oa Holistic Organic Geochemical Characterization of Jurassic Coals of Norway and Examples of Relevance to Subsurface Studies

In petroleum exploration, thin coal layers are often ignored since they do not provide sufficient thickness to be considered as volumetrically significant petroleum sources. However, coals have been observed to produce organic geochemical signals which may affect investigations of migrated petroleum in exploration wells.

Coal layers investigated here are often associated with gas peaks on mud gas logs and the isotopic signature of those gases could be mistaken for migrated gas. Likewise, extracts from drill cuttings covering coal-bearing intervals exhibit molecular attributes that resemble at first glance those of migrated petroleum, also optical detection methods are affected. This makes recognition and typing of petroleum shows challenging, especially when oil-based drilling fluids are employed.

This work aims to understand the geochemical signatures of coals and to produce a reference characterization which could be utilized to recognize interfering coal signals, so that migrated petroleum signature can be detected with higher confidence.