Core analysis with emphasis on carbonate rocks — quality assurance and control for accuracy and representativeness

Abstract

Accurate and representative core data should be used as the ground truth in formation evaluation, reservoir surveillance, and other relevant geoscience applications because the measurements are more direct than estimations from other petrophysical measurements such as logs. To ensure accuracy and representativeness, the rock and fluid samples should represent the reservoir; test conditions, test equipment, and test procedures need to be fit for purpose. In addition, the core analysis program should satisfy clearly defined objectives, which, unfortunately, is not generally applied in the industry. In this paper, we discussed general core analysis data quality assurance and control, with emphasis on carbonate core analysis when applicable. We started with recommended workflows for coring and coring fluid selection, conducting routine and fit-for-purpose special core analysis tests, and core analysis fluid selection and preparation. We then provided some tips and potential pitfalls useful to know in core analysis data quality assurance and control, including core sample screening and selection, criteria used in core sample cleaning and drying, and potential issues related to test conditions and procedures. We also illustrated applications of quality-controlled core data in formation evaluation and reservoir surveillance.