Research On Wellbore Pressure Calculation Method Of High-Sulfur Gas Well With Sulfur Precipitation

During the production process of high-sulfur gas wells,sulfur is often separated out in the wellbore.After the precipitation of sulfur,it will change the flow state of natural gas,which will affect the temperature and pressure distribution of the wellbore.In addition,hydrogen sulfide is highly toxic and corrosive.It makes the downhole pressure gauge test more difficult and more costly,so accurate calculation of the wellbore pressure of high-sulfur gas wells with sulfur precipitation is a key means to master the production performance of gas wells.In this paper,the physical parameters of natural gas and the precipitation state of sulfur in gas wells with high sulfur content are studied.Considering the influence of sulfur precipitation in the wellbore on the flow system,the calculation model of wellbore pressure in high-sulfur gas wells is established.According to this model,the corresponding software is developed to solve the wellbore pressure profile,which provides the basis for the dynamic monitoring of high-sulfur gas wells.The following results have been mainly achieved:(1)For high-sulfur natural gas,the calculation results of seven critical parameter correction methods,eight Z-actor calculation methods,three viscosity calculation methods and two viscosity correction methods are compared.The corresponding calculation program is developed by using C # language,and the calculation method is optimized by adding the experimental data comparison module,and the gas test data of YB-A well is calculated.The calculation results show that the developed software has high accuracy in method optimization.(2)Research the physical properties and state of sulfur in the wellbore.Through literature research,determine the calculation method of the physical properties of sulfur,analyze the source of the elemental sulfur in the wellbore,study the precipitation mechanism of sulfur in the wellbore and the solubility model;by analyzing the force state of the elemental sulfur in the wellbore,deduce the elemental sulfur the calculation method of critical suspension velocity is used to judge the migration state of elemental sulfur in the wellbore,and verify the case in this paper.The results show that the sulfur precipitated in the wellbore in the case can be carried out of the wellhead by natural gas.Use probability theory and mathematical statistics to determine the average particle size method of elemental sulfur is described.(3)For high-sulfur gas wells with constant production,establish a wellbore temperature and pressure prediction model according to the law of conservation of energy.In the wellbore temperature model,the total heat transfer coefficient,Joule-Thomson coefficient,and constant pressure specific heat capacity are introduced to simplify the model.Taking into account the slip phenomenon and the change of sulfur element solubility,the proportion of sulfur element volume in the wellbore is corrected to establish the existence of sulfur precipitation New model for calculating wellbore pressure of high-sulfur gas wells.Use the C# language to solve the model established in this paper by programming,and develop the corresponding software to provide convenient means for the use of the model.(4)Using the model in this paper to calculate the YB-B well,the relative error of the calculated value is only 0.41%,indicating that the model in this paper has high accuracy.Through the sensitivity analysis of the model,it is found that the main cause of the wellbore pressure change is to overcome the friction of natural gas to do work,followed by gravity acting against the natural gas.The sulfur element has little effect on the change of wellbore pressure.The higher the elemental sulfur content,the higher the content of hydrogen sulfide,and the larger the diameter of elemental sulfur all make the increase in wellbore pressure larger.