We assess the effectiveness of complementary geophysical techniques to characterize a Jurassic dolomite confined aquifer at Loma de Ubeda, Spain. This aquifer, which is penetrated by wells in the 100–600-m depth range, is confined by Triassic clays (bottom) and Miocene marls (top). The Jurassic dolomite is characterized by prominent seismic reflectors of high amplitude. Thus, it is readily differentiated from the low-amplitude reflectors of the confining clay-rich Triassic and Miocene materials. Electrical resistivity tomography (ERT) allowed us to detail the characteristics of the aquifer up to a maximum depth of 220 m. Lateral changes in facies and small faults have been identified using ERT. Time-domain electromagnetic (TDEM) is an excellent complement to the two above-mentioned techniques in order to widen the analyzed depth range. We acquire TDEM data with different configurations at multiple study sites while simultaneously varying measurement parameters. In doing so and by comparing the effectiveness of these different configurations, we expand the use of TDEM for aquifer characterization.

Due to recent advances in resistivity well logging theory and practice, new triaxial induction tools sensitive to resistivity anisotropy have been developed. We have used the new sensitivities of these tools and developed 1D-3D inversion schemes capable to reveal details of highly laminated shale reservoirs. The ability to simulate responses of the new tools to arbitrary anisotropic 3D media is key to their successful application. We have examined a new fast 1D electromagnetic modeling method to simulate triaxial logging tool responses. The method is used as a forward engine for a new 1D inversion scheme for anisotropic formation parameters. An important new feature of the modeling method is its ability to model new tool responses to biaxial anisotropic medium, whose anisotropy tensor has up to three different principal values. This feature is particularly useful to evaluate anisotropic and fractured formations. We have also developed a universal medium-independent 3D modeling technique that can simulate new-generation tool responses in arbitrary 3D media including fracturing, and we used it as a full 3D inversion engine. Synthetic responses and several 1D-3D inversion results for a practical triaxial induction tool illustrate new features of the resistivity logs and their applications. The new 3D inversion does not require any preprocessing borehole correction, which can introduce significant errors at bed boundaries and in thin laminations. As a result, a higher spatial resolution of the tool can be provided. The new method was used to demonstrate and exploit high sensitivities of triaxial tensor measurement to all three principal values of the conductivity tensor.

We evaluated the results of a large-scale commercial project that illustrated the capabilities of advanced time-domain electromagnetic (TDEM) technologies powered with integrated interpretation of geologic and geophysical data. To study the hydrocarbon prospectivity of a field in Eastern Siberia, we developed a survey design, and then acquired, processed, and interpreted the TDEM data from 30 profiles (total length 772 km) covering an area of approximately [Formula: see text]. The data were acquired using the conventional TDEM and a novel high-resolution version of TDEM, the focused-source electromagnetic method. We described the geologic framework, data acquisition methodologies, and key results obtained using integrated TDEM, seismic, and well-logging data. The interpretation was used to select well locations for additional exploratory drilling. Postsurvey drilling supported our interpretation. The presented case study demonstrates the value of TDEM in the exploration workflow.

According to the results this method of interpretation Time Domain IP is highly effective (Figure 1). It must be emphasized, that using IP parameters, such as decay time, give us new opportunity for interpretation.

Comparison of results to a standard technique of an electrotomography shows considerable advantage of a new direction.

Межскважинная электротомография (МЭТ) вызванной поляризации (ВП) – одно из развивающихся направлений электроразведки. Разрешающая способность этого метода позволяет детально изучать распределения удельного электрического сопротивления и поляризуемости в условиях сложных сред. Анализ переходных характеристик ВП дает информацию о структуре и текстуре рудных образований. В статье представлена методика обработки и интерпретации данных МЭТ ВП. Приведены результаты МЭТ ВП, на участке с сульфидным оруденением (Кольский полуостров)

We have modified a focusing inversion for electrical and TEM data. The new inversion has been successfully tested on synthetic models. We have demonstrated that modified focusing inversion generates clearer and more focused images for complicated resistivity structures, which can contain inclined boundary.