The laminite quarry showing the high quality laminite at the bottom and the more weathered layers above (Araripe Basin, Brazil)

In December 2016 I was awarded a grant from the Royal Academy of Engineering Newton Fund Research Collaboration Programme to facilitate an exchange with a postdoc (now professor) from the Universidade Federal de Pernambuco (UFPE) in the north east of Brazil. I did write about the project here

The exchange happened in 2017 and I think a little summary of the experience is in order. The exchange was in 2 parts – firstly Tiago visited Heriot-Watt from February to April – to use our rock mechanics facilities, to meet researchers from the institute and to decide on a field and data analysis programme for my visit to Brazil from May to August.

You can watch a summary video here

Project summary
Hydrocarbon discoveries in the pre-salt layer of the Brazilian marginal basin lead to increased interest in lacustrine laminites of the Crato Formation (CF), Araripe Basin, NE Brazil as an analogue for carbonate reservoirs. These Aptian-Albian lacustrine laminites are easy to access at outcrops and the range of facies (laminar, convoluted, concretions), as well as structural heterogeneities (open-mode fractures, faults) make it worth investigating the impact of heterogeneities on fracture formation, networks, fracture flow. Which are all important contributors to production in carbonate reservoirs. And investigate how representative the CF laminites are as an analogue for  lacustrine carbonate reservoirs, offshore Brazil. A summary poster is available here

The team in the rock mechanics lab at Heriot-Watt University from left to right: Tiago, Stephanie (me), Igor & Jim – standing next to the triaxial loading frame used to deform the laminite samples

Research summary                                                                                                                           In this study, different Crato Formation laminites were analysed and characterised using petrophysical and visual techniques, such as porosity, microscopy, X-ray tomography and photographs. After initial analysis 20 samples were deformed triaxially using a range of confining pressures (20MPa – 50MPa). Once peak stress was reached the tests were stopped and the samples removed for analysis of the deformation response. Based on comparison of pre- and post-deformation properties, as well as image analysis indicate a strong link between laminite facies characteristics and deformation response. Even though different deformation responses were observed the overall increase in porosity due to fracturing for non-faulted laminites was 5.94% (±1.66). Laminites sampled from a small fault zone showed an increase in porosity of 17.11% (±4.48) due to triaxial deformation. This indicates that deformation behaviour for laminar laminites could be predicted based on key properties such as porosity, permeability and mineralogy. However, for faulted samples these properties alone cannot predict deformation behaviour. A summary poster about the exchange is available here

What’s next                                                                                                                                    Tiago is presenting our findings in May at the AAPG meeting in Salt Lake City and we are working on writing up the findings for publication at the moment. I recently joint a new research group and will be focusing more on fracture flow but luckily this will also include laminites and more fieldwork in the Araripe Basin in Brazil this summer.

My fieldwork kit – a hip bag, stainless steel water bottle, yellow geological notebook, ruler, scale bar and pen – they will hopefully be in use again soon