Electromagnetic surveying for hydrocarbon reservoirs
First Claim
1. An electromagnetic survey method for surveying an area previously identified as potentially containing a subsea hydrocarbon reservoir, comprising:
- providing an electromagnetic source having a dipole axis and first and second detectors;
moving the electromagnetic source with the dipole axis of the electromagnetic source aligned end-on relative to the first detector so that a first survey data set is sensitive to resistive hydrocarbon layers exploiting largely galvanic effects;
moving the electromagnetic source with the dipole axis of the electromagnetic source aligned with the dipole axis of the electromagnetic source aligned broadside relative to the second detector so that a second survey data set is relatively insensitive to resistive hydrocarbon layers exploiting dominantly inductive effects;
moving the electromagnetic source relative to each detector to collect data over a range of source-to-detector distances; and
processing the first survey data set and the second survey data set.
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Abstract
An electromagnetic survey method for surveying an area previously identified as potentially containing a subsea hydrocarbon reservoir, comprising obtaining first and second survey data sets with an electromagnetic source aligned end-on and broadside relative to the same or different receivers. The invention also relates to planning a survey using this method, and to analysis of survey data taken in combination allow the galvanic contribution to the signals collected at the receiver to be contrasted with the inductive effects, and the effects of signal attenuation, which are highly dependent on local properties of the rock formation, overlying water and air at the survey area. This is very important to the success of using electromagnetic surveying for identifying hydrocarbon reserves and distinguishing them from other classes of structure.
98 Citations
6 Claims
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1. An electromagnetic survey method for surveying an area previously identified as potentially containing a subsea hydrocarbon reservoir, comprising:
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providing an electromagnetic source having a dipole axis and first and second detectors;
moving the electromagnetic source with the dipole axis of the electromagnetic source aligned end-on relative to the first detector so that a first survey data set is sensitive to resistive hydrocarbon layers exploiting largely galvanic effects;
moving the electromagnetic source with the dipole axis of the electromagnetic source aligned with the dipole axis of the electromagnetic source aligned broadside relative to the second detector so that a second survey data set is relatively insensitive to resistive hydrocarbon layers exploiting dominantly inductive effects;
moving the electromagnetic source relative to each detector to collect data over a range of source-to-detector distances; and
processing the first survey data set and the second survey data set. - View Dependent Claims (2, 3, 4, 5, 6)
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Specification