Abstract:
The Lower Acacus reservoir in the northeastern part of Ghadames Basin (Block-114)
forms a tidally influenced deltaic system. Structural and stratigraphic cross-sections that
were constructed using Petrel (Schlumberger Trademark) have shown a general
thickening of the reservoir formation towards the north-northeast. Petrophysically, this
reservoir is divided into three main units based on log characters; these are (Unit A, B,
and C) with Unit A being at the bottom followed by B & C. The petrophysical analysis
using IP (LIoyd’s Register Trademark) indicates that Lower Acacus reservoir is
hydrocarbon bearing in the study area with very good reservoir parameters. Average
volume of shale is around 25 percent, porosity ranges from 15 to 20 percent, and water
saturation is around 35 percent in the oil wells. Hydrocarbon distribution and reservoir
intervals are both mainly controlled by depositional facies and to a lesser extent by
structural influence. Consequently, FMI and core images were analyzed using Techlog
(Schlumberger Trademark) to define the main sedimentary structures in the available
wells. These sedimentary structures were grouped into four main facies in order to
delineate the vertical and lateral variation among the wells in the study area. The
identified facies are heterolithic bedding, crossbedding sandstone, shaly-sand bedding,
and laminated shale facies. The bioturbation activity on these facies might have a direct
influence on the reservoir performance by destroying the rock primary fabric. However,
the association of these facies reflect the tidal effect on the delta as supported by
paleocurrent direction analysis. Additionally, the paleocurrent measurements from the
cross-bedded facies show a dominant bimodal trend towards NW-SE, with modest
polymodal and unimodal models.
