Research paperA dual-porosity model for evaluating petroleum resource potential in unconventional tight-shale plays with application to Utica Shale, Quebec (Canada)

- Tight-shale reservoir contains mixed pore systems with different origins and distinct physical/chemical properties.
- Conventional method of resource assessment cannot adequately address the complexity of mixed storages in tight-shale reservoir.
- An innovative method is proposed for handling mixed storage for improving resource evaluation in unconventional reservoir.
- Pore type and quantities of resource in each pore system provide information useful for resource development planning.

Unconventional tight to shale reservoirs vary from tight sandstone/siltstone to organic-rich mudstone/shale, commonly with mixed lithologies. In such reservoir systems, matrix pores and organic pores with different origins and distinct physical and chemical properties co-exist for hydrocarbon storage. Traditional resource assessment methods, designed for conventional reservoirs, cannot handle the two pore systems properly. This study proposes a dual-porosity model to respond to the need for a new method in assessing hydrocarbon resource potential in such reservoir systems. The dual-porosity model treats the two types of pores separately and derives the resource estimates from different sources of data, thus better characterizing unconventional reservoirs with complicated pore systems. The new method also has the flexibility of assessing resource potential for the entire spectrum of mixed lithologies ranging from a complete tight to a pure source rock (organic-rich shale/mudstone) reservoir. The proposed method is illustrated through the assessment of the in-place petroleum resource potential in the Upper Ordovician Utica Shale of southern Quebec, Canada. The results of the application suggest that the proposed approach effectively handles the two pore systems in tight-shale reservoirs effectively and provides a useful tool for estimating resource potential in unconventional plays.