Analysis of well test data for the estimation of reservoir parameters and the prediction of pressure response using WellTester and Lumpfit

Abstract

This work presents a review of the theoretical background and methodology used in the analysis of well test data from four geothermal wells. The purpose of the well test analysis is to identify the type of reservoir involved and to quantitatively determine the reservoir parameters. The injection well test data of three wells were analysed using the software WellTester and one set of interference test data was analysed by the software Lumpfit. WellTester has been used extensively in Iceland for the estimation of reservoir properties whereas the Lumpfit has been used for future pressure response prediction for various production scenarios as well as to determine some reservoir properties. Important parameters such as transmissivity, permeability, and storativity for groundwater flow models were estimated in order to predict the future availability of the water resource. To determine these parameters and others, injection well test pressure response data from three wells at Hellisheidi high-temperature area were analysed.

The well test analysis results show that the reservoir is generally characterized by good permeability and storativity. Generally, above average values of the injectivity index were also observed. The results for these parameters are in the normal range for Iceland. The second part of the project included an analysis of an interference test at a low temperature field. The entire 232 days of monitoring of pressure response data, taken in one observation well, due to the production of two production wells was simulated by lumped parameter modelling. Modelling showed that different combinations of two- and three-tank closed and open models fit satisfactorily. The future water-level changes in the observation well were predicted, based on three production scenarios. The calculated results for open tank models indicated that this system would be able to sustain an average of 80 kg/s production for ten years without significant pressure drop.