Title: Development of novel sediment tracers: investigating the primary controls on reservoir sandstone quality
Researchers: Jess Franklin, Dr Shane Tyrrell
The key aims of this study are to identify potential causes of provenance-controlled reservoir sandstone heterogeneity from a micro- to a macro depositional system scale. Provenance analysis endeavours to identify the sources of sediment and to help reconstruct a “source to sink” model for sedimentary basins. A range of sedimentary rocks can be derived from similar sources and conversely very similar sedimentary rocks can be produced from diverse sources (von Eynatten and Dunkl, 2012). This is due to a multitude of factors, including climate and tectonics, which influence and modify sediment during generation, transport, storage and diagenesis. This modification of sediment ultimately has a significant impact on the reservoir quality of the resulting sandstone but this relationship is poorly understood. The link between source area sandstone petrography and reservoir quality will be tested and assessed in this study in order to move towards first order quantitative modelling of sedimentary systems and their detrital products. Due to the number of proven and exploited aquifers and reservoirs within the Lower Triassic of NW Europe, intervals are well constrained in terms of their reservoir and aquifer characteristics and behaviour. They are therefore an excellent test-bed for this study. There has been significant work already on determining the provenance of these sandstones, although many questions related to sand supply, climatic controls and sediment recycling remain which can be addressed as part of this project.
The aim of this study is to assess and test the relationship between provenance and reservoir quality. Rigorous testing and application of integrated provenance techniques coupled with the investigation of the key factors influencing reservoir quality during burial and diagenesis will identify potential causes of provenance-controlled reservoir sandstone heterogeneity from a micro- to a macro-depositional system scale. This will be achieved through high resolution sampling, multi-proxy provenance analysis and petrographic/diagenetic assessment of a well characterised, though heterogeneous, sedimentary system – the Lower Triassic of NW Europe. The study will begin in the Slyne Basin where Triassic reservoir sandstones of varying quality have been identified, including those of the Corrib gas field. These types of approaches should ultimately help in achieving a predictive tool for both reservoir sandstone distribution and quality. The reconstruction of Triassic palaeogeography is also a key objective for this project. Although palaeogeoographical reconstructions are well-constrained for the sedimentary systems which fed basins on and offshore Britain during the Triassic, peripheral basins such as the Slyne, offshore west of Ireland and the Ulster Basin, offshore/onshore Northern Ireland are not as well understood. These basins contain reservoir sandstones often of high quality and therefore need to be further studied to allow for de-risking of ongoing hydrocarbon exploration. Triassic sandstones of the Ulster Basin will be targeted to constrain a significant Triassic drainage divide between the Budleighensis River system to the south, and the system supplying the NE Atlantic Margin basins to the west and north, linking to ongoing work in the Slyne Basin.