Rapid Calculation of Optimized Arrays for Long 2-D Survey Lines

Abstract

Previous studies show that optimized arrays generated using the ‘Compare R’ method have significantly better resolution than conventional arrays. This method determines the optimum set of arrays by calculating the change in the model resolution for all the viable arrays (comprehensive data set) for a survey line. The number of possible arrays increases with the fourth power of the number of electrodes. The optimization method faces practical limitations for lines with more than 60 electrodes where the number of possible arrays exceeds a million. Several techniques are examined that can be used for lines with more than 100 electrodes. Recent improvements in the computer GPU reduces the calculation time by a factor of 5. The calculation time can be further reduced by half by using the fact that arrays that are symmetrical about the center of the line produce identical changes in the model resolution values. The calculation time is reduced by another hundred times by using a subset of the comprehensive data set consisting of only symmetrical arrays. Tests with synthetic models show that optimized arrays derived from this subset produce inversion models with differences of less than 10% from those derived using the full comprehensive data set.