Abstract
The reservoir characterization and rock typing is a significant tool in performance and prediction of the reservoirs and understanding reservoir architecture, the present work is reservoir characterization and quality Analysis of Carbonate Rock-Types, Yamama carbonate reservoir within southern Iraq has been chosen. Yamama Formation has been affected by different digenesis processes, which impacted on the reservoir quality, where high positively affected were: dissolution and fractures have been improving porosity and permeability, and destructive affected were cementation and compaction, destroyed the porosity and permeability. Depositional reservoir rock types characterization has been identified depended on thin section analysis, where six main types of microfacies have been recognized were: packstone-grainstone, packstone, wackestone-packstone, wackestone, mudstone-wackestone, and mudstone. By using flow zone indicator, four groups have been defined within Yamama Formation, where the first type (FZI-1) represents the bad quality of the reservoir, the second type (FZI-2) is characterized by the intermediate quality of the reservoir, third type (FZI-3) is characterized by good reservoir quality, and the fourth type (FZI-4) is characterized by good reservoir quality. Six different rock types were identified by using cluster analysis technique, Rock type-1 represents the very good type and characterized by low water Saturation and high porosity, Rock type-2 represents the good rock type and characterized by low water saturation and medium–high porosity, Rock type-3 represents intermediate to good rock type and characterized by low-medium water saturation and medium porosity, Rock type-4 represents the intermediate rock type and characterized by medium water saturation and low–medium porosity, Rock type-5 represents intermediate to bad rock type and characterized by medium–high water saturation and medium–low porosity, and Rock type-6 represents bad rock type and characterized by high water saturation and low porosity. By using Lucia Rock class typing method, three types of rock type classes have been recognized, the first group is Grain-dominated Fabrics—grainstone, which represents a very good rock quality corresponds with (FZI-4) and classified as packstone-grainstone, the second group is Grain-dominated Fabrics—packstone, which corresponds with (FZI-3) and classified as packstone microfacies, the third group is Mud-dominated Fabrics—packstone, packstone, correspond with (FZI-1 and FZI-2) and classified as wackestone, mudstone-wackestone, and mudstone microfacies.
Highlights
The key topic of rock typing is to capture the relationship between petrophysics and geology, and rock type might be reflected as a petrophysically and geologically homogeneous rocks group with characteristic relationships between
Depositional environments are important to the performance of the reservoir as they have a dominant influence on the original pore network of newly deposited sediments, the pore network formation determines the characteristics of the framework grains, such as grain size and sorting, and all these parameters in turn control porosity and permeability; textural features supporting good reservoir quality of a reservoir are coarse-grained sediments with good sorting (Jumat et al 2018)
Six rock types were identified by cluster analysis technique, can be considered as depositional microfacies types (Figs. 14, 15): 1. Rock type-1 represents the very good type and the best rock type, and this type of rocks is characterized by low gamma ray, water saturation, and high values of neutron, sonic, and Rt higher from Rxo and high porosity, can be classified as packstone-grainstone microfacies
Summary
The key topic of rock typing is to capture the relationship between petrophysics and geology, and rock type might be reflected as a petrophysically and geologically homogeneous rocks group with characteristic relationships between. Flow unit is a pore scale method for classification of rock types relative to flow properties based on geological parameters and flow physics, and identifying the flow units has a significant role in flow transmissivity and storage which can be helpful in secondary recovery and more production of the reservoir (Mahjour et al 2016). The reservoir quality of carbonate rocks is usually controlled by the interplay of both the primary depositional and secondary diagenetic parameters. Yamama Formation is one of the giant reservoirs within south part of Iraq, is carbonate heterogeneous reservoir, deposited through the Lower Cretaceous period, within main retrogressive depositional cycles (Berriasian-Aptian) (Buday 1980). Yamama carbonate reservoir in the south of Iraq has been chosen to investigate the reservoir characterization, and many approaches and methods were used to investigate the reservoir characterization and Quality Analysis of Carbonate Rock-Types; these approaches involve: 1.
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