Petrophysical Interpretation Report — 15-135-24,881-00-00
| Well (UWI) | 15-135-24,881-00-00 |
| Log date | Sat Feb 28 00-46-47 2009 |
| Service company | Log Tech |
| Acquisition date (header) | Sat Feb 28 00-46-47 2009 |
| PLSS location | Sec 12 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 | 31c0f4a959a5 |
| 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)
Well 15-135-24,881-00-00 did not converge to a defensible result; this is a bracketed, uncalibrated engineering estimate with one unresolved mechanical objection. The 623.0 m gross interval yields a net-to-gross of 0.020. Net pay spans a P10–P90 range of 0.9 to 104.5 m (P50 14.2 m), a spread driven almost entirely by the cementation exponent 'a', a regional default that swings the estimate by 22.7 m and remains uncalibrated to core. Within the pay intervals, average effective porosity is 0.165, water saturation 0.404, and shale volume 0.205, but these properties inherit the same structural uncertainty because the saturation model rests on an unvalidated 'a'. The result is presented as a bracketed range, not a confident point estimate.
Net pay P10 / P50 / P90 = 0.9 / 14.2 / 104.5 m.
Net pay is dominated by 'a', 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: 59.44–1382.57 m
- Log date: Sat Feb 28 00-46-47 2009
- Service company: Log Tech · Company: Berexco, Inc.
- 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 |
|---|---|---|
| unit_conversion | NPHI | factor 0.01 |
| hard_range_mask | RXO | count 1 |
| hard_range_mask | RT | count 117 |
| hard_range_mask | RMED | count 95 |
| hard_range_mask | RHOB | count 1 |
| hard_range_mask | DRHO | count 4 |
| hard_range_mask | PHID_SVC | count 5 |
| range_warn | GR | count 4 |
| range_warn | RHOB | count 4 |
| range_warn | NPHI | count 3 |
| spike_removal | — | 89 edits |
| degradation | — | 3 edits |
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=34.4, gr_p95=110.4
- Bad-hole: GOOD=0.844, DEGRADED=0.127, EXCLUDED=0.029
- Low-resistivity: rt_threshold=1.79, n_flagged=848, intervals=[[278.6, 282.2], [284.2, 339.1], [345.5, 346.7], [361.8, 362.4], [366.8, 367.1], [399.9, 401.7], [419.9, 421.8], [458.6, 458.7], [459.8, 467.4], [478.7, 480.2]]
6. Data preparation
Edits applied before compute (by type): degradation: 3, hard_range_mask: 6, range_warn: 3, spike_removal: 89, unit_conversion: 1.
7. Interval definition
- Logged interval: 59.44–1382.57 m
- Analysis window (analyst-restricted): 700.0–1323.0 m — gross and NTG are measured over this window
- Gross evaluated interval: 623.0 m
- Computed net-pay runs (pre-merge): 24
- 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 | Density-neutron crossplot, shale-corrected | phie_density_neutron 0.1.0 |
| Sw | Poupon-Leveaux 1971 (Indonesia) | sw_indonesia 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=34.4, gr_p95=110.4
10. Resistivity analysis
Low-resistivity scan: rt_threshold=1.79, n_flagged=848, intervals=[[278.6, 282.2], [284.2, 339.1], [345.5, 346.7], [361.8, 362.4], [366.8, 367.1], [399.9, 401.7], [419.9, 421.8], [458.6, 458.7], [459.8, 467.4], [478.7, 480.2]].
Invasion profile (multi-depth resistivities, 8471 samples): fraction with shallow reading above deep (Rxo/RT > 1.2, invaded/permeable indication): 0.604; reversed (< 0.8): 0.098; median Rxo/RT 1.301; median Rmed/RT 0.961. 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: 0.091, limestone: 0.219, dolomite: 0.247. 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: 12.6 m swing.
