HYDRODYNAMICS AND RESERVOIR EVALUATION STUDY OF THE NUBIA SANDSTONE, OCTOBER FIELD

Abstract

October oil field, the third largest oil field in Egypt following only EI-Morgan and Belayim fields, produced over 600 MMBO from its discovery in 1977 until January, 1997. It is locate.d in the north of the Gulf of Suez, Egypt and discovered by Gulf of Suez Petroleum Company (GUPCO) in May., 1977. The October Field is one of the giant fields in Egypt having reserves greater than 250

MMBO. It is the latest discovered giant field and currently still under development. It lies 150 kilometers southeast of the Suez city and represents the northern giant field in the Gulf of Suez which amounts 350 kms in length and covers an area of25000 kms. The Gulf of Suez basin went through three major depositional periods: Pre-rift, syn-rift, and post-rift sag. the pre-rift section consists of Early Paleozoic to Oligocene (Pre-Miocene) clastics and carbonates, which directly overlie crystalline basement. The syn-rift and post-rift sag consists of Miocene to Holocene sediments, dominated by clastics and evaporites that unconformably overlie the Pre-Miocene. From 1600 to 2000m of pre-Miocene sediments were deposited before the Gulf of Suez rift developed. The syn-rift and post-rift. graben fill section of Miocene age is generally 1000 to 2500m thick. Oil from October field is produced from four stratigraphic horizons: The Cr7taceous Nubia sandstone, the Upper Cretaceous Nezzazat Group, the Miocene Nukhul Formation, and the Miocene As! Member of the Upper Rudeis Formation. The focus of this work was about the pre-rift Nubia sandstone, which contains most of the reserves in October field. The stratigraphic column of October field area consists of a thick clastic section overlying the Basement rocks and underlies a thick evaporite section. This clastic section extends throughout the geologic time from Permo-Carbniferous (Nubia Sandstone) to middle Miocene (Kareem Formation). It includes excellent reservoirs in both pre Miocene (Nubia sandstone and Nezzazat Group) and Miocene ( Nukhul and Upper Rudeis As! Formations) in addition to a very good carbonate source rock in Campanian "Brown limestone" member of the Sudr Formation. The evaporite section represents an excellent cap rock but severely masks the underlying structures by attenuation and multiple-generation, causing difficulties in seismic processing and interpretation. Although four horizons are productive, the Nubia sandstone accounts for 93% of the field reserves. The Nubia sandstones are non marine to marginal marine and are widely distributed throughout the Gulf of Suez. The type log of the Nubia sandstone on October field shows that the most productive zone lies above the M-Il shale marker. In the structurally highest part of the field, the section below M-Il shale produce with some pressure separation from the main part of the section.