In many companies, production forecasting using multiple segments is gaining traction. Theoretically, the multiple segments are used to capture the different flow regimes in the reservoir over a period of time. A three-segment Arps decline model has been prevalently used, where, in early time, an Arps b parameter of 2 is used to denote transient flow;, during middle time, an b parameter of 0.2 to 1 is used; and, during late time, a b parameter of 0 to 0.2 is used to denote the boundary dominated effects. Choosing the segments and the b parameters was usually based on an educated guess about the reservoir and the visual observation of the changing slopes of decline.
The three-segment model presupposes a reservoir behavior that may not be happening in the field, and varying operating conditions can skew the production rate slope and can mask the flow regimes observed in the reservoir, This, in turn, can lead to misleading forecasts. We are proposing a way to remove the guesswork from flow transition, the presupposition of flow regimes in the reservoir, and the masking effects of pressure using rate transient analysis.