Abstract
A novel enhanced oil recovery (EOR) method based on polymer gel-assisted carbon dioxide (CO2) huff and puff was developed aiming to improve the development effect of heavy oil reservoirs with high water cut. The polymer gel prepared using partially hydrolyzed polyacrylamide (HPAM), hexamethylenetetramine, phenol, resorcinol, oxalic acid, and thiocarbamide as raw materials had a special network structure to overcome the challenge of significant heterogeneity in heavy oil reservoirs. The strength of polymer gel reached the maximum value 20,000 mPa·s within 22 h. The temperature resistance and salt resistance of polymer gel directly determined the plugging effect. The polymer gel was placed for 190 days at 85 ℃, and its apparent viscosity retention rate was 66.4%. The salt resistance experiments showed that the apparent viscosity retention rate of this polymer gel at 1.8 wt % NaCl, 0.045 wt % CaCl2, 0.045 wt % MgCl2 was 71.3%, 78.5%, 71.4%, respectively. Huff and puff experiments confirmed that this method could be used to increase the sweep volume and improve the oil displacement efficiency of heavy oil reservoirs with high water cut. Furthermore, the EOR of this method was better than that of water huff and puff, polymer gel huff and puff or CO2 huff and puff.
Highlights
It is well known that the geological reserves of heavy oil are much higher than that of conventional crude oil (Huang et al 2018; Guo et al 2016)
Keep in mind the requirement of enhanced oil recovery (EOR) technology, a novel EOR method based on polymer gelassisted CO2 huff and puff was proposed aiming to develop heavy oil reservoirs with high water cut economically and effectively
Where EOR is enhanced oil recovery of the polymer gelassisted CO2 huff and puff, %; E1 is the oil production of the whole experiment process, ml; E2 is the oil production of water flooding stage, ml; E0 is the amount of crude oil in the sand packed models, ml
Summary
It is well known that the geological reserves of heavy oil are much higher than that of conventional crude oil (Huang et al 2018; Guo et al 2016). The effect of thermal recovery technology in high water cut heavy oil reservoir is generally not satisfactory (Salmo et al 2017; Riazi and Golkari 2016). Chemical cold recovery technology can effectively reduce the viscosity of crude oil and interphase interface tension, the chemical agents are easy to form adsorption on the surface of the rock or dissolve in formation water, resulting in the waste of chemical agents and high cost (Guo et al 2013b; Pei et al 2014; Coskuner et al 2015; Mohsenzadeh et al 2015). Keep in mind the requirement of enhanced oil recovery (EOR) technology, a novel EOR method based on polymer gelassisted CO2 huff and puff was proposed aiming to develop heavy oil reservoirs with high water cut economically and effectively. The apparent viscosity of MPSC after gelling was measured with a Brookfield DV3T viscometer at 65 °C
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