Caractérisation de la thc des quartzites de Hamra Rhourde Nouss (Sud algérien): Apports de l'analyse des carottes, de l'Imagerie, des tests aux puits et implications sur la production

Abstract

The objective of this study is focused on the characterization of the Quartzite reservoir of Hamra in the Rhourde Nouss region (central RN structure) and it aims also at evaluating the impact of natural fractures on the reservoir productivity and profitability. This last consists in compact and thick quartzitic sandstones that have been deposited in a shoreface type environment (before the beach). These quartzites were experienced by long and complex diagenesis that conduct to a degradation of the petrophysical parameters (porosity = 2% to 5%, permeability = 0.1mD). In order to reach the goal, several methods were used namely: a core examination; Borehole imagry, Welltesting analysis together with the application of the WaterCut method. Core examination shows the existence of open-stylolits and micro-fractures which can improve production if they are not filled up with silica and pyrite. Borehole Imagry analysis in the RN114 well has confirmed that approximately 63% of all fractures are favorable. Moreover, the application of the WaterCut initially revealed the existence of an active aquifer at the extreme north-east and south-west limit of the central RN structure. In this aquifer, the fracturing of the structure has increased the escape of water during the exploitation leading to the rapid flooding of some wells (RN110, RNZ130 and RN120) that are located near the faults or fractures. This study highlights that Hamra Quartzites can only be exploited through a well-developed natural fracturing network. The obtained results in the framework of this study evidence the existence of an intense network of fractures of different shapes and different types.