Petrophysics of Lower Cretaceous Platform Carbonate Outcrops in Provence (Se France): Implications for Carbonate Reservoir Characterisation

Abstract

High resolution petrophysical analyses were carried out on Urgonian (Lower Cretaceous) carbonates from outcrops in Provence, SE France. Porosity and permeability were measured on 541 plug samples selected from grain‐supported carbonates analogous to those in the age‐equivalent Shu'aiba and Kharaib Formation reservoirs in the eastern Arabian Plate. The sampling strategy allowed property heterogeneities from centimetre to kilometre scales to be investigated, as well as correlations between porosity and permeability in several different reservoir rock types. Property spatial modelling sensitivity analyses were also undertaken. The relative abundance of microporosity, grain size and sedimentary‐diagenetic anisotropy were the main geological parameters which controlled the petrophysical characteristics of the grainstones studied. Increasing microporosity decreased permeability but resulted in an increase in the homogeneity of the reservoir rocks and therefore in their predictability. An increase in grain size, from fine sand to gravel, and in the amount of intergranular pores, enhanced permeability significantly but resulted in a decrease in the homogeneity (and therefore predictability) of the reservoir rock. At a plug scale, poro‐perm relationships are very good and can be used predictively for fine grainstones dominated by microporosity; but relationships are moderate to weak for coarse rudstones with mixed pore types, including intraskeletal pores. In grainstone units, weak sedimentary anisotropy, such as decametre‐scale cross‐bedding, did not prevent the prediction of the horizontal property distribution from vertical data over a few hundreds of metres. In these units, the lateral correlation of rock properties follows periodic variograms with a 7 m wavelength. The lateral distribution of properties in coarse‐grained and heterogeneous rudstones with complex pore types and intense sedimentary heterogeneities, such as channel structures, was however more difficult to predict from a vertical data set. Upscaling poroperm data from plug scale to reservoir scale is linear in the case of grainstones with intergranular microporosity, but is non‐linear in the case of skeletal rudstones with coarser pore types including skeletal porosity.

The equivalent pore aspect ratio as a tool for pore type prediction in carbonate reservoirs

“…In terms of age, depositional environments and facies, pore types and reservoir properties, the Urgonian limestones from Provence are considered as relevant outcrop analogues of some Middle East carbonate reservoirs such as those of the Thamama, Kharaib and Shuaiba formations (Borgomano et al, 2013). Urgonian limestones from Provence are dominantly microporous (Fournier et al, 2011), but moldic and intergranular porosity may also represent a significant proportion of the pore volume in such reservoirs (Borgomano et al, 2013;Fournier et al, 2014).…”

“…Urgonian limestones from Provence are dominantly microporous (Fournier et al, 2011), but moldic and intergranular porosity may also represent a significant proportion of the pore volume in such reservoirs (Borgomano et al, 2013;Fournier et al, 2014). A scenario of the pore space evolution in the Urgonian limestones from Provence (SE France) has been proposed by Leonide et al (2014): 1) microporous limestones have been interpreted to develop by micrite neomorphism processes in a meteoric shallow-burial setting probably during a regional subaerial exposure event (Albian-lower Cenomanian); 2) tight limestones resulted from an early marine and/or meteoric cementation of the intergranular macropores and intercrystalline micropores and 3) dissolution of aragonitic shells occurred during early (syn-Urgonian) phases of subaerial exposure whereas a later phase of leaching of possible telogenetic origin led to microporosity enhancement and moldic/vuggy porosity development.…”

Depositional Facies, Pore Types and Elastic Properties of Deep‐water Gravity Flow Carbonates

“…Depositional and diagenetic processes are known to strongly control the pore space architecture in carbonate rocks, and therefore the velocity-porosity relationships and the permeability-porosity relationships (e.g. Anselmetti and Eberli, 1993;Borgomano et al, 2013). The large scatter of velocity and permeability values at a given porosity in carbonate rocks makes it difficult to determine reservoir models from seismic inversion methods.…”

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

“…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). The giant oil resources discovered in such microporous reservoirs motivated significant efforts to understand their genesis and evolution (Volery et al, 2010;Deville de Periere et al, 2011), highlighting the importance of unraveling the origin and timing of microporosity formation and stabilization.…”