Flow Unit Characterisation in the Permian‐triassic Carbonate Reservoir Succession at South Pars Gasfield, Offshore Iran

Abstract

The South Pars gasfield (offshore southern Iran) has been investigated in detail in recent studies in terms of depositional, diagenetic and reservoir properties of the Permian-Triassic carbonate succession. In the present paper, a variety of flow unit approaches were applied to identify reservoir (flow) and non-reservoir (baffle or barrier) units within the Permian-Triassic carbonates. The zonation scheme was based on three approaches; (i) flow units were identified using the stratigraphic modified Lorenz plot (SMLP) method; (ii) hydraulic flow units were identified using a parameter known as the flow zone indicator (FZI); and (iii) petrophysical flow units (PFUs) were determined using the pore throat radius (R 35 ) and water saturation (S w ) parameters. Studies of flow units at both macro-and micro-scales showed that flow properties were controlled by both depositional and diagenetic features. In order to construct a reservoir flow model, the flow units and PFUs were correlated between the four wells studied within a sequence stratigraphic framework. SMLP-derived flow units appeared to be distributed homogenously within the reservoir succession resulting in a layer-cake architecture. By contrast, the FZI-derived hydraulic flow units drew attention to the presence of small-scale heterogeneities within the reservoir. A comparison between these methods showed that the flow model derived from PFUs included greater vertical and horizontal heterogeneities, especially in the Upper Dalan Member (upper K4 reservoir unit). This was due to depositional/diagenetic heterogeneities in both lateral and vertical directions, and the parameters applied in the PFU method. The PFU-derived flow model showed a closer relationship to the actual reservoir performance than the flow units derived by the other methods and can therefore be used as the basis for future dynamic flow simulation.

Geologically based integrated approach for zonation of a Late Jurassic–Early Cretaceous carbonate reservoir; a case from Persian Gulf

“…Despite high complexity and heterogeneity of carbonate rocks, careful study of controlling reservoir quality parameters plays a very important role in hydrocarbon exploration and production. Generally, factors leading to complexity and heterogeneity in the carbonate reservoir are multidimensional including depositional facies variations, complex diagenetic evolution and their tectonic history (e.g., fracturing) (Dou et al 2011;Rong et al 2012;Enayati-Bidgoli et al 2014;Mehrabi et al 2015). Porosity values less than 5% barely make hydrocarbon reservoirs and 0.1 millidarcy is the minimum permeability for oil production (Lucia 2007).…”

Diagenetic impacts on hydraulic flow unit properties: insight from the Jurassic carbonate Upper Arab Formation in the Persian Gulf

“…Generally, heterogeneity in carbonate reservoir is forged by the geological context including depositional, diagenetic and pore characterizations which influenced FZI values (Burrowes et al 2010;Enayati-Bidgoli et al 2014;Sfidari et al 2014;Nabawy 2015). Here, using the normal cumulative probability of log FZI, numbers of hydraulic flow units could be determined (Abbaszadeh et al 1996).…”

“…These could lead to a better understanding of reservoir property distribution, resulted from the heterogeneity of carbonate reservoirs. Constructing a two-dimensional model provides a predictable scheme of geological aspects (especially diagenesis), which depicts the reservoir characteristics variation (Rahimpour-Bonab et al, 2012;Enayati-Bidgoli et al, 2014;Mehrabi et al, 2015).…”

Petrophysical Evaluation of a Severely Heterogeneous Carbonate Reservoir; Electrical Image Logs Usage in Porosity Estimation

“…In the northern Arabian Plate, the Permian-Triassic successions are dominated by thick shallow-marine carbonate-evaporite sediments which developed on a passive margin of Gondwana [22]. In the studied field, the Dalan and Kangan formations geometry is stratiform or "layer-cake" [23]. In south of Iran, the Permian-Triassic succession is referred to as the Dalan and Kangan formations ( Figure 1) which are equivalents of the Khuff Formation in the southern Arabian countries [24].…”