Petrophysical Interpretation Report — 15-135-22001
| Well (UWI) | 15-135-22001 |
| Log date | 04/19/81 |
| Acquisition date (header) | 04/19/81 |
| BHT (measured) | 120 DEGF |
| Mud resistivity (RM) | 0.18 OHMM |
| Mud filtrate (RMF) | 0.14 OHMM |
| PLSS location | Sec 28 T19S R21W (map precision ±1.6 km) |
| Larionov variant | old_rocks (degraded) |
| Convergence status | DID_NOT_CONVERGE |
| Confidence tier | ○ BRACKETED |
| Engine versions | calc_vsh 0.1.0 · calc_phie 0.1.0 · calc_sw 0.1.0 · formula_registry 0.1.0 |
| Config hash (SHA-256) | 2a9cb78728e386ab… |
| Git SHA | bd23bea18153 |
| Generated | autonomously, no human in the per-report loop |
Confidence legend. Each result is tagged by parameter provenance: ● FIRM (core-calibrated) · ◐ QUALIFIED (offset-derived) · ○ BRACKETED (regional/global default — read as a range, dominant uncertainty stated). The system does not claim *always correct*; it states how well-supported each number is.
1. Executive summary
⚠️ ABSTENTION — this is NOT a confident estimate. The run did not converge to a defensible result; the numbers below are an uncalibrated engineering estimate, reported for transparency only:
- 1 unresolved MECHANICAL objection(s)
The vintage log covers only the deep consolidated section, so the full logged interval is evaluated — there is no overburden on record to exclude. Within that interval the net pay is 19.4 m with average effective porosity 0.218 and average water saturation 0.375. Monte-Carlo places the P50 net pay at 25.2 m within a P10-P90 range of 9.1 to 44.7 m. CLASS-B VINTAGE WELL: porosity comes from a count-rate neutron transform (engine-anchored, validated against sonic on offset wells; structural approximation) — every number is bracketed and must be read as a range. The run ABSTAINS from a confident estimate: the validators keep an unresolved objection, so the result must be read as a bracketed range, not a point value.
Net pay P10 / P50 / P90 = 9.1 / 25.2 / 44.7 m.
Net pay is dominated by 'Rw', which is a regional DEFAULT (uncalibrated). This is the single largest uncertainty — the result is bracketed, not a confident point estimate.
2. Data inventory (from LAS)
- Curves present (canonical ← raw): GR←GR, NEUT←NEUT, RT←RES
- Logged interval: 1127.46–1352.55 m
- Log date: 04/19/81
- Service company: — · Company: VICENT OIL CORP.
- Field: SCHABEN
- Not provided by LAS (out of scope): core, mud logs, pressure tests, production, completion, formation tops.
3. LAS quality control
| Edit type | Curve | Detail |
|---|---|---|
| spike_removal | — | 5 edits |
| degradation | — | — |
4. Standardization
Raw mnemonics mapped to canonical curve names:
| Canonical | Raw mnemonic |
|---|---|
| GR | GR |
| NEUT | NEUT |
| RT | RES |
5. Per-curve log QC
- GR baseline: gr_p5=23.4, gr_p95=99.2
- Bad-hole: GOOD=0.918, DEGRADED=0.001, EXCLUDED=0.081
- Low-resistivity: rt_threshold=3.49, n_flagged=147, intervals=[[1127.8, 1127.8], [1128.2, 1129.4], [1131.7, 1132.0], [1132.5, 1133.2], [1135.7, 1139.5], [1142.7, 1142.7], [1143.5, 1144.7], [1145.1, 1148.2], [1150.8, 1150.8], [1153.2, 1154.1]]
6. Data preparation
Edits applied before compute (by type): degradation: 1, spike_removal: 5.
7. Interval definition
- Logged interval: 1127.46–1352.55 m
- Gross evaluated interval: 225.1 m
- Computed net-pay runs (pre-merge): 25
- Zonation is computed by depth (no formation tops in LAS).
