In this paper a simulation model of oil shale formation is generated in which the reservoir is heated by downhole heaters and subsurface solid kerogen is converted into liquid and gas hydrocarbons by the function of chemical reactions, temperature and time. On the basis of the results obtained, the alteration in porosity and permeability is evaluated. It is found that the porosity and permeability of oil shale increase significantly as a function of in-situ kerogen conversion into oil and gas. A new mathematical modeling approach is adopted to measure the quantitative change in porosity. It is revealed that the effective porosity of the studied reservoir increases from the initial value of 5% to the final value of 12.5% after in-situ kerogen pyrolysis. In-situ permeability, as a function of porosity, is also modeled and a noteworthy increase is observed. The results are compared with previously published experimental findings and are found to be in a good agreement.
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