Category Archives: Reviews

REVIEW: Purbeck Lacustrine Limestones Field Trip

Review by Dean Baker, Consultant Geoscientist, RISC Advisory

The Late Jurassic Purbeck carbonates form some of the most iconic outcrop exposures in the UK. The aim of this fieldtrip was to present new work on the Purbeck Group resulting from two 3 year industry funded PhD projects at Royal Holloway University, by Arnaud Gallois and Estanislao Kozlowski, supported by Professor Dan Bosence.

On Saturday morning, fuelled by natural enthusiasm (and a full English breakfast!), under glorious September sunshine, we walked to our first locality, Tout Quarry, Isle of Portland. Dan and Arnaud introduced the stratigraphic succession as we observed the boundary between the marine carbonates of the Portland Limestone Group (Tithonian Age) and the non-marine Purbeck Limestones (Lulworth Formation – Tithonian to Barriasian Age). The Purbeck Limestones, the main focus of the trip, were deposited in a shallow lake on the western margin of the Wessex Basin during the late syn-rift phase of basin evolution.

The remainder of the first day was spent at the iconic Lulworth Cove locality. Here we examined the succession in detail, familiarising ourselves with the informal subdivision of the Mupe Member (Lulworth Formation) into high-frequency lacustrine cycles named Skull Cap, Hard Cap and Soft Cap, each separated by thin, irregularly-bedded paleosols. Of particular interest were the thrombolytic microbial mounds, with their irregular geometries and complex interplay with intraclastic peloidal packstone-grainstone intermound facies.

Discussions centred on the variability in geometry and reservoir quality of mound and intermound facies and the complexity in characterising these features in 3D reservoir models. Also, comparisons were drawn with pre-salt basins offshore Brazil and Angola with similarities recognised in basin size, equivalent syn-rift setting, depositional age and some similarity in facies, particularly the highly porous thrombolytic mounds and less porous intermound facies. It was recognised that further study would be required to assess the suitability of the Purbeck Limestones as analogues for South Atlantic pre-salt.

After a brief lunch stop our next locality was the famous ‘fossil forest’ which shows stunning examples of microbial mound formation around in-situ trees that later decayed leaving ‘doughnut’ shaped microbial mounds preserved.

Our final locality for the day was ‘Bacon Hole’ in Mupe Bay. Here we observed the transition from the upper Lulworth Formation to the overlying (younger) Durlston Formation, representing changes in depositional environment from brackish to hypersaline to freshwater. The restrictive environmental conditions were highlighted by distinctive low diversity mollusc- and gastropod-rich shell-beds. After returning to the Isle of Portland the group reassembled in the evening for a traditional pub meal and cold beverage (or two!).

Day 2 brought more sunshine and at our first locality, Portland Bill, we were able to see close-up the transition between the marine Portland Limestones which are thick-bedded oolitic grainstones containing oyster shells, in contrast to the relatively thin-bedded, microbialite-dominated, lacustrine carbonates of the Lower Purbeck Group.

The last locality at God Nore/Freshwater Bay showed further striking instances of irregular microbial mounds in the lower Purbeck. In addition, we observed more examples of thrombolytic microbial mound formation around in-situ trees. In one example, a concentric arrangement of burrowed peloidal packstone with a thrombolite framework on the upper surface can be observed around a central tree mould.

On behalf of myself and the field group I would like to thank Arnaud and Dan for running an excellent fieldtrip, perfectly mixing humour and expert knowledge to deliver an engaging fieldtrip.

On a personal note, as a sedimentologist and geomodeller by background, one thing that always resonates with me after a field trip is the immeasurable value of seeing rocks in the field; being able to visualise the scale and variability of geology in three dimensions. In my opinion, for this reason alone (in addition to fantastic learning, networking and socialising opportunities), it is well worth making the effort to leave the computer screen behind and get out into the field from time to time.

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REVIEW: Petroleum Geology of NE England Field Trip – Mid North Sea High Analogue

Review by Andrew Rodda, DrillingInfo

In the cold mid-October on the NE coast, geologists from far and wide (Aberdeen and London mostly) arrived at the Yorkshire town of Whitby to look at Mid North Sea High analogues of the soon to close (26 October 2016) 29th Licensing Round. The trip was led by Durham University’s Professor Jon Gluyas, Dr Jonny Imber & Professor Andy Aplin; throughout the whole weekend their knowledge proved invaluable and ignited some great discussions. On behalf of everyone who attended the event, we would like to say a very big thank you to them for providing such an insightful and enjoyable weekend.

