Investigation and Evaluation of Reservoir Quality of the Upper Cretaceous Rocks (Belqa Group) in North Jordan (NW Irbid)

Abstract

Upper Cretaceous rocks are widespread in Jordan, covering uncomfortably the rocks of the Lower Cretaceous (Kurnub Sandstone). These rocks consist mainly of limestone, marls, chalk, biogenic chert and phosphate of primarily marine origin. Age determination of these rocks was based on the abundance of macro and microfossil content. Man researchers subdivided the Upper Cretaceous succession. The classification of Powell (1989) is considered in this study, particularly for the Belqa Group, which is of Coniacian to Maastrichtian in age. This investigation will focus on the geology of Wadi Es Sir, Umm Ghudran; Amman silicified limestone, and Al Hisa phosphorite formations, that belong to Ajlun and Belqa Groups respectively. Moreover, sedimentary structures, lithological characteristics Microfacies types and fossil content were evaluated. Using the lithostratigraphy and the fossil content of those formations, 6 Microfacies types were identified. Evaluation of the cross-section, the tectonic processes and the prepared rose diagrams indicate that the study area was affected by compressional as well as by tensional forces. Two major tends of fracturing can be identified in the rose diagrams. The measured physical properties show that the porosity is variable and ranges between 30% and 48%. The bulk density has values between 1.8 and 2.2 g/cm 3 . The different obtained results point out that the studied rocks represent good reservoir.