(334h) Experimental Measurementsof Bubble Point (V-L) and Three-Phase Hydrate Equilibrium Condition (H-Lw-V) for CO2 Rich Gas Mixtures

Bubble point estimation in petroleum industry is the most crucial pressure-volume-temperature (PVT) property especially for strategies concerning the oilfield development such as Enhanced oil Recovery (EOR).Gas hydrate on the other hand plays a significant role in the natural gas production and transmission lines. Its formation in pipelines could prompt to safety hazards to both production and flow assurance problem which leads to economic intimidation. Green house gas like CO₂ is an important constituent in natural gas and its significance in hydrate formation is inevitable. The purpose of this work is to perform systematic measurements for bubble point (V-L) and hydrate-liquid-vapor (H-Lw-V) equilibrium for CO₂-riched synthetic natural gas (SNG) mixtures. Four different SNG mixture were used and purchase from gas walkers SDN BHD Malaysia, with a cylinder capacity of 10L having fill pressure of 45 bar and 0.6/m³ gas volume. The four SNG used in this study contains  components ranges from minimum two to maximum seven, with CO₂ content varies from 69.14% to 72.5%. Data were generated by using PVT equipment  for bubble point measurement with a working temperature ranges from -15^oC to ^oC and pressure from 0 MPa to 10 Mpa , The equipment can be operated with a  pressure ranges from 68 Mpa to 103 Mpa  and temperature  from -20^oC to 175 ^oC, Equilibrium cell enclosed in the equipment has a volume of 200 cc with a visual volume of 100 cc. Temperature , pressure and volume is recorded with accuracy of 0.5^oC , 0.01% full scale and 0.01 ml. Fluid Eval PVT equipment offers full sample visibility from front and back windows and attached  camera device is used for recording sample picture in regular intervals. Similarly for hydrate equilibrium measurements equilibrium cell provided in Hydreval was used to investiagte the thermodynamic equilibrium conditions of hydrate. The measurement is done using step heating tecnique of Tohidi et al with working temperature ranges from 4^oC to 16^oC and pressure 2.55 MPa to 14.61 Mpa. The hydrate cell has a maximum capacity of 80cm³ with  maximum operating pressure is 20MPa with temperature ranges from -20^oC to 150^oC. Also magnetic driven stirrer is provided for homogenous agitation of the fluid sample. Temperature, pressure and volume conditions are measured and recorded in every 2 sec with accuracy of  ±0.1K, ±0.01 MPa and ±0.001 cm³ respectively. Experiment results obtained in this study are then compared with those obtained from PVT modeling softwares. The results attained are in good agreement with commerical PVT software with minimum deviation of -0.22 with bubble point prediction and 0.98 for hydrate equilibrium prediction. The hydrate equilibrium data generated for SNG mixture are also compared with  pure methane and CO₂ and  results obtained with SNG mixture having rich CO₂ content fall in between the pure component vapor-liquid water-hydrate (V-L_w-H) equilibrium data attained in this work.