Petrophysical Interpretation Report — 15-135-25930-00-00
| Well (UWI) | 15-135-25930-00-00 |
| Log date | 10/14/2016 |
| Service company | Pioneer Energy Services |
| Acquisition date (header) | 10/14/2016 |
| PLSS location | Sec 31 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:
- 1 unresolved MECHANICAL objection(s)
The evaluation is restricted to the consolidated section between 1000.0 m and 1370.0 m — the interval above it is not evaluated (unconsolidated, washed-out response). Within that interval the net pay is 65.8 m with average effective porosity 0.204 and average water saturation 0.305. Monte-Carlo places the P50 net pay at 38.3 m within a P10-P90 range of 16.7 to 70.9 m. An independent SP-derived water resistivity of 0.0386 ohm-m (static SP -86.3 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 0.622 over 2375 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 = 16.7 / 38.3 / 70.9 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, NPHI_DOL←CNDL, NPHI_SS←CNSS, PHID_SVC←DPOR, RHOB←RHOB, RMED←RILM, RT←RILD, RXO←RLL3, SP←SP
- Logged interval: 59.44–1370.08 m
- Log date: 10/14/2016
- Service company: Pioneer Energy Services · Company: SCHABEN OIL, LLC
- 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 | PHID_SVC | count 5 |
| hard_range_mask | RHOB | count 1 |
| hard_range_mask | DRHO | count 3 |
| hard_range_mask | RT | count 258 |
| hard_range_mask | RMED | count 77 |
| range_warn | RHOB | count 3 |
| range_warn | NPHI | count 21 |
| spike_removal | — | 146 edits |
| degradation | — | 2 edits |
4. Standardization
Raw mnemonics mapped to canonical curve names:
| Canonical | Raw mnemonic |
|---|---|
| DCAL | DCAL |
| DRHO | RHOC |
| GR | GR |
| NPHI | CNLS |
| NPHI_DOL | CNDL |
| NPHI_SS | CNSS |
| 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=29.6, gr_p95=108.3
- Bad-hole: GOOD=0.54, DEGRADED=0.404, EXCLUDED=0.055
- Low-resistivity: rt_threshold=1.52, n_flagged=821, intervals=[[159.6, 160.2], [237.6, 238.4], [282.5, 284.8], [286.4, 347.3], [351.4, 356.9], [371.2, 371.9], [376.1, 376.9], [409.0, 410.4], [412.2, 412.2], [425.2, 426.1]]
6. Data preparation
Edits applied before compute (by type): degradation: 2, hard_range_mask: 5, range_warn: 2, spike_removal: 146, unit_conversion: 1.
7. Interval definition
- Logged interval: 59.44–1370.08 m
- Analysis window (analyst-restricted): 1000.0–1370.0 m — gross and NTG are measured over this window
- Gross evaluated interval: 370.0 m
- Computed net-pay runs (pre-merge): 55
- 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=29.6, gr_p95=108.3
10. Resistivity analysis
Low-resistivity scan: rt_threshold=1.52, n_flagged=821, intervals=[[159.6, 160.2], [237.6, 238.4], [282.5, 284.8], [286.4, 347.3], [351.4, 356.9], [371.2, 371.9], [376.1, 376.9], [409.0, 410.4], [412.2, 412.2], [425.2, 426.1]].
Invasion profile (multi-depth resistivities, 8185 samples): fraction with shallow reading above deep (Rxo/RT > 1.2, invaded/permeable indication): 0.788; reversed (< 0.8): 0.058; median Rxo/RT 1.614; median Rmed/RT 0.963. 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: 0.104, limestone: 0.244, dolomite: 0.102. 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: 34.3 m swing.
- Formation-temperature correction (Arps, regional-default gradient): Rw ≈ 0.0116 ohm-m at 47.6 °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 | 0.279 | |
| vsh_larionov_tertiary | 0.211 | |
| vsh_linear | 0.388 | |
| vsh_clavier | 0.265 | |
| vsh_steiber | 0.232 | |
| vsh_neutron_density | 0.132 | |
| vsh_multimineral | 0.139 | ✓ |
15. Porosity
Mean porosity by method (effective where shale-corrected; the LLM authors no number):
| Method | Mean porosity | Selected |
|---|---|---|
| phie_density_neutron | 0.097 | ✓ |
| phi_density | 0.120 | |
| phi_neutron | 0.134 |
Service-company porosity curves (cross-check evidence, full-column means): phid_svc: 0.324, nphi_dol: 0.143, nphi_ss: 0.250. Matrix assumptions differ per curve; agreement/disagreement is the analyst's reading.
