A New Method for Modeling Multi-Phase Flowback of Multi-Fractured Horizontal Tight Oil Wells to Determine Hydraulic Fracture Properties
Bibliographic record
Abstract
Abstract Unconventional light oil reservoirs are currently a primary focus of exploration and development activity in North America. Operators are seeking new methods to characterize hydraulic fractures generated during stimulation of multi-fractured horizontal wells completed in these reservoirs, particularly early in the well life. One such method is to quantitatively analyze flowback fluids immediately after fracturing operations. In previous studies it has been shown that flowback fluid rates and pressures can be modeled to obtain hydraulic fracture half-length and conductivity. In this work, we develop an analytical procedure and methods for analyzing pre- and post-breakthrough of hydrocarbons during flowback of light tight oil wells. Flowback of multi-fractured horizontal wells, stimulated with water-based fluids in tight oil reservoirs, often consists of a short period of single-phase (water) flow followed by breakthrough of hydrocarbons, after which multi-phase flow (oil, water and gas) occurs. Our modeling approach therefore accounts for these multiple stages of flowback fluid production. The first flowback regime typically observed is fracture storage/depletion – this stage is analyzed by modeling single-phase depletion of the fracture pore volume from which a pre-hydrocarbon breakthrough estimate of fracture permeability and half-length is obtained. A stress-dependent permeability can be included to account for fracture closure and consequent conductivity loss during flowback. Fracture storage is followed by formation fluid breakthrough, which causes a deviation from the depletion signature. This stage is modeled by assuming transient linear flow of oil and formation water to the fracture, and accounting for consequent multi-phase flow in the fracture. The primary properties adjusted to match pre- and post-hydrocarbon breakthrough fluid production include fracture half-length and permeability, fracture relative permeability, breakthrough pressure and reservoir permeability. We have observed, as have others, that effective fracture half-length may be significantly reduced following hydrocarbon breakthrough. Our new method for tight oil reservoir flowback analysis is tested against a field example. As with previous studies associated with shale gas, significant uncertainty in fracture property estimation results from the analysis, which we will address in future work.
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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 | 0.000 | 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".