Petrophysical Interpretation Report — 15-135-24,859-00-00
| Well (UWI) | 15-135-24,859-00-00 |
| Log date | Fri Nov 07 21-14-21 2008 |
| Service company | Log Tech |
| Acquisition date (header) | Fri Nov 07 21-14-21 2008 |
| PLSS location | Sec 13 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.
⚠️ 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:
- 2 unresolved MECHANICAL objection(s)
- net-pay avg PHIE 0.35 > 0.25 — implausibly high for carbonate
The evaluation is restricted to the consolidated section between 900.0 m and 1328.8 m — the interval above it is not evaluated (unconsolidated, washed-out response). Within that interval the net pay is 36.9 m with average effective porosity 0.348 and average water saturation 0.386. Monte-Carlo places the P50 net pay at 26.7 m within a P10-P90 range of 11.1 to 57.2 m. An independent SP-derived water resistivity of 0.0446 ohm-m (static SP -58.2 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. The Rxo/Rt movable-hydrocarbon index reads a median of 1.182 over 2753 samples — an invasion-based indicator profile, not a saturation. 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 = 11.1 / 26.7 / 57.2 m.
Net pay is dominated by 'm', 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): DCAL←DCAL, DRHO←RHOC, GR←GR, NPHI←CNLS, PHID_SVC←DPOR, RHOB←RHOB, RMED←RILM, RT←RILD, RXO←RLL3, SP←SP
- Logged interval: 59.44–1328.78 m
- Log date: Fri Nov 07 21-14-21 2008
- Service company: Log Tech · Company: American Warrior, Inc.
- Field: Schaben North
- Not provided by LAS (out of scope): core, mud logs, pressure tests, production, completion, formation tops.
3. LAS quality control
| Edit type | Curve | Detail |
|---|---|---|
| unit_conversion | NPHI | factor 0.01 |
| hard_range_mask | RXO | count 1 |
| hard_range_mask | RT | count 140 |
| hard_range_mask | RMED | count 76 |
| hard_range_mask | RHOB | count 2 |
| hard_range_mask | DRHO | count 3 |
| hard_range_mask | PHID_SVC | count 5 |
| range_warn | RHOB | count 3 |
| range_warn | NPHI | count 41 |
| spike_removal | — | 125 edits |
| degradation | — | — |
4. Standardization
Raw mnemonics mapped to canonical curve names:
| Canonical | Raw mnemonic |
|---|---|
| DCAL | DCAL |
| DRHO | RHOC |
| GR | GR |
| NPHI | CNLS |
| PHID_SVC | DPOR |
| RHOB | RHOB |
| RMED | RILM |
| RT | RILD |
| RXO | RLL3 |
| SP | SP |
Unit conversions: NPHI×0.01.
5. Per-curve log QC
- GR baseline: gr_p5=34.9, gr_p95=108.4
- Bad-hole: GOOD=0.464, DEGRADED=0.502, EXCLUDED=0.035
- Low-resistivity: rt_threshold=1.7, n_flagged=805, intervals=[[86.4, 88.4], [202.7, 203.9], [227.5, 228.1], [273.7, 275.5], [279.3, 280.3], [280.9, 281.0], [285.0, 292.5], [293.5, 299.6], [300.7, 330.7], [331.0, 340.0]]
6. Data preparation
Edits applied before compute (by type): degradation: 1, hard_range_mask: 6, range_warn: 2, spike_removal: 125, unit_conversion: 1.
7. Interval definition
- Logged interval: 59.44–1328.78 m
- Analysis window (analyst-restricted): 900.0–1328.8 m — gross and NTG are measured over this window
- Gross evaluated interval: 428.8 m
- Computed net-pay runs (pre-merge): 15
- 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 | 2-mineral volumetric solve (matrix+clay+porosity from RHOB+NPHI) | vsh_multimineral 0.1.0 |
| PHIE | Density-neutron crossplot, shale-corrected | phie_density_neutron 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=34.9, gr_p95=108.4
10. Resistivity analysis
Low-resistivity scan: rt_threshold=1.7, n_flagged=805, intervals=[[86.4, 88.4], [202.7, 203.9], [227.5, 228.1], [273.7, 275.5], [279.3, 280.3], [280.9, 281.0], [285.0, 292.5], [293.5, 299.6], [300.7, 330.7], [331.0, 340.0]].
