Minimum Miscibility Pressure
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Cited by 2 publications
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The objective of this research was to use molecular modeling techniques, coupled with our prior experimental results, to design, synthesize and evaluate inexpensive, non-fluorous carbon dioxide thickening agents.The first type of thickener that was considered was associating polymers. Typically, these thickeners are copolymers that contain a highly CO 2 -philic monomer, and a small concentration of a CO 2 -phobic associating monomer.Yale University was solely responsible for the synthesis of a second type of thickener; small, hydrogen bonding compounds. These molecules have a core that contains one or more hydrogen-bonding groups, such as urea or amide groups. Non-fluorous, CO 2 -philic functional groups were attached to the hydrogen bonding core of the compound to impart CO 2 stability and macromolecular stability to the linear "stack" of these compounds.The third type of compound initially considered for this investigation was CO 2 -soluble surfactants. These surfactants contain conventional ionic head groups and composed of CO 2 -philic oligomers (short polymers) or small compounds (sugar acetates) previously identified by our research team. Mobility reduction could occur as these surfactant solutions contacted reservoir brine and formed mobility control foams in-situ.The vast majority of the work conducted in this study was devoted to the copolymeric thickeners and the small hydrogen-bonding thickeners; these thickeners were intended to dissolve completely in CO 2 and increase the fluid viscosity. A small but important amount of work was done establishing the groundwork for CO 2 -soluble surfactants that reduced mobility by generating foams in-situ as the CO 2 +surfactant solution mixed with in-situ brine. PolymersIn this final report, we review our entire co-polymeric thickener effort and detail, for the first time, the phase behavior and viscosity results of the first non-fluorous, oxygenated hydrocarbon-based, associating polymer CO 2 thickener, poly(vinyl acetate -co -benzoyl 5% ). The CO 2 -philic monomer was vinyl acetate, and the associative thickener monomer was vinyl benzoate. Poly(vinyl acetate -co -benzoyl 5% ), Mw ~ 12000, is capable of increasing the viscosity of CO 2 by 70% at a concentration of 2wt%, a shear rate of ~5000s -1 , 298K and 9500 psia. Unfortunately, poly(vinyl acetate -co -benzoyl 5% ) is not capable of dissolving in CO 2 at pressures close to the MMP, roughly 1200 psia at 298 K. In fact, we are now convinced that a non-fluorous, hydrocarbon-based copolymeric thickener cannot be designed that will dissolve in CO 2 at typical reservoir conditions. Why? Every polymer that we designed using molecular modeling tools was indeed CO 2 soluble, a somewhat remarkable achievement given the small number of CO 2 soluble surfactants that have ever been identified, but each one was less soluble in CO 2 than poly(vinyl acetate). Therefore co-polymeric thickeners based on any CO 2 soluble polymer will undoubtedly be less soluble in CO 2 (i.e. require even greater pressures than 9500 psia)...
The objective of this research was to use molecular modeling techniques, coupled with our prior experimental results, to design, synthesize and evaluate inexpensive, non-fluorous carbon dioxide thickening agents.The first type of thickener that was considered was associating polymers. Typically, these thickeners are copolymers that contain a highly CO 2 -philic monomer, and a small concentration of a CO 2 -phobic associating monomer.Yale University was solely responsible for the synthesis of a second type of thickener; small, hydrogen bonding compounds. These molecules have a core that contains one or more hydrogen-bonding groups, such as urea or amide groups. Non-fluorous, CO 2 -philic functional groups were attached to the hydrogen bonding core of the compound to impart CO 2 stability and macromolecular stability to the linear "stack" of these compounds.The third type of compound initially considered for this investigation was CO 2 -soluble surfactants. These surfactants contain conventional ionic head groups and composed of CO 2 -philic oligomers (short polymers) or small compounds (sugar acetates) previously identified by our research team. Mobility reduction could occur as these surfactant solutions contacted reservoir