Study On Seepage Regularity Of Gas-Liquid Sulfur In High Sulfur Content Gas Reservoir

High sulfur gas reservoirs are widely distributed in Sichuan Basin.During the development of high sulfur gas reservoirs,the solubility of elemental sulfur in sulfur-containing gas is reduced due to the changes of pressure and temperature in formation,Elemental sulfur from the gas precipitates and deposits,and in high temperature conditions,sulfur deposits in the form of liquid,the deposition of liquid sulfur will increase the seepage resistance and reduce the permeability of the formation of porous media,when the liquid sulfur saturation reaches and exceeds its critical flow saturation,gas and liquid sulfur two phases seepage appears in the formation,and ultimately affects the efficiency of high sulfur gas reservoirs.At present,scholars at home and abroad are mainly on the pore damage theory model study for the high sulfur gas reservoir solid sulfur precipitation.However,there is little research on the deposition and migration of liquid sulfur,and the effect of liquid sulfur deposition on the production capacity is less.Therefore,in this paper,on the basis of studying the parameters of high sulfur gas and liquid sulfur,the mechanism of deposition and migration of liquid sulfur and the damage to the gas relative permeability are analyzed,the calculation model of sulfur saturation in high sulfur gas reservoir was established,and the influencing factors were analyzed according to the example calculation.Based on the existing experimental equipment,a high temperature and high pressure gas-liquid sulfur seepage test device was developed.The relative permeability curves of gas-liquid sulfur were measured and the influence of temperature and stress sensitivity on relative permeability was analyzed.Based on the mechanism of liquid sulfur removal from sulfur-containing gas,the mathematic model of gas-liquid sulfur seepage is deduced and solved.Based on the above study,the following conclusions:(1)The fluid properties of high sulfur-containing gas reservoirs need to be corrected due to the presence of acid gases.The model of sulfur saturation prediction is taken into account.Considering the effects of non-Darcy flow and stress sensitivity,the liquid sulfur saturation calculation results are more accurate.(2)The stress sensitivity experiments arc conducted on the core from a specific high sour gas well.The experimental results show that the stress sensitivity of the core is weak and the medium is weak.The relative permeability curves of gas-liquid sulfur arc measured.The results show that the critical flow saturation of liquid sulfur is big,Gas-liquid sulfur two-phase permeation zone is narrow.(3)The effects of temperature and stress sensitivity on the seepage curve are studied.The results show that the eflect of temperature and stress sensitivity on the relative permeability of'gas phase is obvious,and the gas permeability is decreased and the isotonic point is leftward.The influence of temperature and stress on the relative permeability of liquid sulfur is not significant.(4)According to the situation that elemental sulfur precipitates from sulfur-containing gas and forms liquid-liquid two-phase seepage with sulfur-bearing natural gas in liquid form,the differential equation of gas-liquid sulfur seepage is established and solved.Through programming simulation,Migration to shorten the gas production period,the cumulative gas production decreased,the liquid sulfur flow capacity of the worse the impact of gas production capacity.