Lectures

Lectures are open to all and there is no charge for admission. However regular attendees are expected to be members of the society.

Time:
7:45pm for 8:00pm

Venue:
Sorby Room, Wager Building, (formerly Geoscience),
The University of Reading,
Whiteknights, Reading.
Use Car Park 8


2019-07

Monday 1 July 2019

The bizarre Cretaceous limestone reservoirs that formed in lakes at the bottom of the South Atlantic

Dr Paul Wright, PW Carbonate Geoscience


Rifting, volcanism and hydrothermal processes produced one of, if not the most unusual carbonate successions seen in the geological record. During the Aptian, in a transitional interval of South Atlantic opening, from rift to “sag”, vast shallow hyper-alkaline lakes formed in the central South Atlantic, extending from both margins and covering at least 100,000km2.. These lakes generated unique carbonate-silicate successions (the Barra Velha Formation and equivalents), up to 550m thick, which now act as the host for the multi-billion-barrel oil fields off Brazil and are also found off Angola. The very limited catchment geology and hydrology of these lakes precluded the formation of typical evaporite deposits and instead Mg-silicate gels formed associated with a very small range of calcite morphologies, in part growing in the gels. The gels converted to stevensite clays which later underwent congruent dissolution to produce much of the porosity in the reservoirs. The resulting rock fabrics, often visually stunning, present a dilemma for current classifications. Thermo-dynamic modelling and C & O stable isotopes support the sedimentological models, for what was an extreme system lacking in analogues. However, the biggest challenges have not been the limited amount of data from these deep reservoirs and their unique composition, but the effects of “word magic”, that is the (mis)use of terms in the hope their application brings understanding. The misuse of just two or three terms during the discovery phase has resulted in an almost catastrophic misinterpretation of the reservoirs at all scales.

Paul’s academic research has focused on carbonates, paleosols especially calcretes, and taphonomy. He has published over 140 papers in international journals, has co-authored, edited or co-edited 9 books including the main university textbook on carbonate sedimentology with Maurice Tucker.

After graduating with a BSc in geology from Bristol University Paul taught at a high school before studying for a PhD at Cardiff University, followed by a postdoc at the Open University. Later Paul lectured at Bristol University, Reading University (Postgrad Research Inst for Sedimentology) then took up the chair in applied sedimentology at Cardiff University sponsored by BG Group.

After being an advisor to BG for 10 years developing the geological models for BG’s carbonate reservoir portfolio in N Africa, Kazakhstan and offshore India, Paul joined BG in 2007 as a group technical authority, retiring in July 2013. Paul first started studying the Pre-Salt South Atlantic reservoirs in 2006.

Since 2013 Paul has been an independent consultant and is also an Honorary Research Fellow at National Museum of Wales. Paul was awarded AAPG’s Grover E Murray Medal in 2015 as a distinguished educator, and in 2016 SEPM’s (Society for Sedimentary Geology) Pettijohn Medal in recognition of “continuing excellence in advancing many diverse fields of sedimentary geology”.


Programme 2019

The programme for 2019 as currently proposed is also available as a pdf document.

Other programmes

Previous years programmes and other programme information can be found on the About us page.