Exxonmobil Upstream Research Company

Bausch-Lomb Incorporated

Kenneth E Green

Leonard J Srnka

Leslie A Wahrmund

Olivier M Burtz

Dennis E Willen

Scott C Hornbostel

Rebecca L Saltzer

Dmitriy A Pavlov

Denny E Willen

Susan Caballa

Systems and methods which provide electromagnetic subsurface mapping to derive information with respect to subsurface features whose sizes are near to or below the resolution of electromagnetic data characterizing the subsurface are shown. Embodiments operate to identify a region of interest () in a resistivity image generated () using electromagnetic data (). One or more scenarios may be identified for the areas of interest, wherein the various scenarios comprise representations of features whose sizes are near to or below the resolution of the electromagnetic data (). According to embodiments, the scenarios are evaluated (), such as using forward or inverse modeling, to determine each scenarios' fit to the available data and further to determine their geologic reasonableness (). Resulting scenarios may be utilized in a number of ways, such as to be substituted in a resistivity image for a corresponding region of anomalous resistivity for enhancing the resistivity image ().

Systems and methods for subsurface electromagnetic mapping

A method for designing a controlled-source electromagnetic survey that will discriminate between a defined deep marginal-interest reservoir () and specified false positive resistivity structures of concern (). A reservoir model and a false positive model are constructed for each false positive scenario. The resistivity of the false positive model may be tuned to give electromagnetic data similar enough to the reservoir model when forward modeled that any differences fall in the model null space. A null-space discriminating ratio ('NSDR') is defined, for example as the peak normalized difference of the two related modeled electromagnetic field data sets. An area coverage display of NSDR values () allows determination of such additional data as may be needed to distinguish the false positive body, and a survey design is developed accordingly (). Reduction of the number of variables affecting the area coverage displays is a key feature of the method.

Method for electroseismic survey design

Method for generating a three-dimensional resistivity data volume for a subsurface region from an initial resistivity model and measured electromagnetic field data from an electromagnetic survey of the region, where the initial resistivity model is preferably obtained by performing multiple ID inversions of the measured data []. The resulting resistivity depth profiles are then registered at proper 3D positions []. The 3D electromagnetic response is simulated [] assuming the resistivity structure is given by the initial resistivity model. The measured electromagnetic field data volume is scaled by the simulated results [] and the ratios are registered at proper 3D positions [] producing a ratio data volume []. A 3D resistivity volume is then generated by multiplying the initial resistivity volume by the ratio data volume (or some function of it), location-by location []. A related method emphasizes deeper resistive anomalies over masking effects of shallow anomalies.

Method for obtaining resistivity from controlled source electromagnetic data

Method for enhancing resistive anomalies in electromagnetic geophysical survey data. Scaled values of a measured electromagnetic field parameter are plotted on a depth section at locations related to corresponding source/receiver locations. Scaling is performed relative to a reference signal selected to represent a baseline free of unknown resistive bodies. Scaled values are represented by a color scale in the display, and the color scale may be adjusted to enhance perceived anomalies. The method may be employed in either the frequency domain or the time domain.

Method for identifying resistivity anomalies in electromagnetic survey data

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Houston, TX, United States of America

Kenneth E Green