MODELING OF THE THERMOMECHANICAL EFFECT ON GEOTHERMAL WELL INJECTIVITY

• Main Author: Baravanni, Afdhal
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/71528
• Institution: Institut Teknologi Bandung

Reinjection is an important component in geothermal reservoir management to support sustainable resource optimization. Determination of the need for injection wells is calculated from the injectivity obtained during the completion test. Generally, in the calculation of injection capacity, rock formation parameters such as porosity and permeability are assumed to be constant. Meanwhile in reservoirs, changes in temperature due to injection can cause the rock matrix to shrink or expand and have the potential to change the injectivity value of the well due to changes in the permeability of rock formations around the well. This has an impact on the calculation of the injection capacity during the completion test, which could be overestimated compared to the operation, because the temperature of the rock formation during the completion test is much lower than the operating temperature. The formation temperature during the completion test is influenced by the circulation of the drilling fluid, which is relatively cold, while the formation temperature during operation is influenced by the temperature of the separated brine that is reinjected (commonly >120 °C). Injectivity estimates that are too large in a field that has a limited number of injection wells will have the potential to cause a shortage of injection capacity during the operation phase with the risk of reducing the electrical power generated compared to the initial design (curtail). This study aims to create a numerical model that considers the effect of rock thermomechanics on the injectivity of geothermal wells. The thermomechanical effect studied is the change in fracture permeability and porosity due to changes in formation temperature due to injection. The numerical model was built using the TOUGH2 simulator and by the iterative coupling method with the Microsoft Office Excel Visual Basic for Applications (VBA) program changes the rock physical parameters such as permeability and porosity. The numerical model has been successfully developed and can represent changes in injectivity with temperature well. The results of this study are expected to be a reference to calculate the injection capacity estimation to maintain production sustainability.