Neutron scattering study of strain behaviour of porous rocks subjected to heating and unconfined uniaxial compression

Neutron scattering (at ENGIN-X) was used to examine strain distributions in two hydrocarbon reservoir rock types (i.e. sandstone and chalk) under uniaxial stress (up to 35 MPa) at temperature as high as 70 °C to utilise the advantages of neutron scattering to draw a detailed picture of the structural evolution in the porous rock core plugs subjected to heating. Each sample was cylindrical in shape (i.e. 38.1 mm diameter and 48 mm length). The corresponding strain free lattice parameter (d ₀) for each sample at each measurement point at 5 MPa compressive stress condition were obtained by testing at 25°C. Various microstructural and material characterisation were carried out using X-ray diffraction, energy dispersive spectroscopy and scanning electron microscopy. Comparison of Rietveld refinement for multiple peak of crystalline phases in both samples were made. Results are discussed in terms of the influence of temperature and compressive stress on the residual strain profile along radial direction of cylindrical rock sample. It was found that the sandstone sample has significantly high strain bearing capability when compared with the chalk, however, the overall strain profile from the central axis in the radial direction looked very similar.