User:Roryelizaneth22/Porcupine Basin in Southern Ireland

= Hydrocarbon System in the Porcupine Basin: Located Offshore Southwest Ireland =

Introduction
The Porcupine Basin is a Hydrocarbon System that is a Late Jurassic rift located in the offshore Southwest Ireland. This is just one of five Mesozoic basins that are in this area; Celtic Sea Graben System, Central Irish Sea, Rockall, Northwest Ireland Offshore and Porcupine basin. Throughout here we will address the Porcupine Basin's main location, tectonic and geologic setting, stratigraphy, and modern Petroleum Exploration. We will also analyze multiple maps, figures, cross sections, and seismic data.

Location
As stated before this is just one of five Mesozoic basins in the region. The mesozoic extension across north-west Europe and the break-up of Pangea supercontinent. This is evident in the morphology of the basin. The shallowing towards the margins and towards the northern sections is likely to have facilitated fluid migration in the Cenozoic times towards these shallower regions. This is also proved later while addressing the stratigraphy and revisor.

Tectonic/ Geologic Setting
The Porcupine Basin is related to mesozoic extension across north-west Europe and the break-up of the pangea supercontinent.

1. The initial rifting occurred in the Triassic with a series of minor rifting events

- Minor rifting events are zones with linear rfits where the lithosphere is being pulled apart

2. The main rifting developed in the Mid to Late Jurassic

- This lasted about 20 to 30 million years

- This is also evident to major thermal subsidence or uplift

3. Minor rifting then occurred in the Early Cretaceous.

4. Finally, Irregular subsidence in the Tertiary

- Possible lithospheric stretching by rifting or mantle plume.

This all comprises to form the tectonic reconstructions suggest the South Porcupine basin formed a conjugate Margin with the Canadian East orphan Basin. A conjugate margin pair comprises two passive margins now located on different tectonic plates, separated by oceanic crust (including a spreading axis), which were once adjoined in the rift system that preceded the breakup .The three field related to this are Mizzen, Bay du Nord and Harpoon. Mizzen Field.

1. The Mizzen Field is the first oil discovery in the underexplored Flemish Pass Basin, offshore Newfoundland, Canada in 1100m water depth.

2. Bay du nord: Bay du Nord is the first remote, deep water project in the province’s offshore (500kilometresfrom shore and approximately 1,200 metresdeep). It opens a new basin – the Flemish Pass and is the first project to be negotiated under Newfoundland and Labrador’s generic oil royalty regulations.

Cross Section
This cross section shows how the procupine basin formed along with the folding and squeezing that happened. A study by EUROPA Oil and Gas in july 2013 states that residual oil shows reported in Lower cretacesous carbonate reservior. This leads us to discoveries in the Basin structure.

Basin Structure
Based on the findings in the cross-section above, we are able to identifiy this basin is oil prone and came from a carbonate resivior. They display low permability due to diagenesis of the clasitc source, and came from the erosion of caroniferous hinterland. There has also been extreme stretching in this region by rifting on mantle and plume

Stratigraphy/ Revisor
Based off of Croker et al. (1989) the basin can be summarized into three broad-scale stages of the basin evolution. This is based off of 25 wells drilled within the basin. - Pre-rift: consists of rocks of Devonian to Permian age wirhupper Carboniferous rocks being particularly widespread.

- Syn-rift: sequence of Triassic to Jurassic sediments was initially deposited in small northeast southwest-trending basins that were superimposed on older carboniferous fabrics before major north-south rifting began at the end of early Jurassic.

- Thermal sag: began in the early Cretaceous with deposition of a sequence that were capped with upper Cretaceous marine to deltaic sediments that were capped with Upper Cretaceous chalks, and succeeded by a thick Tertiary sequence.

Seismic Data
The PorcupineBasin has provided new insights into the geology and exploration potential of the area, revealing detail previously unseen on available data The North Porcupine Basin has seen the greater amount of exploration activity, with 28 wells drilled to date. Of these, four have tested hydrocarbons: wells 26/28-1 & 26/28-2 (Connemara oil discovery), well 35/8-1 (Burren oil discovery), and well 35/8-2 (Spanish Point gas-condensate discovery). Many of the reservoirs encountered in the North Porcupine Basin did, however, display low permeability due to diagenesis of the clastic source, derived from erosion of Carboniferous hinterland.

Shows geography of basin best

Petroleum Exploration History
A total of 26 exploration wells were drilled in the North Porcupine Basin between 1977 and 2001.

Three noncommercial oil discoveries were Connemara, Spanish Point, and Burren.

First well in the South Porcupine proper was BP 43/12-1 (1988) which targeted a North Sea-style tilted fault block. This established the source rock in South Porcupine, as thin sandstone.

Latest wave of interest was in 2011. They were mostly searching fot postrift submarine fan stratigraphic fan stratigraphic traps.