Improving Alkali Polymer Flooding Economics by Capitalizing on Polymer Solution Property Evolution at High pH

Födisch, Hendrik; Nurmi, Leena; R., Rafael E. Hincapie; Borovina, Ante; Hanski, Sirkku; Clemens, Torsten; Janczak, Alyssia

doi:10.2118/210043-ms

Cited by 3 publications

(11 citation statements)

References 36 publications

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“…The increase was linked to a fast change in the degree of hydrolysis providing a positive impact on viscosity in the soft brine. A more detailed description of the studies can be found in [13,14]. Even though the field temperature in Matzen is 49 • C, the aging was also carried out at 60 • C and 70 • C to accelerate the aging.…”

Section: Resultsmentioning

confidence: 99%

“…For the optimum utility factor, aging of AP slugs is performed to optimize the project economics. This study is a continuation of our previous research [13,14], with an emphasis on AP flooding in reservoir sand packs and reservoir conditions (live oil).…”

Section: Introductionmentioning

confidence: 84%

“…Thermal Aging of Polymer Solutions: Polymer solutions for thermal aging studies were prepared in a glove box under nitrogen atmosphere to ensure an anaerobic environment reflecting field conditions. The method is described more in detail in [13,14]. The aging was conducted in various concentrations.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…Interfacial tension (IFT Upper Phase/Middle Phase) at the fluids' interface was calculated using the volume ratio between the upper phase (UP) and middle phase (MP) using the approach adopted by Liu et al [20] and Hincapie et al [9]. Interfacial tension data were reported in [13,14]; here, we compare results.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…Project economics play a pivotal role for EOR technology applications. For a highly complex case such as AP involving multiple chemical agents, the business case for the project may become unfavorable or hard to justify [13]. With a proper process design, good recoveries can be observed, and it is possible that economics can be improved [9].…”

Section: Introductionmentioning

confidence: 99%

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Optimizing Polymer Costs and Efficiency in Alkali–Polymer Oilfield Applications

et al. 2022

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In this work, we present various evaluations that are key prior field applications. The workflow combines laboratory approaches to optimize the usage of polymers in combination with alkali to improve project economics. We show that the performance of AP floods can be optimized by making use of lower polymer viscosities during injection but increasing polymer viscosities in the reservoir owing to “aging” of the polymers at high pH. Furthermore, AP conditions enable the reduction of polymer retention in the reservoir, decreasing the utility factors (kg polymers injected/incremental bbl. produced). We used aged polymer solutions to mimic the conditions deep in the reservoir and compared the displacement efficiencies and the polymer adsorption of non-aged and aged polymer solutions. The aging experiments showed that polymer hydrolysis increases at high pH, leading to 60% higher viscosity in AP conditions. Micromodel experiments in two-layer chips depicted insights into the displacement, with reproducible recoveries of 80% in the high-permeability zone and 15% in the low-permeability zone. The adsorption for real rock using 8 TH RSB brine was measured to be approximately half of that in the case of Berea: 27 µg/g vs. 48 µg/g, respectively. The IFT values obtained for the AP lead to very low values, reaching 0.006 mN/m, while for the alkali, they reach only 0.44 mN/m. The two-phase experiments confirmed that lower-concentration polymer solutions aged in alkali show the same displacement efficiency as non-aged polymers with higher concentrations. Reducing the polymer concentration leads to a decrease in EqUF by 40%. If alkali–polymer is injected immediately without a prior polymer slug, then the economics are improved by 37% compared with the polymer case. Hence, significant cost savings can be realized capitalizing on the fast aging in the reservoir. Due to the low polymer retention in AP floods, fewer polymers are consumed than in conventional polymer floods, significantly decreasing the utility factor.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 84%

Section: Experimental Methodsmentioning

confidence: 99%

Section: Experimental Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Optimizing Polymer Costs and Efficiency in Alkali–Polymer Oilfield Applications

et al. 2022

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Alkali Polymer Flooding of Viscous Reactive Oil

