Perpustakaan Digital ITB

Production forecast of a geothermal reservoir is important since future performance will be used as a basis to determine make-up well requirement and remaining reserve assessment. The prominent method to perform production forecast is the decline curve analysis based on the Arps method. One of the challenges in using the Arps method is determining the hyperbolic exponent value, b, at the type of hyperbolic decline. This paper aimed to offer two new approaches to find a hyperbolic exponent using Spivey’s methods which are based on binomial and Taylor expansion. Spivey’s methods have not been widely used in geothermal production decline analysis, so it is an opportunity to apply them. These new approaches use iteration and matrix operations such as multiplication, transpose, and inverse. Besides the hyperbolic exponent, the initial decline rate and initial flow rate values are also the outcomes of these new approaches. Developed in a Spreadsheet, the calculation becomes more manageable and more practical. These new approaches are recommended to be used in another geothermal field especially when the production data is smoothly declined.