Keywords: 
• free hydrocarbon content /
• shale /
• organic carbon content /
• water saturation /
• &Delta /
• logR method

Abstract: Research indicates that focus merely on the organic carbon content can not meet exploration needs because the characteristics of the shale formation. The most important issue of the exploration is to evaluate the free hydrocarbon content in shale formation. The relationship between porosity and oil volume in per cubic meter of rock and the relationship between porosity and water volume in per cubic meter of rock have been studied. The result shows that in the oil source rock, the characteristics of oil-bearing is increasing with the increasing of rock porosity. 
  On basis of the analysis of closed cored laboratory data such as the porosity and oil saturation in Shengli Oil field, an new evaluation model is constructed to reflect the free hydrocarbon content.  And the logging interpretation model has also been established by using the deep resistivity curve response value,  porosity and the organic matter maturity to calculate it. The ratio of organic carbon content from free hydrocarbon and total organic carbon content can directly reflect the vertical variation regulation of the free hydrocarbon content, which also indicates the favorable oil and gas exploration section. An example from Luojia area in Zhanhua sag has been reprocessed . A new model of the organic matter maturity was derived based on the experimental data and the depth. The calculating result shows a good application of this method. The indicator of free hydrocarbon enrichment zone can be derived by combining two parameter.
  One is the absolute value of organic carbon from free hydrocarbon, the other is the value between absolute value of organic carbon content from free hydrocarbon and the total organic carbon content. The section with high ratio will be the exploration targets of shale oil reservoir. This idea can provide reference for today’s shale oil and gas exploration.