Application Studies Of Heat Flow Models On Exploration Of Geological Resources

Magmatic activities can enhance the geothermal gradient of sedimentary basins, accelerating the hydrocarbon generation of strata, and promoting the formation of oil and gas reservoirs. Therefore, it is of great significance to study the thermal effect of igneous intrusions on organic-rich wall rocks for evaluation and exploration of oil and gas resources. Temperature-Time index (TTI) is a usual criterion for assessing the history and potential of hydrocarbon generation in sedimentary rocks. Heat flow models as an important tool can be used to reconstruct the thermal evolution history of wall rocks in the vicinity of igneous intrusions and have been applied into the evaluation of oil and gas resources in igneous-intrusion-bearing basins. It is necessary to constantly improving the accuracy and reliability of the heat flow models.By allowing for some additional factors based on the heat conduction models that previous workers constructed, this study quantificationally investigated the effect of the temperature-dependent thermal parameters, the spatial heterogeneity of porosity and the thermal conductivity of wall rocks on organic-matter maturation in the contact aureole. Numerical simulation results indicate:1) under real contact metamorphic conditions, the thermal parameters of argillaceous rocks varies strongly with temperature and the temperature-dependent thermal parameters of the wall rocks may obviously over estimation on the model prediction of the maturation compared to the constant thermal parameters;2)the degree of the effect of the spatial heterogeneity of the porosity are much less than that due to the spatial heterogeneity of thermal conductivity. In addition, by taking a0.9m dyke at Isle of Skey and a15m sill at Cape Verde Rise as an example, we also analyzed the thermal effect of these two intrusions based on one-dimensional and two-dimensional heat flow models and the comparison between the model predictions and the measured vitrinite reflectance. For the former geological example, the heat conduction model of the finite-time intrusion mechanism represents natural conditions, whereas for the latter, the heat convection model approximately reflects the real geological situation. These results show that;1) the effect of difference intrusion mechanisms of magma on the organic-matter maturation of wall rocks is more obvious than that if the pore-water vaporization;2) the spatial range of the thermal effect of igneous intrusions is usually no more than3times the thickness of the intrusions and the thicker the intrusion, the larger proportion of the thick of intrusion;3)using Nu to consider heat convection of pore water in one-dimensional heat flow models can obtain more accurate results in farther distance from contact surface.