8. Methodology
All numbers are produced by the deterministic, golden-tested engine. The LLM only selects methods/parameters and writes prose — it never computes a number. Figures are deterministic renderings of these computed numbers for the human reader; the agent reasons over the numeric EDA digest, not images (the models have no vision).
| Step | Method (frozen) | Version |
|---|---|---|
| Vsh | Larionov 1969 (old rocks) | vsh_larionov_old 0.1.0 |
| PHIE | Vintage count-rate neutron, two-point semilog (class-B, engine-anchored) | phi_neutron_countrate 0.1.0 |
| Sw | Archie 1942 | sw_archie 0.1.0 |
| Net pay | Vsh/PHIE/Sw cutoffs → net sand → net reservoir → net pay | netpay 0.1.0 |
| Uncertainty | Monte Carlo P10/P50/P90 + parameter sensitivity | mc 0.1.0 |
9. Gamma-ray analysis
- Clean baseline gr_min = 20.0 API · shale gr_max = 120.0 API
- Shale index IGR = (GR − gr_min)/(gr_max − gr_min), the basis for Vsh.
- GR baseline check: gr_p5=23.4, gr_p95=99.2
10. Resistivity analysis
Low-resistivity scan: rt_threshold=3.49, n_flagged=147, intervals=[[1127.8, 1127.8], [1128.2, 1129.4], [1131.7, 1132.0], [1132.5, 1133.2], [1135.7, 1139.5], [1142.7, 1142.7], [1143.5, 1144.7], [1145.1, 1148.2], [1150.8, 1150.8], [1153.2, 1154.1]].
11. Water resistivity (Rw)
- Rw = 0.0400 ohm-m · provenance: default
- Sourced by the engine (Pickett / SP / default); never authored by the LLM.
- Net-pay sensitivity to Rw: 25.8 m swing.
- Formation-temperature correction (Arps, gradient from the MEASURED header BHT): Rw ≈ 0.0405 ohm-m at 46.6 °C (evidence only — Sw uses the calibrated Rw).
12. Figures
Composite log
Pickett plot
Buckles plot
Hingle plot
Distributions
Sensitivity tornado
Net-pay Monte-Carlo distribution
13. Shale volume (Vsh)
Mean Vsh by method (selection is the agent's; the LLM authors no number):
| Method | Mean Vsh | Selected |
|---|---|---|
| vsh_larionov_old | 0.197 | ✓ |
| vsh_larionov_tertiary | 0.138 | |
| vsh_linear | 0.294 | |
| vsh_clavier | 0.185 | |
| vsh_steiber | 0.158 |
14. Porosity
_Not computed — no RHOB/NPHI curve for the comparison._
15. Water saturation
Mean Sw (Archie 1942) = 0.780 (a=1.00, m=2.00, n=2.00, Rw=0.0648 ohm-m). Electrical parameters are engine-sourced; alternative Sw models are optional sections.
Mean Sw by method (engine-computed comparison; the LLM authors no number):
| Method | Mean Sw | Selected |
|---|---|---|
| sw_archie | 0.780 | ✓ |
| sw_simandoux | 0.552 | |
| sw_indonesia | 0.639 |
16. Zonation (net-pay intervals)
Raw net-pay runs merged into 16 intervals (gap tolerance 1.5 m); showing the 15 thickest, depth-ordered. Full set traces in the ledger.