The surprising dry and somewhat sunny day started with looking at the potential source rock in the Mid North Sea High. The Early Jurassic Cleveland Basin, Upper Lias Whitby Mudstone Formation was a 105m thick, dark-grey section abundant in shelly fossils. As fresh surfaces from the cliff face were investigated, the striking, unmistakable smell of hydrocarbons was released in to the air. The formation was deposited in poorly oxygenated bottom waters, which have resulted in TOCs of up to 18%. Some caverns have been dug out of the cliff in search of the precious gemstone ‘jet’ derived from decaying wood, sold in the local gem shops.

Next, we climbed 320m up Roseberry Topping in the North Yorkshire Moors. The peak represents a resistant cap of Middle Jurassic Saltwick Formation sandstone, which lies unconformably above the Whitby Formation. As an aside to the licensing round, the faulting in the area was discussed in relation to the prospect of shale fracking, and the day was nicely rounded off with fish and chips.

Sunday saw the rain and winds close in, which the Aberdeen residents are all too familiar with. The cyclic limestones and dolomites of the Permian Zechstein Basin, which have been proven as producing oil and gas reservoirs across offshore Netherlands and into continental Europe were assessed. The Quarrington Old Quarry was also viewed from a distance to observe the Yellow Sandstone-Raisby Formations which gave us a chance to consider them as a potential reservoir rock in the Mid North Sea High. Some geologists amongst us had also done some work on the released OGA funded seismic data available on the Mid North Sea High, and were enthused by the prospect of exploring these potential reservoirs.

The final stop of the trip was Seaham Harbour, which is cut into the Permian Zechstein Seaham Formation, giving an example of the boundaries and structural features in the Zechstein Basin. At this point, the tide was ferociously crashing against the shoreline and we parted our separate ways.

 

REVIEW: GIS for Geoscientists – An Applied Approach for the Petroleum Industry

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Review by Catherine Caulfield, Hannon Westwood

Many thanks to Martin Insley, Tullow Oil and Thomas Goode, IGas Energy for their respective presentations on how ArcGIS can be used to enhance geological workflows. Martin discussed how remote sensing data integrated with map data can be used in the interpretation of surface structure, sediment erosion rates and development planning. He highlighted the impressive level of detail and subsequent value achievable from low cost hardware and software. Further, he discussed the use of oil seep data for the identification of high potential acreage globally. Thomas Goode demonstrated how ArGIS can be used for well location planning onshore UK. His used a very effective “cookie-cutter” analogy to explain how the  buffer tool can be used to exclude no-drill areas from an ordnance survey map leaving potential drill locations. The resulting map can then be overlain with geological maps to determine best well placement.  A special thanks to our co-organisers EPUG, a volunteer-run user group focused on improving and enhancing the use of GIS within the petroleum industry. We would also like to thank Engie for the use of the fantastic venue.

 

REVIEW: Geological Insights from Borehole Imaging

We are grateful to Dr Buchan for an excellent starter guide to borehole imaging.

The talk covered a wide range of topics, from these tools, from sedimentological features to geomechanical and stratigraphical, and how these insights can benefit not only the geologist, but almost all of the different disciplines across the subsurface team. The talk went on to showcase multiple geological features from real BHI data to the attendees, a mix of geologists and engineers from operators and consultancies, having to put their thinking caps on and try to decipher what was going on in the data.

The talk finished with some time left over for questions and discussion over snacks and various nibbles, and the participants provided excellent feedback. We would like to thank Centrica for providing us with an excellent venue for the talk.

