Flow rate calculations

When viewing production data and when using that data to generate forecasts of future production, it is critical that the method used to calculate the rates be known, understood, and used properly. Four commonly used terms used in this regard are "operated-day rate" (op-day), "calendar-day rate" (cal-day), "time on-production", and "load factor".

Note:    The term "injection" can be substituted in all the definitions below where "production" is used.

Operated-day rate

Operated-day rate is defined as the volume of fluid produced or forecast over a period of time divided by the actual on-time during the period in days. For example, if a well produced 300 barrels of oil in a 30 day month, but was only actually producing for 15 days, then:

Operated-Day Rate = 300 Bbls / 15 days = 20 Bbls / day

Calendar-day rate

Calendar-day rate is defined as the volume of fluid produced or forecast over a period of time divided by the number of days in the period, regardless of actual on-time. For example, if a well produced 300 barrels of oil in a 30-day month, but was only actually producing for 15 days, then:

Calendar-Day Rate = 300 Bbls / 30 days = 10 Bbls / day

Time on-production

Time on-production is defined as the period of time a well is actually producing. It is typically expressed in hours or days.

Load factor

Load factor is defined as the ratio of the actual on-time and the period time. For example, if a well produced for 15 days in a 30-day period, then its load factor expressed as a percentage would be:

15/30 * 100 = 50%