Compositional variability in oils and formation waters from the Ayoluengo and Hontomín fields (Burgos, Spain). Implications for assessing biodegradation and reservoir compartmentalization

► This work is an analysis of 13 oils and connate waters from the Basque-Cantabrian Basin (Spain). ► One of the main objectives was to delineate reservoir compartmentalization in the Ayoluengo field. ► Ayoluengo and Hontomín crude oils fall into a one family derived from the same Liassic source rock. ► The Hontomín oil is more mature and it is slightly biodegraded, possibly due to sulfidogen activity. ► All the analyzed formational waters were analogous and can be classified as chloride-calcium type.