Rheology and polymer flooding characteristics of partially hydrolyzed polyacrylamide for enhanced heavy oil recovery

Polymer flooding characteristics of partially hydrolyzed polyacrylamide (HPAM) solution with the addition of NaOH were examined in homogeneous glass‐bead packs. The heavy oil recovery in unconsolidated sandstone formations by applying the alkali‐polymer flooding was observed. Experimental results showed that HPAM solution was sensitive to temperature, salinity, and alkali, finding that alkali‐polymer solutions are more effective in improving viscosity than conventional polymer solutions. The solution of 0.5 wt % NaOH mixed with 1500 ppm HPAM (12 mol % hydrolysis degree) was found to be the optimal choice, which gives rise to the highest viscosity on the rheological characterization. Flood tests using the alkali‐polymer solution showed an increase in oil recovery by 30% over water‐flooding when the water‐cut reached 95%, indicating that alkali‐polymer could be more effective in improving sweep efficiency than polymer flood. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

砾岩油藏聚驱后提高采收率技术研究

在分析聚驱后剩余油的分布特点的基础上,从室内研究和现场应用等方面评价了聚合物驱后进一步提高油田采收率技术———聚合物驱后残留聚合物再利用技术、聚合物驱后深部调剖技术、聚合物驱后高效洗油技术,并结合砾岩油藏的储层物性和已有的砾岩油藏二次开发经验,提出了适合砾岩油藏聚驱后进一步提高采收率技术的方案。     

驱油用水溶性聚合物的研究进展

聚合驱油主要是向注水中加入聚合物,提高水的粘度,减弱水相的粘性指进现象,达到提高原油采收率的目的。本文介绍了聚合驱的驱油机理、三次采油中常用的水溶性聚合物以及新型水溶性聚合物研究进展。     

The performance of polymer solutions in enhanced oil recovery: studies on their rheological,interfacial, and porous media behaviors

Four polymeric solutions based on xanthan, high and low molecular weight sulfonated polyacrylamides, and hydrolyzed polyacrylamide were prepared in aqueous solutions and their behaviors in enhanced oil recovery applications were investigated. The effect of thermal aging on polymer solutions was evaluated through rheological measurement. Pendant drop method was also used for measuring the interfacial tension (IFT) between crude oil and brine containing different polymer solutions. Moreover, the zeta potential of the oil reservoir particles treated with oil and polymer was determined by electrophoresis method in a nano-zeta meter instrument. In addition, sand pack and core flooding setup were used for evaluating the effectiveness of the polymer solutions in porous media. Polymer solutions displayed non-Newtonian behavior in almost the whole range of the shear rate applied; a shear thinning behavior was seen. Furthermore, the aging of polymers in formation water decreased the shear viscosity of all the polymers. The oil/water IFT decreased by the addition of polymers to water. The effect of xanthan polymer on zeta potential value was greater than that of the three acrylamide-based polymers. According to sand pack tests, by increasing the polymer concentration, the incremental oil recovery initially increased up to a polymer concentration of 3,500 ppm and then started to fall. Recovery factor increased from 50 to 65 % using the polymer solution in core flooding experiments. By increasing the injection rate from 0.2 to 3 mL/min, the injected fluid had less time to sweep the pores and consequently the amount of recovered oil decreased.     

Carbon dioxide flooding for enhanced oil recovery: Promise and problems

Of the enhanced oil recovery methods currently being considered for application to many of the nation’s older oil fields, carbon dioxide flooding may offer the largest potential for additional oil recovery. The physical mechanisms by which CO₂ contacts and mobilizes crude oil are reviewed. Influence on the displacement process of factors such as the phase behavior of CO₂-crude oil mixtures, swelling of oil by dissolved CO₂, and reduction of oil viscosity are considered. Adverse effects of the viscous instability which occurs when very low viscosity CO₂ displaces the more viscous oil and water are dicussed. Advantages and disadvantages of three potential methods for controlling the mobility of CO₂ are reviewed: thickening CO₂ with polymeric additives, reduction of CO₂ mobility by high water saturations, and use of surfactants to generate foam-like emulsions of water and CO₂. Field experience to date and the recent surge in field activity are discussed. Finally, a brief assessment of the future of CO₂ flooding research and practice is offered.     

