The current study combined both concepts of structural geology and petrophysical to understand the structural feature of Mishrif Formation and its implication on the petrophysical characterization of the formation in Shuaiba and Rafidhiya Domes (or culminations) in Zubair Field. Shuaiba and Rafidhiya are adjacent domes and these domes belong to the same Field but the domes separated by saddle may related to Basra – Zubair basement fault. The domes have different petrophysical properties of Mishrif Formation; consequently, influenced in water and oil saturation. Therefore, the study tries to understand the structural and petrophysical position of Mishrif Formation of the domes. The structural analysis included geometric and genetic analysis, whereas petrophysical analysis used open hole logs interpretation to determine the petrophysical characteristics (especially the distribution of porosity, permeability, and water saturation. It was  concluded that may a variation in porosity and permeability of Mishrif Formation for Shuaiba and Rafidhiya domes because each dome was formed by a different folding mechanism effected on the petrophysical properties. The structural geology analysis detects that may be Shuaiba dome formed by bending fold mechanism (vertical force of salt structure), while Rafidhiya dome by buckling fold mechanism (parallel force of collision of Arabian and Eurasian plate). These mechanisms may directly be affected in permeability distribution, and consequently on oil and water saturation of Mishrif Formation. Thus, Shuaiba Dome has thinning in hinge area and extensional force leads to create fractures and karst phenomena, and as a result, high permeability in upper Mishrif. On the contrary, Rafidhiya Dome has a thickening feature and there is no indication of karst phenomena and low permeability. Therefore, the Mishrif of Shuaiba dome permeable and oil-saturated, while, it flooded with water in Rafidhiya Dome. The disconnection in reservoir pressure confirmed by difference in initial reservoir pressure of Mishrif Formation of Shuaiba Dome and recent reservoir pressure of Mishrif Formation of Rafidhiya Dome

Nahr Umr oil field is one of the important productive southern Iraqi oil fields. This studyfocuses on the type of fold and faults of the Nahr Umr oil field. A structural analysis(geometric and genetic analyses) performed to identify its type, origin and to find its relevanceto main regional tectonic events. The structural classifications employed well and geophysicaldata through using structure contour maps, cross sections, and seismic section.The structural analysis inferred that fold of Nahr Umr oil field classified as antiform, upright,non-plunge, gentle, supratenous, dome feature, and asymmetrical. The limbs are unequalwhereas the length of left limb shorter than the right limb and its dip is greater than right limb.In addition, the thickness of crest is less than the thickness of limbs. Pattern of faults classifiedas compound, parallel, conjugates and radial with graben structure and these faultsconcentrated on crest of fold. The fold axis is almost N-S at early cretaceous and then clearlyturns to NW-SE and this may due to counterclockwise rotation of Arabian plate. Geophysicalinterpretations and results of structural analysis stated that Nahr Umr oil field formed by threecombined forces which are tectonic movements, reactivated basement, and salt structures.

Mishrif formation is the one of the most important reservoir in Southern – Iraq   and the injection water important to support the reservoir pressure. The current study combined the interpretations of PLT, structural geology and petro-physics to understand the distribution of the injection rate for nine injection wells to the  Mishrif Formation in Shuaiba Dome (or culmination) - Zubair Oil Field. PLT analysis calculated injection rate for Mishrif Formation, structural analysis included geometric and genetic analysis, whereas petrophysics analysis used open hole logs interpretation and core data for the injection wells to determine the petro-physics characteristics (especially the distribution of porosity and permeability). The current study concluded that the injection rate, porosity and permeability of Mishrif Formation distributed unequally across it. This variation is almost regular, whereas the Upper Mishrif more than Lower Mishrif, while Middle Mishrif get the least value. The thickness of Lower Mishrif more than Upper Mishrif. This may affected by a folding mechanism due to tectonic activity (reactivated basement faults and Hormuz salt structures).

No abstract

No abstract