Toward the creation of models to predict static and dynamic fault-seal potential in carbonates

Abstract

In contrast to faults in clastic reservoirs, rules to predict the exploration and production timescale fault-seal potential in carbonates are lacking. This paper provides a summary of carbonate reservoirs with cross-fault column height differences that represent examples of apparent static fault seal, and a summary of observed examples of dynamic fault seal in carbonate reservoirs and aquifers. These include cross-fault differences in water table depths across carbonate–carbonate juxtapositions, cross-fault pressure differences in carbonate aquifers separated by faults, production-induced cross-fault pressure differences in carbonate hydrocarbon reservoirs, sealing behaviour of faults in carbonate reservoirs inferred from well tests, and examples of low fault transmissibilities from history-matching exercises from carbonate reservoirs. This paper also documents the range of compositions of fault rocks in carbonates and the range of permeabilities that have been reported from low-permeability fault cores in carbonate fault zones, as well as the implications of the observed range of fault permeabilities in carbonates for sealing behaviours. The purpose of this paper is not to argue that every fault in a carbonate reservoir will seal or will even be capable of sealing. There are, however, enough examples of faults in carbonates that are sealing in a dynamic sense, and in a static sense, that the topic of carbonate fault seal should warrant much more study. Creation of predictive models will ultimately require a considerable amount of subsurface data, but these models should be created.

Fault Core Thickness: Insights from Siliciclastic and Carbonate Rocks

“…This has significant implications for characterizing the sealing potential and transmissivity of faulted rocks. This is particularly important in carbonate reservoirs [27] since there are less studies on fault seal analysis of such reservoirs than siliciclastic reservoirs. Therefore, in this study, we aim to characterize the fault core and constrain its boundaries by identifying the fault rocks enveloped within the fault core in both siliciclastic and carbonate rocks.…”

Diagenetic evolution of fault zones in Urgonian microporous carbonates, impact on reservoir properties (Provence – SE France)

“…However, they have heterogeneous properties depending on sedimentary, structural and diagenetic factors, inducing high variability of the reservoir permeability (Bruna et al, 2015;Deville de Periere et al, 2011Eltom et al, 2018;Florida et al, 2009;Hollis et al, 2010). Fault zones in carbonates play an important role on reservoir properties (Agosta et al, 2010(Agosta et al, , 2012Caine et al, 1996;Delle Piane et al, 2016;Ferraro et al, 2019;Knipe, 1993;Laubach et al, 2010;Rossetti et al, 2011;Sinisi et al, 2016;Solum et al, 2010;Solum and Huisman, 2016;Tondi, 2007;Wu et al, 2019). Fault zones are complex structures composed of the host rock (undeformed protolith), the damage zone and the fault core (Caine et al, 1996;Logan, 1986, 1987;Hammond and Evans, 2003).…”

“…CC BY 4.0 License. Evans et al, 1997;Molli et al, 2010;Reches and Dewers, 2005;Sinisi et al, 2016;Solum and Huisman, 2016), or mixed zones (Matonti et al, 2012) depending of their architecture and diagenetic evolution.…”

Investigating the controls on fault rock distribution in normal faulted shallow burial limestones, Malta, and the implications for fluid flow

“…Understanding fault rock distributions requires quantifiable physical parameters, such as fault rock thickness (FRT) and fault rock continuity (FRC). Empirical relationships between fault displacement and FRT, recorded from a combination of field and subsurface core studies, enables the prediction of FRT for any fault of known displacement (Hull, 1988;Wibberley et al, 2008;Childs et al, 2009;Solum and Huisman, 2017). This data is directly applicable to the estimation of fault sealing potential over production timescales through the use of transmissibility multipliers (Manzocchi et al, 1999).…”