Petrophysical Interpretation Report — 15-135-26002-00-00
| Well (UWI) | 15-135-26002-00-00 |
| Log date | 6/26/2018 |
| Service company | Pioneer Energy Services |
| Acquisition date (header) | 6/26/2018 |
| 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 | 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)
⚠️ ABSTENTION — this is NOT a confident estimate. The validation loop did not converge and one unresolved mechanical objection remains; the numbers below are an uncalibrated engineering estimate reported for transparency only.
The net-pay interval spans a bracketed range of 7.3 to 139.1 m (P10/P90) with a P50 of 18.7 m across a 610.0 m gross section, yielding a net-to-gross of 0.044. Within the pay, average effective porosity is 0.182, water saturation 0.386, and shale volume 0.131. The single largest uncertainty is formation-water resistivity (Rw = 0.0400 ohm·m), a regional default uncalibrated to core, which drives a 43.9 m swing in net pay. Because Rw dominates the result, the estimate is explicitly bracketed rather than a confident point determination.
Net pay P10 / P50 / P90 = 7.3 / 18.7 / 139.1 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): DCAL←DCAL, DRHO←RHOC, DT←DT, 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: 59.44–1360.02 m
- Log date: 6/26/2018
- 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 | DRHO | count 4 |
| hard_range_mask | RT | count 116 |
| hard_range_mask | RMED | count 54 |
| range_warn | RHOB | count 4 |
| spike_removal | — | 85 edits |
| degradation | — | 3 edits |
4. Standardization
Raw mnemonics mapped to canonical curve names:
| Canonical | Raw mnemonic |
|---|---|
| DCAL | DCAL |
| DRHO | RHOC |
| DT | DT |
| 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=27.9, gr_p95=98.9
- Bad-hole: GOOD=0.729, DEGRADED=0.241, EXCLUDED=0.03
- Low-resistivity: rt_threshold=1.4, n_flagged=834, intervals=[[94.0, 95.4], [279.3, 281.3], [283.2, 283.8], [285.0, 286.8], [289.1, 343.5], [349.1, 351.6], [366.8, 367.3], [404.3, 405.8], [407.4, 408.0], [421.1, 422.3]]
6. Data preparation
Edits applied before compute (by type): degradation: 3, hard_range_mask: 4, range_warn: 1, spike_removal: 85, unit_conversion: 1.
7. Interval definition
- Logged interval: 59.44–1360.02 m
- Analysis window (analyst-restricted): 700.0–1310.0 m — gross and NTG are measured over this window
- Gross evaluated interval: 610.0 m
- Computed net-pay runs (pre-merge): 42
- 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 (Tertiary) | vsh_larionov_tertiary 0.1.0 |
| PHIE | Density-neutron crossplot, shale-corrected | phie_density_neutron 0.1.0 |
| Sw | Simandoux 1963 (shaly sand) | sw_simandoux 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=27.9, gr_p95=98.9
10. Resistivity analysis
Low-resistivity scan: rt_threshold=1.4, n_flagged=834, intervals=[[94.0, 95.4], [279.3, 281.3], [283.2, 283.8], [285.0, 286.8], [289.1, 343.5], [349.1, 351.6], [366.8, 367.3], [404.3, 405.8], [407.4, 408.0], [421.1, 422.3]].
Invasion profile (multi-depth resistivities, 8328 samples): fraction with shallow reading above deep (Rxo/RT > 1.2, invaded/permeable indication): 0.594; reversed (< 0.8): 0.147; median Rxo/RT 1.331; median Rmed/RT 0.969. 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: 0.059, limestone: 0.164, dolomite: 0.225. 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: 43.9 m swing.
