Estimation of hydraulic parameters of shaly sandstone aquifers from geoelectrical measurements

Measuring induced polarization in the time domain with relatively compact multi-channel multielectrode systems is attractive because of the simplicity of the procedure and thus its efficiency in the field. However the use of this technique is sometimes discouraged by the bad quality of the measurements in cases of high electrode contact resistances that can render data interpretation
infeasible or at least unreliable. It is proposed that capacitive coupling in the multi-core electrode cables has a significant role in creating this problem.
In such cases separation of current and potential circuits by using separate multi-conductor cable spreads can yield significant improvement in data quality. The procedure is relatively simple and can be implemented with common resistivity and time-domain IP equipment. We show here three field examples from Southern Sweden, all measured as 2D electrical imaging sections. The first one is an example where the use of a single cable spread is sufficient thanks
to moderate electrode contact resistance and high signal levels. The following two examples are from sites where induced polarization measurements could not yield consistent results using only a single multi-conductor cable spread. Useful results were subsequently obtained by using separate cable spreads.
The first example is a 280 m long line measured over an old covered municipal waste deposit where the waste body stands out as a zone of high chargeability. The second example is a 120 m line measured on a sandy glaciofluvial structure that is host to an aquifer of regional importance. The improvement led to discrimination between materials of different grain sizes, with potential
bearing for understanding the aquifer. The third example is a 300–400 m line measured across an esker lying on clay till. The improvement led to a clear visualization of the esker and to the identification of a possible fault in the underlying gneissic bedrock. In all cases pseudosections and examples of chargeability decay curves are shown and discussed as tools for assessing data quality. Inversion results are shown together with background geological
information and it is concluded that they are in good agreement.

/pdf/improvement-in-time-domain-induced-polarization-data-quality-2h4fjzwdtw.pdf

Improvement in time-domain induced polarization data quality with multi-electrode systems by separating current and potential cables

Remarkable progress has been made in electromagnetic (EM) techniques as applied to the petroleum industry in instruments, data acquisition, and processing and interpretation in China. Included here is equipment, such as high-power Controlled Source EM (CSEM) acquisition systems, acquisition methods, such as the three dimensional small-bin Continuous Electromagnetic Array acquisition method, Time and Frequency Domain Controlled Source Electromagnetic, Borehole-to-surface Electromagnetic technique and marine magnetotelluric method. Data processing methods, such as fast three dimensional inversion using nonlinear conjugate gradients, and data interpretation methods, like Induced Polarization and Resistivity anomalies for hydrocarbon detection, are also included. These new techniques have been applied in petroleum survey and many cases are in complicated areas. They have successfully served the investigation of deep igneous rock reservoirs, and prediction of potential hydrocarbon targets. The cases indicate that electromagnetic techniques can help seismic survey to effectively detect hydrocarbon reservoir and remarkably improve drilling successes.

/pdf/petroleum-electromagnetic-prospecting-advances-and-case-3d275i1l8g.pdf

Petroleum Electromagnetic Prospecting Advances and Case Studies in China

Geophysical Studies in the Caucasus

https://portal.research.lu.se/ws/files/11329856/Measuring_time_domain_spectral_induced_polarization_in_the_on_time_decreasing_acquisition_time_and_increasing_signal_to_noise_ratio_2_.pdf

Measuring time-domain spectral induced polarization in the on-time: decreasing acquisition time and increasing signal-to-noise ratio

In comparing the similarity between time, frequency, and phase measurements as used in the induced polarization method of geophysical prospecting, parameters must first be defined and the basis for comparison established. The conditions for mathematical equivalence then follow in a natural sequence. Laboratory measurements are made on a variety of rock samples to indicate the type of comparison and correlation expected from field measurements. Results indicate that frequency domain and phase measurements are equivalent, but two frequency domain measurements are needed to produce the same amount of polarization information as a single phase measurement. Frequency and time domain measurements will be similar but never equivalent due to the basic differences in their respective parameter definitions.

K. L. Zonge

Papers

Comparison of time, frequency, and phase measurements in induced polarization*