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 engine's; the LLM authors no number):
| Method | Mean Vsh | Selected |
|---|---|---|
| vsh_larionov_old | 0.363 | ✓ |
| vsh_larionov_tertiary | 0.278 | |
| vsh_linear | 0.493 | |
| vsh_clavier | 0.345 | |
| vsh_steiber | 0.302 | |
| vsh_neutron_density | 0.307 | |
| vsh_multimineral | 0.274 |
15. Porosity
Mean porosity by method (effective where shale-corrected; the LLM authors no number):
| Method | Mean porosity | Selected |
|---|---|---|
| phie_density_neutron | 0.055 | ✓ |
| phi_density | 0.094 | |
| phi_neutron | 0.167 |
Service-company porosity curves (cross-check evidence, full-column means): phid_svc: 0.197. Matrix assumptions differ per curve; agreement/disagreement is the analyst's reading.
16. Water saturation
Mean Sw (Poupon-Leveaux 1971 (Indonesia)) = 0.707 (a=1.00, m=2.00, n=2.00, Rw=0.0254 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 | 0.901 | |
| sw_simandoux | 0.681 | |
| sw_indonesia | 0.707 | ✓ |
17. Zonation (net-pay intervals)
Raw net-pay runs merged into 21 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 | 717.3 | 717.7 | 0.5 | 0.222 | 0.464 | 0.167 |
| Z2 | 757.4 | 758.6 | 1.2 | 0.173 | 0.459 | 0.105 |
| Z3 | 821.7 | 822.0 | 0.5 | 0.116 | 0.445 | 0.309 |
| Z4 | 824.3 | 825.1 | 0.9 | 0.126 | 0.437 | 0.319 |
| Z5 | 885.3 | 885.9 | 0.8 | 0.161 | 0.440 | 0.146 |
| Z6 | 889.3 | 890.3 | 1.2 | 0.262 | 0.281 | 0.224 |
| Z7 | 911.0 | 911.5 | 0.6 | 0.143 | 0.451 | 0.250 |
| Z8 | 948.4 | 948.7 | 0.5 | 0.168 | 0.462 | 0.184 |
| Z9 | 1052.0 | 1052.9 | 1.1 | 0.183 | 0.420 | 0.158 |
| Z10 | 1118.8 | 1120.6 | 2.0 | 0.179 | 0.430 | 0.176 |
| Z11 | 1160.8 | 1161.0 | 0.3 | 0.118 | 0.479 | 0.079 |
| Z12 | 1180.0 | 1180.9 | 0.5 | 0.133 | 0.312 | 0.207 |
| Z13 | 1188.3 | 1188.6 | 0.5 | 0.127 | 0.453 | 0.227 |
| Z14 | 1204.7 | 1204.9 | 0.3 | 0.119 | 0.336 | 0.208 |
| Z15 | 1271.0 | 1271.6 | 0.8 | 0.128 | 0.312 | 0.241 |
18. Results
| Quantity | Value |
|---|---|
| Gross interval | 623.0 m |
| Net pay (P10/P50/P90) | 0.9 / 14.2 / 104.5 m |
| Net-to-gross | 0.020 |
| Avg PHIE (net pay) | 0.165 |
| Avg Sw (net pay) | 0.404 |
| Avg Vsh (net pay) | 0.205 |
19. Uncertainty and sensitivity
Monte Carlo, 500 realizations (seed 42). Net pay swing per parameter (one-at-a-time):
| Parameter | Net-pay swing (m) |
|---|---|
| a | 22.7 |
| m | 19.1 |
| Rw | 12.6 |
| n | 4.4 |
Dominant uncertainty: a (swing 22.7 m).
Multi-seed robustness: P50 stable (spread 0.2 m across 4 seeds).
Net pay is dominated by 'a', which is a regional DEFAULT (uncalibrated). This is the single largest uncertainty — the result is bracketed, not a confident point estimate.
20. Permeability (uncalibrated)
- perm_timur: mean k = 173.49 mD
_Uncalibrated screening estimate (no core); Sw used as the Swirr proxy._
21. Electrofacies
Unsupervised k-means on 7327 samples into 4 electrofacies (sample counts: facies 0: 1942, facies 1: 1392, facies 2: 2466, facies 3: 1527). Descriptive only — no core labels.