| Interval | Top (m) | Base (m) | Net pay (m) | Avg PHIE | Avg Sw | Avg Vsh |
|---|---|---|---|---|---|---|
| Z1 | 1160.7 | 1160.7 | 0.2 | 0.116 | 0.413 | 0.287 |
| Z2 | 1162.4 | 1163.6 | 1.4 | 0.329 | 0.403 | 0.224 |
| Z3 | 1171.2 | 1171.8 | 0.8 | 0.153 | 0.362 | 0.061 |
| Z4 | 1189.8 | 1190.9 | 1.1 | 0.242 | 0.390 | 0.214 |
| Z5 | 1197.7 | 1197.7 | 0.2 | 0.123 | 0.490 | 0.145 |
| Z6 | 1230.2 | 1235.2 | 4.6 | 0.231 | 0.290 | 0.125 |
| Z7 | 1240.2 | 1240.4 | 0.3 | 0.145 | 0.403 | 0.221 |
| Z8 | 1266.0 | 1266.1 | 0.3 | 0.329 | 0.342 | 0.322 |
| Z9 | 1268.9 | 1271.6 | 2.6 | 0.197 | 0.417 | 0.294 |
| Z10 | 1273.3 | 1275.6 | 2.4 | 0.259 | 0.359 | 0.201 |
| Z11 | 1282.3 | 1283.7 | 1.4 | 0.260 | 0.471 | 0.227 |
| Z12 | 1328.2 | 1329.5 | 0.8 | 0.153 | 0.324 | 0.289 |
| Z13 | 1337.0 | 1338.4 | 1.1 | 0.195 | 0.334 | 0.323 |
| Z14 | 1340.4 | 1341.0 | 0.8 | 0.147 | 0.442 | 0.292 |
| Z15 | 1342.6 | 1344.9 | 1.5 | 0.132 | 0.461 | 0.266 |
17. Results
| Quantity | Value |
|---|---|
| Gross interval | 225.1 m |
| Net pay (P10/P50/P90) | 9.1 / 25.2 / 44.7 m |
| Net-to-gross | 0.086 |
| Avg PHIE (net pay) | 0.218 |
| Avg Sw (net pay) | 0.375 |
| Avg Vsh (net pay) | 0.215 |
18. Uncertainty and sensitivity
Monte Carlo, 500 realizations (seed 42). Net pay swing per parameter (one-at-a-time):
| Parameter | Net-pay swing (m) |
|---|---|
| Rw | 25.8 |
| m | 21.2 |
| a | 11.9 |
| n | 7.5 |
Dominant uncertainty: Rw (swing 25.8 m).
Multi-seed robustness: P50 stable (spread 2.4 m across 4 seeds).
Net pay is dominated by 'Rw', which is a regional DEFAULT (uncalibrated). This is the single largest uncertainty — the result is bracketed, not a confident point estimate.
19. Derived parameters
- Bulk-volume water (BVW = PHIE*Sw): mean 0.0672 v/v
- Porosity-thickness (Phi·H over net pay): 4.218 m
- Hydrocarbon pore thickness (HCPV = Σ PHIE·(1−Sw)·step): 2.636 m
- Buckles constant (BVW at P10 of net pay): 0.0414 → Swirr (mean) ≈ 0.190 over 127 pay samples
20. Parameters and provenance
| Parameter | Value | Unit | Provenance | Source |
|---|---|---|---|---|
| gr_min | 20.000 | API | default | — |
| gr_max | 120.000 | API | default | — |
| rho_ma | 2.710 | g/cc | default | Schlumberger 1989 |
| rho_fl | 1.000 | g/cc | default | — |
| phie_max | 0.450 | v/v | default | — |
| phi_sh_d | 0.100 | v/v | default | — |
| phi_sh_n | 0.350 | v/v | default | — |
| a | 1.000 | - | default | Winsauer et al. 1952 |
| m | 2.000 | - | default | Archie, G.E. 1942 |
| n | 2.000 | - | default | Archie, G.E. 1942 |
| Rw | 0.040 | ohm-m | default | Kansas Geological Survey 2000 |
| rt_hydrocarbon_floor | 5.000 | ohm-m | default | — |
| vsh_cutoff | 0.350 | v/v | default | — |
| phie_cutoff | 0.100 | v/v | default | — |
| sw_cutoff | 0.500 | v/v | default | — |
| bit_size_config | 7.875 | in | default | — |
| qc_abort_threshold | 0.800 | - | default | — |
| circuit_breaker_n | 3.000 | - | default | — |
The citations table (not RAG) gives each cited parameter exactly one frozen source. Parameters tagged
defaultare regional/global — they drive the bracketed tier.