REVIEW: Structural Geology Field Trip to Bude, North Cornwall

Group Photo

Review by Alastair Burke

Geologically this region is characterised by the presence of Late Carboniferous turbidites that have been heavily folded and faulted by the Late Palaeozoic Variscan collisional orogeny.
The overall theme of this field trip was to examine and demonstrate the relationship and interplay between structure geometry and stratigraphy (in this case variations in the ratio of Sandstone to Mudstone), something that is collectively termed ‘Mechanical Stratigraphy’.
Our first location was Hartland Quay, North of Bude. The weather, rather unusually for a UK based field trip, was fantastic. Our course tutor, Jonathan Turner (a Structural Geologist with BG-Group) gave us an overview of the area (a series of heavily folded turbidites) which at points we struggled to hear due to a rather noisy pair of nesting Peregrine falcons! This area was where John Ramsey, the ‘Father’ of modern structural geology, worked on and devised his theory on the mechanics of chevron folding back in 1974. The quality of the exposure is second to none. The locality demonstrates everything from the small scale deformational features (at individual fold level) through to large scale where a change in the thickness of the sand bodies alters the style of folding from tight chevron to broad low amplitude anticlines.
The second location of the day was Millook Haven, to the South of Bude. This area further demonstrates how changes in the stratigraphy (in this case a series of tabular and evenly bedded turbidites) influenced the style of deformation, expressed as a series of sharp crested and recumbent chevron folds.
Additionally, we saw evidence of how, during the early stages of diagenesis, mudstones and sandstones can respond differently to strain. What we saw was the apparent flow from the mudstone interval into tension cracks developing within the sandstones intervals.
At the end of the day we returned to Bude and reassembled that evening on the beach for a civilised dinner of fish and chips, pizza and wine!
On Day 2 the weather had returned to familiar conditions for a UK based field trip – wind and near horizontal rain! Not to be deterred from our mission, however, and remaining as enthusiastic as ever, Jonathan lead us on a short walk down to Bude beach to the first stop; an exhumed plunging anticline known as the ‘Whaleback’.
The ‘Whaleback’ allowed us to examine in three dimensions the complexity, variation and seemingly conflicting coexistence and expression of both compressional forces (in the form of pressure solution) and tensional forces (expressed as filled fractures) during the generation of the structure. We also saw wonderfully preserved examples of centimetre scale syn-depositional faulting within the mudstone units.
At Upton, South of Bude, we again observed the influence that changes in the ratio of Sand to Mudstone have on the deformation style. In this example, relatively thick channel sands limit the deformational style to a low amplitude anticline with further additional compression accommodated by the formation of thrust related duplexes.
Our final location, Crackington Haven, demonstrated the opposite of what we had seen previously at Upton where thin bedding led to the development of near isoclinal folding.
Thanks must go to Jonathan Turner, the course tutor, for his guidance and expertise during the trip. Jonathan managed to blend and deliver perfectly his academic and industry experience providing what was a very interesting and relevant field trip.
For me personally as an Interpreter/Geophysicist the two key messages that I took away from the field trip were; firstly, how complex and three dimensional these deformational processes actually are and secondly, a firm reminder that when I am at my workstation looking at data it is equally important to have an appreciation not only of what you do see, but also what you don’t see!

Hartland Quay

REVIEW: Maxwell Gas Discovery Oil Finders Lunch

The second AAPG/PESGB Oil Finders Lunch saw 43 people gather at the Atholl Hotel in Aberdeen to hear Mike Cooper of Arenite Petroleum talk about the Maxwell Gas Discovery in the Southern North Sea. Mike gave an overview of the Cleveland Basin and focussed on the Zechstein carbonate reservoirs with particular emphasis on the Plattendolomite. A large structure at Plattendolomite level exists immediately offshore North Yorkshire which has been penetrated by several wells. All these wells encountered gas bearing Plattendolomite which could form a single gas column around 1500’ long.  This large structure is bounded to the west by a fault system called the Peak Graben which runs sub parallel to the coast coming onshore in the Scarborough area. The Plattendolomite reservoir has been charged by Zechstein sourced gas which is distinctly wetter than the more typical Carboniferous sourced gas. Potential Plattendolomite reserves are estimated at 690 bcf and require a well to confirm commercial deliverability. This well could be drilled from an onshore location to the offshore target.

Colin Percival then summarised the Ranger farmin opportunity available from Summit Petroleum. The Ranger prospect has a Balmoral target with oil in place of 65 mmbbl which has a distinct far offset amplitude anomaly interpreted as a hydrocarbon effect. The prospect is to be drilled late 2016/2017 at a dry hole cost of £5.1 – £6.7 million and Summit have 100% equity. Colin then reviewed the 2016 UKCS E&A wells drilled to date (7 including one sidetrack). These include two completed wells (Farragon South and Laverda/Slough), one well currently being sidetracked (Finlaggan) and three active wells (Loanan, Eagle and Winchelsea). The only confirmed discovery to date is Laverda which encountered 13’ net oil pay in the Tay Formation to the north of the Catcher Field which is under development.

