LECO method in estimating richness
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It has been suggested that this article be merged with [[::Using conventional well logs to estimate richness|Using conventional well logs to estimate richness]]. (Discuss) |
| Exploring for Oil and Gas Traps | |
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| Series | Treatise in Petroleum Geology |
|---|---|
| Part | Critical elements of the petroleum system |
| Chapter | Evaluating source rocks |
| Author | Carol A. Law |
| Link | Web page |
| Store | AAPG Store |
Definition of LECO method
The LECO method of estimating total organic carbon (TOC) uses an instrument known as a LECO carbon analyzer to measure TOC values by combusting the organic carbon and measuring the resulting carbon dioxide produced. The LECO method has almost totally been replaced by Rock-Eval pyrolysis. However, data may still be available from prior analysis.
Measuring TOC with LECO
Samples are powdered, weighed, and chemically treated prior to analysis to remove the inorganic carbon (carbonate) from the rock. The sample is then combusted in the presence of excess oxygen, allowing carbon dioxide to form from the free (organic) carbon in the rock.
The amount of carbon dioxide is directly proportional to the amount of organic carbon or the TOC of the rock. However, the TOC value can be inflated due to the presence of sulfur compounds, water, and carbonate if they have not been removed prior to analysis.
Comparing TOC values
The TOC measured by the LECO method does not include a measurement of the free hydrocarbons present in the sample. The free hydrocarbons would be volatized when samples are dried after acid treatment is performed to remove the inorganic carbonate minerals. Thus, if a sample has a high free hydrocarbon content, the LECO TOC value will be smaller than a Rock-Eval TOC value, which includes free hydrocarbons (S1) in the TOC calculation.
See also
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