Unconventional reservoirs, including gas shales and tight gas sands, have gained prominence in the energy sector due to technological advancements and escalating energy demands. The oil industry is eagerly refining techniques to decipher these reservoirs, aiming to reduce data collection costs and uncertainties in reserve estimations. Characteristically, tight reservoirs exhibit low matrix porosity and ultra-low permeability, necessitating artificial stimulation for enhanced production. The efficacy of the stimulation hinges on the organic material distribution, the rock’s mechanical attributes, and the prevailing stress field. Comprehensive petrophysical analysis, integrating standard and specialized logs, core analyses, and dynamic data, is pivotal for a nuanced understanding of these reservoirs. This ensures a reduction in prediction uncertainties, with parameters like shale volume, porosity, and permeability being vital. This article delves into an intricate petrophysical evaluation of the Nene field, a West African unconventional reservoir. It underscores the geological intricacies of the field, the pivotal role of data acquisition, and introduces avant-garde methodologies for depth matching, rock typing, and the estimation of permeability. This research highlights the significance of unconventional reservoir exploration in today’s energy milieu, offering a granular understanding of the Nene field’s geological challenges and proffering a blueprint for analogous future endeavours in unconventional reservoirs.

Aperture, which refers to the opening size of a fracture, is a critical parameter controlling rock mass permeability. Moreover, distribution of permeability within the reservoir is commonly affected by natural fracture occurrences. In a water-based mud environment, borehole-imaging tools are able to identify both location and aperture size of the intersected fractures, whereas in oil-based environment, due to invasion of resistive mud into the fractures, this technique is impractical. Recently, some artificial intelligence techniques facilitated reliable estimations of reservoir parameters. In this paper, a teaching–learning-based optimization algorithm (TLBO) trained an initial fuzzy inference system to estimate hydraulic aperture of detected fractures using well logs responses. Comparing the results with real measurements revealed that the model can provide reliable estimations in both conductive and resistive mud environments, wherever the aperture size is unknown. TLBO, besides of its easier application, outperformed earlier optimization algorithms, which were used to evaluate the method effectiveness.

Insufficient palaeoclimate data from the South Pacific lead to conflicting theories regarding the region's responses to Holocene climate fluctuations. To address this gap in knowledge we present preliminary results from five stalagmites collected from two different caves in the Kingdom of Tonga.Despite their vicinity, Ana Hulu (on Tongatapu Island) and Ana Maui (on ‘Eua Island) caves differ significantly in their microclimatic settings. Ana Hulu is a warm (24.2 °C) and shallow coastal cave, whereas Ana Maui is a deep and relatively cooler cave opening deep in the forest at 188 m above sea level. These differences are likely underpinned in the formation of the well-laminated and coloured stalagmites retrieved from Ana Hulu and the colourless, faint-laminated stalagmites from Ana Maui.The set of U-series dated stalagmites provides an almost continuous record spanning the entire Holocene up to the end of the Younger Dryas (ca. 12,500 years ago). The stalagmites show different growth rates varying from 50 to 300 µm/year. The high-resolution chronology can offer the potential for annually resolved records of infiltration (rainfall) variability, which are likely to be related to shifts of the South Pacific Convergence Zone (SPCZ), the most important tropical South Pacific cloud belt..However, an interpretation of SPCZ shifts based solely on speleothem δ13C and δ18O values is challenging. The potential influence of enhanced evaporation and degassing effects, which may arise from warm temperatures and low cave air pCO2, must be accounted for. A multi-proxy approach on coeval stalagmites has been shown to provide critical information about the role of local hydrology. Thus, we combined the stable isotope ratios values time-series with petrographic observations, high-resolution LA-ICP-MS trace elements data, and synchrotron-radiation XRF elemental mapping. This multi-proxy approach, along with an assessment of crystallization pathways leading to fabrics, is expected to enable robust reconstructions of coeval changes in infiltration regimes and hydroclimate dynamics across the South Pacific.