Seismic Interpretation – Ten Ways to be wrong

Date: Thursday, 21st November 2013

This presentation will take place at the Royal Cambrian Academy headquarters in Crown Lane, Conwy at 6.30pm.  Refreshments from 6.00pm.

Speaker Overview:

Dr Andrew Hopkins is an independent seismic interpretation consultant based in London, where he is currently working on the Carboniferous of the Southern North Sea. Andrew received his BSc from Imperial College in 1980, and has worked for various oil companies, contractors and consultants, including Enterprise Oil, Endeavour Energy, Horizon Exploration, and Helix-RDS, on seismic data from many of the world’s hydrocarbon provinces. In 2007 he completed a PhD at Cardiff University on the seismic interpretation of Cretaceous and Cenozoic contourites in the Walvis Basin, offshore Namibia. Before becoming freelance, Andrew was Chief Geophysicist at African Petroleum.

Abstract:

The last several decades have seen the dynamic growth of a global database of high-quality seismic reflection data, both 2D and 3D, which has been almost entirely driven by hydrocarbon exploration. Consequently, seismic data now provide the pre-eminent means we have of investigating sub-surface geological phenomena which would otherwise be inaccessible. Indeed, seismic interpretation has been the key component of many of the significant advances in structural geology and stratigraphy in recent years. These include for example, major developments in our understanding of fault dynamics, salt tectonics, fluid-rock interactions, igneous and sedimentary intrusions, not to mention the creation of the entire field of seismic and sequence stratigraphy. Although the mechanics of the process of seismic interpretation have been extensively dissected and reviewed in textbooks, courses and on the internet, this talk will propose that a valuable set of insights may yet be gleaned from a little-known and under-appreciated text book, now more than 20 years old. While the subject of “To Interpret the Earth” (1991) by Stanley Schumm, is geomorphology rather than seismic interpretation, its wisdom has relevance across all the earth sciences. Schumm sub-titled his book “Ten Ways to be Wrong” and he identified a series of problems of interpretation by which the unwary geoscientist may be led astray. He placed these problems into three broad classes, scale and place, cause and effect, and system response. The talk will attempt to transpose these “ways to be wrong” from their original geomorphological context into the milieu of the seismic interpreter. Numerous examples from the literature and from the speaker’s experience will be presented.

Directions to the venue:

RCA, Crown Lane, Conwy, LL32 8AN

The North Wales Geology Association proudly presents

“A Journey to the Burgess Shale, British Columbia, Canada”

This meeting to be held at the University of Chester, Large Lecture Theatre: Binks Building, Parkgate Road, Chester. Tea and coffee served from 7PM. Talk will commence at 7:30PM.

Dr Jacqui Malpas of NEWRIGS, Geodiversity Wales and former Post-Doctoral Research Student at the University of Chester.

Since discovering geology as an Open University undergraduate I have dreamt of visiting the most famous fossil site in the world; The Burgess Shale.  This trip was my 60th birthday present.

The Burgess Shale was discovered as the result of two decisions.  The first was Canadian Pacific Railway chose to run their line through the Rockies via Kicking Horse Pass; the second was that the Geological Survey of Canada sent their most experienced geologist, Richard McConnell, to map the geology on either side of the line. Thus in 1886, McConnell was the first geologist to find and collect from the Burgess Shale of Mt. Stephen, which overlooks the village of Field, British Columbia.  McConnell’s report attracted the attention of Charles Walcott a palaeontologist with the United States Geological Survey.  Walcott eventually found the Phyllopod Bed Fossil Ridge, between Wapta Mountain and Mount Field, the main Burgess Shale site, in 1909, 23 years later.  Charles Walcott’s diary of 31st August 1909 reads:

‘Out with Helena and Stuart collecting fossils from the Stephen Formation.  We found a remarkable group of Phyllopod Crustaceans.  Took a large number of fine samples to camp.’

The Burgess Shale, with its remarkable preservation of a diverse fauna with soft-body as well as skeletal parts was previously unknown.  This site and its fossils provide a unique insight into animal life of the early Cambrian Period.

This talk will illustrate some of the history of the site and an overview of the fossils and how they changed the way the evolution of animal life of the Cambrian Period is understood and interpreted.

The Cretaceous and Cenozoic stratigraphy and palaeoclimate of southern coastal Tanzania: results from a decade of fieldwork and scientific drilling

Date: Thursday, 17th October 2013

This presentation will take place at the Royal Cambrian Academy headquarters in Crown Lane, Conwy at 6.30pm.  Refreshments from 6.00pm.

