Geochemical and Petrophysical Evaluation of the Khuff and Hanifa Formations in the Giant North Gas Field, Qatar

Hanafy M. Holail¹ and Mossbah M. Kolkas^2
1 Dean of the Faculty of Science, Alexandria University, Alexandria, Egypt
² The College of Staten Island of the City University of New York (CUNY), New York

Petrographic analysis of selected core samples from Khuff (Permian-Early Triassic) and Hanifa (Lower Jurassic) Formations indicates that their lithologies were deposited within a tidally influenced shallow-marine environment. The lithofacies of the Khuff and Hanifa Formations mainly consists of a basal sandstone unit overlain by a carbonate grainstone, oolitic dolostone, bioclastic mudstone, and dolomicrite with anhydrite laths.

A sequence of diagenitic modification was recorded as follows: 1) deposition of the original sediments; 2) early dolomitization; 2) late dolomitization; and 3) chemical compaction (stylolitization), and precipitation of pore filling calcite and dolomite. Quantitative- petrophysical analyses of some selected core plugs, using a mercury porosimeteric technique, indicate that the petrophysical parameters including porosity, permeability, recovery efficiency, pore diameters, and fluid saturation vary among the rock formations. These variations are controlled by the diagenetic modifications.

Geochemical analysis of the selected samples reveals that the lithologies of the Hanifa Formation contain high organic matters, high genetic potential, and mature kerogen. These factors made the Hanifa Formation an excellent source for the liquid hydrocarbons. Khuff Formation is considered to be an excellent source for gaseous hydrocarbons because it depicts a low content of organic carbon, very low genetic potential, and very high mature organic matters.