New Insights on Mechanisms Controlling Fracturing-Fluid Distribution and Their Effects on Well Performance in Shale-Gas Reservoirs
Bibliographic record
Abstract
Summary Many stimulated shale-gas wells experience surprisingly low fracturing-fluid recoveries. Fracture closure, gravity segregation, proppant distribution, and shut-in (soaking) time have been widely postulated to be the contributing factors. This study examines the effects of these factors on fracturing-fluid distribution and subsequent well performance using flow and geomechanical simulations. In the end, two real-field examples are used to validate the findings in this study. Geomechanical simulation is used to capture the complex post-closure fracture geometry caused by nonuniform proppant distribution. The geometry is then passed into a series of 3D numerical flow models that are constructed using petrophysical parameters, fluid properties, and operational constraints representative of the Horn River shale-gas reservoir. Within the flow simulation, the hydraulic fracture is represented explicitly in the computational domain by means of local-grid refinement, and the physical process of fracture closure during shut-in and production periods is modeled by adjusting the fracture volume and fracture conductivity dynamically. Non-Darcy behavior caused by high gas velocity in the fracture and matrix desorption are considered. The results of the geomechanical simulation confirm the formation of a residual opening above the proppant pack in a partially propped fracture. The residual opening offers a highly conductive flow path for the gas, which is much more mobile than the water-based fracturing fluid, and this difference in mobility further aggravates gravity segregation. Gravity segregation might lead to water accumulating near the bottom of a vertical planar fracture, but reduced fracture conductivity could limit the segregation and promote a more uniform fluid distribution. Water uptake into the matrix is influenced by forced and spontaneous imbibition caused by the large pressure differential across the matrix/fracture interface and matrix capillarity. Additional water is displaced into the matrix as pressure depletes and the fracture closes. Fracturing-fluid-penetration depth increases with shut-in time, resulting in an enhancement in the initial gas rate, but lower late-time production is also observed. Analysis of the residual opening of a partially propped fracture and its role in fracturing-fluid distribution in three dimensions is novel. Field examples suggest that considering the various physical mechanisms investigated in this study could improve the accuracy of the numerical model for history matching and the reliability of the ensuing production forecasting. The findings in this study might provide a better understanding of fracturing-fluid distribution, which is useful for optimizing production strategies and operations concerning hydraulically fractured shale-gas reservoirs.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| 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 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".