13. Figures
Composite log
Pickett plot
Neutron-density crossplot
Buckles plot
Hingle plot
Distributions
Sensitivity tornado
Net-pay Monte-Carlo distribution
14. Water saturation
Mean Sw (Simandoux 1963 (shaly sand)) = 0.757 (a=1.00, m=2.00, n=2.00, Rw=0.0325 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 | 0.848 | |
| sw_simandoux | 0.757 | ✓ |
| sw_indonesia | 0.749 |
15. Zonation (net-pay intervals)
Raw net-pay runs merged into 34 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 | 785.6 | 789.1 | 2.4 | 0.131 | 0.437 | 0.083 |
| Z2 | 790.8 | 793.5 | 2.9 | 0.188 | 0.298 | 0.058 |
| Z3 | 818.2 | 819.6 | 1.5 | 0.171 | 0.443 | 0.091 |
| Z4 | 884.5 | 885.6 | 1.2 | 0.176 | 0.445 | 0.060 |
| Z5 | 888.6 | 889.7 | 0.8 | 0.290 | 0.345 | 0.114 |
| Z6 | 931.9 | 932.7 | 0.9 | 0.266 | 0.338 | 0.259 |
| Z7 | 941.5 | 942.6 | 1.2 | 0.223 | 0.355 | 0.218 |
| Z8 | 1052.0 | 1052.5 | 0.6 | 0.246 | 0.489 | 0.037 |
| Z9 | 1158.8 | 1160.1 | 1.4 | 0.207 | 0.332 | 0.014 |
| Z10 | 1184.1 | 1185.4 | 0.9 | 0.213 | 0.323 | 0.182 |
| Z11 | 1218.6 | 1223.5 | 3.5 | 0.223 | 0.323 | 0.086 |
| Z12 | 1251.8 | 1252.4 | 0.8 | 0.131 | 0.427 | 0.274 |
| Z13 | 1263.5 | 1265.4 | 0.8 | 0.174 | 0.395 | 0.312 |
| Z14 | 1273.1 | 1273.9 | 0.8 | 0.131 | 0.474 | 0.125 |
| Z15 | 1300.9 | 1301.8 | 1.1 | 0.116 | 0.407 | 0.196 |
16. Results
| Quantity | Value |
|---|---|
| Gross interval | 610.0 m |
| Net pay (P10/P50/P90) | 7.3 / 18.7 / 139.1 m |
| Net-to-gross | 0.044 |
| Avg PHIE (net pay) | 0.182 |
| Avg Sw (net pay) | 0.386 |
| Avg Vsh (net pay) | 0.131 |
17. Uncertainty and sensitivity
Monte Carlo, 500 realizations (seed 42). Net pay swing per parameter (one-at-a-time):
| Parameter | Net-pay swing (m) |
|---|---|
| Rw | 43.9 |
| a | 37.8 |
| m | 34.1 |
| n | 10.8 |
Dominant uncertainty: Rw (swing 43.9 m).
Multi-seed robustness: P50 UNSTABLE across seeds (spread 2.6 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.
18. Permeability (uncalibrated)
- perm_timur: mean k = 9.09 mD
_Uncalibrated screening estimate (no core); Sw used as the Swirr proxy._
19. Rock quality (uncalibrated)
- rqi: mean = 0.101
_Built on the uncalibrated permeability; indicative only._
20. Electrofacies
Unsupervised k-means on 3266 samples into 4 electrofacies (sample counts: facies 0: 1246, facies 1: 415, facies 2: 539, facies 3: 1066). Descriptive only — no core labels.
21. Derived parameters
- Bulk-volume water (BVW = PHIE*Sw): mean 0.0567 v/v
- Porosity-thickness (Phi·H over net pay): 3.622 m
- Hydrocarbon pore thickness (HCPV = Σ PHIE·(1−Sw)·step): 2.323 m
- Buckles constant (BVW at P10 of net pay): 0.0460 → Swirr (mean) ≈ 0.256 over 132 pay samples
22. Shale volume (Vsh)
Mean Vsh by method (selection is the agent's; the LLM authors no number):
| Method | Mean Vsh | Selected |
|---|---|---|
| vsh_larionov_old | 0.259 | |
| vsh_larionov_tertiary | 0.184 | ✓ |
| vsh_linear | 0.378 | |
| vsh_clavier | 0.244 | |
| vsh_steiber | 0.207 | |
| vsh_neutron_density | 0.383 | |
| vsh_multimineral | 0.331 |
23. Porosity
Mean porosity by method (effective where shale-corrected; the LLM authors no number):
| Method | Mean porosity | Selected |
|---|---|---|
| phie_density_neutron | 0.102 | ✓ |
| phi_density | 0.094 | |
| phi_neutron | 0.188 |
Service-company porosity curves (cross-check evidence, full-column means): phid_svc: 0.219, nphi_dol: 0.222, nphi_ss: 0.308. Matrix assumptions differ per curve; agreement/disagreement is the analyst's reading.