22. Derived parameters
- Bulk-volume water (BVW = PHIE*Sw): mean 0.0725 v/v
- Porosity-thickness (Phi·H over net pay): 39.813 m
- Hydrocarbon pore thickness (HCPV = Σ PHIE·(1−Sw)·step): 27.759 m
- Buckles constant (BVW at P10 of net pay): 0.0428 → Swirr (mean) ≈ 0.166 over 1014 pay samples
23. Rock quality (uncalibrated)
- rqi: mean = 0.063
_Built on the uncalibrated permeability; indicative only._
24. 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.
25. 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 a — see Uncertainty for the swing.
26. 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: 3, hard_range_mask: 6, range_warn: 3, spike_removal: 89, unit_conversion: 1.
| Validator | Type | Detail |
|---|---|---|
| vsh_phie_anticorrelation | support | Vsh-PHIE Pearson 0.97 > 0.3 (dirty rock + high porosity) |
| rt_sw_consistency | mechanical | 67 depths with Sw<0.4 but RT<5.0 ohm-m |
27. Methodology (decision graph)
flowchart TD
dec_1["decision: step: depth_quality"]
act_1["tool_call: depth_quality"]
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: compare_methods"]
act_4["tool_call: compare_methods"]
dec_5["decision: step: compute_phie"]
act_5["tool_call: compute_phie"]
dec_6["decision: step: rw_evidence"]
act_6["tool_call: rw_evidence"]
dec_7["decision: step: compute_sw"]
act_7["tool_call: compute_sw"]
dec_8["decision: step: compare_methods"]
act_8["tool_call: compare_methods"]
dec_9["decision: step: validate_choice"]
act_9["tool_call: validate_choice"]
dec_10["decision: step: apply_cutoffs"]
act_10["tool_call: apply_cutoffs"]
dec_11["decision: step: run_uncertainty"]
act_11["tool_call: run_uncertainty"]
dec_12["decision: step: objection_profile"]
act_12["tool_call: objection_profile"]
dec_13["decision: step: compute_sw"]
act_13["tool_call: compute_sw"]
dec_14["decision: step: apply_cutoffs"]
act_14["tool_call: apply_cutoffs"]
dec_15["decision: step: run_uncertainty"]
act_15["tool_call: run_uncertainty"]
dec_16["decision: step: lithology"]
act_16["tool_call: lithology"]
dec_17["decision: step: permeability"]
act_17["tool_call: permeability"]
dec_18["decision: step: interval_stats"]
act_18["tool_call: interval_stats"]
dec_19["decision: wasted no-op: compute_sw"]
dec_20["decision: step: electrofacies"]
act_19["tool_call: electrofacies"]
dec_21["decision: step: derived_parameters"]
act_20["tool_call: derived_parameters"]
dec_22["decision: wasted no-op: compute_sw"]
dec_23["decision: step: set_zone_of_interest"]
act_21["tool_call: set_zone_of_interest"]
dec_24["decision: wasted no-op: permeability"]
dec_25["decision: step: rock_quality"]
act_22["tool_call: rock_quality"]
dec_26["decision: step: compute_sw"]
act_23["tool_call: compute_sw"]
dec_27["decision: step: apply_cutoffs"]
act_24["tool_call: apply_cutoffs"]
dec_28["decision: step: run_uncertainty"]
act_25["tool_call: run_uncertainty"]
dec_29["decision: wasted no-op: lithology"]
dec_30["decision: step: interval_stats"]
act_26["tool_call: interval_stats"]
dec_31["decision: wasted no-op: compute_sw"]
dec_32["decision: wasted no-op: compute_sw"]28. 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): a (calibrated by core SCAL — tortuosity factor a).
- Standard curves absent: DT, PEF, CALI.
29. 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.
30. Conclusions
Net pay P10/P50/P90 = 0.9/14.2/104.5 m. The single largest uncertainty is the cementation exponent 'a' (regional default, uncalibrated), which dominates the net-pay spread. The inversion did not converge and carries one unresolved mechanical objection. All reported properties (PHIE 0.165, Sw 0.404, Vsh 0.205) are bracketed estimates; no figure should be read as a firm value.
Appendix A — Ledger excerpt (traceability)
{
"net_pay_total_m": 12.649200000000008,
"net_pay_p10_p50_p90": [
0.9144000000000005,
14.173200000000008,
104.47020000000012
],
"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 | ✓ |