Carbon, Captured: 1D Reactive Transport Modelling of NCG reinjection in Mt Apo Geothermal Production Field

Abstract

This study presents a one-dimensional (1D) radial model to investigate the reactive transport behavior in the Mt Apo Geothermal Production Field, focusing on Well K1’s major feedzone, subject to various reinjection scenarios including neutral brine, binary brine, and a proposed non-condensable gas (NCG)-charged binary brine using TOUGHREACT v4.13 EOS 1. It explores the geochemical and mineralogical changes induced by NCG-charged fluid injection under reservoir conditions. The simulation captures key processes such as dissolution, mineral alteration, and secondary mineral precipitation within the feedzone-to-reservoir flow path. The 1D model results provided insights into potential impacts on injectivity and showed permeability enhancement due to thermal effects, with calcite, dolomite, epidote, illite, and anhydrite undergoing consistent dissolution at different magnitudes under low-pH injection. This 1D modelling approach offers an informative guide for field-scale predictions and supports the development of an effective NCG-geothermal wastewater mixture injection strategies for geothermal reservoir management.