In order to study the effect of different CO2 contents on gas compressibility factor(Z-factor),the JEFRI-PVT apparatus has been used to measure the Z-factor of dry natural gas with CO2 content range from 10.74 to 70.42 mol%at the temperature range from 301.2 to 407.3 K and pressure range from 7 to 44 MPa.The results show that Z-factor decreases with increasing CO2 content in natural gas at constant temperature and increases with increasing temperature for natural gas with the same CO2 content.In addition,the Z-factor of water-saturated natural gas with high CO2 content has been measured.A comparison of the Z-factor between natural gas with and without saturated water vapor indicates that the former shows a higher Z-factor than the latter.Furthermore,Peng-Robinson,Hall-Yarborough,and Soave-Benedict-Webb- Rubin equations of state(EoS)are used for the calculation of Z-factor of high CO2 content natural gas with and without water vapor.The optimal binary interaction parameters(BIP)for PR EoS are presented.The measured Z-factor is compared with the calculated Z-factor based on three models,which shows that PR EoS combined with van der Waals mixing rule for gas without water and Huron-Vidal mixing rule for water-saturated gas,are in good agreement with the experimental data.
Sulfur deposition in the formation,induced by a reduction in the solubility of the sulfur in the gas phase,may significantly reduce the in flow performance of sour gas wells and some wells in sour gas reservoirs have even become completely plugged with deposited sulfur within several months.Accurate prediction and effective management of sulfur deposition are crucial to the economic viability of sour gas reservoirs.In this paper,a dynamic flow experiment was carried out to investigate formation damage resulting from sulfur deposition using an improved experimental method.The core sample was extracted from the producing interval of the LG2 well,LG gas field in the Sichuan Basin.The experimental temperature was 26 oC and the initial pressure was 19 MPa.The displacement pressure continuously decreased from 19 to 10 MPa,and the depletion process lasted 15 days.Then the core was removed and dried.The core mass and core permeability were measured before and after experiments.Experimental results indicated that the core mass increased from 48.372 g before experiment to 48.386 g afterwards,while the core permeability reduced from 0.726 to 0.608 md during the experiment.Then the core was analyzed with a scanning electron microscope(SEM) and energy-dispersive X-ray mapping.The deposition pattern and micro-distribution of elemental sulfur was observed and the deposited elemental sulfur distributed as a film around the pore surface.In addition,a preliminary three-dimensional,multi-component model was developed to evaluate the effect of sulfur deposition on production performance,and the effect of production rate on sulfur deposition was also investigated.Simulation results indicated that the stable production time would be shortened and the gas production rate would be decreased once sulfur deposited in the formation.The increase in deposited sulfur at high flow rates may be attributed to a bigger pressure drop than that at low gas flow rates.Gas production rate has a severe effect on sulfur saturation in the grid of produci
