Addressing Clogging Risks When Injecting Heat-Depleted and Oxygenated Hot Springs Water: Lessons Learnt from Peninsula Hot Springs, Australia
Martin PUJOL, Charles DAVIDSON, Ian BRANDES DE ROOS, Grant BOLTON
Peninsula Hot Springs (PHS) is Australia’s premier hot springs and spa facility with over 500,000 visitors annually. It sources brackish (3 g/L salinity) geothermally heated water at 47°C from two bores targeting the Werribee aquifer (Eastern View Group) at about 640 m depth. The geothermal water is currently mixed with 15°C fresh water ( less than 1 g/L salinity) from a shallower aquifer to create a wide range of bathing offerings. Because of the salinity of the geothermal water, surface water discharge to the environment is problematic. In 2010, PHS completed one injection bore (Injection Bore #1) that has faced severe clogging issues. Plans have been made to modify the system to improve injection efficiency and also to construct two replacement injection bores (Injection Bore #2 and #3) by mid-2019. Geothermal water is also considered to be cooled and used as a substitute for pool temperature regulation. Injection of geothermal water into aquifers composed of interbedded sandstone, silty claystone and coals can be challenging. Clogging issues have impeded the development of many clastic geothermal resources globally and at PHS in particular, clogging issues have resulted in poor injection performance since the first injection bore was commissioned 2010. The following have been cited as causes of clogging in the literature: proliferation of bacteria (biological clogging), suspended particulates, clay dispersion in aquifer matrix, gas bubbles in the water (physical clogging), chemical precipitation in the water and/or in the aquifer (geochemical clogging). While the main causes of clogging have been studied by researchers and been the subject of a number of successful pilot-scale studies for decades, particularly in the oil and gas industry, sparse published information exists in the geothermal literature regarding the key technical solutions and procedures that have guaranteed the success of injection into sandstone aquifers in modern industrial applications. This paper focuses on the review of PHS injection scheme undertaken by the authors in 2018 and design changes that have been implemented subsequently to improve injection efficiency. Issues discussed will include clogging associated with suspended solids, bacteria induced clogging and chemical precipitation. Additionally, the key bore design and surface filtration criteria that will permit successful economic injection of heat-depleted groundwater into the Werribee Formation sandstone aquifer are discussed.
|        Topic: Injection Technology||Paper Number: 23002|