occurred in early Tertiary and caused

the down-thrown to the north and additionally caused the deposition of shallow marine

sediments and Lower Tertiary fluvial.

Phase 4. The evolution of the basin was finally concluded when a culmination of the reversed

movement caused quick flexuring down to the north.

Stratigraphic summary of the basin


Looking at the surface the Wessex Basin, as well as the extensions offshore into the English

Channel, it seems that the basin consists of wide areas of dips and layer-cake geology

differentiated by various belts of monoclonal flexuring. There are at some places faulting and the

dips steep to vertical (Buynevich, 2011).

The lines of disturbance are found adjacent to small anticlinal folds. The structural lines are

majorly east to west in the southern region, but they are a part of an interconnected system across

the Channel and reach the northern France:


Observing the lines closely creates the impression that there are relative movements between the

intervening stable regions. This clearly indicates a basement influence on the sedimentary layers,

most likely reactivated earlier features (Jolley, 2010).

The Jurassic contains three potential source rock intervals:

1.Kimmeridge Clay

2.Oxford Clay

3.Lower Lias


In and around Kimmeridge Bay there is well exposed Kimmeridge Clay, the thickness of the

Kimmeridge Clay layer is around 500m. It is mostly comprise of oil-prone source rock faces.

Then there is Oxford Clay which is well exposed in the Furzy Cliff towards the east of

Weymouth (Wood, 2011).

There is a Lower Lias, which includes the Black Ven Marls, Blue Lias and Belemnite Marls. All

of them contain oil-prone organic-rich source rock faces and are found in the Lyme Regis area.

This section is also under drilling processes by a borehole near Weymouth.


The major 3 reservoirs in the oil fields of Wytch Farm are (Gao, 2013):

• The Frome. A complex reservoir from the middle Jurassic and consists of accumulation

of oyster shells surrounded by mudstones.

• The Bridport: it is a 60m thick heap of fine grained sandstones that was formed by

depositing near the shore in the Early Jurassic.

• The Sherwood reservoir comprises a number of sandstones heaped on top of one another

reaching a 120m thickness caused by the rivers in the Triassic period because the

environment was similar to the environment as in the interior of Australia today. 90% of

the recoverable reserves lie in the Sherwood reservoir.


The Wytch Farm

Summary of Operations

Wytch Farm is situated in one of the most environmentally sensitive areas of the UK and is

counted as one of the largest oilfields. It operates within the southern shores of Poole Harbor,

Furzey Island, and Wareham and at Kimmeridge Bay. It earned the Queens Award in 1995, for

best Environmental Achievement. Currently the production of the farm is 16 000 barrels of oil

per day (crude oil, liquid petroleum gas and gas). It employs 100 people as staff and is connected

to 250 contractors during the operations.


The farm works on conventional method of extraction of oil from oilfields along with some gas

products from oil reservoirs made of sandstone and limestone. The operation is run by Perenco

UK Limited who took the control of the farm and the operation of the oilfield in 2011 from

BP. The current production of the farm is 19 000 barrels of oil equivalent per day (including

crude oil, gas and liquid petroleum gas). Until now, Perenco has not pursued license to search for

shale gas or coal bed methane in Dorset and neither there is any news that Perenco has any such

plans in near future.

In September 2012, Perenco UK Limited submitted application to Dorset County Council for the

extension of the duration of 39 existing planning permissions for the Wytch Farm, Wareham and

Kimmeridge oilfields to 2037. Perenco also held an exhibition for the public in May 2012 and

provided major information related to its applications and recorded feedback of the

public. Dorset County Council sent the applications for further consultations. The planning

committee of Dorset County Council approved the applications in 2013. Perenco is committed

to maintain highest standards of operation and perpetual success in contributing a very positive

societal and economic contribution in the economy.

International Factors affecting Operations at Wytch Farm

There are several international factors that affect the operations of the Wytch farm and the

management has to make adjustments into the operations according to the change in those factors

and international market dynamics. Primarily international policies regarding transportation

industry in order to reduce carbon print affect the operations of all oil extraction, production and

refining organisations. Since transportation sector is the largest consumer of oil energy therefore

changes the policies of transportation industry has direct effects on oil producing companies.

Greenhouse gases (GHG) emissions are studied by decomposing it into carbon intensity, energy


efficiency and total transport demand. Fuel producers such as Wytch Farm are held responsible

for the carbon intensity of fuels, while car manufacturers are assessed for the efficiency of

vehicles, and the consumers are accounted for the demand of fuel. In the European Union and

the US, car manufacturers are regulated in g CO2 per km or mile, i.e. a measure that targets both

carbon intensity of fuels and energy efficiency of cars (Lee et al. 2012).

International quality standards and operating procedures also affect the operations. When

policies and standards change at international level in response to climate, sustainability and

environmental concerns then operating procedures at Wytch farm must also adjust to adapt and

implement those changes for example in order to meet the target set by Kyoto agreement UK has

introduced various laws and regulation such as Climate Change Act 2008 in which Carbon

budget has been introduced as an integral part (Smythe, 104). Now all the sectors and industries

in including the Wytch farm have to cut down the carbon budget by 50% until 2027. In order to

achieve this target the management must plan and introduce certain measures in the operations of

the farm.

