Testing and Application of a Probe Permeameter in the Lower Wilcox Formation, Onshore Texas, USA

Permeability is an important characteristic for reservoir characterization and fluid flow modeling. Besides the more conventional sampling by core plugs and whole cores for measurements, the probe permeameter (sometimes called a mini-permeameter) has provided an alternative, nondestructive method to assess permeability. Application of the probe permeameter, however, may require some care before useful results can be obtained. In this study, we describe the testing and modifications of a commercially available probe permeameter. We identify some limitations and propose two modifications. With the modified device, a core from the Lower Wilcox Formation, onshore Texas, USA, is evaluated for the purposes of assessing CO2 injectivity and trapping in the formation. We find that systematic testing of the probe improved understanding of its response and offers a guide for evaluating any probe permeameter. Problems reported in a prior published study can be remedied, making the probe a reliable device that can measure permeabilities in the range of 0.023 to 760 md. We found problems caused by surface impairment, likely due to the long-term storage of the studied core, which reduced probe permeabilities in the more permeable intervals. We devised an adjustment to the readings to address this issue. We find grain size to be a major control of permeability in the non-marine section of the core (e.g., the fluvial-dominated distributary channels), but grain size has a weaker effect on the marine intervals (e.g., the wave-dominated delta front). CO2 injectivity is predicted to be best in the non-marine intervals (i.e., fluvial facies), but trapping is likely to be modest. Better trapping but reduced injectivity is expected to occur in the marine intervals.