Amer Jassim Al-Khafaji

This study presents an in-depth reservoir properties of the Zubair Formation in the Luhais Oil Field in southern Iraq. Geologically speaking, the formation is situated in the Thamama Group, which is part of the Early Cretaceous Eighth Megasequence (AP8). By integrating wireline log data with 3D structural and petrophysical modeling, the study evaluates the reservoir's spatial heterogeneity and storage capacity. Sandstone intervals with adjacent shale successions comprise most of the Zubair Formation, which has been split into three members and four distinct reservoir units. The upper sand member is the primary interval that contains hydrocarbons, according to the analysis results. Based on petrophysical analyses, the sandstone-dominated Units A and C have good reservoir quality, with moderate-to-high permeability levels between 76 and 328 mD and porosity values between 15% and 25%. Also, these units show quite low water saturation (0.22–0.37), suggesting a high potential for hydrocarbon accumulation. On the other hand, due to their high water saturation and low permeability, Units B and D which have a high shale content act as non-reservoir intervals; these intervals are thought to serve as both hydraulic barriers and potential source rock facies. The most productive zones are contained within the upper sand member, as confirmed by the developed 3D geological and petrophysical models that successfully define the geographic distribution of these characteristics.

The geotechnical soil investigation in Al-Siba District in southern Iraq for a Gas Power Plant Project reveals soft to very soft silty clay soil with varying elastic moduli values across different depths. The soil is divided into six layers, with modulus values ranging from 342.23 m/sec to 548.02 m/sec and 215.43 m/sec to 307.73 m/sec starting from 1.0 to 24.0 m depths, respectively. The Poisson's ratio and Young's modulus values are found to be between 0.21 and 0.325 in BH.3, with the minimum and maximum values being 74.5 and 171.5 MPa. The study has identified zones of weakness at depths of 5-19 meters based on low N-values (Number of blows). The foundation soil demonstrated the ability to withstand double the design load without settlement. Plate load tests and elasticity theory results aligned closely, indicating allowable bearing capacity values between 13 to 25.5 T/m2. A strong correlation is found between subgrade reaction and permanent deformation moduli. Overall, the site's soil characteristics and gas production potential support the recommendation for implementing the Gas Power Plant in Al-Siba District.

Two electrical resistivity profiles were collected throughout the Transform Electrical Station project site in Dewaniya City. Each 30-meter-long profile consisted of four Vertical Electrical Sounding (VES) stations spaced ten meters apart. Data was collected using the Schlumberger array, deemed most appropriate for the study’s targets. The most incredible fit among observed and theoretical curves was determined after gathering field data, smoothing, and processing with IPI@WIN software. VES curves showed a wide range of kinds, which include AKH, HKH, AKQ, KQH, QHQ, HKH, AKQ, and KQQ, suggesting different subsurface lithologies. Data analysis showed five different resistivity zones at each station, indicating differences in subsurface lithology and water quality. The highest investigation depth was 31.8 meters at station 2 in Zone 5, and the lowest was 0.3 meters at the first station in Zone 1. In a similar vein, the lowest layer thickness was 0.3 meters at Station 1 in Zone 1, and the highest thickness was 22.1 meters at Station 7 in Zone 4. These resistivity results are supported by independent data from soil sampling and laboratory testing. Furthermore, incorporating data from water analyses, including parameters such as Total Dissolved Solids (TDS), pH, saturation, and porosity, as well as groundwater parameters like water table depth and its effect on the nearby river, gives important insights into the measured resistivity variations.

The old land of Iraq is characterized by the presence of many oil seepages that date back to the Babylonian time. During the last few years, the country has witnessed an accelerating pattern of earthquakes that may have activated some of the major old faults and released entrapped hydrocarbons that eventually mixed with groundwater. The recent phenomenon of mixing hydrocarbons with this water has resulted in significant economic losses. Many geochemical analyses were conducted for four samples of oil contaminated with groundwater in the Karbala and Najaf regions and compared them with five samples of seep oil in the Ramadi region and one sample of bitumen extracted from the Lower Fars (Fatha) formation of Kifl-1 oil well, to find out the origin of these oils and to identify potential reservoirs that could hold important undiscovered oil reserves. Results indicate that the groundwater oils were highly mature and originated from Lower Cretaceous carbonate sources deposited under upwelling deep water, anoxic conditions. This is roughly corresponding to the bitumen extract sample of the Lower Fars Formation taken from the Kifl-1 oil well, confirming that these oils belong to the reservoir units in this formation and may therefore contain economically amounts of oil.

The Shiranish Formation is cropped out in several areas in northern Iraq. A stratigraphic and facies study was conducted within the Duhok region to determine the sedimentary environment. Three microfacies, reflecting the various subenvironments within different shelf parts of the deep sea, have been identified within the Shiranish Formation. Four depositional environments are identified: slope, the toe of slope, deep shelf, and deep-sea or cratonic deep basin. The Shiranish Formation in the Duhok region, Northern Iraq, was deposited in an open shelf carbonate platform. The Shiranish Formation sequence is divided into six third-order cycles in the study area. These asymmetrical cycles reflect an imbalance between the relative level of the sea and the production of carbonate, and each one reflects a rise in the sea level following a period of standstill. There is a two-sequence boundary type SB-2 that defines the surface. The Shiranish sequence developed in a high-subsidence area that played the main role in the evolution of the formation. It was deposited on a carbonate platform with high subsidence due to major transgression, wherever the successive sea-level rise and stillstand episodes persist.

A suite of crude oil samples from the Cretaceous reservoirs in Halfaya Oilfield, Southern Iraq were analyzed using organic geochemistry analysis to study their geochemical characterization and origin. High sulfur content (3.74 ± 1 wt.%), C₂₂/C₂₁, C₂₉/C₃₀ hopane, ratios, and low C₁₉/C₂₃ and C₂₄/C₂₃ for all oil samples are indicators of marine carbonate environment source. Low pr/ph, Pr/nC₁₇, Ph/nC18, and highest C₃₅S/C₃₄S ratio are consistent with a more reducing carbonate depositional environment. The C₂₈/C₂₉ sterane ratio and stable carbon isotope analysis values of crude oils are suggested Upper Jurassic to Middle Cretaceous anoxic marine carbonate source origin.

Ten oil samples from the Yamama reservoirs and ten extracts of purported source rocks from sixteen wells in the Mesopotamian Basin, Southern Iraq have been analyzed using GC, GC/MS and Stable Carbon Isotope. Yamama oils were non-biodegraded, moderate to higher maturity based on C₂₇Ts of range from 0.17 to 0.77and TAS3 of 0.3 to 0.63, marine carbonate and marl source rocks, deposited under saline, anoxic conditions. Two oil groups were investigated based on the results of the geochemical analysis. These oils have similarly biomarkers ratios to those of the Middle Jurassic to Early Cretaceous source rocks in the Mesopotamian Basin.