Method and apparatus for surveying hydrocarbon reserves

A method comprising:

• measuring radiation levels at a plurality of points in a survey area;
• determining locations of the plurality of points at which the radiation levels are measured;
• recording the radiation levels and corresponding locations of the plurality of points;
• identifying a level of radiation corresponding to non-productive portions of the survey area;
• and
• identifying productive portions of the survey area which have corresponding radiation levels that are less than the level of radiation corresponding to non-productive portions of the survey area.

A system comprising:

• a radiation detector configured to measure levels of radiation emitted from the earth at a plurality of points in a survey area;
• a platform configured to transport the radiation detector over the survey area;
• a position sensor configured to determine position data for the radiation detector at the plurality of points in the survey area;
• and
• a data recorder configured to receive the radiation data from the radiation detector and the position data from the position sensor corresponding to each of the plurality of points in the survey area.