Cross-Plot-Driven Petrophysical and Rock Physics Characterization of Reservoir and Non-Reservoir Zones in the Smeaheia Area, Norwegian North Sea

Abstract

To identify and characterize reservoir and non-reservoir intervals across multiple formations, this paper examines comprehensive petrophysical evaluation and scattered cross-plot analysis using well-log data from Well 32-2-1 in the Smeaheia area of the Norwegian North Sea. The main objective of this study is to delineate lithology variations, detect fluid-bearing zones, and evaluate the key geological and petrophysical factors that control reservoir quality within a heterogeneous sandstone-shale succession.

A suite of well logs including gamma ray, resistivity, density, neutron porosity, and sonic measurements was thoroughly interpreted to identify lithological transitions and potential hydrocarbon-bearing intervals. Cross-plotting techniques were employed to analyze relationships between critical log parameters such as RHOB-NEU, GR-density, and neutron-density separation etc. These crossplots facilitated the differentiation of claystone, shaly-sand, clean sandstone, cemented sandstone, and coal units, while also revealing variations in porosity, mineral composition, and clay content across the well.

The integrated petrophysical analysis highlighted significant vertical heterogeneity, ranging from clean quartz-rich sandstones to shaly sands, claystone-dominated sections, calcite-cemented sands, and thin coal streaks. High gamma-ray, moderate density, and elevated neutron porosity responses delineate clay-rich zones where bound water inflates apparent porosity. Shaly-sand units are identified through intermediate clustering in RHOB-NEU and GR-density crossplots, reflecting mixed mineralogy and moderate effective porosity. Clean sandstone intervals, recognized by low GR and low NEU signatures, exhibit variable reservoir quality controlled by burial compaction and cementation intensity. Zones showing lower-than-expected density and reduced sonic velocity indicate undercompaction and suggest localized overpressure conditions.

Overall, the results of this cross-plot-driven petrophysical evaluation provide new insights into the distribution of porosity, clay volume, compaction state, and lithofacies variability throughout the stratigraphic interval. The interpretation enhances the understanding of reservoir and non-reservoir facies and improves the identification of intervals with potential hydrocarbon significance. The findings of this study contribute to more reliable reservoir characterization and support improved exploration and development strategies within the complex sandstone systems of the Norwegian North Sea.

 

Keywords:  Rock Physics, Petrophysics, Reservoir zone, Cross-Plot, Smeaheia Region.