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 Rw — see Uncertainty for the swing.
26. Data quality and validator objections
Curve provenance (canonical ← raw mnemonic): DCAL←DCAL, DRHO←RHOC, DT←DT, 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: 3, hard_range_mask: 4, range_warn: 1, spike_removal: 85, 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 | 32 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: histogram"]
act_2["tool_call: histogram"]
dec_3["decision: step: compare_methods"]
act_3["tool_call: compare_methods"]
dec_4["decision: step: crossplot"]
act_4["tool_call: crossplot"]
dec_5["decision: step: set_zone_of_interest"]
act_5["tool_call: set_zone_of_interest"]
dec_6["decision: step: compare_methods"]
act_6["tool_call: compare_methods"]
dec_7["decision: step: compute_sw"]
act_7["tool_call: compute_sw"]
dec_8["decision: step: validate_choice"]
act_8["tool_call: validate_choice"]
dec_9["decision: step: rw_evidence"]
act_9["tool_call: rw_evidence"]
dec_10["decision: step: apply_cutoffs"]
act_10["tool_call: apply_cutoffs"]
dec_11["decision: wasted no-op: compute_sw"]
dec_12["decision: step: run_uncertainty"]
act_11["tool_call: run_uncertainty"]
dec_13["decision: step: permeability"]
act_12["tool_call: permeability"]
dec_14["decision: wasted no-op: permeability"]
dec_15["decision: step: rock_quality"]
act_13["tool_call: rock_quality"]
dec_16["decision: step: electrofacies"]
act_14["tool_call: electrofacies"]
dec_17["decision: step: lithology"]
act_15["tool_call: lithology"]
dec_18["decision: step: objection_profile"]
act_16["tool_call: objection_profile"]
dec_19["decision: step: derived_parameters"]
act_17["tool_call: derived_parameters"]
dec_20["decision: wasted no-op: lithology"]
dec_21["decision: wasted no-op: permeability"]
dec_22["decision: wasted no-op: compute_sw"]
dec_23["decision: wasted no-op: compute_sw"]
dec_24["decision: wasted no-op: lithology"]
dec_25["decision: wasted no-op: compute_sw"]
dec_26["decision: wasted no-op: lithology"]
dec_27["decision: step: compute_vsh"]
act_18["tool_call: compute_vsh"]
dec_28["decision: step: compute_phie"]
act_19["tool_call: compute_phie"]
dec_29["decision: step: compute_sw"]
act_20["tool_call: compute_sw"]
dec_30["decision: wasted no-op: compute_sw"]
dec_31["decision: step: apply_cutoffs"]
act_21["tool_call: apply_cutoffs"]
dec_32["decision: step: run_uncertainty"]
act_22["tool_call: run_uncertainty"]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): Rw (calibrated by produced-water salinity or a Pickett/SP Rw calibration).
- Standard curves absent: 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: PEF, CALI.
- Results are uncalibrated; accuracy depends on data not provided.
30. Conclusions
The interpretation is bounded by the BRACKETED confidence tier: all petrophysical parameters carry regional/default provenance and the result reads as a plausible range contingent on an assumed Rw. The Monte Carlo spread (P10 7.3 m, P50 18.7 m, P90 139.1 m) reflects this dominant uncertainty. No core, mud-log, pressure-test, or production data were available to calibrate Rw, Vsh, PHIE, or Sw cutoffs. The non-converged validation and outstanding mechanical objection reinforce that these figures should not be used for reserves booking or development decisions without further data acquisition and calibration.
Appendix A — Ledger excerpt (traceability)
{
"net_pay_total_m": 26.974800000000016,
"net_pay_p10_p50_p90": [
7.299960000000005,
18.66900000000001,
139.1259600000002
],
"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 | ✓ |