21. Petrophysical cutoffs
Boundary-inclusive criteria applied by the engine (netpay) to flag reservoir:
| Stage | Criterion | Cutoff | Provenance |
|---|---|---|---|
| Net sand | Vsh ≤ cutoff | 0.350 | default |
| Net reservoir | + PHIE ≥ cutoff | 0.100 | default |
| Net pay | + Sw ≤ cutoff | 0.500 | default |
Cutoff values are engine parameters (never LLM-authored); the dominant net-pay uncertainty is Rw — see Uncertainty for the swing.
22. Data quality and validator objections
Curve provenance (canonical ← raw mnemonic): GR←GR, NEUT←NEUT, RT←RES.
QC edits applied before compute — degradation: 1, spike_removal: 5.
| Validator | Type | Detail |
|---|---|---|
| vsh_phie_anticorrelation | support | Vsh-PHIE Pearson 0.99 > 0.3 (dirty rock + high porosity) |
| rt_sw_consistency | mechanical | 4 depths with Sw<0.4 but RT<5.0 ohm-m |
23. Methodology (decision graph)
flowchart TD
dec_1["decision: step: compare_methods"]
act_1["tool_call: compare_methods"]
dec_2["decision: step: compute_vsh"]
act_2["tool_call: compute_vsh"]
dec_3["decision: step: compute_phie"]
act_3["tool_call: compute_phie"]
dec_4["decision: step: compare_methods"]
act_4["tool_call: compare_methods"]
dec_5["decision: step: compute_sw"]
act_5["tool_call: compute_sw"]
dec_6["decision: step: apply_cutoffs"]
act_6["tool_call: apply_cutoffs"]
dec_7["decision: step: run_uncertainty"]
act_7["tool_call: run_uncertainty"]
dec_8["decision: step: derived_parameters"]
act_8["tool_call: derived_parameters"]24. Data gaps for calibration
This is a LAS-only study. Data that would calibrate the interpretation is absent:
- Core (routine + SCAL): would anchor PHIE and Archie m, n, a.
- Pressure tests (RFT/MDT): would give true fluid contacts and gradients (log-based).
- Production/flow data: would test the net-pay flag against deliverability.
- Dominant net-pay uncertainty driver (from the sensitivity): Rw (calibrated by produced-water salinity or a Pickett/SP Rw calibration).
- Standard curves absent: RHOB, NPHI, SP, DT, PEF, CALI, DCAL.
25. Limitations
- LAS-only study: no core calibration, no pressure tests (no true fluid contacts), no production, no mud logs, no formation tops (zonation computed by depth).
- Standard curves absent in this well: RHOB, NPHI, SP, DT, PEF, CALI, DCAL.
- Results are uncalibrated; accuracy depends on data not provided.
26. Conclusions
Vintage class-B well: logged interval covers only the deep consolidated section (no overburden recorded), GR-only clay indicator, count-rate porosity with engine anchors, Archie saturation. Structural-uncertainty caveat applies to every number. Method choices were made against the engine's numeric comparisons, not by preference; the comparison tables show the rejected alternatives beside the selected method. All numbers in this report come from the deterministic engine; the analyst chose the interval, the methods and the analyses, and wrote this prose — nothing more. Remaining uncertainty is dominated by the uncalibrated regional parameters.
Appendix A — Ledger excerpt (traceability)
{
"net_pay_total_m": 19.354799999992792,
"net_pay_p10_p50_p90": [
9.113519999996608,
25.222199999990607,
44.65319999998337
],
"driving_params": {
"a": 1.0,
"m": 2.0,
"n": 2.0,
"Rw": 0.04
},
"claim_verifier": {
"result": "PASS",
"flags": [],
"tone_flags": []
}
}Appendix B — Completeness gate
| Item | Present |
|---|---|
| QC edits recorded before compute | ✓ |
| Every number ledger-traced | ✓ |
| Confidence tier on the run | ✓ |
| Parameter citations frozen | ✓ |
| Validator objections listed, not hidden | ✓ |
| Uncertainty propagated (Monte Carlo) | ✓ |
| Claim verifier run on prose | ✓ |