Production forecast can be performed by using reservoir simulation, production decline analysis. For the field where there is sufficient history production data, production decline analysis is more accurate. Austar Gas has book reserve for more than 100 companies using production decline analysis. Production decline analysis is a basic tool for forecasting production from a well or well group once there is sufficient production to establish a decline trend as a function of time or cumulative production. The technique is more accurate than volumetric methods when sufficient data is available to establish a reliable trend and is applicable to both oil and gas wells.
Accordingly, production decline analysis is most applicable to producing pools with well established trends. It is most often used to estimate remaining recoverable reserves for corporate evaluations but it is also useful for waterflood and enhanced oil recovery (EOR) performance assessments and in identifying production issues/mechanical problems. Deviations from theoretical performance can help identify underperforming wells and areas and highlight where well workovers and/or changes in operating practices could enhance performance and increase recovery.
To the geologist, production decline analysis of an analogous producing pool provides a basis for forecasting production and ultimate recovery from an exploration prospect or stepout drilling location. A well’s production capability declines as it is produced, mainly due to some combination of pressure depletion, displacement of another fluid (i.e., gas and/or water) and changes in relative fluid permeability. Plots of production rate versus production history (time or cumulative production) illustrate declining production rates as cumulative production increases. In theory, production decline analysis is only applicable to individual wells but in practice extrapolations of group production trends often provide acceptable approximations for group performance. The estimated ultimate recovery (EUR) for a producing entity is obtained by extrapolating the trend to an economic production limit. The extrapolation is valid provided that :
• Past trend(s) were developed with the well producing at capacity.
• Volumetric expansion was the primary drive mechanism. The technique is not valid when there is significant pressure support from an underlying.