Crosswell Electromagnetic Resistivity Tomography: Pushing the Limits

Sanni, Modiu; Yeh, Nai-Shyong; Al-Afaleg, Nabeel; Al-Kaabi, Abdulaziz; Levesque, Cyrille; Donadille, Jean-Marc; Mark, Shouxiang

doi:10.2118/105353-ms

Cited by 10 publications

(1 citation statement)

References 7 publications

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“…Crosswell EM measurements are emerging as reservoir-characterization and -monitoring tools that add greatly to the understanding of reservoir heterogeneity and fluid-front monitoring over time (Sanni et al 2007;Marion et al 2011). Traditional well-log data provide high-resolution measurements of the formation very close to the wellbore, whereas surface-based methods provide a larger volume of investigation but with coarser resolution.…”

Section: Introductionmentioning

confidence: 99%

Crosswell Magnetic Sensing of Superparamagnetic Nanoparticles for Subsurface Applications

et al. 2015

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Stable dispersions of superparamagnetic nanoparticles that are already in use in biomedicine as image-enhancing agents also have potential use in subsurface applications. Surface-coated nanoparticles are capable of flowing through micron-sized pores across long distances in a reservoir, with modest retention in rock. These particles change the magnetic permeability of the flooded region, and thus one can use them to enhance images of the flood. In this paper, we model the propagation of a "ferrofluid" slug in a reservoir and its response to a crosswell magnetic tomography system.This approach to monitoring fluid movement within a reservoir is built on established electromagnetic (EM) conductivity-monitoring technology. In this work, however, we investigate the contrast between injected and resident fluids when they have different magnetic permeabilities. Specifically, we highlight the magnetic response at low frequency to the magnetic excitations generated by a vertical magnetic dipole source positioned at the injection well. At these frequencies, the induction effect is small, the casing effect is manageable, the crosswell response originates purely from the magnetic contrast in the formation, and changes in fluid conductivities are irrelevant.The sensitivity of the measurements to the magnetic slug is highest when the slug is closest to the source or receivers and lower when the slug is midway in the interwell region. At low frequencies, the magnetic response of the ferrofluid slug is largely independent of frequency. As expected for the conductive slug, the sensitivity of the inductive measurements is negligible at low frequencies whereas significant levels of detectability result at higher frequencies. We demonstrate sensitivity to the vertical boundaries of the slug by shifting the vertical position of the excitation source relative to the magnetic slug. The slug geometry plays a key role in determining the magnetic response. With a fixed volume of ferrofluid, there is an optimum slug geometry that results in the maximum magnetic response. Hydrodynamic dispersion of the slug has negligible effect on the magnetic response during early stages of the waterflood. As the slug travels farther into the formation, however, dispersion reduces the concentration of nanoparticles, and the spatial contributions of the magnetic measurements are more diffuse. We illustrate how these low-frequency excitation behaviors are consistent with the quasistatic magnetic dipole physics. The fact that the progress of the magnetic slug can be detected at very early stages of the flood, that the traveling slug's vertical boundaries can be identified at low frequencies, and that the magnetic nanoparticles can be sensed well before the actual arrival of the slug at the observer well provide significant value of the use of the magnetic-contrast agents in crosswell EM tomography.

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Section: Introductionmentioning

confidence: 99%

Crosswell Magnetic Sensing of Superparamagnetic Nanoparticles for Subsurface Applications

et al. 2015

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Long-Distance Crosswell EM Logging of Copper Ore Using Borehole-Surface Current Injection in Slim Holes

Dang

Zhao

Guo

et al. 2022

IEEE J. Sel. Top. Appl. Earth Observations Remote Sensing

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Crosswell electromagnetic (EM) methods are widely used in subsurface geophysical prospecting because they can achieve more effective long-distance detection than single-well methods. However, a large-diameter borehole is required to increase the magnetic moment of the magnetic dipole source. For the long-distance detection of copper ores, which is usually performed in slim holes, we present a borehole-surface currentinjection-based crosswell EM logging method. Considering the cost of deploying casing, we inject a low-frequency AC directly into the ground, and converging current is formed around lowresistance anomalies in the formation. Then, the distribution of the anomalies can be inferred by detecting the low-frequency alternating magnetic field of the converging current in the receiver well. Moreover, to further improve the detection performance, we design a placement scheme for the grounding electrode for multianomaly crosswell detection based on the Gauss-Newton inversion algorithm, where the EM responses for different grounding electrode locations are analyzed. Field experiments are conducted using two slim open holes spaced approximately 1000 m apart for the detection of two copper ores. Through the processing and interpretation of measured EM signals, the conductivity imaging results of the crosswell EM method indicate that the measured distribution of anomalies is consistent with prior knowledge obtained from numerous single-well loggings, demonstrating the feasibility of the proposed application for long-distance crosswell EM logging in slim open holes.

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3-D Crosswell Electromagnetic Inversion Based on General Measures

Wang

Shen

2021

IEEE Trans. Geosci. Remote Sensing

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Crosswell Electromagnetic Resistivity Tomography: Pushing the Limits

Cited by 10 publications

References 7 publications

Crosswell Magnetic Sensing of Superparamagnetic Nanoparticles for Subsurface Applications

Crosswell Magnetic Sensing of Superparamagnetic Nanoparticles for Subsurface Applications

Long-Distance Crosswell EM Logging of Copper Ore Using Borehole-Surface Current Injection in Slim Holes

3-D Crosswell Electromagnetic Inversion Based on General Measures

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