Formation and Distribution of Tight Sand Gas Reservoirs in the Sichuan Basin, China
Bibliographic record
Abstract
Located in the central west of China, the Sichuan Basin is abundant in natural gas resources. It is the earliest basin where natural gas was discovered and utilized in the world. After more than 60 years’ exploration, many gas fields have been found in the Paleozoic - Mesozoic carbonate and clastic formations. The basin has become a critical production base in China for its cumulative proved recoverable gas reserves of more than 8000×10 8 m 3 , and gas production over 150×10 8 m 3 in 2010. During the past decade, many tight gas reservoirs have been found in the Xujiahe coal measures of the upper Triassic continental deposits. Based on lithology, this suite of formation can be divided into six members from bottom to top. The source rocks are the coal beds and carbon-bearing mudstones in Xu1, Xu3 and Xu5 members with relatively high organic carbon contents and type III kerogen; the reservoir rocks are the tight sandstones in Xu2, Xu4 and Xu6 members. The source rocks and the reservoirs distribute alternatively and widely in “sandwiched” structure, providing favorable conditions for natural gas accumulating near source. As the formations are gentle and lack of structural traps, the lithologic gas reservoirs dominate the Xujiahe tight sandstones. Both coal-measure source rocks and sandstone reservoir distribute in strong heterogeneity, leading to thin gas-layers in the reservoir, poor continuity in plane, and varying full-up ratio and gas saturation in the gas reservoir. Within the 80,000 km 2 area, the Xujiahe Formation has the features of widespread gas-bearing beds and local gas enrichment. The current high-yield gas wells are mainly distributed in the tectonic highs or fractured zones in the areas with effective source-reservoir assemblages. The resources assessment is made considering the tight gas accumulating intensively into reservoir. It reveals the favorable gas-bearing area up to 6-7×10 4 km 2 and the estimated recoverable gas reserves of 2-3×10 12 m 3 in the Xujiahe Formation. Key words: Sichuan Basin; Tight sandstone; Coal measures; Tight gas; “Sandwiched” structure; Resources
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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 | 0.002 | 0.002 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".