Speaker Overview:

Paul Pearson is a micropalaeontogist and palaeoclimatologist at the School of Earth and Ocean Sciences, Cardiff University.  Paul received a BA in geology at Oxford University and a PhD on the evolution of planktonic foraminifera at Cambridge University.  He worked as a postdoctoral research fellow at Cambridge and Bristol before moving to Cardiff in 2003. Paul is interested in biostratigraphy, evolution and palaeoclimate, focusing mainly on the Cenozoic era.  He has helped develop palaeoclimate proxy methods such as oxygen isotope palaeothermometry and boron isotope pCO₂ reconstruction.  Paul has sailed twice with the Ocean Drilling Program and has conducted fieldwork in many places including Tanzania, Mozambique, Java, New Zealand and Trinidad.  He has directed onshore scientific drilling projects in Tanzania and Java.

Abstract of talk:

The Late Cretaceous to Oligocene Kilwa Group of southern coastal Tanzania is a thick succession of hemipelagic clays with accessory siliciclastic and limestone inter-beds. It is renowned for the spectacular preservation of its carbonate microfossils (forams, calcareous nannoplankton and others) which are important for taxonomy, stratigraphy, and the application of palaeoclimate proxies. A campaign of shallow coring using small mobile rigs at 40 sites distributed over about 100 km of strike has allowed us to recover about half of the stratigraphy in core, including important new records through the Paleocene / Eocene and Eocene / Oligocene transition intervals.

This work has been augmented by offshore piston coring and seismic surveying. Detailed study has resulted in over 35 peer-reviewed publications so far, including a new appreciation of tropical climate evolution since the Cretaceous, and insights into the structural geology and hydrocarbon potential of the area. There is still much potential for further discovery: A new deep cored reference section is planned onshore by the International Continental Drilling Project, with scientific aims linked to a planned offshore drilling expedition by the Integrated Ocean Drilling Program.

Directions to the venue:

RCA, Crown Lane, Conwy, LL32 8AN

Integrated petroleum systems & play fairway analysis in a complex Palaeozoic basin: Ghadames – Illizi Basin, North Africa

Date: Thursday, 19th September 2013

This presentation will take place in the Royal Cambrian Academy headquarters in Crown Lane, Conwy at 6:30pm.  Refreshments from 6:00pm.

Speaker Overview:

Dr Richard Dixon is a geologist with BP Exploration based in the London area where he is part of BP’s Exploration Assurance Team. Richard received his BSc & PhD from University College Cardiff. He then joined Robertson Research in 1985 as a sedimentologist working for them in North Wales & Aberdeen until 1988 when he joined BP. Richard spent 8 years working the North Sea & Faeroe – Shetland Basins mainly in development & appraisal roles, before moving to international exploration in 1996. For the last 17 years Richard has worked regional exploration projects across the globe, including the North Slope, North Africa, East Siberia, Sakhalin, Trinidad & Venezuela, India East Coast, West Africa (Angola & Gabon) & Brazil. For the last 3 years Richard has also been involved in teaching the Petroleum Geoscience MSc class at the University of Manchester and was appointed as visiting professor (Basin Analysis & Petroleum Geoscience Group) earlier this year.

Abstract:

The Ghadames–Illizi Basin is a highly productive petroleum province with a long exploration history in Algeria, Libya and Tunisia (from the late 1950s to present day). Ongoing exploration success in all three countries suggests that it will continue to provide attractive exploration targets in the future. The basin has a long and complex geological evolution characterized by multiple phases of subsidence punctuated by significant regional uplift events. Two ‘world-class’ petroleum source rocks of different geological age are present (Lower Silurian and Upper Devonian) with similar depositional environments and geochemical characters. Both source horizons have generated significant volumes of oil and gas. Petroleum migration is strongly influenced by the stratigraphic architecture of the basin fill, notably distribution of regional seals and the complex patterns of subcrop and onlap across regional unconformities. Multiple reservoir–seal combinations are presented by Late Ordovician glaciogenic sediments and younger Silurian through to Carboniferous paralic sequences. Integrating the stratigraphic relationships with the complex burial history of the basin (timing of uplift, degree of tilting, amount of section removed by erosion) is not a trivial task, but is key to exploration success in such a complex basin. With the aid of 3D basin reconstruction and fluid flow modelling software, we can attempt to capture the stratigraphic and structural complexity and make exploration predictions. If basin modelling techniques are to be optimally applied in such settings, a fully integrated and geologically realistic approach involving biostratigraphers, sedimentologists, structural geologists, geophysicists and geochemists is required. A modelling approach, workflow and some results will be presented.

This talk was presented in 2010 at the Barbican Conference. The paper is published – Petroleum Geology Conference series doi: 10.1144/0070735 Petroleum Geology Conference series 2010, v.7; p735-760 and available through the Lyell Collection.

