| Title | Inverse Numerical Modeling of Rantau Dedap Geothermal Field After Six Exploration Wells |
|---|---|
| Authors | Alexandre BACQUET, Alfianto PERDANA PUTRA, Grimur BJORNSSON, Andri ARNALDSSON |
| Year | 2016 |
| Conference | Stanford Geothermal Workshop |
| Keywords | numerical simulation, inverse modeling, iTOUGH2, Sumatra |
| Abstract | In 2014-2015, six deep exploration wells were drilled in Rantau Dedap geothermal greenfield located in South Sumatra, Indonesia. The exploration program being completed, Supreme Energy Rantau Dedap consortium in collaboration with Warm Artic Ehf built and calibrated the numerical model of the reservoir in a very time efficient way to carry out the reserves assessment of the field. A large contribution to this efficiency has come from the use of the iTOUGH2 program which automatically calibrates a TOUGH2 numerical model against most of the observed data collected over the exploration period by solving the inverse problem. According to the conceptual model that depicts a large reservoir strongly controlled by faults at depth, the model follows a single porosity approach where the near vertical faults are explicitly defined at their true locations and with their own properties. The model has limited thickness and extent, tight lateral boundaries, and can therefore be regarded as conservative. 36 parameters were inverted for at maximum, most of them being the horizontal and vertical permeabilities of the faults and rocks defined in the model, and the characteristics (rate and possibly enthalpy) of the deep upflow and surface outflow. The final results of the inversion are very consistent with the conceptual model, with a high enthalpy deep upflow connected to a wide and permeable shallow outflow through a few high permeability faults hosted at depth by a tight matrix. The resulting match of the observed data is satisfactory, except for two wells on the northwestern side whose temperature reversals are not reproduced properly by the model. This misfit highlights the necessity to improve the faults description in the West and Southwest parts of the field by acquiring more structural data. |