Near Well Damage. Assessment, Remedial and Prevention. Application to Geothermal District Heating Systems

Abstract

The development of geothermal district heating (GDH) systems applying the multi-doublet (doublet, triplet clusters) concept of Geoheat farming has resulted in several instances in well damage and of severe exploitation losses whose origin proved often ambiguous. Based on field observation, monitoring and modelling of a variety of well and reservoir environments of a variety of well and reservoir environments a relevant damage spectrum of the well sand face and near well space is derived according to the assumed/verified source mechanisms induced by either or both the fluid production or/and injection processes. As a result a tentative classification is suggested which highlights the main identified damage mechanism – native particle entrainment, thermochemical supersaturation/precipitation of sensitive crystal species, formation of long term compaction, flow channelling – which modify the initially assessed/presumed temperature/flow pattern favouring flow path plugging and skin cake build-up. A methodology is proposed for properly assessing well/formation impairment, implementing efficient remedial/preventive procedures from field tests and predictive modelling.