Hincapie

Borovina

Clemens

et al. 2022

SPE Annual Technical Conference and Exhibition

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Displacing viscous oil by water leads to poor displacement efficiency owing to the high mobility ratio and viscous fingering. Polymer injection increases oil recovery by reducing viscous fingering and improving sweep efficiency. We are showing how Alkali-Polymer (AP) flooding is substantially improving production of reactive viscous oil from a Romanian oil field. IFT measurements, coreflood and micro-model experiments were used to understand and optimize the physico-chemical processes leading to incremental oil recovery. Extensive IFT measurements were performed at different alkali and AP concentrations. In addition, phase behavior tests were done. Furthermore, micro-model experiments were used to elucidate effects at the pore-scale and as screening tool for which chemicals to use. Single and two-phase coreflood experiments helped defining the displacement efficiency on a core scale. Various sequences and concentrations of alkali and polymers were injected to reduce costs and maximize incremental recovery of the reactive viscous oil. IFT measurements showed that saponification (110 μmol/g saponifiable acids) at the oil-alkali solution interface is very effectively reducing the IFT. With time, the IFT is increasing owing to diffusion of the generated soaps away from the interface. Phase experiments confirmed that emulsions are formed initially. Micro-models revealed that injection of polymers or alkali only leads to limited incremental oil recovery over waterflooding. For alkali injection, oil is emulsified due to in-situ saponification at the edges of viscous fingers. AP injection after waterflooding is very effective. The emulsified oil at the edges of the viscous fingers is effectively dragged by the viscous fluid substantially increasing recovery. Corefloods confirmed the findings of the micromodels. In addition, the effect of di-valent cations for the selection of the polymer concentration was investigated. Water softening leads to significantly higher viscosity of the AP slug than non-softened brine. Reducing the polymer concentration to obtain the same viscosity as the polymer solution containing divalent cations resulted in similar displacement efficiency. Hence, significant cost savings can be realized for the field conditions, for which AP injection is planned after polymer injection. The results show that alkali solutions lead to initial low IFT of reactive viscous oil owing to soap generation at the oil-alkali solution interface increasing with time due to diffusion. Injecting alkali solutions into reactive viscous oil is not effective to reduce remaining oil saturation, a limited amount of oil is mobilized at the edges of viscous fingers. AP flooding of reactive viscous oil is substantially increasing incremental oil recovery. The reason is the effective dragging of the mobilized oil with the viscous fluid and associated exposure of additional oil to the alkali solutions. Furthermore, the economics of AP flooding projects can be substantially improved by adjusting the polymer concentration to the AP slug containing softened water.

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Synergies of Alkali and Polymers - Decreasing Polymer Costs and Increasing Efficiency

Hincapie

Borovina

Clemens

et al. 2022

Day 3 Wed, November 02, 2022

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Alkali injection leads to in-situ soap generation of high TAN number oil and residual oil reduction accordingly. We are showing that the performance of AP floods can be optimized by making use of lower polymer viscosities during injection but increasing polymer viscosities in the reservoir owing to "aging" of the polymers at high pH. Furthermore, AP conditions enable reducing polymer retention in the reservoir decreasing the Utility Factors (kg polymers injected / incremental bbl. produced). Phase behavior tests were performed to understand the oil/alkali solution interaction and interfacial tension (IFT) was measured. Micromodel floods addressed displacement effects while two-phase core floods covered the displacement efficiency of alkali polymer solutions. We used aged polymer solutions to mimic the conditions deep in the reservoir and compared the displacement efficiencies and the polymer adsorption of non-aged and aged polymer solutions. IFT measurements showed that saponification (41 μmol_g saponifiable acids) at the oil-alkali solution interface is very effectively reducing the IFT. Alkali phase experiments confirmed that emulsions are formed initially and supported the potential for residual oil mobilization. Aging experiments revealed that the polymer hydrolysis rate is substantially increased at high pH compared to polymer hydrolysis at neutral pH resulting in 60 % viscosity increase in AP conditions. Within the reservoir, the fast aging of polymer solutions in high pH results in increase to target viscosity while maintaining low adsorption owing to alkali and softened water. Hence, injectivity of alkali polymer solutions can be improved over conventional polymer flooding. The two-phase experiments confirmed that lower concentration polymer solutions aged in alkali show the same displacement efficiency as non-aged polymers with higher concentrations. Hence, significant cost savings can be realized capitalizing on the fast aging in the reservoir. Due to the low polymer retention in AP floods, less polymers are consumed than in conventional polymer floods significantly decreasing the Utility Factor (injected polymers kg/incremental bbl. produced). Overall, the work shows that Alkali/Polymer (AP) injection leads to substantial incremental oil production of reactive oils. A workflow is presented to optimize AP projects including near-wellbore and reservoir effects. AP flood displacement efficiency must be evaluated incorporating aging of polymer solutions. Significant cost savings and increasing efficiency can be realized in AP floods by incorporating aging of polymers and taking the reduced polymer adsorption into account.

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Improving Alkali Polymer Flooding Economics by Capitalizing on Polymer Solution Property Evolution at High pH

Cited by 3 publications

References 36 publications

Optimizing Polymer Costs and Efficiency in Alkali–Polymer Oilfield Applications

Optimizing Polymer Costs and Efficiency in Alkali–Polymer Oilfield Applications

Alkali Polymer Flooding of Viscous Reactive Oil

Synergies of Alkali and Polymers - Decreasing Polymer Costs and Increasing Efficiency

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