Effect of Viscosity of Alkaline/Surfactant/Polymer (ASP) Solution on Enhanced Oil Recovery in Heterogeneous Reservoirs
Bibliographic record
Abstract
Abstract There have been numerous laboratory experimental studies and field tests on ASP flooding. Most of the laboratory experiments focused mainly on the effect of the ultra-low oilwater interfacial tension on oil recovery. The relationship between the viscosity of ASP solution and oil recovery efficiency of ASP flooding has not been well understood. In this paper, the relationship between the viscosity of ASP solution and oil recovery in heterogeneous porous models was studied. More than 50 ASP flood tests were conducted using artificial models. These models were made to have different permeability variation coefficients so that ASP floods in homogeneous and heterogeneous reservoirs could be simulated. Sixteen ASP solutions were prepared and used in ASP flood tests. Based on the results of ASP flood tests, the effects on tertiary oil recovery of NaOH concentration and of the balance between the IFT reduction and viscosity increase were discussed. For heterogeneous models, it was found that there existed a minimum viscosity value of ASP solution for ultra-low IFT system to fully function in improving residual oil recovery. This minimum viscosity is defined as critical displacement viscosity in this study. When the viscosity of a ASP solution is lower than the critical displacement viscosity, the oil recovery efficiency of ASP flooding is dominated by the viscosity of the ASP solution; the reduction in interfacial tension to an ultralow level contributed little to oil recovery. When the viscosity is higher than the critical displacement viscosity, both the viscosity and ultra-low IFT contributed to oil recovery. This critical displacement viscosity should be one of the important parameters which can be used to optimize the chemical formula of a ASP flood for a target reservoir. Introduction As a relatively new technology of tertiary oil recovery, alkaline/surfactant/polymer (ASP) flooding has been studied extensively in the last two decades. [1–9] ASP flooding enhances oil recovery through two major mechanisms: increasing the viscosity of displacing solution to improve the sweep efficiency by using polymer and reducing oil-water interfacial tension (IFT) to a very low value (∼10–3 mN/m) to improve the pore level displacement efficiency through the synergetic effect of surfactant and alkaline. [10].Field tests and laboratory studies have shown that ASP flooding is more efficient than any single component flooding, such as alkaline, surfactant, or polymer flooding. [6–8] At present, it is a promising tertiary recovery method and is getting increasingly more attention. Seven field ASP floods have been implemented in Daqing oilfield, China. It was found that in the early stage of some tests high alkaline concentrations could cause alkaline scale problems in the oil formation and the wellbore [8,9,11]. In addition, high alkaline concentration could weaken the efficiency of polymer in increasing the viscosity of the ASP solution. Therefore, the polymer concentration in some field tests was increased from 1,200mg/L to 1,800mg/L, and then to 2,300 mg/L in order to ensure that the viscosity of ASP solution was not lower than 30mPa.s. It was predicted that, with this level of viscosity of the displacing fluid, the oil recovery of ASP flooding could be as high as 20% original oil-in-place (OOIP).
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".