Verification and Calibration
Verification of the geological reconstruction and calibration of the thermal history model involves comparison of calculated parameters with measured data, availability of which will depend upon the exploration maturity of the study area. Calibration involves comparison of measured and calculated parameters, most commonly, but not limited to, formation temperature for calibration of heat flux and geochemical maturity indices (vitrinite reflectance, spore colour index, fission track etc.) for calibration of palaeo-heat flux and thicknesses of section removed as a result of uplift and erosion. Modelling is often an iterative process, to arrive at an optimum fit between measured and calculated parameters. Bounds for specific input parameters may be established by sensitivity analyses. By varying selected input parameters – e.g. heat flux, estimates of eroded section etc. – it is possible to test and verify different geological models and to evaluate the likelihood of successful drilling for various scenarios.
Source rock maturation and hydrocarbon generation are thermodynamic processes and are therefore dependent upon temperature and also time, through the duration and rate of heating. The thermal decomposition of organic material is simulated by first-order reaction kinetics incorporating the Arrhenius rate equations and distributed activation energy models. Kinetic parameters are dependent upon kerogen type and source rock facies. Kinetic parameters for specific source rocks may be derived by laboratory pyrolysis analyses and incorporated into the basin modelling. Simulations provide rate of generation and enable quantitative estimation of the amount of hydrocarbons formed. APT provide laboratory heating analyses for determination of source rock kinetic parameters, by both open-system pyrolysis and closed-system pyrolysis.
For matters regarding Petroleum Systems Analyses contact Mark Bastow (Mark.Bastow@aptec.no).