brine and formed mobility control foams in-situ.The vast majority of the work conducted in this study was devoted to the copolymeric thickeners and the small hydrogen-bonding thickeners; these thickeners were intended to dissolve completely in CO 2 and increase the fluid viscosity. A small but important amount of work was done establishing the groundwork for CO 2 -soluble surfactants that reduced mobility by generating foams in-situ as the CO 2 +surfactant solution mixed with in-situ brine. PolymersIn this final report, we review our entire co-polymeric thickener effort and detail, for the first time, the phase behavior and viscosity results of the first non-fluorous, oxygenated hydrocarbon-based, associating polymer CO 2 thickener, poly(vinyl acetate -co -benzoyl 5% ). The CO 2 -philic monomer was vinyl acetate, and the associative thickener monomer was vinyl benzoate. Poly(vinyl acetate -co -benzoyl 5% ), Mw ~ 12000, is capable of increasing the viscosity of CO 2 by 70% at a concentration of 2wt%, a shear rate of ~5000s -1 , 298K and 9500 psia. Unfortunately, poly(vinyl acetate -co -benzoyl 5% ) is not capable of dissolving in CO 2 at pressures close to the MMP, roughly 1200 psia at 298 K. In fact, we are now convinced that a non-fluorous, hydrocarbon-based copolymeric thickener cannot be designed that will dissolve in CO 2 at typical reservoir conditions. Why? Every polymer that we designed using molecular modeling tools was indeed CO 2 soluble, a somewhat remarkable achievement given the small number of CO 2 soluble surfactants that have ever been identified, but each one was less soluble in CO 2 than poly(vinyl acetate). Therefore co-polymeric thickeners based on any CO 2 soluble polymer will undoubtedly be less soluble in CO 2 (i.e. require even greater pressures than 9500 psia)...
The technical feasibility of using flare gas in the miscible gas flooding enhanced oil recovery (MGF-EOR) is evaluated by comparing the minimum miscibility pressure (MMP) obtained using flare gas to the MMP obtained in the conventional CO2 flooding. The MMP is estimated by the multiple mixing cell calculation method with the Peng-Robinson equation of state using a binary nC5H12-nC16H34 mixture at a 43%:57% molar ratio as a model oil. At a temperature of 323.15 K, the MMP in CO2 injection is estimated at 9.78 MPa. The MMP obtained when a flare gas consisting of CH4 and C2H6 at a molar ratio of 91%:9% is used as the injection gas is predicted to be 3.66 times higher than the CO2 injection case. The complete gas-oil miscibility in CO2 injection occurs via the vaporizing gas drive mechanism, while flare gas injection shifts the miscibility development mechanism to the combined vaporizing / condensing gas drive. Impact of variations in the composition of the flare gas on MMP needs to be further explored to confirm the feasibility of flare gas injection in MGF-EOR processes. Keywords: flare gas, MMP, miscible gas flooding, EORAbstrakKonsep penggunaan flare gas untuk proses enhanced oil recovery dengan injeksi gas terlarut (miscible gas flooding enhanced oil recovery atau MGF-EOR) digagaskan untuk mengurangi emisi gas rumah kaca dari fasilitas produksi migas, dengan sekaligus meningkatkan produksi minyak. Kelayakan teknis injeksi flare gas dievaluasi dengan memperbandingkan tekanan pelarutan minimum (minimum miscibility pressure atau MMP) untuk injeksi flare gas dengan MMP pada proses MGF-EOR konvensional menggunakan injeksi CO2. MMP diperkirakan melalui komputasi dengan metode sel pencampur majemuk dengan persamaan keadaan Peng-Robinson, pada campuran biner nC5H12-nC16H34 dengan nisbah molar 43%:57% sebagai model minyak. Pada temperatur 323.15 K, estimasi MMP yang diperoleh dengan injeksi CO2 adalah 9.78 MPa. Nilai MMP yang diperkirakan pada injeksi flare gas yang berupa campuran CH4-C2H6 pada nisbah molar 91%:9% sangat tinggi, yakni sebesar 3.66 kali nilai yang diperoleh pada kasus injeksi CO2. Pelarutan sempurna gas-minyak dalam injeksi CO2 terbentuk melalui mekanisme dorongan gas menguap (vaporizing gas drive), sementara pelarutan pada injeksi flare gas terbentuk melaui mekanisme kombinasi dorongan gas menguap dan mengembun (vaporizing/condensing gas drive). Pengaruh variasi komposisi flare gas terhadap MMP perlu dikaji lebih lanjut untuk menjajaki kelayakan injeksi flare gas dalam proses MGF-EOR.Kata kunci: flare gas, MMP, miscible gas flooding, EOR
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