Reservoir quality and diagenesis of Triassic sandstones and siltstones from arid fluvial and playa margin environments: a study of one of the UK's earliest producing oilfields



Scorgie, James C, Worden, Richard ORCID: 0000-0002-4686-9428, Utley, James ORCID: 0000-0003-0397-5607 and Roche, Ian P
(2021) Reservoir quality and diagenesis of Triassic sandstones and siltstones from arid fluvial and playa margin environments: a study of one of the UK's earliest producing oilfields. Marine and Petroleum Geology, 131. p. 105154.

[img] Text
Scorgie-Worden 2021 accepted text-figs-tables 20-5-21.pdf - Author Accepted Manuscript

Download (2MB) | Preview

Abstract

The Triassic stratigraphy of the UK contains many major reservoir rock units, present in all major offshore and onshore basins, historically resource rich in oil, gas and water. The Ormskirk Sandstone Formation (Sherwood Sandstone Group) and Tarporley Siltstone Formation (Mercia Mudstone Group) represent the main reservoirs found in in one of the UK’s earliest producing oilfields at an unusually shallow depth of 30 to 90 m. In this study, environments of deposition present, maximum burial depth, and reservoir quality are evaluated from well Formby-7 using modern analytical techniques. Wireline data and core analysis data were made available by Aurora Energy Resources for the purposes of this study. Formby-7 was continuously cored so that the whole section was logged for sedimentary structures and grain size. Optical analysis of thin sections was conducted, along with SEM-EDS, using thin sections from core plugs. The Ormskirk Sandstone Formation was deposited in a proximal setting by a braided, dryland river with aeolian influence; the Tarporley Siltstone Formation was deposited in a more distal setting on the margins of a playa environment. The study found that the reservoir quality is excellent in the deeper Ormskirk sediments, but relatively poor in the overlying Tarporley sediments. Good reservoir quality present in the Ormskirk Sandstone Formation is linked to early depositional textures, grain size (medium sand) and general lack of pore-filling cements. In the Tarporley, reservoir quality is poor due to the grain size (very fine sand) and the variable presence of pore-filling gypsum associated with playa deposits. Minor feldspar diagenesis (both dissolution and precipitation) occurred in both the Sherwood and Mercia sediments. The small degree of mechanical compaction and lack of any signs of mesodiagenesis suggest that the clastic sediments in the Formby-7 well have not been buried deeper than about 1,000 m. The findings reported here can be used to help the understanding of UK Triassic sedimentology and reservoir quality for oil and gas, geothermal energy, CCS (carbon capture storage) and water supply.

Item Type: Article
Uncontrolled Keywords: East Irish Sea Basin, Sherwood Sandstone Group, Mercia Mudstone Group, Reservoir quality, Diagenesis, Gypsum cement, Calcite cement, Dolomite cement, Compaction, Secondary dissolution, Ormskirk Sandstone Formation, Tarporley Siltstone Formation
Divisions: Faculty of Science and Engineering > School of Environmental Sciences
Depositing User: Symplectic Admin
Date Deposited: 24 May 2021 08:13
Last Modified: 04 May 2023 08:56
DOI: 10.1016/j.marpetgeo.2021.105154
Related URLs:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3123560