The lunch was kindly sponsored by Arenite Petroleum.


The next Oil Finders Lunch will be on Thursday 1st September when Apache will give a talk on their current activity on the UKCS.
If you are interested in presenting at the Oil Finders Lunch please contact colin.percival@parkmeadgroup.com

 

YP Seminar Review: The UK’s Energy Crisis

Review by Alexandra Inchenko, BP 

We were reminded that the oil industry saved the whales and fuelled the industrial revolution as Professor Jon Gluyas set the scene for an evening on the UK’s energy crisis. Energy is often described as a ‘trilemma’ between sustainability, security and equity and Jon’s talk addressed each of these. The UK had its glory days in the 80’s and 90’s when it was self-sufficient in oil, gas and coal but in the early 2000’s we switched from a net exporter to a net importer with slowing production from the North Sea and the closure of coal mines; and this gap is rapidly widening. Electricity production may have become greener with the switch from coal to gas and the closure of the coal industry ‘accidentally’ cleaned the air (and significantly reduced UK seismicity) but recent years have seen the death of costly green energy policies.

Jon highlighted how serious concerns about UK energy security are; with three occasions since 2010 when our gas supply has barely met demand. However, it’s not all doom and gloom, household spend on energy as a proportion of income has been decreasing since the 1960’s and the UK has an enormous resource base; we just need some innovative ways of exploiting it. He suggested we should ensure we get the last drops out of our oil fields whilst capturing carbon through EOR with anthropogenic CO2 and find a way to harness all that ‘hot air’ in London.

Jon’s talk was enlightening and engaging but the evening really came to life during the questions, with lively conversations on fracking, CCS, Lord Browne’s zero carbon initiative and how we’re going to meet the COP21 agreement.

Thanks to Jon on behalf of all the attendees for a fascinating evening and many thanks to Schlumberger for hosting this event.

Review: Making the World your Oyster

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The DEVEX YP event featured a wide range of industry panellists including Nigel Bradburn of Energy Institute, Willie Reid, Director of Strathyclyde Oil and Gas institute, Jackie Mann, Senior Vice President Human Resources, Proserv, Dan Purkis, Technology Director and Co-Founder, Well- SENSE, Mark Lappin, Director of UK/Netherlands Exploration and Subsurface, Centrica as well as John Costaschuk Reservoir Engineer BP and SPE representative.

The discussions were informative and motivational, with an emphasis on encouraging young professionals to be resilient and innovative during this challenging time. We were encouraged to find ways of accessing free training and to continuously learn and develop our skills. Mark emphasized that we should always seek to add value to our skill set, thinking of ourselves as a business, focused on growth. Willie challenged us to find what we are passionate about, to enjoy what we do and to discover and remain true to our values. Jackie’s key point was that we should seek to develop our own opportunities and be versatile enough to maximize them. Dan highlighted that we should remain passionate and think about how we use our time while John encouraged us to harness the power of our networks.

Overall it was a very good session with the main takeaway being that we should embrace the opportunity to follow a multidisciplinary career path. The question we will be asked of our experience during this downturn is…what did you learn? Let’s make the answer a good one.

Review: Seismic Reflection Fundamentals

Review by Chris Lloyd

I had the pleasure of attending the three-day Seismic Reflection Fundamentals course held at the PESGB training centre in Croydon in May 2016. The course was delivered by Dr. William Ashcroft (former lecturer at University of Aberdeen) to a diverse audience with varying career paths and experience levels, from young geoscientists through to seasoned consultants. For some this was their first dealings with seismic, while for others it was just a refresher.

The course was well-prepared for us all on arrival. We each received a take-home copy of William’s textbook ‘A Petroleum Geologists Guide to Seismic Reflection’ along with a condensed version of the book specifically created for this event. For those that learn by doing, this was a great course. Throughout the three-days, lectures were broken up by a number of tutorials to get hands on practise of what you had just learned during the lecture. Instead of using advanced software where many different factors have to be in-putted and considered, William had developed his own basic processing software which meant the key concepts could be easily understood step by step.

