In order to quantify the high vertical and lateral petrophysical variability of the Late Ordovician sandstones of the Mamuniyat Formation, the GHE methodology (Corbett et al. 2004) has been applied to several fields of the Murzuq Basin in Libya. These reservoirs are characterized by various facies associations and depositional environments as locally interpreted from core.
The Mamuniyat Formation is a major oil reservoir in the Murzuq Basin of Libya, made up of massive sandstones, representing a low-stand system track. The formation can be subdivided into Lower (LM), Middle (MM) and Upper Mamuniyat (UM) as recognized in outcrops and correlated to the sub-surface. LM commonly consists of fine- to medium-grained sands, deposited in a shelf-shoreface to tidally influenced estuarine setting, whereas heterolithic ripple laminated, dewatered, and slumped sediments typify the MM. Deposition occurred in a rapidly prograding, unstable braid-delta front system fed by melting ice sheets. UM represents the most prolific reservoir section with typically (very) coarse-grained to pebbly sands of a braided system in an active glacial outwash plain.
The complex facies associations entail large internal reservoir variability as reflected by routine core analysis data (poro-perm), log data and the petrophysical interpretation. The Global Hydraulic Element (GHE) approach is tested as a rock typing tool for response and synthesis of all parameters and critical path in the reservoir modeling work flow.
In this study ten (10) GHE have been identified for the Mamuniyat Fm. Detailed quality control of the log and core data available have been conducted. The methodology involves the analysis of the routine core porosity and permeability and calculation of the Normalized Porosity (ϕz), Reservoir Quality Index (RQI) and Flow Zone Indicator (FZI). Statistical analysis on GHE and Facies Associations has been performed to better define their relationship.