Petrography and diagenesis of cavity-fill dolocretes, Kuwait

•Karst cavity-fill dolocrete is a new mode of dolocrete occurrence.•It is developed by groundwater dolocretisation of cavity-fill siliciclastics.•It is developed through successive stages of karstification and dolocretisation.•Hydrocarbon seepage may have played a role in the development of these dolocretes.•Karst cavity-fill dolocrete may impact the petrophysics of carbonate rocks.

Cavity-fill dolocretes within the palaeokarst zone of the Middle Eocene chertified dolomicrite Dammam Formation are exposed within a quarry located on the top of Al-Ahmadi ridge in southern Kuwait. They are characterised by the abundance of zoned and spherulitic dolomite. These dolocretes are formed by massive precipitation of primary dolomite into cavity-fill siliciclastics within phreatic groundwater conditions during arid to semi-arid period. Successive stages of karstification and dolocretisation are responsible for the development of two types of cavity-fill dolocretes, namely; mature and immature dolocretes. The association of diagenetic alunites with the cavity-fill dolocretes suggests that hydrocarbon seepage may have played a role in the development of these dolocretes. It is suggested that the occurrence of similar diagenetic setting within carbonate sequence may potentially affect their reservoir characteristics.