Green Clays: Uses and Pitfalls

Date: Thursday, 18th April 2013

Venue: Royal Cambrian Academy headquarters in Crown Lane, Conwy @ 6:30pm.  Refreshments @ 6:00pm.

Abstract:

There was a time when field geologists were content to call green granules in sedimentary rocks glauconite and have done with it, in fact the practice continues up to a point and two of the localities I shall discuss have been so described in the past, somewhat erroneously.

The seminal work of Odin and others in the 1980s showed that, in recent sediments, green granules of the chlorite family of clays (odinite-rich verdine) were only found in recent, shallow marine, low latitude sediments, while glauconitic granules occur on the outer shelf. I shall show that, in this instance the present is not necessarily a key to the past. In ancient sediments both chloritic clays and glauconite can be demonstrated to have formed in non-marine sediments, while glauconite in situ has been recorded in shallow (<50m?) marine sediments. The picture is further “muddied” by the fact that glauconite may be reworked into fluvial/estuarine sediments.

As glauconite is more clearly associated with very low rates of sediment deposition than are the chloritic clays, it may be that glauconitised faecal pellets are more frequently at an advanced stage of maturation, and hence induration, when buried, than are pellets replaced by chlorite. In terms of reservoir quality this means that glauconite is less likely to result in poor reservoir quality than is odinite (or chlorite as it becomes with diagenesis). The fact that odinite-rich verdine deposits are found nearshore and seaward of deltas and estuaries suggests higher rates of sedimentation, and hence less chance of the pellets becoming sufficiently mineralised to be firm enough to resist compaction. If, at some stage in the transformation, clay is dissolved, this may provide the solutes necessary for chlorite rim precipitation, but at present this remains speculative.

Speaker Biography:

Dr Jenny Huggett is the proprietor of Petroclays, a consultancy specialising in clay mineral, and general clastic sediment analysis and petrography.

Petroclays was formed in 1990, and now in addition to working for the petroleum industry, works part time as a researcher and supervisor at the Natural History Museum, and the University of Oxford, Earth Sciences Department.  From 1982 until 1990 Jenny was employed as a sedimentologist by BP.  She obtained both her BSc and PhD from Imperial College, London.

Diagenetic modification of carbonate platforms from extensional basins: a step towards predictive models?

Date: Thursday, 21st March 2013

Venue: Cambrian Academy headquarters in Crown Lane, Conwy @ 6:30pm.  Refreshments @ 6:00pm.

Abstract:

It is widely acknowledged that diagenetic processes play a fundamental role in determining the volume, shape, size and distribution of porosity on carbonate platforms.  However, our ability to predict the shape, size and distribution of diagenetic products is limited.  In part this reflects the paucity of integrated, multi-disciplinary, multi-scale outcrop studies that reconstruct the temporal and spatial controls on the processes that controlled diagenetic fluid flux, and hence porosity modification.  This presentation will focus upon an ongoing research programme at University of Manchester into the diagenetic modification of carbonate platforms in extensional basins.  The studies combine quantitative, multi-scale descriptions of sedimentological, diagenetic, structural and petrophysical features.  These data are supplemented by geochemical analyses and interpreted in the context of the tectonostratigraphy and burial history of the basin.  Key datasets are taken from the Lower Carboniferous of North Wales and Northern England, and Eocene of the Sinai rift.  The diagenetic overprint of these areas will be compared, focusing in particular on dolomitisation, mineralisation and calcite cementation, and the potential to extract rules that better predict porosity distribution will be assessed.

Speaker Biography:

Dr Cathy Hollis is Senior Lecturer in Petrophysics and Petroleum Geocience at University of Manchester, where she leads a team of postgraduate and postdoctoral researchers working on industrially sponsored and research council funded projects in the UK, Europe, North Africa and the Middle East.  Her research focuses primarily on the diagenetic modification of carbonate platforms during burial  Cathy received her BSc from University of Birmingham in 1990 and PhD from University of Aberdeen in 1995.  She then worked as a consultant carbonate sedimentologist for Badley Ashton and Associates Ltd., during which time she established their Middle East office in the UAE (1999-2001).  In 2001, Cathy joined Shell International Exploration and Production in The Netherlands, where she worked for six years conducting both technical service support and research.   Between 2005 and 2007, she led the Carbonate Research Team for Shell and was Subject Matter Expert in Carbonate Diagenesis.

Figure 1: Asbian and Brigantian (Dinantian) Limestone, Great Orme, Llandudno, which underwent multiple phases of post-depositional porosity modification, including karstification and meteoric diagenesis, dolomitisation, fault controlled carbonate cementation and mineralisation

Directions to the venue:

RCA, Crown Lane, Conwy, LL32 8AN