The Zagros basin (Iraq) constitutes a rich petroleum province. The Lower Cretaceous Qamchuqa Group comprises one of its major reservoirs. Data from about 30 wells, drilled in a limited sector corresponding to a northwest-southeast anticlinal structure situated in the Kirkuk region, permit analysis of several sedimentological and diagenetic events that led to the formation of this reservoir.

Facies changes took place and divided the structure into three parts: the northwestern part in which neritic facies dominate, the central part in which basinal influence is considerable, and the southeastern part that shows basinal mudstone-type facies.

The Lower Cretaceous carbonate platform in the northwestern part of the study area displays good primary porosity. During the course of burial, high secondary porosity related to dolomitization appeared. However, a major part of the porosity was produced when the reservoir was fractured during the Priabonian after the collision between the Arabian and Eurasian plates.

Lopatin's method suggests that organic matter maturation started during the Turonian (around 90 Ma), whereas most of the maturation developed during the Miocene due to the rapid accumulation of foreland basin sediments containing evaporite facies (lower Fars Formation) followed by the accumulation of thick upper molasse-type sediments from the erosion of the Zagros Mountains. The accumulation of sediments enhanced the total tectonic subsidence. During this period, the relatively brief time spent by the source rock in a given temperature interval was compensated for by a rapid rise in temperature. This late thermal maturation period controlled most of the transformation of the organic matter into hydrocarbons.