Local Social, Economic and Environmental Factors

In contrast to most of the European countries, there is no dominant national oil company in the

UK, therefore the government of UK interacts and intervenes in the operations of oil and energy

sector with the help of following department of Energy & Climate Change (DECC), Department

for Business, Innovation & Skills (BIS), Department for Communities and Local Government

(DCLG), Department for Environment Food & Rural Affairs (Defra), Department for Transport

(DfT), HM Treasury (HMT). The Environment Agency (EA) is the UK administrator and

English regulator for the EU Emissions Trading System. EA influences energy sector and


respective energy efficiency as well as greenhouse gas emissions reductions by introducing

regulations and inspections such as business premises in the context of pollution prevention and

control, and landfill sites (landfills emit the greenhouse gas methane). The EA also targets

reduction in greenhouse gas emissions by exercising regulatory rights in other areas of expertise

for example water, waste, flood and coastal risk management (Goldman, Goldberg and Grant,

2013).

The UK government is seeking to make improvements in the efficiency of various vehicles such

as trucks, busses and aero planes. Such policies will have a downward impact on the fuel

consumption and ultimately on the supply and demand of oil energy and thus will affect

operations of the Wytch farm to make adjustment accordingly to maintain profitability b

The UK government is encouraging the roll-out of the gas grid to remote regions of the country

to promote substitution of kerosene with natural gas. This will not only yield environmental

benefits but also reduction in sulphuric and Carbon dioxide emissions. Additionally it has been

observed that traffic congestion is a significant factor that increases the aggregate consumption

of oil fuels. Thus a reduction in the traffic congestion will ultimately reduce carbon emissions

and will reduce the aggregate demand for oil fuels. Wytch farm must monitor such policies to

make necessary adjustments promptly to adjust with the future changes in the demand of oil

fuels (Atkinson, 2011).

Impact of renewable Energy Sources

The government is striving to continually reduce heating oil use particularly by using renewable

energy sources such as biomass, as a substitute to existing oil sources. Although the gas network

covers most of the housing unit in the country yet there is a limited oil demand by those housing


units developed outside the city. Once they gain a suitable size the gas network will most

probably will reach them causing further reduction in the demand for the oil (Twidell, 2012).

Future of Wytch Farm

Considering the fact that Oil is a significant part of global energy market, it is expected that oil

market is likely to grow along with the growth in energy market which is growing continually

particularly in developing markets. Although oil continues to lose market share yet aggregate

consumption (maintaining demand) and production (maintaining supply) are expected to grow

slowly as compared to the past mostly due to the policy changes targeted to curb the pace of

increase in demand. The impact of high prices also affects the total production (Johnson, 2013).

The Wytch farm currently, employs an approximately 100 Perenco employees and around 250

agencies/contractors staff to successfully operate in the oilfields. The quality of job and salaries

of the employees are above average and 300 supporting jobs are also associated with the Wytch

farm for example by supplies and services. Additionally over the extended period the Wytch

farm is expected to support jobs directly and indirectly (Wien, 2011).

The permission for the extension of the life of oilfields should be granted in order to keep these

jobs until 2016 (at which the oilfields are expected to expire) and beyond. In addition to the

employment impacts, there are other positive economic and fiscal outcomes of the Wytch farm

and if closed the results of shutdown of such refineries would lead to significant reduction in tax

income for both local and national government.


References

Atkinson, G., Hamilton, K., Ruta, G., & Van Der Mensbrugghe, D. (2011). Trade in ‘virtual carbon’: Empirical results and implications for policy. Global Environmental Change, 21(2), 563-574.

Benjaafar, S., Li, Y., and Daskin, M. (2013). Carbon footprint and the management of supply chains: Insights from simple models. Automation Science and Engineering, IEEE Transactions on, 10(1), 99-116.

Buynevich, I V. (2011). Geology and Geoarchaeology of the Black Sea Region: Beyond the Flood Hypothesis: Volume 473 of Geological Society of America Special Paper, Volume 473 of Special papers. Geological Society of America;

Gao, D. (2013). Tectonics and Sedimentation: Implications for Petroleum Systems, AAPG Memoir 100: Volume 100 of AAPG Memoir. AAPG;

Gąsiewicz, A and Słowakiewicz, M. (2014). Palaeozoic Climate Cycles: Their Evolutionary and Sedimentological Impact: Volume 376 of Geological Society of London Special Publications. Geological Society of London;

Goldman, M., Goldberg, R., and , M. (2013). The Case for an Enhanced and Updated International Air Transportation Policy. Air & Space, 26(2).

Johnson, H. D. (2013). Integrated MSc Petroleum Courses at Imperial College. In GeoSkill 2013.

Jolley, S J. (2010). Reservoir Compartmentalization: Issue 347 of Geological Society special publication, Volume 347 of Special publication - Geological Society of London. Geological Society of London;

Law, R D. (2010). Continental Tectonics and Mountain Building: The Legacy of Peach and Horne: Issue 335 of Geological Society special publication, Volume 335 of Special Publication 335 Series, Geological Society (London), Volume 335 of Special publication - Geological Society of London. Geological Society of London;

Lee, J., Cullum, D. D., Friedheim, J., and Young, S. (2012). A New SBM for Narrow Margin ERD Drilling. In IADC/SPE Drilling Conference and Exhibition. Society of Petroleum Engineers.

Parker, D. (2009). The Official History of Privatisation Vol. I: The Formative Years 1970-1987: Government Official History Series. Routledge;

Smythe, D. K. (2014). Planning application no. SDNP/1305896/CM by Celtique Energie to drill at Fernhurst, West Sussex: Critique of environmental statement in the context of relevant geology and hydrogeology.

Twidell, J., & Weir, T. (2012). Renewable energy resources ED2. Taylor & Francis.

Wien, G. (2011). Wytch farm Oil Field-Subsurface Coursework.


Wood, L (2011). Shale Tectonics: AAPG Memoir 93: Volume 93 of AAPG Memoir. AAPG;

1 petroleum region of wessex basin topic: petroleum region ... · in and around kimmeridge bay...

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