Heliyon (Nov 2020)
Asserting the pertinence of the interdependent use of seismic images and wireline logs in the evaluation of selected reservoirs in the Osland field, offshore Niger Delta, Nigeria
Abstract
This study presents a correct time and depth correlations with enhanced velocity analysis, based on two reservoir horizons mapped across two wells (Osl-1 and Osl-2). It involves the use of high-resolution images to delineate the complex geological structures associated with Reservoir A-horizon (R-Ah) and Reservoir B-horizon (R-Bh) based on 3-D seismic sections and wireline logs. It focuses on showcasing magnified images of the well to seismic tie (W-ST), to enhance appropriate times and depths posting to aid correct determination of the pay thicknesses (Pt), drainage areas (Ad) and the mapping of other probable areas within the hydrocarbon field. The idea is to magnify the points of interested at very close intervals (≤2 feet) to enable the mapping of the actual positions and times of events within the reservoirs. The aim is to enhance better results and confidence in the interpretation, as such, reduce the uncertainty regarding hydrocarbon viability and volume estimation. R-Ah is tracking below 9550 feet and 2.460 s in Osl-1. It is below 9510 feet at 2.450 s in Osl-2. Similarly, R-Bh is tracking below 10550 feet at 2.655 s in Osl-1 and below 10520 feet at 2.650 s in Osl-2. R-Ah is about 70 feet (21.34 m) thick across Ols-1 and Osl-2 while R-Bh is 70 feet (21.34 m) thick and 100 feet (30.48 m) in Osl-1 and Osl-2 respectively. In total, Ad is 172 acres (69.6 × 104 m2) for R-Ah and 206 acres (83.4 × 104 m2) for R-Bh while the Pt is 140 feet (42.67 m) for R-Ah and 170 feet (51.82 m) for R-Bh. Possible wellbore positions to aid future developmental activities could be within the south-east, south-west and north-west directions of Osl-1 and Osl-2. The field is viable with regards to hydrocarbon availability, and the use of high-resolution images has aided accurate evaluation of Pt and Ad, hence, increased the confidence in the results of the interpretation.
