Experimental and Modeling Phase Behaviour Studies of Water-Solvent-Bitumen System

Solvent-aided thermal recovery methods for production of bitumen and heavy oils have recently gained interest. In these methods, mixture of saturated steam and solvent is co-injected into bitumen and heavy oil reservoirs. Measurement and thermodynamic modeling of phase behaviour and thermo-physical properties are necessary for finding better understandings of complex systems of water-solvent-bitumen and more accurate numerical simulation and optimization of solvent-aided thermal recovery methods. In this work, binary systems of water-solvent, water-bitumen and solvent-bitumen were studied. For each binary system, a specified experimental apparatus was designed and fabricated. Water solubility in bitumen was measured at temperature ranges up to 493 K. Density and viscosity of bitumen rich phase were measured to investigate effect of water dissolution on thermo-physical properties of bitumen phase. For solvent-water system, water content of methane, ethane and propane were measured at high temperatures and moderate pressures. Solubility of methane, ethane, propane and butane in MacKay River bitumen were measured as well as density and viscosity of solvent-saturated bitumen phase. Cubic-plus-association equation of state (CPA-EoS) was used to model the phase behaviour of the binary systems. Soave-Redlich-Kwong (SRK) equation of state combined with Wertheim’s first-order thermodynamic perturbation theory (TPT-1) were used to treat the physical and association interactions, respectively. The results showed that CPA-EoS accurately reproduces the solubility data of water content of n-alkane solvents, water solubility in bitumen, and solvent solubility in bitumen accurately. Ternary system of water-solvent-bitumen was studied by measurement of solvent solubility in bitumen as well as density and viscosity of bitumen rich phase in the presence and absence of water. The results showed that the presence of water decreases the solvent solubility in bitumen phase. CPA-EoS tuned using the experimental solubility data of the binary systems was found capable in representing the phase behaviour of the ternary system. Correlations were developed for density and viscosity of bitumen rich phase using the experimental data of the binary systems

Investigation of Underground Sour Gas Storage in a Depleted Gas Reservoir

Underground Gas Storage (UGS) involves storage of large quantities of natural gas to support the natural gas demand in domestic, commercial and industrial areas. Storage of sour gas can be advantageous from economic standpoint, as it reduces treatment costs and increases the potential of production from shared reservoirs. This paper investigates feasibility of UGS in one of Iranian depleted fractured gas condensate reservoirs. Compositional simulation was employed to build dynamic reservoir model, develop the history matching phase of the reservoir and construct Injection/Withdrawal (I/W) cycles. One sweet gas stream and three sour gas streams with different compositions were tested for storage into reservoir during summer season. Results of simulation showed that presence of H2S and CO2 in the injected gas stream improves condensate production. Condensate Production Enhancement (CPE), defined as the percentage of condensate recovery increase due to sour gas injection relative to the sweet gas injection, was calculated for different compositions of storage gas. Also, Condensate Holding Ratio (CHR), defined as the ratio of condensate in the withdrawn sour gas to that in the withdrawn CH4, was estimated for different storage gas compositions. Results showed that CPE has a higher rate in earlier cycles and declines at later cycles. CHR is higher for sour gas storage compared to sweet gas. Furthermore, heating value of produced gas was calculated in all I/W cycles and compared with heating value of injected gas. It was indicated that difference between heating value of produced and injected gas increases with increase of H2S and CO2 content of the injected gas. Also, it was found that the reservoir has lower pressure rise at the end of I/W cycles in the case of underground sour gas storage compared to sweet gas storage. The presence of acid gas components decreases the z-factor of injected gas stream resulting in smaller difference between z-factors of injected gas and reservoir fluid

Investigation of Underground Sour Gas Storage in a Depleted Gas Reservoir

Underground Gas Storage (UGS) involves storage of large quantities of natural gas to support the natural gas demand in domestic, commercial and industrial areas. Storage of sour gas can be advantageous from economic standpoint, as it reduces treatment costs and increases the potential of production from shared reservoirs. This paper investigates feasibility of UGS in one of Iranian depleted fractured gas condensate reservoirs. Compositional simulation was employed to build dynamic reservoir model, develop the history matching phase of the reservoir and construct Injection/Withdrawal (I/W) cycles. One sweet gas stream and three sour gas streams with different compositions were tested for storage into reservoir during summer season. Results of simulation showed that presence of H2S and CO2 in the injected gas stream improves condensate production. Condensate Production Enhancement (CPE), defined as the percentage of condensate recovery increase due to sour gas injection relative to the sweet gas injection, was calculated for different compositions of storage gas. Also, Condensate Holding Ratio (CHR), defined as the ratio of condensate in the withdrawn sour gas to that in the withdrawn CH4, was estimated for different storage gas compositions. Results showed that CPE has a higher rate in earlier cycles and declines at later cycles. CHR is higher for sour gas storage compared to sweet gas. Furthermore, heating value of produced gas was calculated in all I/W cycles and compared with heating value of injected gas. It was indicated that difference between heating value of produced and injected gas increases with increase of H2S and CO2 content of the injected gas. Also, it was found that the reservoir has lower pressure rise at the end of I/W cycles in the case of underground sour gas storage compared to sweet gas storage. The presence of acid gas components decreases the z-factor of injected gas stream resulting in smaller difference between z-factors of injected gas and reservoir fluid

Investigation of Underground Sour Gas Storage in a Depleted Gas Reservoir

Underground Gas Storage (UGS) involves storage of large quantities of natural gas to support the natural gas demand in domestic, commercial and industrial areas. Storage of sour gas can be advantageous from economic standpoint, as it reduces treatment costs and increases the potential of production from shared reservoirs. This paper investigates feasibility of UGS in one of Iranian depleted fractured gas condensate reservoirs. Compositional simulation was employed to build dynamic reservoir model, develop the history matching phase of the reservoir and construct Injection/Withdrawal (I/W) cycles. One sweet gas stream and three sour gas streams with different compositions were tested for storage into reservoir during summer season. Results of simulation showed that presence of H2S and CO2 in the injected gas stream improves condensate production. Condensate Production Enhancement (CPE), defined as the percentage of condensate recovery increase due to sour gas injection relative to the sweet gas injection, was calculated for different compositions of storage gas. Also, Condensate Holding Ratio (CHR), defined as the ratio of condensate in the withdrawn sour gas to that in the withdrawn CH4, was estimated for different storage gas compositions. Results showed that CPE has a higher rate in earlier cycles and declines at later cycles. CHR is higher for sour gas storage compared to sweet gas. Furthermore, heating value of produced gas was calculated in all I/W cycles and compared with heating value of injected gas. It was indicated that difference between heating value of produced and injected gas increases with increase of H2S and CO2 content of the injected gas. Also, it was found that the reservoir has lower pressure rise at the end of I/W cycles in the case of underground sour gas storage compared to sweet gas storage. The presence of acid gas components decreases the z-factor of injected gas stream resulting in smaller difference between z-factors of injected gas and reservoir fluid