Petrographical and Petrophysical Porosity Evaluation for Subsurface Cretaceous Nubia Sandstone at South-Ghara Oil Field, Gulf of Suez, Egypt

Abstract

AbstractDue to information scarcity of the study area so, this work is trying to uncover an important subsurface Nubia sandstone oil reservoir characteristics mainly in terms of porosity using petrographic description in addition to porosity measurements for the core samples raised from two wells (GH404-A2A and GH404-A3B) at South-Ghara oil field, Gulf of Suez region. The studied Nubia Sandstones are mainly classified as quartz arenite. The recorded quartz types indicate that the studied Nubia Sandstone in the two wells has originated from plutonic and high rank metamorphic rocks. The general scarcity of feldspar could be related to its decomposition due to the low topography associated with warm and humid climate. The total porosity of (15) selected sandstone samples representing the Nubia Sandstone was measured by a Helium porosimeter. The average measured value for the studied samples of the Nubia Sandstone is 15.24% and 12.22% for the two wells (GH404-A3B and GH404-A2A), respectively. The value indicates a fair porosity. The recorded porosity type is interparticle, based on the petrographic investigation. The precipitated cement, in the form of iron oxides, calcite, evaporate and silica, as quartz overgrowth or chalcedony are the most effective factors in reducing the primary porosity of the studied rocks. Also, authigenic clay minerals and feldspar influenced primary porosity by reduction.