From 1 - 6 / 6
  • The use of synthetic samples for rock physics experiments in the lab is a common practice for reservoir characterization and reservoir studies. This dataset gather ultrasonic P- and S-wave velocities and attenuations, electrical resistivity, axial and radial strains, permeability and mineralogical composition, of two synthetic and two natural sandstones, measured at variable realistic reservoir conditions of stress. The data were collected during an original study which aimed to assess the extent to which the measured properties between synthetic and natural sandstones are comparable. The work was accepted for publication in Geophysical Prospecting on the 01/10/2018, which can be accessed following the link: https://doi.org/10.1111/1365-2478.12699 Falcon-Suarez, I.H., Amalokwu, K., Robert, K., North, L., Best, A.I., Delgado-Martin, J., Callow, B., Sahoo, S.K. (accepted). Comparison of stress dependent geophysical, hydraulic and mechanical properties of synthetic and natural sandstones for reservoir characterisation and monitoring studies. Geophysical Prospecting

  • Cyclic loading stress-strain data in polycrystalline antigorite serpentinite, at various confining pressures and temperatures. This dataset is used and fully described/interpreted in the paper: David, E.C., N. Brantut, and G. Hirth, Sliding crack model for non-linearity and hysteresis in the triaxial stress-strain curve of rock, and application to antigorite deformation, submitted to J. Geophys. Res. Overview Rock type Vermont antigorite-rich (>95%) serpentinite. See submitted paper for details. The sample is isotropic. Apparatus Oil-medium triaxial apparatus (Rock Physics Ensemble, University College London). For description, see David el al. (2018), Absence of stress-induced anisotropy during brittle deformation in antigorite serpentinite, J. Geophys. Res., 123, 10616-10644. Griggs-type solid medium apparatus (Brown University). For description, see David, E.C., N. Brantut, and G. Hirth, Sliding crack model for non-linearity and hysteresis in the triaxial stress-strain curve of rock, and application to antigorite deformation, submitted to J. Geophys. Res., and references therein. Files description 1-existing data from David et al., JGR, 2018: The text file "Vermont-antigorite-roomT-150MPa-stress-strain-cyclicloading-UCLtriax" gives the axial stress (in direction 1, see submitted paper) and the axial strain (in percent, in direction 1, see submitted paper), at room temperature and 150 MPa confining pressure, in the oil triaxial apparatus at UCL. The mechanical data (stress, strain) have been corrected from internal friction and machine stiffness, respectively. The data are from David el al. (2018), Absence of stress-induced anisotropy during brittle deformation in antigorite serpentinite, J. Geophys. Res., 123, 10616-10644. 2-new data: The text file "Vermont-antigorite-roomT-1000MPa-stress-strain-cyclicloading-Griggsapparatus" gives the axial stress (in direction 1, see submitted paper) and the axial strain (in percent, in direction 1, see submitted paper), at room temperature and 1000 MPa confining pressure, in Griggs solid medium apparatus at Brown University. The mechanical data (stress, strain) have been corrected from internal friction and machine stiffness, respectively. The text file "Vermont-antigorite-400C-1000MPa-stress-strain-cyclicloading-Griggsapparatus" is the equivalent of the file described just above at a temperature of 400C. The text file "Vermont-antigorite-500C-1000MPa-stress-strain-cyclicloading-Griggsapparatus" is the equivalent of the file described just above at a temperature of 500C.

  • These data contain time series of stress, strain, confining pressure, elastic wave velocities of samples of Vermont antigorite and Westerly granite deformed under hydrostatic and triaxial conditions at room temperature and dry conditions. This dataset is used and fully described/interpreted in the paper: David, E.C., N. Brantut, L.N. Hansen and T.M. Mitchell, Absence of stress-induced anisotropy during brittle deformation in antigorite serpentinite, submitted to J. Geophys. Res.

