Fischer Assay

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Fisher Assay pyrolysis incorporates a defined heating rate and condenser to determine the amount of oil, gas, and water that can be “cooked” out of an oil shale or similar source rock.  

Weatherford Laboratories has adapted method ASTM D3904 to determine the quantity of oil in an oil shale.


Originally developed for coal retorting, the Fischer Assay process has been modified to evaluate oil shales.

Approximately 100 grams of oil shale is placed inside an enclosed steel retort/condenser system.  The retort (rock) is heated to 500°C which produces oil, water, and gas that is collected and quantified either directly (water and oil) or by difference (gas).

Our broad geochemical analyses capabilities can provide additional information on the oil shale source rock.

Additional rock analysis (Total Organic Carbon, Rock-Eval, Source Rock Analysis) can provide additional information regarding the source rock. Oil collected from the Fischer Assay process can be analyzed by a variety of methods we have in house, including gas chromatography.

Fischer Assay Deliverables

  • Water Yield – Amount of water produced by the sample reported as a weight percent of total amount of rock pyrolyzed

  • Oil Yield – Quantity of oil produced by the sample reported as a weight percent of total amount of rock pyrolyzed

  • Gas-Plus-Loss – Total amount of gas produced and any losses that may have occurred, calculated by weight difference

  • Spent Shale – Amount of rock that was not converted to gas, water, or oil, including the remaining mineral matter and the coke produced from pyrolysis

  • Density of the oil collected 


Our Fischer Assay method provides standardized data ideal for oil-shale resource evaluation and comparing the ability of various oil shales to produce oil.