Petrophysical Interpretation Report — 15-135-25697-00-00
| Well (UWI) | 15-135-25697-00-00 |
| Log date | Thu Dec 12 11-33-25 2013 |
| Service company | SUPERIOR WELL SERVICES INC. |
| Acquisition date (header) | Thu Dec 12 11-33-25 2013 |
| PLSS location | Sec 1 T20S 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.
⚠️ claim verifier FLAGS: 1 number(s) not traceable to the ledger
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)
- net-pay avg PHIE 0.30 > 0.25 — implausibly high for carbonate
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 176.0 m with average effective porosity 0.302 and average water saturation 0.341. Monte-Carlo places the P50 net pay at 216.9 m within a P10-P90 range of 119.9 to 391.4 m. An independent SP-derived water resistivity of 0.0565 ohm-m (static SP -34.4 mV; offset-median mud-filtrate resistivity 0.110 ohm-m — a declared cross-well assumption) supports the regional default, and the Monte-Carlo Rw range is narrowed to the field SP band with recorded provenance. 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 = 119.9 / 216.9 / 391.4 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←NEU, RT←GUARD, SP←SP
- Logged interval: 0.00–1340.97 m
- Log date: Thu Dec 12 11-33-25 2013
- Service company: SUPERIOR WELL SERVICES INC. · Company: MUSTANG ENERGY CORPORATION
- 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 |
|---|---|---|
| hard_range_mask | RT | count 114 |
| range_warn | GR | count 1 |
| spike_removal | — | 153 edits |
| degradation | — | — |
4. Standardization
Raw mnemonics mapped to canonical curve names:
| Canonical | Raw mnemonic |
|---|---|
| GR | GR |
| NEUT | NEU |
| RT | GUARD |
| SP | SP |
5. Per-curve log QC
- GR baseline: gr_p5=22.6, gr_p95=101.2
- Bad-hole: GOOD=0.968, DEGRADED=0.0, EXCLUDED=0.032
- Low-resistivity: rt_threshold=2.16, n_flagged=854, intervals=[[26.4, 28.2], [29.3, 29.6], [30.3, 32.3], [85.2, 86.0], [103.3, 103.8], [110.6, 111.1], [159.3, 159.7], [167.9, 170.7], [173.3, 173.6], [176.8, 176.8]]
6. Data preparation
Edits applied before compute (by type): degradation: 1, hard_range_mask: 1, range_warn: 1, spike_removal: 153.
7. Interval definition
- Logged interval: 0.00–1340.97 m
- Gross evaluated interval: 1341.0 m
- Computed net-pay runs (pre-merge): 144
- 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=22.6, gr_p95=101.2
10. Resistivity analysis
Low-resistivity scan: rt_threshold=2.16, n_flagged=854, intervals=[[26.4, 28.2], [29.3, 29.6], [30.3, 32.3], [85.2, 86.0], [103.3, 103.8], [110.6, 111.1], [159.3, 159.7], [167.9, 170.7], [173.3, 173.6], [176.8, 176.8]].
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: 348.1 m swing.
- Formation-temperature correction (Arps, regional-default gradient): Rw ≈ 0.0397 ohm-m at 33.4 °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 | 0.279 | ✓ |
| vsh_larionov_tertiary | 0.200 | |
| vsh_linear | 0.401 | |
| vsh_clavier | 0.263 | |
| vsh_steiber | 0.223 |
14. Porosity
_Not computed — no RHOB/NPHI curve for the comparison._
15. Water saturation
Mean Sw (Archie 1942) = 0.690 (a=1.00, m=2.00, n=2.00, Rw=0.0598 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 | 0.690 | ✓ |
| sw_simandoux | 0.550 | |
| sw_indonesia | 0.545 |
16. Zonation (net-pay intervals)
Raw net-pay runs merged into 70 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 | 32.6 | 57.0 | 22.7 | 0.324 | 0.424 | 0.243 |
| Z2 | 61.4 | 66.4 | 2.7 | 0.324 | 0.380 | 0.278 |
| Z3 | 75.3 | 80.9 | 3.2 | 0.276 | 0.422 | 0.239 |
| Z4 | 86.1 | 90.8 | 3.2 | 0.338 | 0.405 | 0.279 |
| Z5 | 112.6 | 115.5 | 2.3 | 0.353 | 0.378 | 0.231 |
| Z6 | 117.5 | 123.6 | 5.2 | 0.264 | 0.436 | 0.169 |
| Z7 | 128.2 | 137.3 | 6.7 | 0.239 | 0.456 | 0.038 |
| Z8 | 146.3 | 150.7 | 3.4 | 0.335 | 0.430 | 0.293 |
| Z9 | 308.2 | 312.0 | 2.3 | 0.348 | 0.472 | 0.091 |
| Z10 | 326.1 | 339.2 | 11.9 | 0.353 | 0.462 | 0.069 |
| Z11 | 574.1 | 597.0 | 20.7 | 0.291 | 0.271 | 0.078 |
| Z12 | 599.4 | 601.8 | 2.6 | 0.195 | 0.420 | 0.220 |
| Z13 | 603.4 | 622.2 | 18.1 | 0.320 | 0.214 | 0.040 |
| Z14 | 625.0 | 662.6 | 37.5 | 0.322 | 0.186 | 0.031 |
| Z15 | 1334.4 | 1337.8 | 2.3 | 0.162 | 0.423 | 0.136 |
17. Results
| Quantity | Value |
|---|---|
| Gross interval | 1341.0 m |
| Net pay (P10/P50/P90) | 119.9 / 216.9 / 391.4 m |
| Net-to-gross | 0.131 |
| Avg PHIE (net pay) | 0.302 |
| Avg Sw (net pay) | 0.341 |
| Avg Vsh (net pay) | 0.128 |
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 | 348.1 |
| m | 190.2 |
| a | 154.1 |
| n | 76.8 |
Dominant uncertainty: Rw (swing 348.1 m).
Multi-seed robustness: P50 UNSTABLE across seeds (spread 32.9 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 0.1126 v/v
- Porosity-thickness (Phi·H over net pay): 53.246 m
- Hydrocarbon pore thickness (HCPV = Σ PHIE·(1−Sw)·step): 35.580 m
- Buckles constant (BVW at P10 of net pay): 0.0515 → Swirr (mean) ≈ 0.170 over 1155 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←NEU, RT←GUARD, SP←SP.
QC edits applied before compute — degradation: 1, hard_range_mask: 1, range_warn: 1, spike_removal: 153.
| Validator | Type | Detail |
|---|---|---|
| vsh_phie_anticorrelation | support | Vsh-PHIE Pearson 0.99 > 0.3 (dirty rock + high porosity) |
| rt_sw_consistency | mechanical | 135 depths with Sw<0.4 but RT<5.0 ohm-m |
| net_pay_plausibility | irreducible | net-pay avg PHIE 0.30 > 0.25 — implausibly high for carbonate |
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, 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, 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": 176.0220000000001,
"net_pay_p10_p50_p90": [
119.87784000000008,
216.94140000000013,
391.42416000000037
],
"driving_params": {
"a": 1.0,
"m": 2.0,
"n": 2.0,
"Rw": 0.04
},
"claim_verifier": {
"result": "FLAGS",
"flags": [
34.4
],
"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 | ✓ |