Remittance Statements

A friend shared with me data shown on her 04/17 remittance statement covering production of GAS from more than 50 wells.

Another friend shared with me data shown on her 05/17 remittance statement covering production of OIL from more than 50 wells, the same wells as the other friend holds.

The statements were from the same operator. The only difference was one statement was for GAS produced, the other friend's statement was for OIL produced.

Each receives only one statement per month from the same operator.

This is hard for me to understand. What appears to have happened?