Improvement of Condensate Well Permeability Induced by Steam Condensate Injection: Modeling the Condensate-Rock Interaction using CHIM-XPT

Steam condensate reinjection Well 5 in the Southern Negros Geothermal Production Field initially had low permeability and did not attain the required reinjection capacity. However, the acceptance increased by ∼38 kg/s over a period of ∼5 months since it was commissioned. Geochemical modelling using the CHIM-XPT software was conducted to investigate the role of mineral dissolution on the permeability improvement in Well 5. At less than one gram rock titrated, there was an observed steep increase in SiO2(aq) and Na+ concentrations, indicating quartz and silicate mineral dissolution from the andesitic host rock. Total molality of SiO2(aq) changed from 4.74x10−5 to 6.80x10−3 (mol/kg solution). Major dissolution occurs at lower titrated rock mass, and this likely occurs at the section of the rock near the open hole section where the condensate and host rock first interact in the reservoir. Subsequent injection of condensate could have induced more dissolution of the quartz and silicate minerals from the rock, which further initiated an increase in permeability.