Invasion profile (multi-depth resistivities, 8037 samples): fraction with shallow reading above deep (Rxo/RT > 1.2, invaded/permeable indication): 0.558; reversed (< 0.8): 0.094; median Rxo/RT 1.265; median Rmed/RT 0.929. Raw-curve facts; naming moveable hydrocarbon is the analyst's judgement.
11. Density-neutron crossplot lithology
Matrix point-shares (fraction of points near each matrix line): sandstone: 0.047, limestone: 0.049, dolomite: 0.065. Engine crossplot output; naming the dominant lithology is the analyst's judgement. Comparison with core/mud log: not available (LAS-only).
12. 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: 8.2 m swing.
- Formation-temperature correction (Arps, regional-default gradient): Rw ≈ 0.0553 ohm-m at 45.6 °C (evidence only — Sw uses the calibrated Rw).
13. Figures
Composite log
Pickett plot
Neutron-density crossplot
Buckles plot
Hingle plot
Distributions
Sensitivity tornado
Net-pay Monte-Carlo distribution
14. Shale volume (Vsh)
Mean Vsh by method (selection is the agent's; the LLM authors no number):
| Method | Mean Vsh | Selected |
|---|---|---|
| vsh_larionov_old | 0.346 | |
| vsh_larionov_tertiary | 0.268 | |
| vsh_linear | 0.469 | |
| vsh_clavier | 0.330 | |
| vsh_steiber | 0.291 | |
| vsh_neutron_density | 0.192 | |
| vsh_multimineral | 0.167 | ✓ |
15. Porosity
Mean porosity by method (effective where shale-corrected; the LLM authors no number):
| Method | Mean porosity | Selected |
|---|---|---|
| phie_density_neutron | 0.201 | ✓ |
| phi_density | 0.252 | |
| phi_neutron | 0.187 |
Service-company porosity curves (cross-check evidence, full-column means): phid_svc: 0.382. Matrix assumptions differ per curve; agreement/disagreement is the analyst's reading.
16. Water saturation
Mean Sw (Archie 1942) = 0.711 (a=1.00, m=2.00, n=2.00, Rw=0.1018 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 | 0.711 | ✓ |
| sw_simandoux | 0.677 | |
| sw_indonesia | 0.677 |
17. Zonation (net-pay intervals)
Raw net-pay runs merged into 9 geological intervals (gap tolerance 1.5 m).
| Interval | Top (m) | Base (m) | Net pay (m) | Avg PHIE | Avg Sw | Avg Vsh |
|---|---|---|---|---|---|---|
| Z1 | 958.1 | 959.7 | 1.1 | 0.359 | 0.483 | 0.000 |
| Z2 | 967.4 | 971.9 | 3.4 | 0.415 | 0.460 | 0.000 |
| Z3 | 981.6 | 995.5 | 12.8 | 0.346 | 0.402 | 0.000 |
| Z4 | 997.3 | 1001.4 | 4.3 | 0.288 | 0.402 | 0.000 |
| Z5 | 1021.8 | 1022.1 | 0.5 | 0.304 | 0.439 | 0.000 |
| Z6 | 1027.2 | 1027.9 | 0.9 | 0.381 | 0.464 | 0.000 |
| Z7 | 1030.2 | 1036.6 | 6.6 | 0.391 | 0.285 | 0.000 |
| Z8 | 1040.4 | 1042.0 | 1.7 | 0.362 | 0.351 | 0.000 |
| Z9 | 1045.9 | 1052.5 | 5.8 | 0.301 | 0.384 | 0.000 |
18. Results
| Quantity | Value |
|---|---|
| Gross interval | 428.8 m |
| Net pay (P10/P50/P90) | 11.1 / 26.7 / 57.2 m |
| Net-to-gross | 0.086 |
| Avg PHIE (net pay) | 0.348 |
| Avg Sw (net pay) | 0.386 |
| Avg Vsh (net pay) | 0.000 |
19. Uncertainty and sensitivity
Monte Carlo, 500 realizations (seed 42). Net pay swing per parameter (one-at-a-time):
| Parameter | Net-pay swing (m) |
|---|---|
| m | 30.5 |
| a | 13.7 |
| n | 8.8 |
| Rw | 8.2 |
Dominant uncertainty: m (swing 30.5 m).
