Implications on oil trapping in the Kifl field of Iraq through geophysical investigations

Document Type : Research Paper

Authors

1 Institute of Geophysics, University of Tehran, Tehran, Iran.

2 Directorate of Education of Basra, Ministry of Education, Basra, Iraq.

3 School of Mining Engineering, College of Engineering, University of Tehran, Tehran, Iran.

4 Department of Applied Geology, College of Sciences, University Babylon, Babylon Iraq.

Abstract

Potential field geophysical measurements were conducted at the west of Kifl region in central Iraq to image a plausible oil-trapping reservoir. Ground-based magnetometry and gravimetry surveys were conducted to investigate this region by covering an area of 16  24 km through designing a regular grid spacing of 250 m. After preprocessing potential field data, different filters were utilized to separate the residuals from the regional anomalies. The complicated tectonic setting of the studied area was imaged by recognition of the fault system through simulation of the magnetic and gravity anomalies, where it facilitates the configuration display of the oil-trapping mechanism. The geometry of a fault system was derived from parametric inversion of gravity data. The magnetic anomalies were extended with the trends of NS, NW and NE and reached to a maximum value of 55 nT. However, the gravity anomalies appeared with the same extensions and values ranging from -3.3 to 1.5 mGal. The intense magnetic susceptibility amount of the reservoir rocks is arising from chemical processes and iron-oxide ion replacements, accompanying with the migration and accumulation of hydrocarbon. Incorporating the results from the Euler’s depth estimation, parametric data modeling along with logging data assisted simultaneous modeling of the magnetic and gravity data. The 2D geological model of the subsurface layers at the Kifl area presents a graben-horst fault system within a thick sequence of sediment. Geological characteristics extracted from geophysical data modeling provided insightful information on the nature and essence of the hydrocarbon reservoirs in the Kifl area. It has formed through tectonic deformation and tension over the Arabian plate during Permian – Paleocene cycle. Hence, it can be concluded that aforementioned fault system has clearly divided the hydrocarbon reservoirs.

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