Reservior Characterization of The Hartha Formation, Southern Iraq

Abstract

Well log analysis of selected sections in southern Iraq revealed that primary porosity is the most effective parameters. Secondary porosity seems to be related mainly to dissolution and dolomatization. The Hartha Formation has good water saturation and low production except in the eastern and central part of the study area. Two reservoir units were recognized in Mj-2 whereas only one in Ga-1.
The values of velocity deviation in most wells show high positive deviation, this may indicate relatively high velocity in regard to porosity where pores are commonly not connected such as in interaparticle or moldic porosity. A positive deviation also may indicate low permeability. Negative deviation zone (Only in Ak-1) may represent caving or irregularities of the borehole wall despite the fact that fracture porosity has always been included in the secondary porosity.
The primary porosity of the upper reservoir unit shows a clear increase to the southeast mainly towards the deep outer ramp area where deep and baisnal facies dominated. It is located within the Highstands Systems Tract (HST) where the effect of mixing dolomitization is present. The effective porosity values show little variation in the whole study area with a clear increase eastward.