A process-based approach to diagenesis- what is it and can it really help us to reconstruct fluid flow in carbonate rocks

C. Hollis, A. Al Hajri, H. Corlett, M. Frazer, J. Hirani, A. Juerges, R. Newport, D Hodgetts

    Research output: Contribution to conferenceOther

    Abstract

    It is widely acknowledged that diagenetic processes play a fundamental role in determining the volume, shape, size and distribution of porosity in carbonate rocks by dissolution, cementation, mineral transformation, compaction and fracturing. The product of each diagenetic event will be governed by the origin and volume of fluid, its circulation mechanism, the precursor permeability architecture and a spectrum of thermo- and physio-chemical factors.Traditionally, diagenetic studies have considered each of these parameters to a greater or lesser extent within statically-visualised conceptual models. What has been more difficult to visualise is how each event proceeds in time and space. It has also been difficult to test the influence that each diagenetic product has on resultant permeability architecture, and hence the flow and reaction pathways of subsequent fluids. With the advent of new technologies and computing power there is an opportunity to advance our understanding of this feedback mechanism and move towards more predictive diagenetic models. Such a process-based approach to determining the spatial distribution of rock properties, particularly within hydrocarbon-bearing carbonate reservoirs, is gaining popularity.With this in mind, this presentation aims to a) consider what such a so-called process-based approach to predicting the distribution of a diagenetic products actually is, and b) initiate a discussion as to whether it helps to advance our ability to forward-predict both palaeo- and present day fluid flow. Although it seems logical that reconstruction of successive diagenetic events as a function of their hydro-geological regimes should improve our ability to predict rock composition and petrophysical properties, the inherent challenges of multi-scale rock characterisation and geochemical analysis of discrete cement zones can make it difficult to geochemically fingerprint diagenetic products. Furthermore, unravelling a coherent interpretation of often subtly-varying geochemical signatures (eg. differentiating fluid evolution from fluid mixing) and reconstruction of fluid-metal-rock interactions all provide significant challenges that should be rationally assessed and discussed.In order to achieve this, results from a spectrum of studies (discussed in more detail within supporting presentations) will be used. The studies all aim to back-strip the diagenetic history of a range of carbonate successions within the context of their tectono-stratigraphic history, and assess whether it is possible to predict the distribution, geometry and petrophysical properties of their diagenetic products. In addition to field, petrographical, geochemical, petrophysical and structural data, the studies are variably supported by digital outcrop modelling, high resolution imaging of porosity and reactive transport models. These methods should allow us to quantify the shape, size and geometry of diagenetic products. Basin modelling allows reconstruction and mapping of palaeo-pressure and temperature and, by integration of hydrogeological and geochemical rules, forward-modelling of fluid migration and reaction pathways. Preliminary results of a project to test a data-rich conceptual diagenetic model of the Carboniferous of the UK will be presented. What remains to be evaluated is whether such a data-intensive, complex and even nebulous workflow moves us closer to being truly predictive or whether there are simply too many unknowns.
    Original languageEnglish
    Publication statusPublished - Jul 2011
    EventBathurst Meeting of Carbonate Sedimentologists - University of Bristol
    Duration: 12 Jul 201115 Dec 2011

    Conference

    ConferenceBathurst Meeting of Carbonate Sedimentologists
    CityUniversity of Bristol
    Period12/07/1115/12/11

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