Occurrence And Relationship Of The Aqra, Bekhme And Govanda Formations In The Soran (Rawanduz) Area, Kurdistan Region, Northeastern Iraq

The present study focuses on the presentation of field and laboratory evidences for the first record of the Aqra Formation (Maastrichtian) outcrop at the top of the Tanjero Formation in the Soran area, Erbil Governorate. The previous studies indicated its outcrops as Middle Miocene Govanda Formation between Merga Red Bed Series and Tanjero Formation. The present study discusses relations of this outcrop with Govanda and Bekhme formations in the Sulaimani and Duhok governorates in terms of environment and tectonics. In the Soran area, the formation has variable thickness ranging between 2-160 m and underlies either Red Bed Series or Govanda Formation (Middle Miocene). The study documented many stratigraphic and paleontological evidences to prove occurrence of the Aqra Formation in the area. Additionally, we discussed the significance of its occurrence in detail by which many tectonic and stratigraphic issues of the area are unlocked. One of the issues is occurrence of Tanjero Formation between the Aqra and Bekhme formations and it separates the two formations in two different age ranges and tectonic episodes. Another issue is the documentation of the occurrence of the Aqra Formation inside the Thrust Zone by which the distribution of the formation is extendable beyond Main Zagros Thrust Fault. The study includes a detailed stratigraphic column and tectonic model of the formation to show the coastal area, patchy reef, and shelf environment of the Aqra Formation

Petroleum System Modelling of the Akri-Bijeel Oil Field, Northern Iraq: Insights From 1-Dimensional Basin Modelling

The petroleum system of the Akri-Bijeel oil field shows that the Palaeogene formations such as the Kolosh Formation seem to be immature. However, the Jurassic–Lower Cretaceous source rocks such as those from the Chia Gara, Naokelekan, and Sargelu formations are thermally mature and within the main oil window because their vitrinite reflectance (Ro%) values are >0.55%. The Triassic Kurra Chine and Geli Khana formations are thought to be in the high maturity stage with Ro values ≥1.3% and within the wet and dry gas windows, whereas the older formations are either within the dry gas zone or completely generated hydrocarbon stage and depleted after the hydrocarbons were expelled with subsequent migration to the reservoir rock of the structural traps

Abnormality of geothermal gradients in Iraqi western desert inferred from borehole temperatures

Geothermal gradient is an important tool in petroleum exploration and critical to several reservoir evaluations. Borehole Temperature data from 14 wells are utilized to find the geothermal tendency of the Western Desert in Iraq. The discrepancies in geothermal gradients throughout the area are a consequence of variability of sediment's thermal conductivity, direction of groundwater flow, fault pattern, and heat generation. High value converts liquid hydrocarbon to dry gas and low value will not help organic matter to reach maturity level. The lowest gradient within the units above Palaeozoic Era's section is 12.2 °C/km for well KH-9/7 in the eastern part of the area and the highest is 31.3 °C/km for well KH-5/4 in the middle part of the region. Whereas, the highest geothermal gradient which is 61.0 °C/km within the Palaeozoic section is recorded within Akkas Formation in 2100-2350 m subsurface. The mean geothermal gradient in Western Desert is 26 °C/km within the units younger than the Palaeozoic, but this average rises up to 40 °C/km within Palaeozoic units due to existence of Silurian hot shales and heat flow from the Proterozoic section especially from Halaban Group andesites

Geothermal gradients in Iraqi Kurdistan deduced from bottom hole temperatures

Bottom hole temperature (BHT) data from 12 oil wells in Iraqi Kurdistan were used to obtain the thermal trend of Iraqi Kurdistan. Due to differences in thermal conductivity of rocks and groundwater movement, variations in geothermal gradients were observed. The highest geothermal gradient (29.2 °C/km) was found for well Taq Taq-8 in the Low Folded Zone (central part of the area). The lowest geothermal gradients (14.9 °C/km) were observed for well Bekhme-1 in the High Folded Zone (northern and northeastern parts of the area). The average regional geothermal gradient for Iraqi Kurdistan is 21 °C/km

Multiple linear regression approach for the vitrinite reflectance estimation from well logs: A case study in Sargelu and Naokelekan Formations – Shaikhan-2 Well, Shaikhan oil field, Iraq

The sonic and resistivity logs for Sargelu and Naokelekan Formations in well Shaikhan-2 are utilized to predict vitrinite reflectance values. The precise prediction of vitrinite reflectance can be done based on well logs by applying multiple linear regressions method. This method is an extension from the regression analysis, which incorporates independent values to predict a dependent value. It is expected that both sonic and resistivity log readings in source rock that has reached oil window and hydrocarbons are cooked out of that, to be higher than source rock that is still in diagenesis stage and has not produced any oil and gas. Possible mechanisms to explain decreasing resistivity with increasing maturity include the existence of a conductive petroleum phase (pyrobitumen) and the increase in residual water salinity driven by water vapor solubility in the produced gas. The best matching between the vitrinite reflectance measured from the cutting samples and the vitrinite reflectance predicted from the log data in the well Shaikhan-2 has achieved. Keywords: Shaikhan-2, Sonic log, Resistivity log, Vitrinite reflectance, Multiple linear regression, Sargelu Formation, Naokelekan Formatio