Source Rock Evaluation

There are many reasons and ways for source rock evaluation methods, to obtain petroleum and other gases or oils and countless ways to extract these items.

As rocks are obviously buried, the contained organic matter is heated or matured within the Earth’s geothermal gradient, to generate petroleum. The thermal level of maturity for source rocks is consequently a basic and critical parameter in assessing petroleum prospectively of exploration acreage.

They hydrocarbon potential of a source rock comprising insoluble organic materials, capable of generating hydrocarbons upon pyrolysis and regular hydrocarbons or further maturation is analytically determined. In the instant invention, a particulate sample of the source rock is slurred with a solvent to extract the hydrocarbons there form and provide a first solution for analysis.

Then the extracted sample is again slurred with a solvent and the resulting slurry is heated to a temperature sufficient to pyrolyze the insoluble organic material to liquid hydrocarbons. They liquid hydrocarbons dissolve in the solvent to provide a second solution for analysis. The two solutions are then analyzed independently for hydrocarbon content.

Originating from organic material in rocks, petroleum and the capacity of organic matter to have developed oil or gas in the past can be inferred in part from the organic material and its present degree of thermal maturity.

Groundbreaking analyses of the Early Cretaceous foundation rocks in the Otway Basin has exposed a thick, mature; organic-rich source rocks containing gas- and oil-prone marcerals exist to the Northwest of Portland in the Tyrendarra Embayment and around the Prot Campbell region. The sampling opportunities for source rock evaluation are geographically and stratigraphically imperfect because only a small portion of the onshore Victorian Otway Basin is deeply drilled.

Biomarker analyses designate that gas-prone marcerals are the most abundant and wide-spread. Oxic, open plain and shallow lacustrine environment conditions prevailed over most of the Northern areas. By dissimilarity, deeper water plummeting conditions prevailed in the Southern and North-Western marginal areas.

Progenitor hydrocarbon materials are predominantly asphaltic/aromatic but in some locations, the organic contents contain more paraffinic and naphthenic compounds. In addition, hydrocarbon generative potential ranges from excellent to poor; and the liquid hydrocarbons are present in some of the deep shale’s.

Several of the hydrocarbons that were migrated and generated in the Portland region and in the Port Campbell region, were most likely pooled in existing stratigraphic traps.  

Most structural traps were formed during the Palaeocene uplift event in the Portland region and during the Oligocene uplift event in the Port Campbell region. These structural traps, particularly those in the Port Campbell Embayment, have been loaded by the continuing oil and gas generation and expulsion form the Aptian-Albian source rock.

Despite the lack of state-wide sampling opportunities, analytical results suggest that the most prospective areas for oil and gas – so far as close proximity of reservoir and seal rocks to thick, rich mature source rock is concerned – are within the Casterton and Lindon to Pine Lodge regions, in the Portland/Tyrendarra Embayment and between Peterborough and Port Campbell offshore and along from the present Victorian coastline.

Many companies, for a price, will provide evaluations of petroleum source rocks. They use organic carbon content, hydrocarbon content, kerogen maceral analysis, visual kerogen and vitrinite reflectance.

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