| High sulfur gas reservoir may face elemental sulfur precipitation sedimentation and plugging wellbore in the process of development,seriously,maybe forced to stop production.And the issue of sulfur deposition is a complex problem involving physical parameters change such as temperature,pressure and so on.In high sulfur gas wells producing water,because the high content of hydrogen sulfide,complex fluid phase behavior change caused by the wellbore temperature and pressure change,it is difficult to locate the position of separate sulfur out and the position of sulfur deposition due to lack of proper technology.In order to make up for the shortcomings of existing technologies,at first,this paper first calculates and corrects the physical parameters of mixed fluid,and then,on this basis,establishes a prediction model of sulfur deposition rule in wellbore for different well types.Then the temperature and pressure model of water-producing gas well is established by considering the actual heat dissipation process of fluid and combining with the thermodynamic law and kinetic theory.Finally,these models were coupled and programmed by MATLB.It could predict the changes in the whole profile of wellbore temperature and pressure as well as the sulfur precipitation time,location,deposition time and location,etc by the programmer.Through the above research work,the paper has obtained the understandings as following:(1)The calculation of physical parameters:fitting the calculation fonnula of water physical parameters suitable for high-temperature and high-pressure gas Wells,according to the data in the manual of thermodynamics.Compared and analyzed the variety of calculation methods for different physical parameters,and then use VB to compile relevant software,and compared the calculated results with the experimental values to optimize the deviation factor and viscosity calculation and correction model for high-sulfur gas.The functional relations of temperature and pressure with deviation factor,viscosity and thennodynamic parameters of mixed fluid were obtained.(2)The prediction of sulfur deposition rule:in order to improve the applicability of the empirical formula of sulfur solubility,this paper obtained the relationship between sulfur solubility and temperature and pressure by fitting the experimental data tested,and determined the sulfur precipitation location and amount based on this judgment.Considering the structural characteristics of Wells with different well types,finally,the sulfur deposition and diffusion model was obtained,based on the critical suspension velocity of sulfur elements in different gas Wells and the theory of mass and heat transfer.Verification by example,the error is 1.2%,and Formation temperature,Formation pressure,hydrogen sulfide content,water production,well structure,production rate and production time have obvious influence on the sulfur deposition rule.(3)The temperature and pressure model for water production gas well,when calculating the radial heat within the wellbore and formation of thermal consideration into unsteady process,got the value of the heat by mathematical physics equations generation into the thermodynamic model to establish high sulfur water production of gas well unsteady temperature model.On the basis of defining the flow phase(gas-water two-phase,gas-water-solid and gas-water-liquid sulfur multi-phase)and flow pattern,the wellbore pressure model is established by considering the influence of well body structure,sulfur scale and liquid film on pressure drop.The example shows that the temperature error prediction model has a small calculation error of 5%,and the conclusion was drawn that:hydrogen sulfide content,water yield,well structure and output have great influence on temperature and pressure.(4)Coupling the sulfur deposition rule model with the temperature and pressure model by MATLAB,and the accuracy of the model was verified by the example,which was more accurate than the pipesim software and the classical model. |
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