Summary
Salt diapirs formed in the Arabian basins are genetically related to Ara salt deposits of Infracambrian Hormuz Group. In Kuwait, diapiric salt bodies are not discernable in seismic. Instead, possibility of salt pillow development at greater depth exists, as is evident from a north Kuwait well. Episodic growth of salt pillows and their spatial movement from deeper to shallower depth through fault conduits manifest structural reliefs in the overlying strata The structures with large relief may be ‘visible’ in the conventional structure maps of the overlying formations whereas subtle ones may appear in the horizon based seismic attributes in the form of anomalies. In this context, some of the circular anomalies mapped in time and other seismic attributes within Triassic and upper Paleozoic sequences in Umm Gudair area, south Kuwait, are analyzed. Lensoidal seismic signatures in association with faults imaged much below these features are attributed to salt pillows. Discrete salt pillows might have formed in the deep-seated Hormuz basin in the area. Their subsequent movement to different stratigraphic levels through reactivated faults could have produced subtle structures in the overlying formations.
Some of the prominent structures explored in Kuwait are devoid of hydrocarbons in Paleozoic reservoirs. Probably these structures suffer from trap integrity, either due to through-going leaky faults or intense fracturing. However, buried structures formed by subdued salt tectonics, such as the ones mapped in the study area, may have hydrocarbon entrapment in the Paleozoics.
Introduction
Deeply buried salt turns into viscous material and starts flowing under suitable pressure, temperature and geological conditions. Initial swelling of salt stock takes the shape of pillow which, in turn, deforms the overlying rocks and sets in differential loading in the system. As the sedimentation continues in the basin, diapiric stage is reached eventually when the low density salt pierces through overlying brittle rock to move to shallow depth.
Salt diapirs and salt-cored structures formed in the Arabian basins are understood to have been sourced by thick Infracambrian-Cambrian Ara salt of Hormuz Group (A.S. A. Shaharan and M.G. Salah, 1997). The surface exposed diapirs in Central Oman consist of Hormuz salt and metamorphic rock fragments that were brought from a depth of 8km or so (Thomas, et al, 2014). Zagros mountain ranges in Iran are known to have many exposed salt domes originated from Hormuz salt basin below (Kent, 1979). In close vicinity to Kuwait, Jabel Sanam salt diapir of South Iraq is situated. K-Ar dating and chemical analysis of surface samples from the diapir suggests their origin to be Hormuz salt (Al-Bassam, 2011).
