Advanced Assessment of Low Resistivity Pay in the SAG Reservoirs of the BERKINE Basin Using the Multidetector Pulsed Neutron Tool RMT 3D

Abstract

The SAG (Silurien Argilo-Greseux) reservoirs in the Berkine Basin comprise several units (N, M, A & B) characterised by thinly-laminated, high bound water content and low resistivity pay (LRP) phenomena. Conventional petrophysical evaluation methods often struggle to accurately identify hydrocarbon productive zones in such reservoirs, leading to their bypass. This project aims to tackle these challenges by employing advanced logging technologies, specifically a Multidetector Pulsed Neutron Tool RMT-3D. We will adopt an integrated approach that combines SIGMASAT to determine saturations of saline water and hydrocarbons, alongside SATG to assess gas saturation. This methodology seeks to provide a more accurate assessment of fluid saturations across various intervals in SAG reservoirs, where traditional methods fall short. Key findings indicate that conventional logging often shows low resistivities and high-water saturations, especially in the SAG A1 unit, which behaves almost like an aquifer. In contrast, SIGMASAT and SATG analyses reveal substantial hydrocarbon saturations, including gas and light oil, in the SAG units 'A1&A2' and 'M2'. Production logging confirms total downhole production rates of 571 m³/d of light oil (condensate) and 192.6 m³/d of gas from specific intervals, highlighting the potential of SAG reservoirs. This well has been recognized as one of SONATRACH's standout discoveries in 2023.