Structural Study of the Late Oligocene-Early Miocene Sequence in Khabaz Oil Field, NE of Iraq

Abstract

Khabaz Oil Field is located in Kirkuk, about 20 Km southwest of Kirkuk City between Jambour and Bai Hassan oil fields. Tectonically, it is located on the Unstable Shelf within the Low Folded Zone (Zagros Fold Belt). Six wells in Khabaz oil field with two seismic lines (Line K8 and KK54) are used to conduct the geometric analysis, which include the description of fold and fault systems for the purpose of understanding the structural setting of Jeribe (Early Miocene) and Azkand (Late Oligocene) formations in this field. Khabaz structure is a double plunging positively inverted subsurface asymmetrical anticline influence the whole pre-Holocene sedimentary sequence. The interlimb angle of this structure ranges between 137º to 151º which is classified as a gentle anticline. The dip values of the axial surface range between 82 – 84º, so it can be classified as an upright fold with a general trend NW-SE. The core of the anticline is bounded by two high angle dipping reverse fault splay dipping toward each other. These faults pushed the core of the anticline upward with respect to the limbs of the structure. The Southwestern limb is affected by several high angle inverted faults that were possibly bifurcated from one or two major faults. The Northeastern limb is also influenced by a series of high angle reverse, some are dipping toward the core of the structure and few others are dipping toward the limbs. Some of these faults especially those influenced the southwestern limb of the anticline were inherited from the original normal faults that bounding the graben structure developed during the deposition of the Shiranish Formation. During the Late Plio-Plistocene contraction phase, the sense of slip on these faults were inverted and the faults migrated upward into the Tertiary sequence resulting in the formation of the positively inverted structure.