1. A computer-implemented method for synthesizing one or more well logs, the method comprising: collecting at least one output log of a first well bore from measurements with a radioisotopic source; collecting at least one input log of the first well bore from measurements by a non-radioisotopic logging tool; training a neural network via a computer to predict the output log from the at least one input log; collecting at least one input log of a second well bore from measurements by the non-radioisotopic logging tool; and processing the at least one input log of the second well bore to synthesize at least one output log of the second well bore.