Applications of Weak Gel for In-Depth Profile Modification and Oil Displacement
Bibliographic record
Abstract
Abstract Water breakthrough is a common problem when an oil field is waterflooded. Polymer solutions are widely applied to resolve the water channeling problem in deep formations. In practice, polymers are used in deep formation treatments either to block in-depth high permeability zones or to improve the mobility ratio. However, the major challenge for in-depth profile modification is how to deliver the gelling solution to the target zones. To this end, a polymer solution has to be injected at a high concentration. Thus, such a treatment sometimes becomes uneconomical. On the other hand, polymer flooding is ineffective primarily due to the viscosity loss caused by mechanical and chemical degradation. In this paper, a weak gel system is developed and used as an in-depth profile modification agent and as an oil displacement agent in a heterogeneous reservoir. The gel system has relatively low strength but can still be crosslinked in the reservoir formation. In comparison with a pure polymer solution, it suffers from less mechanical and chemical degradation because of its crosslink reaction. The EOR mechanisms of the weak gel system are described briefly. The detailed effects of polymer concentration, crosslinker concentration, temperature, and pH on gelation time are studied. Also the rheological properties, gelation range, and gel strength are examined. The coreflood results provide experimental evidence that the weak gel acts both as an in-depth profile modification agent and as an oil displacement agent. Furthermore, pilot tests have been performed in the Gudong and the Gudao oil fields of the Shengli oil field in China since 1992. The cummulative incremental oil production has been over 58,000 tonnes at the end of 2001. Introduction Waterflooding is the most widely used technology for improving oil recovery. However, early water breakthrough is a common problem encountered in almost every waterflooded oil field. Severe water channeling can result in low waterflooding efficiency and sometimes even make waterflooding uneconomical. There are several reasons for water breakthrough. Sometimes, it happens near the wellbore region, such as breakthrough along the casing due to poor cementing quality. In other cases, water breakthrough occurs in a deep formation because of its heterogeneity or fractures. In addition, because of the mobility difference between the displacing phase and the displaced phase, the former tends to bypass the latter in a homogeneous formation. In this case, viscous fingering is inevitable and early water breakthrough occurs in the producers(1–3). Different technologies have been implemented to reduce the high water-cut caused by water breakthrough, among which the most widely used is polymer injection. In general, polymer is increasingly used in chemical EOR in two traditional ways: either as an in-depth profile modification agent in conformance control, or as an oil displacement agent in polymer flooding. For conformance control, polymer and crosslinker are injected into formations to reduce large channeling through fractures or high permeability zones without damaging the productivity of the hydrocarbon. However, due to the prompt crosslink reaction, gel is sometimes formed near the wellbore.
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How this classification was reachedexpand
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 | 0.002 | 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".