Multi-seed robustness: P50 stable (spread 1.2 m across 4 seeds).
Net pay is dominated by 'm', which is a regional DEFAULT (uncalibrated). This is the single largest uncertainty — the result is bracketed, not a confident point estimate.
20. Derived parameters
- Bulk-volume water (BVW = PHIE*Sw): mean 0.1088 v/v
- Porosity-thickness (Phi·H over net pay): 12.836 m
- Hydrocarbon pore thickness (HCPV = Σ PHIE·(1−Sw)·step): 7.911 m
- Buckles constant (BVW at P10 of net pay): 0.0887 → Swirr (mean) ≈ 0.255 over 242 pay samples
21. 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.
22. 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 m — see Uncertainty for the swing.
23. Data quality and validator objections
Curve provenance (canonical ← raw mnemonic): DCAL←DCAL, DRHO←RHOC, GR←GR, NPHI←CNLS, PHID_SVC←DPOR, RHOB←RHOB, RMED←RILM, RT←RILD, RXO←RLL3, SP←SP.
QC edits applied before compute — degradation: 1, hard_range_mask: 6, range_warn: 2, spike_removal: 125, unit_conversion: 1.
| Validator | Type | Detail |
|---|---|---|
| vsh_phie_anticorrelation | support | Vsh-PHIE Pearson 0.87 > 0.3 (dirty rock + high porosity) |
| rt_sw_consistency | mechanical | 24 depths with Sw<0.4 but RT<5.0 ohm-m |
| model_mismatch_nd | mechanical | low-porosity RHOB median 1.93 ~ sandstone (2.65), not assumed rho_ma 2.62 |
| net_pay_plausibility | irreducible | net-pay avg PHIE 0.35 > 0.25 — implausibly high for carbonate |
24. Methodology (decision graph)
flowchart TD
dec_1["decision: step: set_zone_of_interest"]
act_1["tool_call: set_zone_of_interest"]
dec_2["decision: step: compare_methods"]
act_2["tool_call: compare_methods"]
dec_3["decision: step: compute_vsh"]
act_3["tool_call: compute_vsh"]
dec_4["decision: step: compute_phie"]
act_4["tool_call: compute_phie"]
dec_5["decision: step: compare_methods"]
act_5["tool_call: compare_methods"]
dec_6["decision: step: compute_sw"]
act_6["tool_call: compute_sw"]
dec_7["decision: step: apply_cutoffs"]
act_7["tool_call: apply_cutoffs"]
dec_8["decision: step: run_uncertainty"]
act_8["tool_call: run_uncertainty"]
dec_9["decision: step: derived_parameters"]
act_9["tool_call: derived_parameters"]
dec_10["decision: step: lithology"]
act_10["tool_call: lithology"]25. 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): m (calibrated by core SCAL — cementation exponent m).
- Standard curves absent: DT, PEF, CALI.
26. 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: DT, PEF, CALI.
- Results are uncalibrated; accuracy depends on data not provided.
27. Conclusions
Consolidated from 900 m (2.46). N-D clay ~0.11 -> Archie. 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": 36.88080000000002,
"net_pay_p10_p50_p90": [
11.06424000000001,
26.670000000000016,
57.150000000000034
],
"driving_params": {
"a": 1.0,
"m": 2.0,
"n": 2.0,
"Rw": 0.04
},
"claim_verifier": {
"result": "FLAGS",
"flags": [
2.46
],
"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 | ✓ |