Production Enhancement with a New Acid in Tight Sandstone Reservoirs: Accelerating Guar Breaking and Minimizing Formation Damage
Bibliographic record
Abstract
ABSTRACT: Crosslinked guar is suitable for the stimulation of thick tight sandstone reservoir, which can enhance the height and length of propped fractures. However, conventional gel breakers can leave residues that causes formation damage. Acid can accelerate the gel breaking rate, but it may cause secondary precipitation damage after reacting with the reservoir rock. In this study, a new acid with a low reaction rate, chelating effect, and high gel breakage is developed that can enhance the conductivity of created fractures by minimizing gel residues and inhibiting secondary precipitations after acidification. The breaking rate of the crosslinked guar by a conventional gel breaker and the new acid is compared, during which the viscosity of the solution, the molecular weight, residues, and the change of pressure with time before and after displacement damage are measured with time. The results show that the gel breaking speed of adding new acid is twice that of adding conventional gel breaker. The average relative molecular weight of the polymer in the gel breaker is reduced by 20%, and the median particle size is less than 50 μm. The permeability recovery rate of adding the new acid is much higher than that of adding conventional gel breaker. The content of metal ions in the flowback liquid is much higher than that of the initial control sample, indicating that the acid system contains chelator has a better ability to inhibit secondary precipitation. Field test shows that the average daily oil production of a single well reaches 30 tons/day after the new acid is used. 1. INTRODUCTION Tight sandstone reservoirs are widely distributed, such as San Juan basin in the United States, Alberta basin in Canada, Ordos and Tarim Basin in China. Tight sandstone is defined as permeability less than 0.1 × 10−3 μm1 2 (Law et al., 1986). It is mainly caused by the massive precipitation of authigenic clay minerals, the crystallization of cement, and the change of primary pores. Compared with conventional reservoirs, tight sandstone has the characteristics of extremely low porosity and permeability, sensitive permeability to stress and high bound water saturation, and has fracture structures such as microfractures, cleavage fractures, and bedding fractures (Shanley et al., 2004).
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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 | 0.000 |
| 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".