Applying Decline Cumulative Production Analysis (DCPA) to Geothermal Resources

Abstract

A new decline curve analysis has been developed for geothermal resources in Steady state condition, in the present work it has been plotted the natural log of Decline cumulative production (Ln (QD)) versus the natural log of cumulative production (Ln(Q)) and natural log of time ((Ln(t)) respectively. The graphs show linear relationships and combining equations determined by least squares fitting, it is possible to yield a new decline curve equation. Types curve in a semi-log plot shows a linear relationship between dimensionless production rate(qd) and time. The present contribution has been applied at one steam geothermal well data from Kamojang Indonesia and one geothermal power plant in Nicaragua operating below its installed capacity and it has been possible to get the power generation forecasting at the currently condition. Deviations from the decline curve behavior can be related with changes in operational conditions, wells behavior, work overs or changes in reinjection strategies. These perturbations can be used to identify changes effects and to assist at the reservoir engineer in quantifying results of the field management.