Petrophysics Summer School

Lucy Manifold, Postgraduate Student, University of Manchester

lucyEarly on Monday morning, I arrived at the University of Leicester alongside 29 other early career researchers, representing 19 nationalities and travelling from 11 countries, to begin a much-anticipated week of interactive training on the fundamentals and applications of petrophysics.

Following a warm and energetic welcome by chief organiser Dr Sally Morgan, Prof Sarah Davies delivered the rationale for the IODP (International Ocean Discovery Program) and ECORD (European Consortium for Ocean Research Drilling) expeditions which follow four major research themes: planetary dynamics, deep life, climate, and geohazards. Although there is room for “blue-sky science”, the oceanic drilling programs are applicable to the nuclear waste, renewables, water resource and hydrocarbon industries.

Sarah outlined the numerous measurements made by the impressively diverse downhole logging tools; namely gamma density, P-wave velocity, electrical/magnetic susceptibility and neutron porosity, all of which are analysed on board the expedition. Microbiological measurements have also become increasingly important, involving rapid freezing of samples for preservation purposes. Sarah attributed the huge scientific success of the borehole research community to its integrated approach and collaborative research which has led to over 100 international publications.

After our whistle-stop introduction to the course, Dr Pete Fitch (Imperial College London) threw us head-first into “petrophysics 101” and taught what would normally be a two-day course into a three-hour masterclass. Pete emphasised the importance of thinking of subsurface rocks as a combination of solids and liquids with a series of practical exercises, including use of the Archie Equation, AKA the “holy grail” of petrophysics. The day was finished off by two industry case studies (formation pressure by Dr Louise Anderson (Total E&P) and estimation of in-situ hydrocarbons by Dr Sam Matthews (BP)) sandwiched between a talk on measuring core physical properties by Briony Shreeve (Geotek Ltd) using a multi-sensor core logger and x-ray imaging.

Most attendees brought a poster which summarised their current research. This stimulated diverse and interesting discussion during coffee breaks. It was clear that there was an impressive breadth of research being undertaken and it was fantastic to network with geologists from all corners of the globe and all specialities.

Our industry-focussed first day was succeeded by a series of academia-led talks and workshops on Tuesday, including a detailed overview of expeditions undertaken by D/V Chikyu by Yoshinori Sanada, who had travelled all the way from Japan (JAMSTEC) to speak to us. Two technique-specific talks gave us a detailed insight into acoustic logging (Dr Gilles Guerin) and the integration of core, log and seismic (Dr Angela Slagle, both Lamont-Dohert Earth Observatory), which emphasised the complications associated with integrating multi-scale data of various resolutions; a challenge which geologists often face. The day ended with two case-study talks which demonstrated real applications of petrophysics. Dr Annick Fehr (Aachen University (European Petrophysics Consortium)) talked to us about Baltic Sea Paleoenvironments and made sure we were paying attention with an interactive ‘Pingo’ quiz and last but not least, Dr Trevor Williams (JOIDES Resolution Science Operator, Texas A&M University) spoke about his research on Mediterranean Contourites. The evening kicked off with a private viewing (and a beer!) of the fossil collection at the New Walk Museum, introduced by palaeobiologist Dr Tom Harvey (University of Leicester).  A delicious curry ensued for an authentic Leicester experience.

The field trips on Wednesday were much welcomed after our intense introduction to petrophysics. We set off to Weatherford Laboratories where we were split into four tour groups based on the petrophysical techniques/applications we were most interested in: acoustic, electric, nuclear and “other” (e.g. NMR). We were shown the initial stages of tool development, right up to tool normalisation using a series of blocks of different rocks and elements with known properties. Considering the size of the tool strings (several meters) I think that we were all surprised to find they were powered by AA batteries (albeit hundreds – if not thousands – of them). At the BGS Core Store in the afternoon we were first given a tour of the core store. We were suitably impressed again by the amount of core in the first warehouse which turned out to only represent 1% of all UK Core! The final part of the day involved comparing gamma, density and resistivity readings alongside actual core to identify what may be the cause of extreme values.

core_storeProf Sarah Davies outlining our task for the afternoon at the Core Store, British Geological Survey

The final two days were a crash course in Schlumberger’s borehole software platform – TechLog. Techlog allows users to integrate, review and analyse various data collected by downhole logging and compare this information between different well sites. Rudi Mathers took us through the fundamentals of the program in a logistical step-by-step manner, such as importing information and adjusting the parameters of data. By day two, we were ready to make some petrophysical calculations, including water saturation using the infamous Archie’s Law. We were given a final slot of time to put our newly acquired skills to the test by undertaking an exercise based on real data from the Asian Monsoon expedition (Expedition 346).

techlogLearning the ropes of TechLog with Rudi Mathers

The week was wrapped up with a workshop from Dr Erwan Le Ber who brought together everything we had learnt in the week through an exercise in planning the logging for a drilling expedition from start to finish. Erwan used the Chicxulub expedition to exemplify this, during which he had been a Petrophysics Staff Scientist. The impressive 200 km wide, 30 km deep crater, which was the focus of the expedition, was formed by a 10 km wide meteorite and marked the end of the dinosaurs (K-Pg boundary). The site was picked due to the presence of 65 Ma tektites – typical features at impact sites whereby immense pressures and temperatures allow rocks to behave like fluids, forming unusual textures. Erwan continued by explaining the order in which drilling, casing, coring and measuring of the borehole takes place, followed by measurement limitations (e.g. borehole temperature). Finally, we were able to plan our own logging programme for the expedition with depth and time limitations using a simple Excel spreadsheet.

It was a real shame for the week to end and I think we all gained an appreciation for the value in primary data collection, as well as a few new friends. In reference to Angela Slagle’s talk, we cannot directly measure the answer to the scientific question which we are trying to find out. However, we can figure out what we can measure and how this relates to what we want to know, and I think that the IODP embodies this. Each expedition collects a huge array of data which will be open for public use after a one year memoriam period and it is very exciting to wonder what questions might be answered in the future. I feel very lucky to have been able to attend such a superb course and I would like to offer my very special thanks to the University of Leicester for hosting and UK IODP for sponsoring my attendance.
everyoneAll staff, students and early career researchers who attended the first petrophysics summer school at the University of Leicester

 

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