| Title | A Novel Analytical Solution for Single Well Thermal Transient Testing in an Idealized Single Fracture Geothermal System |
|---|---|
| Authors | Friedrich MAIER, Ibrahim KOCABAS |
| Year | 2013 |
| Conference | Stanford Geothermal Workshop |
| Keywords | SWIW, thermal injection-shutin-backflow tests, temperature transients (signals), analytical solution, optimization |
| Abstract | Recently, heat has emerged as a useful type of tracer in geothermal reservoir studies in which thermal transients have been monitored and temperature is employed as the state variable. The single well thermal transient testing has also gained popularity in the last decade. One important type of single well thermal transient testing is called as injection-shut-in and backflow tests which is quite important for geothermal reservoir characterization and sensible energy storage in aquifers. In this work we present a novel real space analytical solution for analyzing the spatial temperature distributions as well as the temporal temperature return profiles of the non isothermal injection-shut-in-backflow tests. The new solution developed using iterated Laplace transform is both simple and computationally efficient and hence readily amenable to nonlinear parameter estimation. The derived spatial and temporal profiles are both coded in a nonlinear regression program written in Matlab to employ in nonlinear curve fitting and parameter estimation. The programs are validated by fitting the model to a synthetic data with a certain random noise. Then a parameter sensitivity analysis is presented for the three dimensionless numbers to identify the collective role of the physical parameters and to help designing the future single well nonisothermal injection tests. The new analytical model which is an extension of a previous work is now capable of providing a more comprehensive insight into the collective roles of the parameters controlling heat transport in a single fracture/matrix system and hence designing reinjection operations in geothermal reservoirs or sensible energy storage in aquifers. |