A 3D seismic fracture interpretation method for exploration of Lower Dakota alluvial gas sands, San Juan Basin, New Mexico
Bibliographic record
Abstract
The first phase of a U.S. Department of Energy (DOE) — funded project has been successfully completed (GeoSpectrum, Inc. 2003). Reservoir fractures are predicted using multiple azimuth seismic lineament mapping in the Lower Dakota reservoir section. A seismic lineament is defined as a linear feature seen in a time slice or horizon slice through the seismic volume. For lineament mapping, each lineament must be recognizable in more than one seismic attribute volume. Seismic attributes investigated include: coherency, amplitude, frequency, phase, and acoustic impedance. We interpret that areas having high seismic lineament density with multi-directional lineaments are associated with high fracture density in the reservoir. Lead areas defined by regions of “swarming” multi-directional lineaments are further screened by additional geologic attributes. These attributes include reservoir isopach thickness, indicating thicker reservoir section; seismic horizon slices, imaging potentially productive reservoir stratigraphy; and a collocated cokriged clay volume map for the reservoir zone computed from near trace seismic amplitude (an AVO attribute) and a comprehensive petrophysical analysis of the well data to determine discrete values of clay volume at each well. This map indicates where good/clean reservoir rock is located. We interpret that clean/low clay reservoir rock is brittle and likely to be highly fractured when seismic lineaments are present. A gas sensitive AVO seismic attribute, near trace stacked phase minus far trace stacked phase, phase gradient, is used to further define drill locations having high gas saturation. The importance of this attribute cannot be understated, as reservoir fractures enhance reservoir permeability and volume, they may also penetrate water saturated zones in the Dakota and/or Morrison intervals and be responsible for the reservoir being water saturated and ruined. Seismic interval velocity anisotropy is used to investigate reservoir potential in tight sands of the Upper Dakota up hole from the main reservoir target. We interpret that large interval velocity anisotropy is associated with fracture related anisotropy in these tight sands. A four well drilling program is planned to test GeoSpectrum's fractured gas reservoir prospects and exploration technology. The first well, the Canyon Largo Unit No. 452 (Site 4) was drilled and completed last January 14th and had an initial production of 4 MMCFGPD from the Lower Dakota Encinal Formation. The well continues to produce at about 1.4 MMCFGPD at 175 PSI and is one of the better wells in the field, and a very good well in this area of the basin. Information on the well can be found in the Petroleum Technology Transfer Council (PTTC) Network News, 1st Quarter, 2004. If drilling results continue to be successful, GeoSpectrum's fracture detection methodology is ready to be applied on a commercial basis.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".