Bouchrara, Slim (_) | MacGregor, Lucy (_) | Alvarez, Amanda (_) | Ellis, Michelle (_) | Ackermann, Rolf (_) | Newton, Paola (_) | Keirstead, Robert (_) | Rusic, Alburto (_) | Zhou, Yijie (_) | Tseng, Hung-Wen (_)
Electrical anisotropy has a strong effect on CSEM data (Ramananjaona et al, 2011), and understanding this effect is key in ensuring robust survey design and well constrained data analysis (MacGregor & Tomlinson, 2014). Electrical anisotropy can also provide key information that can be used to understand regional variations in rock physics properties as well as provide possible indications to geological drivers in an area, such as uplift. To date there have been no systematic regional studies of electrical anisotropy in background geological structure. Addressing this need, by investigating electrical anisotropy variations across the Barents Sea is one of the main goals of the industry funded ERA consortium.
Bulk anisotropy values were derived from CSEM data for each of the major stratigraphic units across the Barents Sea. This was achieved by performing 1D anisotropic inversion of CSEM data acquired around well bores, and tying the horizontal resistivity to the induction log measurements from these wells. Results were then mapped and regional trends are investigated. The modelling confirms the presence of high electrical anisotropy ratios in the Barents Sea area and a correlation between anisotropy ratio and formation age: In general the older the formation, the higher the anisotropy ratio. Although resistivity varies regionally, the variation in anisotropy ratio is less pronounced.
The anisotropy analysis covers multiple Barents Sea areas and includes 20 drilled wells. The wells included in this study have been subdivided in 10 different groups based on their geographical location (Table 1). Note that in area 10 (Hoop) no wells were available, and results are based solely on CSEM data. For each area CSEM data were inverted to determine resistivity and anisotropy values.