Data generated at UCL on a conventional triaxial apparatus used to deform three different sandstones at room temperature and 150 °C. The data includes the raw mechanical data (time, load, displacement, pore pressure, pore pressure volume and confining pressure) and the meaningful processed data used to plot figures and draw main conclusions (stress, strain, pore volume change, effective mean stress, inelastic strain, yield points and Youngs modulus). The three sandstones used were Bleursville, Locharbriggs and Boise Sandstone, and are denoted by data files SS, L and MBO respectively. This dataset is used in the paper: M. Jefferd, N. Brantut, P.G. Meredith and T.M. Mitchell, Compactive Deformation of Sandstone under Crustal Pressure and Temperature Conditionsserpentinite, submitted to J. Geophys. Res. And in the UCL PhD Thesis M.Jefferd, Sandstone under Crustal Pressure and Temperature

Field photographs of rock formations or modern precipitates from the sedimentary environment. Samples were collected throughout the UK. This data was collected between February 2019 and November 2019. This data was collected to better understand the low temperature cycling of Telurium (Te) and Sellenium (Se) in the geological environment. For example, a range of ochre samples were included in this data. Ochres are a modern precipitate commonly found in rivers and streams which flow through geographical areas with a history of mining resources which are rich in sulphides. Iron from the sulphides are leached out and deposited downstream, coating river and stream beds, giving a red, yellow or orange colouration. Ochres can be a sink for trace metals such as Te and Se, therefore studying these environments could be informative from a resource perspective but also from an environmental hazard perspective. This data would be useful for researchers who require reference photographs for similar studies or as an aid for resampling.

Data recorded during hydrostatic pressurisation and triaxial rock deformation experiments of Westerly granite and Darley Dale sandstone. Data consists of mechanical data (load, displacement, confining pressure) and pore pressure data (up- and downstream pore pressure, upstream intensifier volume, four pore pressure transducers mounted on sample). Contains all data necessary to evaluate the results presented in the paper entitled: 'Fluid pressure heterogeneity during fluid flow in rocks: New laboratory measurement device and method' by Brantut and Aben, submitted to Geophysical Journal International, and available at arXiv (arXiv:2006.16699).

Loan IDA number IDA271576. Microbial DNA concentrations from DNA extraction using Qiagen PowerSoil Pro DNA Extraction kit and subsequent PCR from shale and sandstone core samples collected and preserved for microbiology (shale SSK111456 and sandstone SSK111457) from UKGEOS Glasgow Observatory, borehole GGC01. DNA extractions and subsequent amplification using PCR indicate levels of microbial DNA below detection limits. Samples and data are derived from the UK Geoenergy Observatories Programme funded by the UKRI Natural Environment Research Council and delivered by the British Geological Survey.

X-ray CT scan dataset of Darley Dale sandstone sample tts6. This sample was deformed in a true triaxial apparatus, and is fully described in the PhD thesis of Stuart (1992, UCL). The sample is a cube, measuring approximately 50 mm on a side. The sample experienced two sets of true triaxial deformation (test DDSS0009 and DDSS0010), with different applied stresses in the 1, 2 and 3 directions. This deformation produced distinct families of brittle microcracks, which were detected using acoustic emissions and seismic velocity analysis. This X-ray CT scan dataset was collected in 2019 at the University of Aberdeen by Dr Stewart Chalmers and Dr Dave Healy.

The dataset describes the results of high pressure experimental measurements of three contrasting 'tight' rocks; a Bowland Shale, a Haynesville shale and Pennant sandstone. The results are tabulated as a csv file, listing experimental parameters, confining pressure, argon gas pore pressure and permeability. complementary measurements of key petrophysical data are provided - bulk modulus of compressibility, porosity TOC and density.

These images were acquired using micro computed tomographic imaging of 7 sandstone plugs taken at various depths in the Sellafield borehole 13B. SF696 (63.8 m), SF697 (76.1 m), SF698 (96.98 m), SF699 (126.27 m), SF700 (144.03 m), SF701 (172.16 m) and SF702 (181.39 m). These samples are further detailed and analysed in the following article: http://dx.doi.org/10.1144/petgeo2020-092

EPSRC grant EP/L012227/1: Development of Unified Experimental and Theoretical Approach to Predict Reactive Transport in Subsurface Porous Media. The effect of pore-scale heterogeneity on non-Darcy flow behaviour is investigated by means of direct flow simulations on 3-D images of Bentheimer sandstone and Estaillades carbonate. The critical Reynolds number indicating the cessation of the creeping Darcy flow regime in Estaillades carbonate is two orders of magnitude smaller than in Bentheimer sandstone, and is three orders of magnitude smaller than in the beadpack. Also available at https://www.digitalrocksportal.org/projects/11, DOI:10.17612/P77P49. Further details can be found in Bagus P. Muljadi, Martin J. Blunt, Ali Q. Raeini, Branko Bijeljic. The impact of porous media heterogeneity on non-Darcy flow behaviour from pore-scale simulation. Advances in Water Resources. 2015. http://dx.doi.org/10.1016/j.advwatres.2015.05.019.

P* data obtained through hydrostatic loading experiments, using triaxial experimental apparatus, as well as yield curve data obtained through differential loading tests, prior to the discovery of P* for different synthetic sandstones. The methodology used was taken from Bedford et al. (2018, 2019). Grain size analysis data obtained using a Beckman Coulter LS 13 320 laser diffraction particle size analyser. Particle analysis was conducted on five different synthetic sandstones with different grain size distributions. Secondary electron and backscatter electron SEM images for natural and synthetic sandstones. Secondary electron images were stitched together to form a whole core image. They were then binarised following the methodology of Rabbani and Ayatollahi. (2015). Hexagon grid size data used to obtain the correct grid size for performing porosity analysis across an mage using Fiji software (Brown, 2000). Bedford, J. D., Faulkner, D. R., Leclère, H., & Wheeler, J. (2018). High-Resolution Mapping of Yield Curve Shape and Evolution for Porous Rock: The Effect of Inelastic Compaction on 476 Porous Bassanite. Journal of Geophysical Research: Solid Earth, 123(2), 1217–1234. Bedford, J. D., Faulkner, D. R., Wheeler, J., & Leclère, H. (2019). High-resolution mapping of yield curve shape and evolution for high porosity sandstone. Journal of Geophysical Research: Solid Earth. Brown, G. O., Hsieh, H. T., & Lucero, D. A. (2000). Evaluation of laboratory dolomite core sample size using representative elementary volume concepts. Water Resources Research, 36(5), 484 1199–1207. Rabbani, A., & Ayatollahi, S. (2015). Comparing three image processing algorithms to estimate the grain-size distribution of porous rocks from binary 2D images and sensitivity analysis of the grain overlapping degree. Special Topics & Reviews in Porous Media: An International Journal, 6(1).

These images were acquired using micro computed tomographic imaging of 4 sandstone plugs taken at various depths in the Glasgow UKGEOS borehole GGC01. GG496 (170.07 m), GG497 (168.66 m), GG498 (73.37 m) and GG499 (135.06 m). These samples are further detailed and analysed in the following article: http://dx.doi.org/10.1144/petgeo2020-092.