The Evaluation And Application Of Volcanic Fluids On Hydrocarbon Generation Of Source Rocks

Combination of source rocks and volcanic sedimentary contact is particularlyimportant for hydrocarbon accumulation. The volcanic materials brought by magmationhave important implications for hydrocarbon generation and formation reservoir. Duringor after the volcanic rocks forms together with a quantity of volcano fluids which has asignificant influence on the chemical properties of surrounding strata. The process ofvolcano fluids effect on source rocks is very complex which includes hydrogenation,heating effect, catalysis, and so on. The simulation experiment about volcano fluids effecton sources rocks is hard to operate and the data are difficult to achieve quantitativeanalysis caused by complex composition of volcano fluids. Based on thermal simulationexperiment, the impact of volcanic fluids on source rocks is studied, the mathematicalmodel of the motion evolution of the volcanic fluids is builded and the motion evolutionlaw of volcanic fluids is analyzed in Xujiaweizi Fault Depression of Songliao Basin.Themigration of volcanic fluids is marked.The areas influenced by volcanic fluids aredelineated by using the Laplacian operator. In a summary, the research contents andconclusions basically including the following three points:(1) The discussion about different kinds of volcanic fluids effect on different kinds ofsource rocks hydrocarbon generation.In this study, after168experiments, it is the first time for the semi-quantitative andquantitative evaluation of acidic and basic volcanic fluids effect on hydrocarbongeneration of source rocks. The results of experimental show that in the range of300℃-350℃, acidic volcanic fluids plays both a role in promoting for non-hydrocarbon andhydrocarbon gas. The basic volcanic fluids have an inhibition for non-hydrocarbon gasesgeneration, to hydrocarbon gases show that firstly promoting, then inhibition effect. In the range of400℃-450℃, both volcanic fluids show a significant inhibition to hydrocarbongases, while a promoting to the non-hydrocarbon gases. The basic volcanic fluids effect onthe component of liquid saturated hydrocarbon by narrowing its carbon number range.And there is no effect on the acidic volcanic fluids doing to the component of liquidsaturated hydrocarbon. In the range of300℃-350℃, acidic volcanic fluids play a role inpromoting effect for liquid hydrocarbon generation, and the basic volcanic fluids play arole in inhibiting the quantity of liquid hydrocarbon generation. In the range of400℃-450℃, both acidic and basic volcanic fluids have a role in promoting effect for liquidhydrocarbon production.(2) The discussed on the multivariate analysis of thermal simulation experimentaldata.The experimental data are analyzed through empirical orthogonal function.Theresults show that the temperatures have a positive correlation with CH4、C2、C3、iC4-nC5,total hydrocarbons and total non-hydrocarbon and total gas yield, while have a negativecorrelation with CO2、CO、H2S gas yield. There is a critical temperature in the thermalsimulation experiment, when the experimental temperature is below critical temperature,gas production increases with increasing temperature, when the experimental temperatureisabove critical temperature, the gas production decreases with increasing temperature.The critical temperature of the dry system is exist in350℃-400℃. while the fluids systemin400℃-450℃which shows that acidic and basic volcanic fluids make the criticaltemperature go up.(3) The numerical simulation of volcanic fluids evolution and typical examplesanalysis.The mobility of volcanic fluids is depended on many factors, but primarily oncomposition, temperature, and pressure. Generally, a higher content of SiO2and Al2O3inthe volcanic fluids can result in an increased viscosity. However, volatiles contained in thevolcanic fluids can reduce its viscosity. Factors such as viscosity, porosity, permeabilitycharacteristics of surrounding rocks and formation pressure, determine the distribution range of the volcanic fluids. This article takes Xujiaweizi Fault Depression in Songliaobasin as an example, using the whole-rock compositions of volcanic rocks to calculatevolcanic fluids parameters such as density, viscosity under the specific temperature andpressure conditions. At the same time, according to physical property of present formationand geophysical data, ancient burial depth, ancient porosity and ancient formation pressurewere recovered. On this basis, concept of volcanic fluids potential is introduced into thenumerical simulation of evolution of volcanic fluids. All above the data are used tocalculate volcanic fluids potential for the first time in Xujiaweizi Fault Depression.Ultimately, we concluded the results in Xujiaweizi that the influence area of volcanicfluids in Yingcheng Formation I to the source rocks of the Shahezi Formation is about628km2, while Yingcheng Formation III influences161km2.