Design and experimentation of a high-temperature-pressure dynamic ignition simulation system
[Objective]Ignition is a crucial initial step in in-situ combustion.The ignition process is accompanied by complex physical and chemical changes,and the oxidation parameters rapidly change.As in-situ combustion occurs underground,researchers cannot obtain its direct dynamic information.Therefore,they must acquire this information through combustion tube experiments.However,traditional combustion tube experiments are typically large in scale and require considerable labor.Thermal analysis experiments,while easy to perform,cannot be extrapolated to detect the overall oxidation behavior of crude oil.Maintaining consistency between the experimental process and the actual formation conditions is challenging.To address the challenges posed by high temperature,high pressure,and rapid temperature changes during crude oil combustion,this paper presents the design of an experimental device for ignition simulation.The device can capture dynamic combustion information.[Methods]Both ends of the combustion tube are sealed with double-layer high-temperature-resistant graphite rings,which can withstand a pressure of 10 MPa.The combustion tube comprises GH4169 alloy,which exhibits excellent high-temperature and thermal fatigue resistance.An online controller self-tunes the PID parameters and incorporates fuzzy control for adjustments,which ensures consistency between the output and target temperatures to simulate actual conditions.This results in a temperature control accuracy of±0.1 ℃.The online output gas monitoring system can continuously monitor the composition of the output gas components in real time and includes an alarm function.The injection system replicates the gas circulation state within the stratum.Its functions include supplying oxygen,regulating the flow rate,controlling back pressure,and injecting liquid.The tail gas generated in the in situ combustion ignition experiment contains water vapor,sand,and oil.To prevent pipeline blockage and protect the experimental equipment from damage,the tail gas must be treated.The treatment process involves pressure reduction,filtration,dehydration,and drying.[Results]Functional experiments show the following:① in the blank heating experiment at a heating rate of 0.5 ℃/min,the temperature difference between the tube wall and center is only 6.3 ℃,which is lower than that of similar domestic and international devices;② during crude oil ignition experiments under different pressures,higher pressure results in lower ignition points of the crude oil;③ the change in ln(ln(C1/C2))with T-1 during the experiment is bounded by an inflection point that shows an obvious stage.The linearity improves only when the temperature exceeds the inflection point.Apparent activation energies and pre-exponential factors were calculated for the HTO stage(230～400 ℃)under various pressure conditions.The results indicated that higher pressure led to lower crude oil ignition points,inflection point temperatures,and apparent activation energy.This suggests that increasing pressure can enhance the thermal oxidation of crude oil.[Conclusions]This experimental device can be used to calculate the kinetic parameters of crude oil oxidation,which provides essential data to support the implementation of in-situ combustion,air drive,and numerical simulation in the field.
in-situ combustionignition parameters simulationexperimental systemapparent activation energy analysisignition evaluation
万方数据
维普
