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Quantification and spatial distribution of pore‐filling materials through constrained rock physics template and fluid response modelling in Paleogene clastic reservoir from Cauvery basin, India
Author(s) -
Das Prabal Shankar,
Chatterjee Rima,
Dasgupta Sumangal,
Das Ranajit,
Bakshi Debjani,
Gupta Mukesh
Publication year - 2019
Publication title -
geophysical prospecting
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.735
H-Index - 79
eISSN - 1365-2478
pISSN - 0016-8025
DOI - 10.1111/1365-2478.12715
Subject(s) - petrophysics , geology , clastic rock , diagenesis , cement , mineralogy , well logging , porosity , paleogene , structural basin , geomorphology , geotechnical engineering , materials science , geophysics , composite material
Sands belonging to Kamalapuram Formation of Paleocene‐Eocene age are deposited in Cauvery basin as incised valley fill during a regressive cycle. Here we attempt to quantify the influence of diagenesis on pore‐filling materials using rock physics template constrained by geohistory modelling. Primarily, porosity–velocity and acoustic impedance – the ratio of P‐wave and S‐wave velocity ( V P / V s ) cross‐plots are used as rock physics templates. Rock physics template has efficiently quantified pore‐filling materials namely; contact cement and non‐contact cement. The estimated contact cement and non‐contact cement are correlated with conventional petrophysical logs within the selected depth interval. Further, this correlation is used to interpret the composition of pore‐filling materials. Shallower depth intervals (I and II) exhibit moderate non‐contact cement (4–5%) and insignificant contact cement (1–2% approx.) depositions. However, deeper interval (III) records a significant amount of pore‐filling materials amounting average of 12% non‐contact cement and 4% contact cement. Pore‐filling materials demonstrate a positive correlation with the depth of burial. The fluid response is substantially affected by the degree of diagenesis, composition and spatial distribution of pore‐filling materials. Shallower depth intervals (1770–1786 m and 1858–1878 m) are relatively more sensitive to fluid changes as it is affected by insignificant contact cement. The depth interval 1770–1786 m shows class II (oil) and class III (gas) amplitude variation with offset anomalies. The sand occurring in depth interval 1858–1878 m demonstrates class IIP (oil) and II (gas) anomaly. The deeper interval (2118–2170 m) is comparatively stiffer and demonstrates class I amplitude variation with offset (oil and gas sand) anomaly.