| Title | Numerical Pressure Transient Analysis of CO2-Containing Geothermal Reservoirs During Draw-Down Buildup Testing |
|---|---|
| Authors | Gitta SEPTIANI, Daniel W. ADITYATAMA, Eylem KAYA, Sadiq J. ZARROUK |
| Year | 2020 |
| Conference | World Geothermal Congress |
| Keywords | Pressure transient analysis, geothermal well testing, CO2, drawdown buildup test |
| Abstract | Pressure transient testing in geothermal reservoirs involves a complex process of heat transfer and flow of multiphase fluids. Many geothermal reservoirs also contain considerable amounts of non-condensable gases (NCG), especially CO2. Those conditions further complicates the analysis of geothermal well test data as the current pressure transient analysis (PTA) methods are mainly developed for single-phase flow and slightly compressible fluids. The purpose of this paper is to examine the suitability and accuracy of commonly used analytical PTA methods under multi-phase and multi-component conditions. Various numerical models were created to simulate geothermal reservoirs containing single-phase and two-phase mixture of water-CO2 during draw-down build-up tests. The corresponding pressure responses from the numerical models were then analysed using analytical models to estimate reservoir properties. The results were investigated to assess the accuracy of the interpretation. The parameters used to analyse the pressure transient analysis were subjected to sensitivity analysis to identify their effect on the characteristic appearance of the pressure derivative plot shapes. The results obtained show that conventional analytical methods using pressure derivative can be reliably used to some extent in CO2-containing reservoirs when no flashing takes place. However, several factors and variables that might mislead the interpretation of PTA data. The results are an attempt to lay the groundwork for future use of PTA in CO2 rich geothermal fields. |