Porosity and Permeability in the Silurian Lockport Group and Salina Group A-1 Carbonate

Presented by Shuo Sun, PhD, Western University Presented at EPEX 2022: OPI 59th Conference and Trade Show was presented May 31, 2022. For conference details and to download the full program: http://www.ontariopetroleuminstitute.... The Lockport Group comprises stacked carbonates in ascending order: Gasport, Goat Island, Eramosa, and Guelph formations. These carbonates are amongst the most economically significant sedimentary rocks in southern Ontario because in the deeper subsurface they are significant oil/gas plays and natural gas storage reservoirs. This succession is overlain by the evaporitic-carbonate Salina Group strata that comprise, in ascending order: A-1 Unit (A-0 Carbonate, A-1 Evaporite, A-1 Carbonate), and overlying A-2 Carbonate, forming a self-sourcing hydrocarbon play together with the Lockport Group. New mapping results indicate that pinnacle structures and inner-pinnacle karst in this carbonate succession developed in a broad inner ramp transitioned east- and southeast-ward into mid-ramp and more open marine environments. Porosity and permeability analyses are examined from 150 cored petroleum wells stored in the Oil, Gas and Salt Resources Library (OGSRL), including three located in the subsurface of inter-pinnacle karst zone, 54 within the pinnacle structures in carbonate ramp and 93 in the restricted to open marine, inner-middle carbonate ramp. The datasets comprise 11,759 validated porosity and vertical and/or horizontal permeability analyses, derived primarily from the dolostones of Guelph Fm and dolostones/limestones of A-1 Carbonate. Dolomitization is interpreted to have been caused by circulation of hyper-saline marine water prior to the deposition of A-2 Anhydrite. Regional porosity and permeability distribution trends indicate strong correlation with lithofacies, paleo-karstic zones and dolomitization. Carbonates in the inter-pinnacle karst have relatively high porosity and permeability with pore systems dominated by irregular, karstic vugs and interparticle and intercrystalline microporosity resulting from fabric-preserving dolomitization and/or paleo-karstification. Calcite-cemented dolostone as karst rubbles are very common in the Guelph Formation with sharp and irregular contact with the highly dolomitized mudstone matrix. Although these dolostones have non-fabric selective vugs, pores appear to be effective for fluid flow by the enclosing microporosity systems, as indicated by their relatively high permeability. Within pinnacle structures, the dolostones in Guelph and A-1 Carbonate formations show wide variation in porosity and permeability possibly due, in part, to the heterogeneity of lithofacies and diagenetic fabrics. Porosity types include irregular, cm-sized vugs along karstic conduits and interparticle and intercrystalline micro-porosity enhanced by dolomitization. These carbonates show good porosity-permeability correlation. In the variably karstic carbonate bank and platform settings, porosity-permeability in Guelph to A-1 Carbonate show a general decrease from southwest to northeast. In oil/gas pools in western Lake Erie, the higher porosity is controlled by biohermal facies and dolomitization of the Guelph and Goat Island formations. Cavities, vugs and intercrystalline porosity dominate the system. The fabric-preserving dolomitization may have been controlled by diagenetic fluids (modified marine water). Northeastwards, the relatively lower porosity may indicate fabric destruction during early diagenesis under open-marine conditions. --------------------- Ontario Petroleum Institute http://www.ontariopetroleuminstitute.com OGSR Library Website: http://www.ogsrlibrary.com Twitter:   / ogsrlibrary   Instagram:   / ogsrlibrary   Facebook:   / oilgasandsaltresourceslibrary   Linkedin:   / ogsrlibrary   All information contained herein is provided to users "as is". In no event shall OPI, OGSR Library or any third parties mentioned in the video be liable for any damages whatsoever (including, without limitation, direct, incidental or consequential damages, lost profits, or damages resulting from lost data or business interruption). Before acting on the information in this video you must verify it with a competent authority. Mention of various companies or governments in any video does not constitute an endorsement by these entities. With Thanks to: Shuo Sun (presenter) Matt Dupont (video editor) Ben “DJ Benane” Somers (original soundtracks)