Using CSEM to monitor production from a complex 3D gas reservoir—A synthetic case study

Abstract

The marine controlled-source electromagnetic (CSEM) method is most commonly used in targeted exploration or appraisal studies as a tool for detecting and delineating hydrocarbon reservoirs (see, for example, Constable and Srnka 2007). Whereas seismic surveys can detect the structures that may contain hydrocarbons with great accuracy, distinguishing hydrocarbon fluids from water within these structures is more problematic. Originally developed in the late 1970s (Young and Cox, 1981), the CSEM method uses a high-powered horizontal electric dipole (HED) to transmit a low-frequency electromagnetic signal through the sea floor to an array of multicomponent electromagnetic receivers. Bulk electrical resistivity of the sea floor can be determined at scales of a few tens of meters to depths of several kilometers. In many cases this resistivity is driven by the fluid content and saturation of subsurface formations.

Practical Applications of Time-lapse Seismic Data

“…Equally important is their suggestion that those changes can be characteristic of the depletion geometry. Andréis and MacGregor (2011) produce qualitative anomaly maps, along with inversion that employs constraints taken from seismic and well-log data. Andréis and MacGregor (2011) produce qualitative anomaly maps, along with inversion that employs constraints taken from seismic and well-log data.…”

“…However, Orange et al (2009) also note that the ability to interpret such changes might require a high degree of repeatability -better than 5% and more likely 1% to 2% nonrepeatable noise. Andréis and MacGregor (2011) conclude that the changes in environmental conditions and acquisition geometry can be accounted for in the inversion, so the requirements for repeatability might be relaxed. Andréis and MacGregor (2011) conclude that the changes in environmental conditions and acquisition geometry can be accounted for in the inversion, so the requirements for repeatability might be relaxed.…”

Marine controlled-source electromagnetic interferometry

“…They propose to use permanent monuments at the ocean bottom to which the receivers can be attached by remotely operated vehicles. Andreis & MacGregor (2010) simply assume the usage of a permanent receiver system to overcome this issue.…”

Time-lapse controlled-source electromagnetics using interferometry

“…Th ey propose to use permanent monuments at the ocean bottom to which the receivers can be attached by remotely operated vehicles. Andreis and MacGregor (2010) simply assume the usage of a permanent receiver system to overcome this issue.…”