Petrophysical Interpretation Report — 15-135-22865
| Well (UWI) | 15-135-22865 |
| Log date | 07/24/85 |
| Acquisition date (header) | 7/24/85 |
| BHT (measured) | 120 DEGF |
| Mud resistivity (RM) | 0.12 OHMM |
| Mud filtrate (RMF) | 0.1 OHMM |
| PLSS location | Sec 1 T20 R22W (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 12.8 m with average effective porosity 0.214 and average water saturation 0.356. Monte-Carlo places the P50 net pay at 18.3 m within a P10-P90 range of 10.8 to 32.5 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 = 10.8 / 18.3 / 32.5 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: 1127.76–1342.03 m
- Log date: 07/24/85
- Service company: — · Company: DREILING LTD. OF COLORADO
- Field: SCHABEN S.
- 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 | — | 9 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=21.2, gr_p95=117.3
- Bad-hole: GOOD=0.96, DEGRADED=0.0, EXCLUDED=0.04
- Low-resistivity: rt_threshold=4.76, n_flagged=138, intervals=[[1129.6, 1130.0], [1130.5, 1130.7], [1132.2, 1136.8], [1138.7, 1139.2], [1140.9, 1142.4], [1142.7, 1144.4], [1146.2, 1146.5], [1148.5, 1148.6], [1149.7, 1152.3], [1153.1, 1153.2]]
6. Data preparation
Edits applied before compute (by type): degradation: 1, spike_removal: 9.
7. Interval definition
- Logged interval: 1127.76–1342.03 m
- Gross evaluated interval: 214.3 m
- Computed net-pay runs (pre-merge): 17
- 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=21.2, gr_p95=117.3
10. Resistivity analysis
Low-resistivity scan: rt_threshold=4.76, n_flagged=138, intervals=[[1129.6, 1130.0], [1130.5, 1130.7], [1132.2, 1136.8], [1138.7, 1139.2], [1140.9, 1142.4], [1142.7, 1144.4], [1146.2, 1146.5], [1148.5, 1148.6], [1149.7, 1152.3], [1153.1, 1153.2]].
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: 20.0 m swing.
- Formation-temperature correction (Arps, gradient from the MEASURED header BHT): Rw ≈ 0.0468 ohm-m at 47.1 °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 | 0.247 | ✓ |
| vsh_larionov_tertiary | 0.189 | |
| vsh_linear | 0.341 | |
| vsh_clavier | 0.235 | |
| vsh_steiber | 0.207 |
14. Porosity
_Not computed — no RHOB/NPHI curve for the comparison._
15. Water saturation
Mean Sw (Archie 1942) = 0.750 (a=1.00, m=2.00, n=2.00, Rw=0.0666 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 | 0.750 | ✓ |
| sw_simandoux | 0.465 | |
| sw_indonesia | 0.566 |
16. Zonation (net-pay intervals)
Raw net-pay runs merged into 12 geological intervals (gap tolerance 1.5 m).
| Interval | Top (m) | Base (m) | Net pay (m) | Avg PHIE | Avg Sw | Avg Vsh |
|---|---|---|---|---|---|---|
| Z1 | 1152.1 | 1152.4 | 0.5 | 0.262 | 0.443 | 0.119 |
| Z2 | 1157.8 | 1160.4 | 2.7 | 0.219 | 0.377 | 0.007 |
| Z3 | 1204.9 | 1204.9 | 0.2 | 0.257 | 0.462 | 0.319 |
| Z4 | 1213.3 | 1216.6 | 2.7 | 0.209 | 0.350 | 0.057 |
| Z5 | 1222.9 | 1226.7 | 3.8 | 0.228 | 0.297 | 0.057 |
| Z6 | 1262.5 | 1263.1 | 0.8 | 0.130 | 0.421 | 0.162 |
| Z7 | 1269.3 | 1269.3 | 0.2 | 0.251 | 0.473 | 0.324 |
| Z8 | 1276.7 | 1278.0 | 0.9 | 0.271 | 0.389 | 0.274 |
| Z9 | 1284.1 | 1284.3 | 0.3 | 0.128 | 0.429 | 0.130 |
| Z10 | 1309.3 | 1309.4 | 0.3 | 0.177 | 0.252 | 0.249 |
| Z11 | 1312.2 | 1312.6 | 0.3 | 0.128 | 0.471 | 0.005 |
| Z12 | 1320.1 | 1320.1 | 0.2 | 0.112 | 0.385 | 0.094 |
17. Results
| Quantity | Value |
|---|---|
| Gross interval | 214.3 m |
| Net pay (P10/P50/P90) | 10.8 / 18.3 / 32.5 m |
| Net-to-gross | 0.060 |
| Avg PHIE (net pay) | 0.214 |
| Avg Sw (net pay) | 0.356 |
| Avg Vsh (net pay) | 0.082 |
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 | 20.0 |
| m | 12.3 |
| a | 8.4 |
| n | 2.9 |
Dominant uncertainty: Rw (swing 20.0 m).
Multi-seed robustness: P50 UNSTABLE across seeds (spread 3.7 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 0.0657 v/v
- Porosity-thickness (Phi·H over net pay): 2.735 m
- Hydrocarbon pore thickness (HCPV = Σ PHIE·(1−Sw)·step): 1.774 m
- Buckles constant (BVW at P10 of net pay): 0.0482 → Swirr (mean) ≈ 0.226 over 84 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: 9.
| Validator | Type | Detail |
|---|---|---|
| vsh_phie_anticorrelation | support | Vsh-PHIE Pearson 0.97 > 0.3 (dirty rock + high porosity) |
| rt_sw_consistency | mechanical | 13 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": 12.801599999995233,
"net_pay_p10_p50_p90": [
10.82039999999597,
18.28799999999319,
32.46119999998791
],
"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 | ✓ |