Method for conducting an efficient and interpretable controlled-source electromagnetic reconnaissance survey for buried hydrocarbons. While a part of the survey area is being set up for measurement and data are being acquired, data from a nearby part of the survey area, surveyed just previously, are being rapidly processed and analyzed (110). If the analysis shows resistive anomalies of interest in a portion of a survey area, a fine-grid survey is quickly designed for that portion, and that survey is conducted next before moving source and receivers to a more distant part of the survey area.