U-Pb dating of calcite cement and diagenetic history in microporous carbonate reservoirs: Case of the Urgonian Limestone, France

Nicolas Godeau,Philippe Leonide,Abel Guihou,Axel Gerdes,Pierre Deschamps,Jean-Pierre Girard,Anthony Tendil,Bruno Hamelin

doi:10.1130/g39905.1

Nicolas Godeau, Philippe Leonide + Show 6 more

Open Access

PDF Available

https://doi.org/10.1130/g39905.1

Copy DOI

Export

Save

Cite

Abstract
Highlights/Summary
Full-Text PDF
Similar Papers

Abstract

Listen

Abstract Microporous carbonates can constitute excellent hydrocarbon reservoirs if their micropore and/or nanopore structure is sufficiently developed and continuous. In such deposits, assessing the exact timing of reservoir property stabilization is critical to better understand the postdepositional processes favorable to the creation or preservation of porosity. However, placing reliable and accurate chronological constraints on the formation of microporosity in these reservoirs is a major challenge. In this study we performed absolute U-Pb dating of calcite cements occurring in the Urgonian microporous limestone (northern Tethys margin) of southeastern France. U-Pb ages ranging between 96.7 ± 4.9 Ma and 90.5 ± 1.6 Ma were obtained on the major calcitic phase responsible for the cementation, and therefore the stabilization of microporosity, indicating that this diagenetic process occurred synchronously at the regional scale following an extended subaerial exposure. Our results show that (1) the mineralogical stabilization process responsible for the formation of an excellent pervasive microporous network took place relatively early, and (2) the so-acquired reservoir quality was preserved for more than 90 m.y. These observations emphasize the importance of long exposure periods and associated meteoric influx for the formation and preservation of good microporous reservoirs.

Highlights

Establishing the relative chronology of diagenetic transformation from thin section petrography is of outmost importance but it is not sufficient to link the evolution of petrophysical properties in reservoirs with basin-scale structural and burial events in a proper temporal framework
Recent development of U-Pb dating of carbonates by laser ablation– inductively coupled plasma–mass spectrometry (LA-ICP-MS) applied directly on thin sections or slabs opened a wealth of possibilities with which to date calcite-cemented fossils (Li et al, 2014), calcite-filled veins (Coogan et al, 2016; Roberts and Walker, 2016; Nuriel et al, 2017) or paleosols (Methner et al, 2016)
In our study we combined the advantages of the two approaches, the rapid identification of appropriate samples by use of the laser ablation technique and the accuracy of isotope dilution to obtain robust absolute ages on the formation of microporosity in a typical micritic carbonate formation

Summary

Introduction

Establishing the relative chronology of diagenetic transformation (paragenesis) from thin section petrography is of outmost importance but it is not sufficient to link the evolution of petrophysical properties in reservoirs with basin-scale structural and burial events in a proper temporal framework. The studied samples belong to the Urgonian Limestone (UL) formation of Barremian–Aptian age located in southeastern France (Fig. 1), considered to be a good analog of major microporous carbonate reservoirs in the Middle East (Borgomano et al, 2013).

Results

Conclusion