16. Water saturation
Mean Sw (Archie 1942) = 0.738 (a=1.00, m=2.00, n=2.00, Rw=0.0219 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 | 0.738 | ✓ |
| sw_simandoux | 0.639 | |
| sw_indonesia | 0.669 |
17. Zonation (net-pay intervals)
Raw net-pay runs merged into 36 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 | 1011.2 | 1020.2 | 9.1 | 0.311 | 0.215 | 0.000 |
| Z2 | 1031.7 | 1036.6 | 5.0 | 0.400 | 0.191 | 0.000 |
| Z3 | 1190.2 | 1192.8 | 2.7 | 0.221 | 0.305 | 0.013 |
| Z4 | 1219.4 | 1220.7 | 1.5 | 0.133 | 0.236 | 0.149 |
| Z5 | 1224.4 | 1226.1 | 1.8 | 0.197 | 0.375 | 0.176 |
| Z6 | 1234.0 | 1235.8 | 2.0 | 0.175 | 0.345 | 0.129 |
| Z7 | 1261.6 | 1263.2 | 1.8 | 0.228 | 0.295 | 0.220 |
| Z8 | 1268.9 | 1273.3 | 3.4 | 0.173 | 0.331 | 0.130 |
| Z9 | 1277.4 | 1279.2 | 2.0 | 0.185 | 0.340 | 0.158 |
| Z10 | 1309.1 | 1312.3 | 2.1 | 0.195 | 0.270 | 0.184 |
| Z11 | 1316.4 | 1318.6 | 2.3 | 0.207 | 0.269 | 0.167 |
| Z12 | 1320.2 | 1323.6 | 2.1 | 0.146 | 0.327 | 0.112 |
| Z13 | 1334.7 | 1337.5 | 2.4 | 0.155 | 0.239 | 0.084 |
| Z14 | 1339.0 | 1346.5 | 7.3 | 0.123 | 0.309 | 0.213 |
| Z15 | 1350.1 | 1357.0 | 4.7 | 0.119 | 0.445 | 0.152 |
18. Results
| Quantity | Value |
|---|---|
| Gross interval | 370.0 m |
| Net pay (P10/P50/P90) | 16.7 / 38.3 / 70.9 m |
| Net-to-gross | 0.178 |
| Avg PHIE (net pay) | 0.204 |
| Avg Sw (net pay) | 0.305 |
| Avg Vsh (net pay) | 0.104 |
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 | 35.4 |
| Rw | 34.3 |
| a | 8.8 |
| n | 7.2 |
Dominant uncertainty: m (swing 35.4 m).
Multi-seed robustness: P50 UNSTABLE across seeds (spread 4.7 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 0.0514 v/v
- Porosity-thickness (Phi·H over net pay): 13.436 m
- Hydrocarbon pore thickness (HCPV = Σ PHIE·(1−Sw)·step): 9.719 m
- Buckles constant (BVW at P10 of net pay): 0.0339 → Swirr (mean) ≈ 0.166 over 432 pay samples
21. Permeability (uncalibrated)
- perm_timur: mean k = 209.02 mD
_Uncalibrated screening estimate (no core); Sw used as the Swirr proxy._
22. Rock quality (uncalibrated)
- rqi: mean = 0.260
_Built on the uncalibrated permeability; indicative only._
23. Electrofacies
Unsupervised k-means on 2060 samples into 4 electrofacies (sample counts: facies 0: 308, facies 1: 426, facies 2: 616, facies 3: 710). Descriptive only — no core labels.
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 m — see Uncertainty for the swing.
26. Data quality and validator objections
Curve provenance (canonical ← raw mnemonic): DCAL←DCAL, DRHO←RHOC, GR←GR, NPHI←CNLS, NPHI_DOL←CNDL, NPHI_SS←CNSS, PHID_SVC←DPOR, RHOB←RHOB, RMED←RILM, RT←RILD, RXO←RLL3, SP←SP.
QC edits applied before compute — degradation: 2, hard_range_mask: 5, range_warn: 2, spike_removal: 146, unit_conversion: 1.
| Validator | Type | Detail |
|---|---|---|
| vsh_phie_anticorrelation | support | Vsh-PHIE Pearson 0.95 > 0.3 (dirty rock + high porosity) |
| rt_sw_consistency | mechanical | 91 depths with Sw<0.4 but RT<5.0 ohm-m |
27. 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: permeability"]
act_10["tool_call: permeability"]
dec_11["decision: step: rock_quality"]
act_11["tool_call: rock_quality"]
dec_12["decision: step: electrofacies"]
act_12["tool_call: electrofacies"]
dec_13["decision: step: lithology"]
act_13["tool_call: lithology"]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): m (calibrated by core SCAL — cementation exponent m).
- 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
From 1000 m (2.50). N-D clay ~0.08 -> 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": 65.83680000000004,
"net_pay_p10_p50_p90": [
16.74876000000001,
38.32860000000002,
70.88124000000005
],
"driving_params": {
"a": 1.0,
"m": 2.0,
"n": 2.0,
"Rw": 0.04
},
"claim_verifier": {
"result": "FLAGS",
"flags": [
0.08
],
"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 | ✓ |