Determination of Mass Transfer Coefficient of Methane in Heavy Oil-Saturated Unconsolidated Porous Media Using Constant-Pressure Technique

Measuring the solubility and diffusivity of methane in porous media saturated with oil is critical for analyzing the process of solvent-based recovery of heavy oil reservoir. In this study, a modified pressure-pulse decay (PPD) method is presented to measure the mass transfer coefficients of methane in porous media saturated with heavy oil as well as the solubility and diffusivity of methane in bulk oil under the same experimental conditions as those used in a comparison. The experiments are conducted under constant boundary pressure in a PVT cell, and the pressure is controlled using an auto pump, which continuously compresses the volume of an intermediate container. The accumulated volume change instead of the pressure change is recorded with time. The nonequilibrium boundary condition (BC) model is used to analyze the experimental process. The general solution of the mathematical model is derived using the Laplace transform and the approximate analytical solution of the accumulated dissolved gas is further presented for post processing of the experimental data. The mass transfer coefficients are estimated through using a multilevel single-linkage (MLSL) method to match the approximate solution with the recorded experimental data. The estimation of the parameters shows that the mass transfer coefficients are pressure dependent and that a high boundary pressure contributes to the mass transfer of methane in heavy oil due to a reduction in viscosity or density. The interface mass transfer coefficient (<i>k</i>_int) and interface saturated concentration (<i>c</i>_int) in porous media saturated with oil and bulk oil are almost the same under the same experimental conditions. The sensitivity analysis shows that the increase of the effective diffusion coefficient (<i>D</i>_eff) and <i>k</i>_int contributes to enhancing the rate of mass transfer in the oil phase and that Henry’s law constant (<i>H</i>) has no effect on the equilibrium time but only affects the initial saturated concentration at the interface or the total dissolved gas. The modified PPD method is robust, efficient, and easy to use in the laboratory

Effect of PEO-PPO-ph-PPO-PEO and PPO-PEO-ph-PEO-PPO on the Rheological and EOR Properties of Polymer Solutions

The rheological properties of partially hydrolyzed polyacrylamide (HPAM) and PEO-PPO-ph-PPO-PEO (BPE) or PPO-PEO-ph-PEO-PPO (BEP) block polyether solutions are investigated here. Another hydrophobically associating polymer (HMPAM) is chosen as a contrast. The rheological results show that the elastic modulus (G′) and viscous modulus (G″) of HPAM/BPE and HPAM/BEP solutions first increase then decrease, while the viscosities of HMPAM/BPE and HMPAM/BEP solutions decrease with the increase of block polyether concentration. The HPAM/BPE solution has a larger viscosity than HPAM/BEP, while the HMPAM/BPE solution has a lower viscosity than HMPAM/BEP. The polymer solutions containing BEP have larger G′ and G″ values than the solutions with BPE. Furthermore, the block polyethers reduce the sensitivity of viscosity to temperature. BEP is more effective to stabilize the viscoelastic property and improve the temperature resistance than BPE in HMPAM system. BEP has a better property to enhance the salt tolerance of the polymer solution than BPE. Moreover, the enhanced oil recovery (EOR) experiments show that HPAM/block polyether mixed solution has a larger oil recovery than HPAM, and HPAM/BEP system has a larger enhanced effect than HPAM/BPE solution

Phase Behavior for Poly(vinylacetate) + Carbon Dioxide + Cosolvent Ternary Systems

Experimental cloud point and bubble point data of ternary mixtures for poly­(vinylacetate) (PVAc) and cosolvents in carbon dioxide (CO₂) are studied using the supercritical CO₂ phase behavior device. The cloud point and bubble point pressures are determined by measuring the resistance variation of photoresistance. Acetate acid and ethyl acetate have been selected as the cosolvents. These systems show phase behavior over a temperature range of 308.2–338.2 K and pressure of up to 50 MPa. The transition point pressure increases as the temperature increases. The transition point isopleths for the PVAc + CO₂ + cosolvent ternary systems show upper critical solution pressure types. The cloud point and bubble point curves for the PVAc + CO₂ + cosolvent systems decrease rapidly as the cosolvent concentration increases. When the mass ratio of PVAc and cosolvents is fixed at 1:7, the transition point pressures increase as CO₂ increases. Compared with acetic acid and ethyl acetate, the transition point pressures of the PVAc + CO₂ mixtures, containing the two cosolvents, show that the pressure for acetate acid is less than that of ethyl acetate under the same conditions. The phase behaviors of these ternary systems are calculated using the perturbed-chain statistical associating fluid theory equation of state by adjusting the binary interaction parameter <i>k</i>_ij. Our models are in very good agreement with the experimental data

Aggregation Behaviors of PEO-PPO-ph-PPO-PEO and PPO-PEO-ph-PEO-PPO at an Air/Water Interface: Experimental Study and Molecular Dynamics Simulation

The block polyethers PEO-PPO-ph-PPO-PEO (BPE) and PPO-PEO-ph-PEO-PPO (BEP) are synthesized by anionic polymerization using bisphenol A as initiator. Compared with Pluronic P123, the aggregation behaviors of BPE and BEP at an air/water interface are investigated by the surface tension and dilational viscoelasticity. The molecular construction can influence the efficiency and effectiveness of block polyethers in decreasing surface tension. BPE has the most efficient ability to decrease surface tension of water among the three block polyethers. The maximum surface excess concentration (Γ_max) of BPE is larger than that of BEP or P123. Moreover, the dilational modulus of BPE is almost the same as that of P123, but much larger than that of BEP. The molecular dynamics simulation provides the conformational variations of block polyethers at the air/water interface