Flow units and rock type for reservoir characterization in carbonate reservoir: case study, south of Iraq

Abstract

The current work is focused on the rock typing and flow unit classification for reservoir characterization in carbonate reservoir, a Yamama Reservoir in south of Iraq (Ratawi Field) has been selected, and the study is depending on the logs and cores data from five wells which penetrate Yamama formation. Yamama Reservoir was divided into twenty flow units and rock types, depending on the Microfacies and Electrofacies Character, the well logs pattern, Porosity-Water saturation relationship, flow zone indicator (FZI) method, capillary pressure analysis, and Porosity-Permeability relationship (R35) and cluster analysis method. Four rock types and groups have been identified in the Yamama formation depending on the FZI method, where the first group represents the bad reservoir quality (FZI-1) (Mudstone Microfacies and Foraminiferal wackestone Microfacies), the second group reflects a moderate quality of reservoir (FZI-2) (Algal wackestone-Packstone Microfacies and Bioclastic wackestone-Packstone Microfacies), the third group represents good reservoir quality (FZI-3) (Peloidal Packstone-Grainstone Microfacies), and the fourth group represents a very good reservoir quality (FZI-4) (Peloidal-oolitic Grainstone Microfacies). Capillary pressure curves and cluster analysis methods show four different rock types: a very good quality of reservoir and porous (Mega port type) (FZI-4) (Peloidal-oolitic Grainstone Microfacies) with a low irreducible Water saturation (Swi), good quality of reservoir and porous (Macro port type) (FZI-3) (Peloidal Packstone-Grainstone Microfacies), moderate quality of reservoir (Meso port type) (FZI-2) (Algal wackestone-Packstone Microfacies and Bioclastic wackestone-Packstone Microfacies), and a very fine-grained with bad reservoir quality (Micro port type) (FZI-1) (Mudstone Microfacies and Foraminiferal wackestone Microfacies) and with the higher displacement of pressure). These capillary pressure curves support the subdivision of the main reservoir unit to flow units.

Permeability Prediction in One of Iraqi Carbonate Reservoir Using Statistical, Hydraulic Flow Units, and ANN Methods

“…This revealed that geological conditions corresponded to each other [16], [17]. The equation is simplified if permeability and porosity are measured in millidarcy and fraction, respectively [18].…”

3D Reservoir Rock Type Model Based on Cluster Analysis Technique for Rumaila Formation in the Ahdeb Oil Field, Central Ira

“…Figure (6) shows histograms and cross-plots for the Rumaila Formation groups between the wells used as generated by a k-means cluster analysis. Researchers in [20] were built four rock types and groups which are identified in the Yamama formation depending on the FZI method but in the current study, four rock types were defined and distributed vertically and horizontally among the 10 wells examined depending on Cluster Analysis Technique as shown in Figures (8) and (9).Each rock type is characterized by response of porosity and shale volume as well as microfacies type: The units of Rumaila Formation are characterized by the following:…”

Non-pollen palynomorph and palynofacies assemblages from the Lower Cretaceous of Iraq: A glimpse into palaeobiology and palaeoenvironment

“…It is evident that the Yamama Formation is acting as a series of source-reservoir units in the petroleum system of southern Iraq, indeed, it forms a series of highly productive carbonate reservoirs in many of the super-giant oil fields in southern Iraq (e.g. Sadooni 1993; Aqrawi et al 2010; Abeed et al 2011; Al-Jawad & Saleh 2020).…”

“…The Lower Cretaceous Yamama Formation is one of the main carbonate reservoirs as well as good source rocks in southern Iraq and is equivalent to the Minagish Formation in Kuwait (Aqrawi et al 2010; Al-Khafaji et al 2022). Its facies change both laterally and vertically and it, therefore, acts as a source rock in some locations in southern Iraq, but not in others (Abeed et al 2011; Al-Jawad & Saleh 2020). This study is based on the palynological examination of five subsurface core samples (Table 1) from the Yamama Formation from boreholes R-167, Ru-158, Su-08, and Zb-42 in southern Iraq (Fig.…”