Spatially resolved multidimensional NMR relaxometry and diffusometry for rock core analysis at high temperatures and pressures

MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington, New Zealand, Magritek Ltd., Wellington, New Zealand Fluids confined in reservoir rocks may differ significantly in their properties depending on temperature or pressure [1,2]. Here we report on a setup allowing to saturate and flood rock cores under reservoir conditions in the laboratory. To this end a commercial pressure cell (Daedalus Innovations LLC), compatible for the use with NMR, was assembled within a 2 MHz NMR Rock Core Analyzer (Magritek Ltd.). This setup allows for temperatures of up to 150○C and a pressure of up to 6000 psi. We implemented relaxation measurements to obtain spatially resolved 1D T1 and T2 distributions [3,4]. Both methods enable one to obtain resolved pore scale information along the rock core axis. Moreover, when applying the two methods subsequently it allows one to investigate the heterogeneity of rock samples based on the differences of T1 and T2 distributions in each slice. Different fluids saturating and flooding rock cores at the same time may be discriminated by their molecular mobility. Therefore, the diffusion coefficient (D) was added as an additional dimension for the case of the aforementioned T2 imaging method as shown in Fig. 1. This allows to distinguish different fluids (flowing or resting) while changing experimental parameters such as temperature or pressure, ultimately leading to a better understanding of the flooding process.