Reservoir zonation and discrimination using the routine core analyses data: the Upper Jurassic Sab’atayn sandstones as a case study, Sab’atayn basin, Yemen

Abstract

Sab’atayn basin is one of the two main hydrocarbon fields in Yemen. The present study is a trial to use the measured conventional core analysis data to define the potential reservoir zones in Alif and Seen members in Sab'atayn basin and to discriminate them into conductive and superconductive zones, and into potential and impervious zones using the concept of Reservoir Quality index (RQI), the Flow zone Index (FZI), and the Reservoir Potentiality Index (RPI). Samples from Alif and Seen members are composed mostly of pebbly quartz arenite, sometimes of dolomitic and ferruginous quartz arenite. Based on the petrophysical behavior, the studied Alif member is subdivided into three petrophysical facies in Alif 003 well and into two facies in Alif 005 well. Seen member is also subdivided into two petrophysical facies in Alif 005 well. The bulk density of the measured Alif and Seen samples is dependent mostly on the measured porosity with no dependence on the grain density. Due to the measuring technique, summation fluid porosity shows scattered data and is not recommended to be used for further development and exploration of future plans in the studied field. The reservoir zonation and discrimination shows a main reservoir body in Alif member in both Alif 003 and Alif 005 wells, with very good and excellent potentiality (RPI, 4–5) in Alif 003 well. The reservoir potentiality decreases to the southwest of the field in Alif 005 well, where the RPI varies from 2 to 4, ranked as fair to very good. Downward, Seen member is characterized mostly by negligible, poor to fair petrophysical data in the most top parts (RPI, 1–3). The quality controlled parameters, RPI and FZI, are mostly controlled by horizontal permeability ‘K’ and can be calculated precisely in terms of it.