Technology Focus: Formation Evaluation (February 2025)

Formation evaluation combines well logs, core and fluid analysis, and interpretation techniques to characterize subsurface formations. It spans the entire life cycle of a field, from exploration to abandonment, and bridges all subsurface disciplines. As reservoir complexity and energy-transition demands grow, the industry is developing new logging technologies, integrating multidisciplinary functions, and conducting new experiments to address new challenges. This Technology Focus highlights three papers from conventional, unconventional, and carbon-storage projects. New logging technologies are leading the way for well placement in conventional reservoirs. Paper SPE 222993 discusses the use of modern ultradeep azimuthal resistivity (UDAR) tools for horizontal well placement in low-resistivity, low-contrast, and thinly laminated clastic reservoirs. This work combines prewell modeling, a new near-bit UDAR transmitter design, and an optimized inversion algorithm to enable real-time decision-making and maximize reservoir exposure. Pore pressure in unconventional reservoirs significantly affects well performance. Paper URTeC 4042140 examines regional pore-pressure variations in the Permian Basin’s producing strata, highlighting vertical and lateral heterogeneities on a basinwide scale. The Midland Basin Spraberry is near or below the hydrostatic pressure gradient, whereas the Wolfcamp Formation is mostly overpressured. These observations could be of great importance for estimating recoverable resources. In carbon-storage projects, the potential loss of CO2 injectivity in saline aquifers from brine dryout and salt accumulation near the wellbore remains uncertain. Paper SPE 219993 designs laboratory and digital analyses of sandstone cores to calibrate petrophysical and dynamical properties upon salt precipitation and flow reduction. The cores undergo repeated brine infiltration and drying cycles, followed by high-resolution 3D imaging and pore-scale simulation to visualize and quantify the effect of salt accumulation on permeability. The calibrated results can be integrated into reservoir models to evaluate injectivity impairment caused by salt clogging. Recommended additional reading at OnePetro: www.onepetro.org. SPE 222205 - Caprock Assessment for a Carbon Capture and Storage Project in Abu Dhabi, Part 1: The Critical Role of Geochemistry in Carbonate Saline Aquifers by Oluwaseun A. Fadipe, Abu Dhabi National Oil Company, et al. URTeC 4023323 - Ascertaining the Presence of Open Fractures in Tight Carbonate Reservoirs With Integrated Solution by Kim Long Nguyen, Kuwait Oil Company, et al. SPE 222295 - Enhancing Clay-Rich Clastic Gas Reservoir Characterization: Ensemble-Style Workflow Investigating Convergence of Independent Water-Saturation Methods by E. Tyurin, BP, et al.