Evaluation of Mercury Intrusion and Capillary Pressure Results: Development of a New Methodological Approach for Analyzing Carbonates

Abstract

Mercury injection capillary pressure (MICP) testing of carbonate rocks has been used extensively in industry and academia to evaluate bulk porosity, pore-throat size, and pore-size distributions for the purpose of reservoir characterization. The integration of MICP data into static and dynamic petrophysical flow models has proven to be a valuable tool in maximizing hydrocarbon recovery. However, inaccuracies in MICP results can significantly impact reservoir volume estimates and projected hydrocarbon recovery. This study quantifies differences in MICP-determined petrophysical properties of representative carbonate rock fabrics found within the Silurian Niagaran pinnacle reef complexes of the Michigan Basin. The objectives of this research are to: (i) characterize pore-throat and pore-size distributions using petrographic and MICP testing; (ii) evaluate the observed lack of hysteresis between intrusion and extrusion data; (iii) assess variability in MICP testing methods, like maximum injection pressure and the equilibration time associated with incremental intrusion pressure intervals. Evaluating the effects of equilibration time from 40 seconds (Trial 1) to 100 seconds (Trial 2) at low pressure (0-100 psi) showed substantial variability. Preliminary analysis of patchy macro-pore dominated fabrics in Trials 1 and 2 showed that the bulk porosity determined by MICP changed from 15.8% to 20.1%, and mean pore diameter changed from 3.03 μm to 2.05 μm, respectively. Furthermore, a 3% difference in pore-throat radius (μm), 25% difference in cumulative Hg saturation, and 74% difference in incremental intrusion sampling (mL/g) were observed between Trials 1 and 2. This study demonstrates how different MICP methodologies can affect the accuracy of petrophysical data that are used to populate static and dynamic models, and perhaps more importantly to make predictions about secondary hydrocarbon recovery.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016