This is somewhat dependent on how the field infrastructure is set up, but if you have liquids production (oil or condensate) you need to request the following:
1. Tank gauges - these are the daily measurements of the liquid volume in each production tank
2. Tank strap tables - these are tables that convert the height of liquid (i.e. the tank gauge) in a production tank to a liquid volume
3. Run tickets (including seal records) or LACT meter readings - run tickets are the statements generated for each truckload of oil hauled from location (seal records are unique seals placed on tank valves to ensure that there has been no tampering). If oil is not trucked from tanks, it is measured with a LACT meter (Lease Automatic Custody Transfer meter) which measures all oil sent through a pipeline
4. Well test records - if more than one well produces to a common production tank before the oil and water is metered, the operating company will periodically conduct a test on each well in order to allocate the volume read at the production tanks to each producing well
For gas production, you will need the following:
1. Gas meter readings - assuming gas is sold (rather than flared or vented) there will be two meter readings - one from the operating company and one from the purchaser (gas plant). Request both - they should be extremely close.
2. Gas measurements - you will need to know the BTU (energy) content of the gas being sold and the gas analysis (which reports the fraction of the gas that is methane, ethane, propane, butane ,etc.)
3. Plant statements - when gas is sold to a gas plant or run through a gas plant, the plant must record the plant liquids (or natural gas liquids) that are stripped from the gas. This volume will be related to the BTU content of the gas and gas analysis. The amount of plant liquids that belong to the operating company (and you) is also dependent on gas processing contracts.
Feel free to send me an email if you need help with specific questions. Good luck.