This work explores a probabilistic modeling workflow and its implementation targeting CO

Carbon dioxide (CO

Since the carbonate–clay buffering system is a reversible process, the CCR mechanism may act either as a CO

Outline of the two possible alternative scenarios according to the conceptual approach proposed in

The study of

Location A in Fig.

Location B corresponds to large depths. High temperature values that are expected to take place at such locations tend to remarkably shift the equilibrium towards the right-hand side of the CCR reaction, a high amount of CO

Otherwise,

These aspects are fully recognized by

In this context, an appraisal of this probabilistic approach considering a fully three-dimensional scenario with the ensuing quantification of the amount of CO

The study is structured as follows.
Section

The reference system considered in this study is a three-dimensional realistic sedimentary basin with a deposition history spanning a temporal window of 135 Ma (millions of years before present) and characterized by the deposition sequence listed in Table

Sequence of sediments deposited during the 135 Ma of basin deposition history and sediment density.

The basin stratigraphy at the present time (which is taken as

Sketch of the three-dimensional sedimentary basin setting considered at the present time, i.e.,

The geo-history of the basin is reconstructed using the widely tested and documented burial model E-SIMBA™

Figure

Evolution of temperature (

Considering the reference geological setting described above, we investigate separately three differing CCR formulations which can be considered at the basis of CO

Depending on the CCR investigated, we consider a given mineralogical composition of sediments, as listed in Table

Composition of the mineralogical scenarios used for the investigation of the three CCRs considered. The mass of CO

Our study relies on a given model structure, thus neglecting uncertainty in the latter. We rest on the equilibrium-based approach employed by

Given a generic mineral, aqueous or gaseous phase (Ph), it is always possible to describe the speciation in water of mineral phase Ph upon relying on a set of aqueous basis species

We introduce here a generalized CCR formulation in the form of

We can express the equilibrium constant of the CCR (

The partial pressure of CO

Evolution of the mean log

According to the conceptual model of

For a selected observation time (

We provide an estimate of the rate of CO

We tackle probabilistic modeling of the CCRs introduced in Sect.

By relying on the

Figure

Spatial distribution of

Furthermore, our results show that the three CCRs examined yield markedly different ranges of values of

The differences observed in

Figure

Probability density functions (pdfs) of

Similar observations can be made from the sample pdf of

Figure

Mean (

The extent of the impact of the CCR formulations considered on the occurrence of CO

Maximum depth attained at each point of the basin

Our probabilistic workflow documents that the characteristic temperature and pressure associated with the activation of the CCR mechanism are driven by (a) the considered CCR formulation and (b) the mineralogical assemblage constituting the buffering systems. Thus, the probability of CO

The probabilistic delineation of the source location may profoundly depend on the CCR mechanism employed in the modeling workflow.
This result is of key relevance in light of a subsequent analysis involving modeling of transport, migration, and accumulation of the generated CO

When dealing with subsurface CO

the solution of Eqs. (

starting from the cumulative probability distribution of

a given scenario pp

For the considered time

Figure

Three-dimensional illustration of activation surfaces yielded by pp

Comparison of Fig.

Three-dimensional illustration of activation surface yielded by pp

The overall estimated CO

Mean(

We rely on a probabilistic modeling framework to model CO

Here, we consider a three-dimensional system with a diagenetic history feasibly encountered in a real geological setting.
We analyze the impact of three different CCR formulations and mineral assemblage on (i) the probability of CCR activation as a function of temperature and pressure; (ii) the frequency of activation as a function of depth; and (iii) the shape and extent of the surface delimiting the three-dimensional CO

The temperature and pressure of activation depend on the CCR considered.
Modifying the reference CCR can lead to a markedly different scenario in terms of depth of the source and extent of the activation surface. We rely on geochemical equilibrium and quantify uncertainty associated with model parameters and inputs, the latter source of uncertainty corresponding to the uncertainty in the information required to describe the reference system

We quantify the way the considered input and parametric uncertainty propagates onto estimates of generated mass of CO

We show that the shape of the CO

Data can be accessed at

The supplement related to this article is available online at:

GC performed numerical simulations, contributed to designing the research methodology, analyzed data, created figures, and wrote the first draft; CG contributed to designing the research methodology and contributed data; MDR provided research funding and contributed data; AG supervised the research, contributed to designing the research methodology, discussed the results, and contributed to the writing; GP supervised the research, contributed to designing the research methodology, discussed the results, and contributed to the writing.

Alberto Guadagnini is a member of the editorial board of the journal.

We are grateful to Brian Berkowitz and three anonymous reviewers for their constructive reviews and comments.

The study is financed by the Eni SpA R

This paper was edited by Brian Berkowitz and reviewed by three anonymous referees.