  • This dataset contains raw experimental triaxial testing data as outlined in "Castagna, A., Ougier‐Simonin, A., Benson, P. M., Browning, J., Walker, R. J., Fazio, M., & Vinciguerra, S. (2018). Thermal damage and pore pressure effects of the Brittle‐Ductile transition in Comiso limestone. Journal of Geophysical Research: Solid Earth, 123(9), 7644-7660.s, http://dx.doi.org/10.1029/2017JB015105". The data is provided in a .zip folder containing the files of 16 experiments that are accompanied by a README file for introduction. Files format is Microsoft Excel Worksheet (.xlsx) and data are tabulated. Each file contains the corresponding relevant sample’s details, and each column of data is clearly labelled, units included. For each experiment, time, radial and axial pumps volume displacements and pressures, top and bottom pore fluid pumps volume displacements and pressures, internal temperature, LVDT signals were recorded. Twenty right cylindrical samples of ‘Comiso’ limestone (Ragusa Formation; Sicily) were tested in triaxial compression at a range of confining pressures simulating depths of 290 m, 620 m, 1.2 km, and 2.0 km respectively, assuming an average density of the over-burden load of 2470 kg/m3. Prior to strength test, each sample was either oven dried (ca. 12 hours at 85 °C followed by cooling in a desiccator for 1 hour) or water saturated (samples in distilled water under vacuum for 24 hours). A subset of these samples has also been thermally treated at 150, 300, 450 and 600oC to induce thermal cracking prior to the mechanical testing. All tests were conducted at 10-5 s-1 axial strain rate in assumed drained conditions when relevant, and at room temperature. For saturated tests, the initial loading was applied in two steps, first by increasing Pc hydrostatically (σ1=σ2=σ3) until the desired confining pressure was reached, and then introducing pore fluid pressure, as per the functionality of the experimental set-up. The experiments were conducted by Drs A. Castagna, M. Fazio and P. Benson using the Snachez triaxial cell at the Rock Mechanics Laboratory of the University of Portsmouth. All responsible for the collection and initial interpretation of the data. Only 17 experiments are reported in this set of data; the missing 3 datasets are believed to be only available on the local computer storage of the triaxial apparatus used at that time.

  • NERC grant NE/R013535/1. Here we present the dataset collected during a brine-CO2 flow-through test using a synthetic sandstone with oblique fractures, performed under realistic reservoir conditions stress. We monitored geophysical, mechanical and transport properties, for drainage and imbibition conditions, representative of the injection and post-injection stages of the CO2 storage process. We collected ultrasonic P- and S-wave velocities and their respective attenuation factors, axial and radial strains, electrical resistivity, pore pressure, temperature and brine and CO2 partial flows (from which relative permeability was later calculated).

  • This dataset contains raw (clean but not interpreted) triaxial compressive strength data of tests conductive at elevated pressure and temperature as outlined in "Vannucchi, P., Clarke, A., de Montserrat, A., Ougier-Simonin, A., Aldega, L., & Morgan, J. P. (2022). A strength inversion origin for non-volcanic tremor. Nature Communications, 13(1), 2311. https://doi.org/10.1038/s41467-022-29944-8". The data is provided in a .zip folder containing the files of 5 experiments that are accompanied by a README file for introduction. Files format is Microsoft Excel Worksheet (.xlsx) and data are tabulated. Each file contains the corresponding relevant sample’s details, and each column of data is clearly labelled, units included. For each experiment, time, axial force, axial displacement, axial stress, confining displacement, confining pressure, axial strain A and B, axial average strain, circumferential extensometer, circumferential strain, volumetric strain, internal temperature, and axial delta P were recorded. Triaxial testing was undertaken using the MTS 815 servo-controlled stiff frame inside a vessel capable of a confining pressure up to 140 MPa at the Rock Mechanics and Physics Laboratory, British Geological Survey, UK. The confining cell is fitted with external heater bands and utilizing utilizes cascade control from internal and external thermocouples (accurate to ± 0.5°C). An initial axial pre-load of 2.3 kN was applied, to ensure a stable contact and alignment of the platens. The confining pressure vessel was then closed and filled with mineral oil confining fluid. The axial pre-load was maintained whilst the confining pressure was applied at 2 MPa/min to 60 or 120 MPa; these values were chosen to approximately bracket the pressures at the up-dip limit of seismic nucleation, corresponding to 2 – 4 km depth (Arroyo et al., 2014). At this point, whilst held in axial force and confining pressure control, the rig was heated at 2°C/min to 60°C to approximate the average temperature conditions at the depth of the up-dip limit of seismic nucleation (Harris and Spinelli, 2010). The samples were then left for approximately 1 hour allowing thermal equilibrium to be reached throughout the confining fluid and the samples. Once stable, axial loading was initiated in constant axial strain rate control at a rate of 5.0 x 10-6 s-1 until macroscopic failure occurred or a significant amount of post peak-stress axial strain was recorded (between 2% and 5%). We note that one test was conducted at the higher temperature of T=120°C with a result within 2.5% of the strength at T=60°C (Table 1). As this is below the expected sample-to-sample variability, no further temperature studies were conducted. The axial load, axial load actuator displacement, axial stress (s1), differential stress (Q=s1 - s3), confining pressure Pc (= s2= s3), confining pressure actuator displacement, axial strain (eax), circumferential strain (ecirc) and temperature were monitored throughout at sampling frequencies of 1s and 0.5kN. File names are: YYYY-MM-DD_LabProjectNumber_SiteName-SampleNumber