Trapping Mechanism Of Hydrocabon Inclusion In Carbonate And Its Response To Hydrocarbon Accumulation

Hydrocarbon inclusions were valued in mineralise and petroleum area. But because the composition and thermodynamic behavior of hydrocarbon were complexity, there were some problems in recovery of capture condition and mechanism. Synthetic inclusions can be used to verified assumptions. In this paper, hydrocarbon inclusions were synthesized in calcite under high pressurem and temperature. Ten series of experiments with different aim were carried out in calcite. The effect of different oil/water ratios, temperature, pressure, salinity and distinct petroleum to hydrocarbon inclusion trapped in carbonate were disscussed. And microthermometry, Raman spectrum, infrared spectrum and chromatographic analysis were carried out on synthetic hydrocarbon inclusions to gain their homogenization temperature(Th), salinity, composition and phase transition. Based on these parameters, Trapping Mechanism of Hydrocabon Inclusion in Carbonate and Its Response to Hydrocarbon Accumulation were discussed.Synthetic hydrocarbon-bearing inclusions in carbonate at the temperature and pressure which were closed to natural reservoir and pure oil was new development of inclusion synthesized. Some new knowledge and inspiration about hydrocarbon accumulation and reservoir geology were bring out by the experiment.Through microthermometry, There were different between average of aqueous inclusions'Th in main distribution range and temperature set in experiment. Because the different was resulted from differential pressure, it was changed along with pressure changed. Using this different, calibration curve of aqueous inclusions with different salinity were established. Trapping condition of synthetic inclusions were resumed by using thermodynamic analogy software FIT and calibration curve,and which was coincidence with experimental pressure. After pressure correction, the trapping temperature and presssure of brine inclusions was coincidence with experimental condition, which demonstrated that brine inclusions could record their trapping conditions in reservoir.Freezing method and Raman spectrum were adopted to carry out low temperature in-situ measurement on aqueous inclusions. It was found from measurements that brine lixiviant trapped in inclusions was representative of original salinity and composition of mother solution. NaCl-H2O solution with different concentration were freezed for Raman spectrum measurement. The curve to define salinity of NaCl-H2O system was presented utilizing relationship between ratio of peak of hydrate and ice and salinity.Homogeneous and heterogenetic hydrocarbon trapping mechanism were present on the basis of experimental result, multiphase filtration mechanism in reservoir and recovery of inclusion trapping condition. Homogeneous trapping were classified as oil and water (oil dominance or water dominance) and pure oil condition. Combined with mechanism of crystal growth, four trapping model were presented. And they were point model, line model, area model and volume model.Because of composition differentiation of oil, two type degree of ripeness oil could be trapped in inclusions in experiment with one oil. And the differentiation mechanism could be divided as physical mechanism which was chromatograph and chemical mechanism which was pyrolysis of oil.Inclusions trapping would be constrained but not ceased by high O/W ratios. And inclusions could record rapid hydrocarbon accunulation. And the whole procedure of accunulation could be recorded in inclusions. The critical period of hydrocarbon charging correspond with great quantity of inclusions trapping. Relative high temperature could generate acid diagenetic environment which constrainted growth of calcite and inclusion trapped through denudation. In contrary, relative low temperature could generate alcaline diagenetic environment which accelerated growth of calcite. Inhibition of clean oil to growth of calcite was more intensive than that of heavy oil. higher salinity solution was favour of growth of calcite. But excessive salinity would slow down crystal growth. So crystal growth would be high efficient in particular salinity limit.The relationship between Th and composition, shape and size of inclusions synthized were discussed. Composition of inclusion was main affecting factor of its Th and there was no obvious relationship between shape and size and Th of inclusion. Inclusions with regulation shape and approximate gas/liquid ratios should be selected for thermometry. Adopt the peak of Th distribution range and abandon the discrete value.