The lectures on the first day focused on the building blocks of a seismic profile, from the basics such as wave motion and the wavelet itself, through to data acquisition. In the tutorials we were able to create our own waves using William’s software and experiment with different values to see how the wavelet changed. In the afternoon we moved onto areas such as common mid-point shooting/ stacking and its associated advantages such as reducing the signal to noise ratio. After speaking with another attendee who was a geologist, I was told how beneficial even this basic information would be for the next time he has to communicate with the geophysicists.

Once everyone had a rough understanding of how a seismic profile is created, on the second day we went straight into looking at how the subsurface affects the seismic profile both in 2D and 3D. Lectures were given on a number of topics such as the relationship of P-wave velocity and lithology, and how a fault can cause sideswipe in 2D seismics. In the tutorials we moved away from the processing software for a while and used the old fashion pencil to paper, picking out faults and following formation tops across the profiles.

The final day continued on from analysing seismic response to subsurface features such as bright spots and flat spots in the profiles. We closed with a series of small tutorials on the West Sole gas field in the North Sea Basin, all addressing the task of converting TWT to depth. For this we carried out exercises such as completing TWT contour lines across a time slice, or calculating the average velocity for the top of the Rotliegendes formation, all of which had a common goal to allow cross reference of wells with the seismic profiles.

In summary, this was a very worthwhile course for all participants, and was presented in a clear and precise way. Although not everything could be covered over the three- days, the extensive detail of the textbook should answer any questions that do arise in the future. I would definitely recommend this course to anyone that needs to brush up on their seismic knowledge or for someone who wants to learn it from scratch. I want to thank the PESGB and Dr William Ashcroft for delivering the course in such a competent way.

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Review: Soft Rock, Hard Rock and a Trace of Heavy Metal

Bob LeppardReview by Stephen Pickering, NExT, Schlumberger plc

The Geological Survey map of Great Britain shows that the sediments at outcrop in central London comprise Eocene London Clay, Bagshot Beds and Quaternary glacio-fluvial sediments.  However imagine my surprise as I walked down Piccadilly, St James’s Street and Pall Mall to find outcrops of Cretaceous Rudistid Marbles, Jurassic Portland and Bath Limestones, Silurian Burlington Slate, Dalradian Connemara Marble and Monian Jaspers.  In addition there were numerous granites and marbles of the type more commonly found in Scandinavia, Lake District, Greece, Aberdeenshire, Cornwall and Carrara, Italy.   Did William Smith get it wrong I ask?

I was actually on the Soft Rock, Hard Rock and a Trace of Heavy Metal trip lead by Bob Leppard.  I did not see Roy Wood, Led Zeppelin or Jimi Hendrix but the building stones of London.  Bob has lead this particular trip for 30 years, initially for the non-technical staff at a company he worked for in Pall Mall.  Typical field trip weather prevailed, decidedly cool and damp but this did not deter because the information shared by Bob was so interesting.

Not only was the course extremely informative geologically but it had the added bonus of Bob’s insights into the Georgian and Victorian history and the architecture of St James’s, London.  There were many interesting anecdotes about Lobb’s, shoemakers to many famous people including George Bernard Shaw, and where the first bowler hats were made for a Mr. Coke. Berry Brothers wine merchants which was once a grocers and where people went to get weighed in the absence of personal bathroom scales circa 1698, and the building which was the Texas Embassy when Texas was a sovereign state (1836-1846).   Particularly interesting was Schomberg House once resided in by Gainsborough.  On the top of this building once stood the “celestial bedroom” but to find out more you need to go on the trip.

Going back in geologic time I was particularly impressed by the Portland Roach Stone of the Economist Building, St James’s Street containing Aptyxiella portlandica moulds, the so called Portland Screw. (Figure 1), and the Serpentinite doorframe around 18 Pall Mall and Bob’s erudite explanation of its formation from a Peridotite on a mid-oceanic ridge (Figure 2)

Bob has probably lead more field trips for the PESGB than any other individual in our history and he deserves a tremendous thank you from all PESGB members.   Thank you Bob for a very enjoyable evening.

Make sure you book the field trip in 2017!

Figure 1 Portland Roach Stone, Economist Building, St James’s Street
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Figure 2 Serpentinite 18 Pall Mall
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