Research and scholarship
The Albian clastic reservoir evolution of the east-southeast of the Mesopotamian Basin: Geological Modelling evaluation
The Mesopotamian basin is delineated by two main faults: Abu Jir and Zagros Deformation Front (ZDF). More recent researches suggest new northern continuation for Abu Jir fault that presented new area for the basin, in addition to extending it north-westwards to include Al Jazira area which was considered as a part of Rutba-Al Jazira zone. Rutba-Al Jazira zone was proposed to be the northern part of long-lived N-S trending Hail-Rutba arch, while it has been separated from each other in new studies. In Iraq, Abu Jir fault divided the Arabian platform to an unstable shelf in the east that encloses the Mesopotamian basin and a stable shelf in the west that includes the western desert zone (The previous Rutba subzone). Hence, in the new tectonic division, the Mesopotamian zone consists of three subzones: Basrah subzone in the south, the Mesopotamian subzone in the middle and Al Jazirah subzone in the north. Basrah subzone is characterized by its N-S trend folds that are mainly attributed to Precambrian-Cambrian salt distribution. The Mesopotamian subzone is dominated by two types of NW-SE trending folds: Simple buckle folds and fault-related folds. Al Jazira subzone shows two trends of structures: NW-SE fault-related folds and ENE- WSW trend structures.
To achieve a comprehensive view of the Mesopotamian basin evolution, there are few studies had carried on. The migration of depocenters of Phanerozoic successions inside and outside of the Mesopotamian basin has been suggested that was not clearly explained. However, some studies show the steady westward migration of foreland basins during Cenozoic that eventually formed the Mesopotamian foreland basin in Neogene. In terms of geodynamics, this basin located on the northeast margin of the Arabian plate where Neo-Tethys ocean opened after Late Permian-Triassic rifting. The arc-continent collision of Late Cretaceous initiated Zagros orogeny and resulted in some local foreland basin in parallel to it. The main stage of Zagros orogeny has been started in Eocene by the continent-continent collision that developed the Mesopotamian foreland basin.
In Mesozoic, the main discovered petroleum source rocks and reservoirs of the basin had been formed. Jurassic and Late Cretaceous hosted organic-rich basins that became source rocks later. The variation in the depositional environments during Cretaceous provided good reservoirs within the basin. There are just two clastic formations in the Mesozoic succession that the Albian clastic Nahr Umr formation represents the second deltaic system within the Arabian plate. This formation has a wide distribution in the east and northeast of the Arabian plate. The Arabian shield in the west of the plate was suggested as the main clastic source for this formation. The Albian facies changed to be carbonate-dominated in the east. This formation has been studied in the middle and the south of Mesopotamian basin while the south-east part has been less studied. This Albian clastic formation shows a lateral facies change and a lateral change in reservoir properties in the south-east of the Mesopotamian basin where is less studied. This lateral facies change that has been also recorded in the Aptian carbonate formation, was related to a tectonic activity such as the activity of Tikrit-Baghdad faults, while the continuation of these faults in the project area, the south east of the Mesopotamian basin, has not been proved. This project aims to study and assess this tectonic activity using burial history charts and applying backstripping and then to investigate the depositional environment in sequence stratigraphy concept and recognise its sequences and to find the relationship between the depositional environment and reservoir properties. For this purpose, depth maps, well logs, final well reports and geological evaluation studies for 8 oil fields within the project area, have been provided. Drill cuttings/cores samples also will be provided to study petrography, Quartz and heavy mineral grain size distributions and to analysis sandstone horizons by SEM for identifying their depositional environment and their pores types. Shale horizons will be analysed by XRD to distinguish clay types. Based on well log interpretation, a 3D facies model will be constructed and will compare with the 3D reservoir property model to show the relationship between them.