Editing Dinantian and Namurian depositional systems in the southern North Sea

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== Introduction ==
 
== Introduction ==
The main thrust of Carboniferous hydrocarbon exploration in the southern North Sea has focused on the Westphalian succession as a provider of both gas-prone source rocks (coals) and sandstone reservoirs in both coal-bearing and redbed facies. Older Carboniferous intervals have received less attention, because their sourcing potential is less obvious, they tend to be very deep, reservoir quality is generally rather poor, and some traps require intra-Carboniferous seals, which are thought less obvious than the well established Permian Zechstein and Silver-pit seals. In spite of rather low levels of encouragement from exploration efforts targeting Namurian and Dinantian reservoirs, the deeper Carboniferous levels remain relatively unexplored, and potential remains. Gas discoveries in Dinantian and Namurian sandstone reservoirs in areas distant from Coal Measures Group occurrences point to both source and reservoir potential in these older rocks. The comparative lack of field developments is a function of field size, reservoir quality and distance from existing infrastructure. Oil and gasfields sourced from Namurian and Dinantian mudstones and, in some cases with Namurian sandstone reservoirs, are features of both onshore eastern England and the Irish Sea. Although most offshore gas accumulations depend on sealing at the base-Permian Unconformity, onshore oilfields demonstrate the viability of intra-Carboniferous seals for oil and there is evidence that some Carboniferous mudstone intervals act as seals for gas in the southern North Sea (e.g. well 43/20b-2).
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The main thrust of Carboniferous hydrocarbon exploration in the southern North Sea has focused on the Westphalian succession as a provider of both gas-prone source rocks (coals) and sandstone reservoirs in both coal-bearing and redbed facies. Older Carboniferous intervals have received less attention, because their sourcing potential is less obvious, they tend to be very deep, reservoir quality is generally rather poor, and some traps require intra-Carboniferous seals, which are thought less obvious than the well established Permian Zechstein and Silver-pit seals. In spite of rather low levels of encouragement from exploration efforts targeting Namurian and Dinantian reservoirs, the deeper Carboniferous levels remain relatively unexplored, and potential remains. Gas discoveries in Dinantian and Namurian sandstone reservoirs in areas distant from Coal Measures Group occurrences point to both source and reservoir potential in these older rocks. The comparative lack of field developments is a function of field size, reservoir quality and distance from existing infrastructure. Oil and gasfields sourced from Namurian and Dinantian mudstones and, in some cases with Namurian sandstone reservoirs, are features of both onshore eastern
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England and the Irish Sea. Although most offshore gas accumulations depend on sealing at the base-Permian Unconformity, onshore oilfields demonstrate the viability of intra-Carboniferous seals for oil and there is evidence that some Carboniferous mudstone intervals act as seals for gas in the southern North Sea (e.g. well 43/20b-2).
  
 
This paper attempts to summarize the sedimentary regimes in which Dinantian and Namurian successions of the southern North Sea were deposited and the constraints that this places on the hydrocarbon potential of the area. It is derived, to a large extent, from work over the past 12 years on multi-client studies and on an appreciation of time-equivalent outcrop analogues in northern England and Ireland.
 
This paper attempts to summarize the sedimentary regimes in which Dinantian and Namurian successions of the southern North Sea were deposited and the constraints that this places on the hydrocarbon potential of the area. It is derived, to a large extent, from work over the past 12 years on multi-client studies and on an appreciation of time-equivalent outcrop analogues in northern England and Ireland.

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