| Baiyinchagan depression in Erlian basin is a lacustrine sedimentary basin, andthree sets of hydrocarbon source rock and various genetic types of crude oil had beenfound, two new oilfields had already been built in it. But it’s hydrocarbon generationmechanism is not clear, and the potential of hydrocarbon resource is not clear too.This restricted to select it’s next exploration directions severely.The paper adopted the new thinking on basin evolution and hydrocarbongeneration and accumulation. According to the principle of combining experimentalsimulation with numerical simulation, combining sample testing with inversion, itstudied hydrocarbon generation mechanism of Baiyinchagan depression regarding asa unified body of basin evolution and hydrocarbon generation and accumulation.Especially through the hydrocarbon generation and expulsion simulation experimentin limited space and the analysis of physical field characteristic in basin liftingprocess, the paper studied the hydrocarbon generation and accumulation process andcalculated the quantities of hydrocarbon generation and expulsion, and re-recognitedthe potential of hydrocarbon resource, and analysised the control action ofhydrocarbon generation characteristics on the distribution of reservoir, and furtherpointed out favorable exploration directions.According to the main problems of the study of hydrocarbon resource andaccumulation, first of all, using the formation-pore and hot-pressing hydrocarbongeneration and expulsion simulation instruments, carrying out hydrocarbon generationand first expulsion experiments of source rock samples in simulated geologicalconditions systematically, and studying on hydrocarbon generation and expulsion ofhydrocarbon source rock in the condition of limited space with water. Combining withbasin modeling technology, the paper determined the calculating modules ofhydrocarbon generation and expulsion and the quantitative evaluating mode ofhydrocarbon generation and expulsion efficiency in the basin scale dynamically, anddetermined the models of maturity-porosity, maturity-oil yield, maturity-oil saturationof pore space, and firstly established the quantitatively calculating model ofhydrocarbon generation and expulsion in limited space on the depression.There are many unconformities in Baiyinchagan depression. Calculating ondenudation thickness is always a difficulty and key problem in sedimentary basin research. In order to investigate the effect of denudation to hydrocarbon generationand accumulation in the area, it calculated the denudation thickness of the depressfirstly adopting the method of astronomical geologic age. Using logging andstratigraphic data to calibrate the date and age of Baiyinchagan depression in about0.4million years, and combining with the calculation methods of deposition rate anddenudation thickness, it determined the erosion time, rate and thickness during thelifting time overall. The erosion time is the longest in the later period of Saihantalaage about5.89million years, and the denudation thickness is between220to310meters in the north and south belts of Baiyinchagan depression.Using sandstone rebound simulation experiment and theoretical calculation, itdetermined the calculating model of sandstone rebound quantity, and restored state ofthe ancient pressure between before and after denudating during basin lifting overallthrough studying on quantitative relation between the increased amount of sandstonerebound and the reduced amount of effective overburden pressure in different depthon the chart. The sandstone rebound thickness is between0.5and12meters, and theancient pressure difference is between0.2and3.5MPa between before and afterSaihantala denudation period.Finally applicating the quantitatively calculating model of hydrocarbongeneration and expulsion in finited space, it calculated the total quantity ofhydrocarbon generation of the three sets of hydrocarbon source rock about61.505×10~8t, the total quantity of hydrocarbon expulsion about10.315×10~8t, and thepotential of hydrocarbon resource is increased in Baiyinchagan depression. Theancient pressure difference between before and after the denudation in the later periodof Saihantala age is the power source of hydrocarbon migration and accumulation,and the oil fields having been found locate on the relatively high value zone of ancientpressure difference.The paper can provide a reference of quantitatively studying on hydrocarbongeneration and accumulation for the similar basins to deepen the petroleum geologicalresearch, and providing a basis for exploration decision-making and deployment. |
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