Prediction Of Wellbore Temperature And Pressure In High Sulfur Gas Wells

The main difference between the high-sulfur gas reservoir and the conventional gas reservoir is that the high hydrogen sulfide content and the complex phase change in the wellbore makes it difficult to enter the downhole temperature and pressure gauge.In order to make full use of the high-sulfur gas wellhead test data for dynamic monitoring,This paper focus on the fluid physical parameters,the special phase change to bulid the dynamic prediction model of sulfur deposition in high sulfur content gas wells.Using the model to determine the location of sulfur precipitation and the amount of precipitation and sulfur diffusion deposition,Based on the actual thermal conductivity and fluid flow law of wellbore to build the unsteady temperature and pressure model,The unsteady temperature,pressure model and the sulfur deposition diffusion model are calculated by coupling programming,using data on the bottom of the wellhead to provide a basis for dynamic monitoring of high sulfur gas reservoir,In the analysis of wellbore temperature,pressure distribution and sulfur deposition prediction,the main achievements are as follows:(1)The calculation of the physical properties of the high-sulfur natural gas(deviation factor,viscosity,the parameters of the heat transfer)is carried out by Preferred parameter model and compile program.It is concluded that due to the change of the temperature and pressure in the wellbore,The natural gas properties and thermophysical parameters related to the thermal process vary with time and well depth.(2)The theoretical method of sulfur deposition prediction:analyze the complex phase change in the wellbore,couple the temperature and pressure model of the wellbore,calculate the sulfur precipitation and precipitation position and the force analysis is carried out to determine the critical suspension velocity and the critical flow.The sedimentary diffusion model established by mass transfer theory is used to predict the deposition.(3)The unsteady-state temperature and pressure model of the wellbore:The thermal conductivity of the wellbore and the formation is considered as unsteady heat conduction.The laplace transform and stefest numerical inversion are used to solve the thermodynamic model.And combined with the fluid thermodynamic model to obtain the temperature model.The different pressure models are used for the flow of different gas flows(single gas phase,gas-liquid,gas-solid two-phase),and the temperature and pressure model is solved and programmed.(4)The results show that the results of this model are close to the measured data and the accuracy is high.The factors influencing the temperature and pressure are as follows:yield,specific heat,total heat transfer coefficient,fluid composition and the wellbore structure.The results show that the production time,production,specific heat,total heat transfer coefficient have great influence on the temperature.The fluid composition and the diameter of the well have a great influence on the pressure,and the production time,the critical sulfur solubility,the fluid composition,the yield have a great influence on the precipitation location,precipitation and sulfur scale thickness.