Research On Reservoir Wellbore Integrated Simulation For The Sour Gas Reservoirs

There are many sour gas reservoirs in Sichuan Basin,China.Compared with the conventional gas reservoirs,the gas composition of this kind gas reservoirs contains sour gas such as H2S,CO2.There is sulfur dissolved in the gas as well.The existence of sour gas influences gas properties.Along with the production of gas reservoir,the declion of formation pressure leads to the precipitation of sulfur which makes the gas flow become the complicated gas-solid phase flow.The deposition of sulfur can influence the porosity and permeability.For the wellbore of sour gas well,the sour gas,the sulfur carried out from the formation and the precipitated sulfur in the wellbore will influence the distribution of wellbore temperature and pressure.The fluid flow in the formation and wellbore is a continuous process,the change of formation condition will result in the variation of wellbore temperature and pressure.Building a model which can describe the seepage of sour gas reservoir and wellbore flow and solving the model can reflect the change of dynamic parameters.It can provide a reference for the efficient development of sour gas reservoirs.The goal of this paper is realizing the formation-wellbore integrated simulation for the sour gas reservoirs.The main works and conclusions are as follows.(1)The research on the flow characteristics of sour gas reservoir fluid includes source and quality of H2S,characteristics of sulfur dissolution and precipitation,migration and settlement,the calculation of high sulfur gas property parameters.The Z factor,viscosity and density of sour gas need to be corrected.(2)A gas-solid phase seepage model used for describing fluid flow in the formation was built based on the Warren-Root dual media model.Numerical solution was used for solving the model.By comparing with data in the literature,the correctness of the model was verified.The reason for sharp drop of bottom hole pressure was analyzed.(3)A model calculating the wellbore temperature and pressure was built for the single gas phase and gas-solid phase.The coupled algorithm was given in the paper.By comparing with commercial software Pipesim,the correctness of this model was guaranteed.By using the model to calculate single gas phase and gas-solid phase wellbore temperature and pressure,we found that the wellbore temperature and pressure of gas-solid phase are both lower than that of the single gas phase.The reason for this phenomenon was that energy loss and heat loss for gas-solid phase are both higher than that of single gas phase.When the sulfur particles are just little,the difference between the gas-solid phase wellbore temperature and pressure and that of single gas phase is very small.(4)Based on the formation gas-solid seepage model and the wellbore temperature pressure model,the integrated simulation for the formation and wellbore can be realized by the connection of bottom hole pressure.(5)In order to analyze the effect of sulfur precipitation and deposition on the formation and wellbore.A mechanism model was bulit.The influence was analyzed by considering sulfur deposition and not considering sulfur deposition.The influence of sulfur deposition quantity was analyzed by changing the initial sulfur.The simulation results indicate that sulfur deposition reduce the stable production time,the more of the initial sulfur,the shorter of the stable production time.The deposition quantity has little influence on the wellbore temperature.(6)A real gas field integrated simulation was simulated for the sour gas reservoir.The dynamic change of the sulfur deposition,porosity,permeability,wellbore temperature,wellbore pressure and so on were present.It can provide a reference for dynamic prediction of the high sulfur gas reservoirs.