| Autor: |
Ademilola, J. A., Adeoti, L., Adeogun, O. Y., Obafemi, S., Wei Ren, Yakubu, D. A. |
| Předmět: |
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| Zdroj: |
Professional Geologist; Apr-Jun2023, Vol. 60 Issue 2, p16-24, 9p |
| Abstrakt: |
Shear wave (S-wave) velocity estimation from Castagna's equation is often inadequate in gas-saturated reservoirs. For example, at our study site examined here (Joshzoic Field, Niger Delta), the calculation of S-wave velocity from Castagna's equation suggests that reservoirs are water-bearing, whereas neutron and density logs indicate that the reservoirs are gas-bearing. As a result, we integrated Fluid Replacement Modeling (FRM) with water saturation (Sw) values from each gas-saturated reservoir in the Joshzoic Field, to properly re-evaluate the S-wave velocity for gas sand. Wireline log signatures were employed to identify hydrocarbon-bearing reservoirs and compute Sw values. FRM and rock physics crossplots were used to re-evaluate S-wave velocity and identify gas-bearing reservoirs. The Poisson's ratios of the three reservoirs calculated from the S-wave derived from Castagna's equation range from 0.30-0.33, indicating that the reservoirs are water-bearing, whereas the neutron and density log signature of the three reservoirs (Sand A, Sand B, and Sand C) analyzed in this study show that the reservoirs are gas-bearing. Further investigation via rock physics crossplots after FRM with the Sw value of each reservoir shows anomalous zones that are plotted away from the wet background trend. The three gas-filled reservoirs are characterized by a high value of P-impedance and Mu-Rho with a low value of Vp/Vs ratio, Poisson's ratio, and Lambda-Rho, suggesting that the reservoirs are saturated with gas (which agrees with the neutron and density log signature). This study demonstrates, by developing a new integrated approach to determine S-wave velocity in gas-saturated reservoirs, the inadequacy of Castagna's equation in evaluating S-wave velocity in gas-bearing reservoirs. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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