Differential imaging of porous plate capillary drainage in laminated sandstone rock using X-ray micro-tomography

The experimental determination of representative capillary pressure curves as a function of saturation is of utmost importance for the determination of the initial reservoir fluid distribution and subsequent flow properties under production. We design an experimental procedure to image porous plate capillary drainage using X-ray micro-tomography based on differential imaging for a laminated sandstone micro core (4.86 mm in diameter). The pore structure, including the sub-resolution micro pores, was characterised and quantified using both the initial dry scan and the scan fully saturated with Potassium Iodide (KI) doped brine (30 wt%). During the porous plate capillary drainage, nitrogen (N2) was injected at a constant pressure and the capillary pressure was controlled by the pressure drop through the core sample. A full range of capillary pressure curve against saturation from 0 to 1.17 MPa is provided from the image analysis and is compared with the Special Core Analysis (SCAL) for the original core (35 mm in diameter). We are also able to discern that brine remained predominantly within the sub-resolution micro-pores, such as regions of fine lamination. Moreover, brine covering the rock grain surface and in the corners of the macro-pores can also be visualised.