提高三次采油用聚合物耐温抗盐性的研究进展

综述了国内外三次采油用五大类驱油耐温抗盐水溶性聚合物的研究现状,提出一种提高聚丙烯酰胺类聚合物耐温抗盐性能的的新方法：即开发一种廉价高效二价金属离子络合剂。分析了二价金属离子络合剂的作用机理,并明确了以后的研究方向。     

Surfactant flooding characteristics of dodecyl alkyl sulfate for enhanced oil recovery

Surfactant-enhanced oil recovery is a type of enhanced oil recovery (EOR), a method to produce residual oil by injecting surfactant solution into the reservoir. The application of surfactant EOR requires knowledge of the phase behavior for more efficient production of residual oil.In this study, the relationship between dodecyl alkyl sulfate and some specific crude oils was examined through phase behavior test. It was found that the branched surfactant was more effective than the linear surfactant. The system was stable at salinities <3 wt%. On adding a small amount of co-surfactant, the emulsion activity was increased.The gravity drainage flooding test (GDFT) was performed to determine the potential of dodecyl alkyl sulfate to produce residual oil in porous media. It was found that the solution could be flooded at temperatures of 60 °C or higher. In the core flooding test, injecting one pore volume of 2 wt% surfactant solution with 3 wt% salinity produced 26.6% more oil after water flood. With the addition of only 0.01 wt% co-surfactant, oil production increased by 1.6%. Contrary to the phase behavior test, the linear surfactant produced 1.3% more oil than the branched surfactant in the core flooding test.     

驱油用烷基苯工业化生产研究

通过进行小批量的驱油用烷基苯生产试验,制定出了切实可行的生产方案,并顺利完成工业化试验和增产试验,驱油用烷基苯产量达到1.6万t/a,试验产品经测试在大庆三厂油水条件下能够达到10-3mN/m的超低界面张力,能够满足大庆三元复合驱强碱体系矿场试验的需求.     

Performance of fly ash based polymer gels for water reduction in enhanced oil recovery: Gelation kinetics and dynamic rheological studies

The complexity of well and reservoir conditions demands frequent redesigning of water plugging polymer gels during enhanced oil recovery (EOR). In the present study, we developed coal fly ash (CFA) based gels from polyacrylamide (PAM) polymer and polyethyleneimine (PEI) crosslinker for water control in mature oil fields. The CFA acts as an inorganic additive to fine-tune gelation performance and rheological properties of PAM/PEI gel system. Hence, effects of various CFA (0.5 to 2 wt%), PAM (2 to 8.47 wt%) and PEI (0.3 to 1.04 wt%) concentrations on gelation kinetics and dynamic rheology of pure PAM/PEI gel and PAM/PEI-CFA composite gels were studied at a representative reservoir temperature of 90 oC. Experimental results reveal that gelation time of pure PAM/PEI gel increases with increasing CFA addition. Further observation demonstrates that increasing PAM and PEI concentrations decreases the gelation times of PAM/PEI-CFA composite gels. Gelation time was found to be within 3-120 hours. Understanding the property of reaction order enables better prediction of gelation time. Dynamic rheological data show that viscoelastic moduli (G′ and G″) of various PAM/PEI-CFA composite gels improved better as compared to the pure PAM/PEI gel across the strain-sweep and frequency-sweep tests. SEM analysis of selected samples at 72 hours and 720 hours of gelation activity consolidated gelation kinetics and dynamic rheological results. These polymer gels are excellent candidates for sealing water thief zones in oil and gas reservoirs.     

Characterization of polyacrylamides used in enhanced oil recovery

Polyacrylamides can be readily characterized using techniques such as IR spectroscopy, ¹³C-NMR, elementary analysis, TGA, and x-ray diffraction. The first three techniques can also be used quantitatively to measure the degree of hydrolysis of the polymers, without the need to know accurately the weight of the sample. The presence of inorganic salts, such as Na₂SO₄, Na₄(CO₃)SO₄, and Na₂CO₃, is readily detected via IR or wide-angle x-ray diffraction. No evidence of crystallinity is found in the samples studied.