A BIG-DATA META-ANALYSIS OF MICROPOROSITY OCCURRENCE IN CARBONATE ROCKS

Microporosity is important because it contributes to reservoir storage in giant oil and gas fields, and it is a likely factor contributing to the longevity of aggregates used in concrete. Due to the recent proliferation of scholarship and the easy access to digital full-text databases, we performed a “big data” meta-analysis of microporosity occurrences reported in the literature to answer the following questions: is microporosity more abundant in limestones or dolostones? In certain types of accumulations (e.g. ramps vs. platforms); depositional environment; depositional textures; allochems; times in geologic history?

Of 162490 online records, 2252 contain reference to microporosity (i.e. the search term “micropo-”) in the full text of the article, while only 84 contain a reference in their title or 190 in their abstract. One-third of the records were abstracts, with the rest representing peer-reviewed literature and conference papers. About one-third of all results related to carbonates. These approximately 700 documents list over 900 stratigraphic units from 58 countries, 85% of which were limestone, and 16% dolostone. Dolostone microporosity is reported more in continental, ramp, and attached platform accumulation types, whereas limestone microporosity is reported more frequently in isolated platforms and pelagic deposits. Dolostone microporosity was reported more often in lake, peritidal and platform interior depositional environments, whereas limestone microporosity more so in margin, slope and basin environments. Relative abundance of microporosity is similar in wackestones and packstones regardless of lithology, but microporous chalks and grainstones are more commonly limestones, while microporous mudstones are more commonly dolostones. In dolostones, microporosity is equally reported in peloids and ooids, but more commonly reported in fossils and less in intraclasts. In limestones it is relatively most reported in fossils, and in declining abundance in ooids, peloids, and intraclasts.

Microporous units were identified from all geological periods of the Phanerozoic. Microporosity reported in the Paleozoic is most commonly from dolostones, while limestone microporosity is more commonly reported since the Jurassic.