Online Journal for E&P Geoscientists

Abdullatif, Osman M.^*1; Makkawi, Mohammad ¹; Al Ramadan, Khalid ¹; Eltom, Hassan ¹; Yassin, Mohamed A.¹; Sitouah, Mohamed ²
(1) Earth Sciences, KFUPM, Dhahran, Saudi Arabia. (2) RI, KFUPM, Dhahran, Saudi Arabia.

The objective of this study is to provide an overview of the results of the field sedimentologic and stratigraphic performed at outcrop scale. This results presented here are part of an approach integrating field high resolution stratigraphic and sedimentologic analysis, outcrop gamma ray survey, terrestrial lidar survey, laboratory porosity-permeability and petrographic analysis. Such data may be useful for identifying reservoir architecture, correlation and modeling of subsurface reservoir. The Late Jurassic outcrop section time-equivalent to Arab D reservoir studied at Wadi Nisah is composed from bottom to top of Jubaila Formation overlain by Arab D member. Stratigraphic correlation of 14 outcrop sections, based on facies, stratigraphic sequence analyses and gamma-ray pattern, was used as a framework for mapping the distribution of facies at outcrop scale. Seven facies were identified and include dolomite, massive mudstone and wackstone, oncoidal wackstone and packstone (rudstone), fossiliferous peloidal packstone, laminated mudstone, laminated fossiliferous sandy grainstone, collapse breccias. These facies were interpreted to be deposited in intertidal, lagoon and lower and upper slope into ramp crest paleoenvironments. The stratigraphic analysis revealed composite sequences and several high resolution frequency sequences. Ten fourth order cycles three of which are in the lower part (upper Jubaila Formation) and seven of which in the upper part (Arab-D Formation were recognized. The three cycles in the upper Jubaila Formation show repeated cyclicty of shoaling upward. Laterally these cycles are correlatable all over the measured sections and show a similarity in thicknesses, facies and biofacies components. The results from the outcrop analog study may be used to reduce uncertainty and help to define and determine facies distribution, correlation and prediction of reservoir architecture at inter-well spacing.